The mud of argillaceous soft rock is an important crux of long-term large deformation and instability of coal mine argillaceous rock mass roadways. Aiming at the poor injectability of cement slurry to micro-cracks in the rock mass during the mudstone grouting reinforcement process，which leads to poor anti-seepage and reinforcement effect，the feasibility of a new type of nano-silica sol grouting for the anti-seepage reinforcement of argillaceous rock mass was systematically studied. Based on the micelle structure of silica sol，the gel principle of silica sol is clarified，and the particle size grade of grouting silica sol is optimized. The basic physical and mechanical properties of silica sol and the basic anti-seepage characteristics of consolidated argillaceous soft rock are analyzed. The results show that silica sol has significant advantages over conventional grouting materials in terms of grout injectability，gel volume stability，and anti-seepage of the grouting structure. But the gel strength is less. The pore volume and permeability of argillaceous rock mass can be significantly reduced by silica sol grouting bonding，and the permeability coefficient can be reduced to 10－9 cm/s，which can meet the anti-seepage project of grouting argillaceous micro-cracked rock mass in coal mine roadways need. Aiming at the inefficiency of conventional silica sol grouting method for argillaceous rock mass matrix system grouting，based on the affinity between mudstone micro-cracks and silica sol，the grouting method of silica sol self-absorption infiltration grouting method for argillaceous rock mass was studied. The imbibition grouting of 0.1–40 mD low-permeability muddy core was realized，and the mechanism of imbibition grouting of silica sol was revealed from the microscopic scale. The results show that the grouting permeability of silica sol to low-permeability mudstone can be further improved by using the imbibition property. Aiming at the insufficient strength of silica sol-gel，a cross-scale composite modified slurry with silica sol as the main component and high injection height reinforcement was preliminarily developed by using aluminate cement as the modified reinforcing agent. The slurry material has outstanding performance in injectability，rheology，gel controllability，and stone body strength and volume stability，and can achieve dual functions of sealing and strengthening argillaceous rock mass.

In order to study the dynamic mechanical properties and crack extension law of water-saturated fractured sandstone，sandstone specimens with seven prefabricated crack inclinations(0°，15°，30°，45°，60°，75°，and 90°) were saturated with water，and impact compression tests were carried out with the split Hopkinson pressure bar(SHPB) test device. The results show that the dynamic stress-strain curves of prefabricated and natural sandstone samples with different inclination angles are similar，and can be roughly divided into three stages. The dynamic compressive strength，dynamic strain and dynamic elastic modulus all showed an overall trend of decreasing and then increasing with increasing fracture inclination. Compared with prefabricated natural sandstone specimens，the dynamic compressive strength and dynamic elastic modulus of the water-saturated sandstone specimens were slightly increased，while the dynamic strain was reduced，showing the Stefan effect of water action under dynamic loading conditions. With the change of fracture inclination，the failure modes of water-saturated sandstone specimens are tensile，shear and tension-shear composite failure modes. The fracture inclination is 0° and 15° for type II failure，30°‐75° for I-II composite failure，and 90° for type I failure. The crack initiation position of prefabricated fractured sandstone specimens is mainly concentrated near the fracture tip，and the crack initiation angle decreases with the increase of the fracture inclination angle，and the crack initiation angle at the incident end is larger than that at the transmitted end.

In the process of mining deep coal resources，the occurrence of strong mine earthquakes has become an important reason restricting the safe and efficient production of deep coal mines. The sudden release of strain energy caused by the instant breaking of key strata in deep coal mining is one of the important causes of the mining-induced seismicity. Aiming at the 63upper06 working face of the Dongtan coal mine，the PFC2D numerical software is used to simulate the failure process of overlying key strata in the process of coal mining. The evolution of the mining stress field is also investigated. Utilizing the single generalized displacement thick beam mechanics theory，the mechanical process of multiple key strata is inferred. The results indicate that the overlaying key strata failure types could be classified as suspended failure and overhanging failure. The vertical stress in overlying strata steadily decreases while the horizontal stress rises during mining as a result of the force arching effect of the changing mining stress field. The maximum tensile stress formula，maximum suspension distance，suspension distance of key strata before suspension，and mechanical mechanism of key strata covering deep coal mining are all derived. The research results are of great significance for the advancement of the theory of coal overburden migration in deep mining.

It is easy that the pile develops necking which can limit pile shaft resistance and cause the reliability index of bearing capacity for piles to reduce resulting in safety hazards to the project. Transparent soil technology is incorporated to load vertically on one intact pile with cap and seven necking piles with caps and the reduction coefficient of bearing capacity is investigated. The total probability formula is employed to investigate the influences of necking parameters(length，location，and diameter) on the reliability index of pile capacity. Subsequently，the speckle field of soil around piles is treated assisted with MatPIV software to obtain the soil displacement around piles，then the reduction reasons of reliability index caused by the necking to limit piles shaft resistance is explained. The study shows that the load capacity reduction coefficient and the reliability index change in the same trend，with the increase of the neck length，the closer the neck location to the top of the pile，the smaller the load capacity reduction coefficient and the reliability index，the more severe the loss of bearing capacity of the pile.

In order to investigate progressive damage and permeability evolution of sandstone under direct- shearing conditions，a group of numerical models based on physical experiments are established using the particle flow code in two-dimension(PFC2D). Four different levels of normal stresses are set to discuss meso-crack propagation features，energy dissipation mechanism，and permeability evolution characteristics of sandstone in the process of direct-shearing. The results show that the mesoscopic cracks gradually expanding，merging，connecting，nucleating，and finally forming an obvious macroscopic shear band，and the total number of cracks after failure increases with the increase of the normal stress. In addition，the total energy input in the pre-peak stage is mainly stored in the form of the strain energy of interparticle bonding bonds，and the dissipated energy increases rapidly in the post-peak stage. The dissipated energy is close to 40% of the total energy when the numerical rock samples fail completely. Furthermore，the permeability variation is governed by the preferred seepage channels in the rock sample，and the sudden increase of permeability is the manifestation of the transformation of“pore flow”into“fracture flow”during direct shearing process.

Given the technical challenges of insufficient image clarity and inaccurate quantitative characterization in the in-situ detection of pore structures on low reflection rock walls，this paper proposes a quantification method of pore structure in low illuminance borehole images based on pixel spatial Information. By synchronously utilizing borehole wall images and point cloud data to obtain pixel spatial feature information of non-standard cylindrical borehole shapes，the quantification process of pore structure in low reflection characteristic rock layers under complex geological conditions is achieved. Firstly，based on the low illumination borehole wall image features with alternating light and dark textures that are often formed in the actual drilling environment and testing process，a borehole wall eccentricity image correction model that is suitable for the actual hole testing environment is constructed to form a cosine light and dark texture suppression function that can effectively weaken the hole wall light and dark texture phenomenon. Subsequently，a low illumination borehole wall image enhancement algorithm based on detail feature weighted fusion is proposed to enhance the texture information of low illumination borehole wall images. Finally，combining the division of pixel spatial cells and the calculation of horizontal and vertical scales of pixel spatial points，a pore structure quantification method utilizing pixel spatial information is formed. At the same time，combined with practical case analysis，the correctness and superiority of the method proposed in this paper are verified. The results show that the method can obtain pixel spatial feature information of borehole walls in non-standard cylindrical drilling shapes，which can provide a new technical method and means for in-situ detection of pore structures in low reflection characteristic rock layers under complex geological conditions.

The contradiction between high stress and low strength in deep surrounding rock of coal mines is a key factor leading to large deformation and failure in deep roadways. In order to investigate borehole pressure relief technology in soft rock of deep roadways，the evolution characteristics of the disturbed stress field were analysed. Then，the mechanism of borehole pressure relief in soft rock under high stress is revealed，and the reasonable design method of borehole group is proposed. Three layout modes of pressure relief boreholes were proposed，including parallel layout，fan-layout and pipe-shed layout. The advantages and disadvantages of each layout modes were compared and analysed. Finally，an application experiment is carried out in a deep roadway with soft rock in Guqiao Coal Mine. A total of 96 pressure relief boreholes were drilled using the fan-shaped layout method. Surface displacement monitoring results indicated that，compared with the roadway near similar geological conditions in the non-depressurized area，the deformation of the surrounding rock in the depressurized section can be reduced by about 35.71%，the roof subsidence by approximately 33.43%，and the floor heave by approximately 35.84%. The stress release rate at 12 m depth inner the rock mass is approximately 18.5%. Our research demonstrates that reasonable drilling pressure relief can effectively reduce the concentrated stress，which is conducive to the stability control of roadway and the prevention and control of large deformation disasters. Pressure relief technology using dense borehole can be applied as an auxiliary means for the prevention and controlling large deformation disasters in deep，high-stress，weak surrounding rock.

The effectiveness of conventional anchor-cable support is limited for the large deformation of mining-induced roadway. The paper uses theoretical analysis，numerical simulation，and engineering case analysis to investigate the stress distribution of the surrounding rock，the size of the plastic zone，and the effect of deformation and failure control caused by conventional anchor-cable support in mining roadway. The results show that：(1) Bidirectional non-isobaric stress environment around the mining roadway promotes the development of the plastic zone from circular to elliptical or even butterfly-shaped，which is significantly affected by the strength of the surrounding rock. (2) Conventional anchor-cable support cannot significantly improve the stress field around the mining roadway. The control rate of continuous deformation of the surrounding rock in the roadway by strengthening support is related to the basic stress. (3) The stability control of the surrounding rock in the mining roadway should mainly rely on stress regulation，supplemented by conventional support. Flexible support combined with grouting modification and reinforcement of sensitive areas is the key. The research results can help to further understand the effect of conventional anchor-cable support on mining roadway and provide reference for surrounding rock control.

In deep engineering，the development and application of novel metallic materials has attracted many attentions. Although previous studies have demonstrated the importance and mechanical advantages of using high-strength and high-toughness steels in rock support system，its energy absorption characteristics under the influences of prestressing and rock loading remains still unclear. Therefore，based on the crystal plasticity method，this study takes novel high-strength and high-toughness bolt steel as an example to compare and analyze the mechanical and energy absorption characteristics of various metallic rock support materials. Meanwhile，the crystal plasticity model based on underlying physical mechanisms was used to study the effects of varying prestresses and rock loading rates on the energy absorption characteristics of high-strength and high-toughness bolt steel. The research results show that the development of energy absorption density of conventional metallic rock support materials meets a bottleneck. Distinct from the trade-off relationship between energy absorption density and ultimate tensile strength of conventional metallic rock support materials，the high strength(＞940 MPa) and large elongation(＞0.4) characteristics of novel high-strength and high-toughness bolt steel result in its extremely high energy absorption density of 3.5?108 J/m3，which is about 3–7 times that of conventional metallic rock support materials. The results of crystal plasticity simulations show that the material’s energy absorption characteristics can be further improved by adjusting the prestress and controlling the rock loading rate. For instance，the effective energy absorption rate of the material can be rapidly increased by applying high prestress，and it can resist the influence of rock loading rate. As the prestress is increased close to the yield stress of the material and the rock loading rate is controlled below 10－2 MPa/s，the high-strength and high-toughness bolt steel can obtain the largest effective strain(＞0.54) and the highest effective energy absorption density(＞4.5?108 J/m3)，which can optimize the energy absorption characteristics of high-strength and high-toughness bolt steel. The research results provide theoretical basis and technical guidance for practical application of high-strength and high-toughness steel for rock support engineering in high in-situ stress field.

In order to explore the mechanical properties and reasonable parameter values of deep buried soft rock，
the triaxial tests were conducted under high confining pressure conditions to study the mechanical properties of Silurian shale in the water diversion project from Three Gorges reservoir to Hanjiang river. Based on the experimental results，the influence of different dip angles on the mechanical properties and failure modes of shale was analyzed. Based on various methods such as experimental research，theoretical analysis，engineering analogy and inversion，and normative verification，a reasonable mechanical parameter values for deep buried soft rock is proposed. At the same time，the outer envelope of the inversion value of crustal stress was used to determine the crustal stress values for different burial depths in the soft rock cave section. Through research，it has been found that as the confining pressure increases from low to high，the cohesive force of rock samples continuously increases，and the internal friction angle continuously decreases. When the dip angle of the bedding plane is 0°，the strength of the shale sample is the highest. When the dip angle of the bedding plane is 55°，the strength is the lowest，and the rock failure surface at this angle is consistent with the bedding plane. Based on the results of triaxial compression tests，H-B strength criterion，analogy of tunnel engineering in the same stratum，and theoretical inversion using convergence constraint method，a reasonable mechanical parameter value method for deep buried soft rock is summarized，which can reflect the influence of confining pressure on the equivalent mechanical parameters of rock mass. Finally，the strength-to-stress ratio and excavation deformation were used to predict and evaluate the deformation level of deep buried soft rock in the water diversion project from Three Gorges reservoir to Hanjiang river.

The dynamic disturbance effect has a major effect on the stability and safety of subsurface geotechnical engineering and slope engineering. In order to account for the effects of dynamic disturbance on creep damage to soft rock，this research presents a novel synergistic damage calculation approach based on the evolution law of viscosity coefficient. In order to characterize the evolution law of creep damage and deformation of soft rock under the influence of dynamic disturbance effect，it accomplishes the quantified expression of the evolution of viscosity coefficient at each stage of creep damage. A one-dimensional creep damage model of soft rock was constructed using the element model approach，based on the unique evolution equation of viscosity coefficient in each stage of soft rock creep under the influence of synergistic damage effect and the enhanced Newtonian body element. Building a three-dimensional creep damage model of soft rock under the influence of the synergistic damage effect，the plastic flow rule was presented on this basis. The suggested one-dimensional and three-dimensional creep damage models were verified for accuracy using the Levenberg-Marquardt optimization algorithm，and the model parameters were set using the soft rock creep test results under the influence of the dynamic disturbance effect. The findings showed that the accelerated creep phase in particular，in the one- and three-dimensional creep damage models，may better represent the time-varying deformation of soft rock brought on by dynamic disturbance effects. The correctness and applicability of the suggested creep damage models were carefully evaluated and examined，and a sensitivity analysis of the important creep damage model parameters was also carried out.

In order to study the temporal and spatial variations in surrounding rock displacement during the process of combined open-pit and underground mining，this study focuses on the Dahongshan iron mine combinded open-pit and underground mining project. Specifically，the microseismic events occurring between exploration lines A34 and A37 were examined to discern the patterns of their distribution. Moreover，a novel rock damage model，incorporating microseismic events，was developed and integrated into numerical simulations to analyze the progressive rock damage and displacement within the combined mining zone of exploration lines A34–A37. It is worth noting that the preliminary findings indicate that the inhibitory effect of the F2 fault on rock mass movement resulting from underground mining has become largely ineffective，except for a localized inhibitory effect near the 775 m elevation. Consequently，the estimated collapse angle of the surrounding rock is determined to be 79.3°，while the displacement angle amounts to 74°. To ascertain the reliability of the numerical simulations based on the microseismic monitoring-derived rock damage model，stochastic medium ore drawing theory，along with field measurements of surface subsidence，was employed to validate the simulated conclusions concerning rock displacement. Encouragingly，the outcomes of the validation process confirm the credibility and robustness of the simulation results. Overall，this research makes significant contributions to the analysis of rock mass displacement in the context of combined open-pit and underground mining，thereby providing invaluable insights and serving as a fundamental reference for future investigations in this domain.

Determining the scope of the rock mass blasting damage zone is important for evaluating the stability of underground engineering surrounding rock under blasting and controlling bedrock damage under excavation. A method based on wave velocity field inversion was proposed to determine the rock blasting damage zone scope quantitatively. This method was based on multistencils fast marching methods(MSFM) and simultaneous iterative reconstructive technique(SIRT). The effectiveness of the proposed method was verified by comparing the inversed wave velocity field with the known one. Blasting and wave velocity measurement simulations were carried out on the self-developed finite-discrete element solver OpenFDEM. The waveform data were processed using a self-programmed post-processing program，and thus the post-blasting wave velocity field was reconstructed. Based on the relationship between the changing rate of wave velocity and the degree of rock mass damage in the current code，the areas with different wave velocity changing rates were compared with the areas of cracks. The scopes of the blasting damage zone with different damage degrees were quantified using the ratio of the equivalent radius to the blast hole radius. 10% and 15% of the wave velocity changing rate were used as the thresholds for defining slightly and completely damage of the rock mass，respectively. The ratio of the equivalent radius of the slightly damage zone and the damage zone to the radius of the blast hole is about 11.86 and 7.2，respectively. As the blast load increases，the shape of the damage zones with different damage degree becomes irregular and the equivalent radius increases. The study results are expected to provide a reference for determining the scope of the blasting damage zone in the field.

The accurate determination of the boundary equation is crucial for classifying and identifying cracks in the process of rock fracture using the RA(Rise Time) and AF(Amplitude Ratio) values of acoustic emission. The granite shear acoustic emission monitoring experiments were carried out. Based on the crack classification method using RA-AF，the influences of the slope k and intercept b of the boundary equation on the crack classification results were analyzed. Utilizing the turning point detection algorithm for curves(kneedle algorithm)，a method for accurately determining the boundary equation was developed，and the crack classification results were analyzed. The results indicate that both the slope k and intercept b of the boundary equation have an influence on the crack classification results，which is related to the magnitudes of the two values. There exist critical values for both the critical slope and critical intercept. When these values are smaller than the critical values, the classification results are greatly affected，whereas when they exceed the critical values，the classification results are almost unaffected. The kneedle algorithm for curve inflection point detection can effectively determine the critical points of the boundary equation slope and intercept，providing a method and basis for accurately determining the critical slope and intercept in the boundary equation. Compared to the boundary equation without intercept, if the boundary equation has an intercept b，the proportion of shear cracks will increase by approximately 20%. The research findings provide a basis for determining the boundary equation for classifying rock tensile-shear cracks using RA and AF values，which contributes to the application of this method in rock mechanics.

To understand the effect of mineral composition and grain size on mechanical properties of rock better，the basic data of mineral composition，mineral micro-mechanical properties，grain size and shape of four kinds of marble are obtained in this paper. Then their strength parameters，deformation properties and failure modes are tested for further analysis. The results indicate that：(1) The strength of Chenzhou，Fangshan，Carrara and Hezhou marble decreases while their ductility increases in sequence，that is，the strength and brittleness of dolomite marble is greater than that of calcite marble. (2) Considering only the effect of grain size，the strength and brittleness of rock decreases with increasing grain size. However，when considering other factors(mineral composition，micro-mechanical properties) together，it is possible that rocks consisting of larger grains present a higher strength and more brittle behavior. (3) The cohesion of rock is positively and linearly correlated with uniaxial compressive strength，while it is weakly correlated with tensile strength. (4) The ratios of uniaxial compressive strength to tensile strength are significantly different from that predicted by the extended Griffith theory，while the ratios of crack initiation stress to tensile strength maintain around 7–12. (5) During triaxial compression test，the confining pressure fluctuates slightly above the target value，and the overall synchronization exists between the variation of the confining pressure and the axial stress. The results not only enhance the understanding of mineral grain size effect and enrich the theoretical knowledge of rock mechanics，but also provide a large number of basic data for further marble engineering evaluation and calculation analysis.

To address the problem of gas drainage in coal mines，improve the sealing effect of gas drainage boreholes and explore the mechanical property deterioration and crack expansion of rock grouting body affected by slit after the grouting sealing of gas drainage boreholes，industrial CT scanning and triaxial compression tests of rock grouting body were carried out to analyze the deterioration of the mechanical properties and the law of crack propagation caused by slitting after the failure of rock grouting bodies. The results show that the two-dimensional fracture rate and fractal dimension increase linearly with the number of slits and reach their peak values near the slitting position after the failure of rock grouting samples under the condition of triaxial stress. The drilling slits have a guiding effect on the fracture propagation of rock grouting bodies. In addition，the distribution range of cracks in samples is the smallest when the number of slits is 1. The three-dimensional fracture fraction and fractal dimension of samples increased linearly with the number of slits，while the Euler number decreased linearly with the number of slits. It shows that drilling and cutting could improve the fracture connectivity and make the fracture network more complicated. Additionally，the compressive strength of rock grouting samples with four different slit number decreases with the increase of slit number while the permeability of the samples decreases with the increase of slit number. It is reasonable to determine the number of slitting as 1–2. The rationality of the integrated technology of slotting grouting and sealing was verified.

Grotto temples are located in environments that are subject to long-term alternating effects of cooling and heating，and temperature variations commonly lead to changes in the mechanical properties of the grotto surrounding rock. The sandstone of the Dazu Grottoes in Chongqing was taken as the research object in this paper. The mechanical properties of grotto sandstone were investigated by uniaxial compression test and Brazil split test，and the stress-strain curve，strength，peak stress and strain，elastic modulus，and failure mode of grotto sandstone under different temperature and heating-cooling conditions were analyzed. The results show that the uniaxial compressive strength of sandstone decreased after 10 heating-cooling cycles. Compared to natural cooling，water cooling significantly reduced the uniaxial compressive strength of sandstone. The tensile strength of the sandstone was strongly influenced by the cooling method，with the lowest tensile strength under the low-temperature water cooling cycle. The peak strain of sandstone decreased after 10 heating-cooling cycles. Compared to natural cooling，water cooling cycles decreased the elastic modulus of sandstone，and it also decreased as the number of cycles increased from 5 to 10. The failure mode of sandstone under uniaxial compression was mainly shear failure，which became complex after heating-cooling cycles. The main difference of the failure modes of sandstone under Brazilian splitting was the shape and number of cracks. After water cooling cycles，the main crack of sandstone changed from linear to arc or formed secondary cracks.

The initiation and propagation law of hydraulic fractures in altered gold ore hold paramount importance for the hydraulic fracturing exploitation of gold mines. This study conducted true triaxial hydraulic fracturing experiments on altered gold ore under varying water injection rates，minimum horizontal principal stresses，and angles between water injection holes and joint surfaces. Results indicate that：(1) when the difference in horizontal principal stress for altered gold ore ranges from 1 to 3 MPa，initiation stress spans 22.2 to 40.0 MPa. With increasing water injection rates(from 5 mL/min to 15 and 30 mL/min)，initiation stress rises by 17.4% and 34.3%，respectively. An elevation in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) results in initiation stress increases by 37.4% and 80.2%，respectively. The angle between water injection holes and joint surfaces(from 0° to 45 and 90°) induces initiation stress increases by 6.3% and 24.9%，respectively. Altered gold ore，under similar in-situ stress conditions，exhibits higher initiation stresses compared to sedimentary rocks. (2) Hydraulic fractures in altered gold ore can be categorized into two modes: linear and polygonal propagation. Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min) results in heightening perpendicularity between the fracture propagation direction and the minimum horizontal principal stress direction，with a reduction in the number of turns from 2 times to 0. An increase in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) leads to an increase in the number of turns from 0 to 1 and 3 times，with larger turning angles. With the increasing angle between water injection holes and joint surfaces(from 0° to 45 and 90°)，interference from joint surfaces is intensified，causing propagation deviations towards the joint surfaces. Hydraulic fractures in altered gold ore predominantly exhibit main fractures，with fewer and simpler secondary fractures，whereas sedimentary rocks display a higher number of complexly distributed secondary fractures. (3) The fracture surfaces in altered gold ore can be classified based on morphological characteristics into smooth and rough surfaces. Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min) results in a decrease in protrusion size on the fracture surfaces，with the protrusion area decreasing from 63% to 45% and 0%. Increasing the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) leads to an increase in the protrusion area from 0% to 40% and 45%. Increasing the angle between water injection holes and joint surfaces(from 0° to 45° and 90°) all maintains joint surface features on the fracture surfaces with smooth and non-protruding characteristics. The fracture surfaces of altered gold ore are rough，while those of sedimentary rocks are comparatively smoother.

To investigate the evolutionary patterns of resistivity and acoustic emission in sandstone with varying saturation levels under different loading paths，particularly focusing on the resistivity characteristics during the quiescent phase of acoustic emission，we conducted uniaxial，constant amplitude cyclic loading，and increased amplitude cyclic loading tests on dry，semi-saturated，and saturated red sandstone specimens，respectively. The test results reveal a close correlation between resistivity changes and stress levels，offering insights into internal pore alterations and the compaction，initiation，and development of micro-cracks within the rock under loading conditions. As saturation increases，the quiescent period of acoustic emission before failure exhibits a significant extension. The variation in resistivity effectively mirrors the propagation of sub-critical cracks and the accumulation of internal damage within the rock during the quiescent phase of acoustic emission. Under distinct loading paths，the conduction mechanism in dry specimens is primarily skeleton conduction，demonstrating an overall upward trend. In contrast，saturated specimens predominantly exhibit water conductivity，leading to a downward trend in resistivity. During cyclic loading，when stress levels exceed 50% of the peak strength，the Kaiser effect in red sandstone with different saturations diminishes，giving way to the Felicity effect，accompanied by a declining Felicity ratio.

In order to explore the dynamic response characteristics of the rock mass with different combined dip angles under impact load，the dynamic impact tests of the rock mass with six different combined dip angles of granite and sandstone were carried out by using the separated Hopkinson pressure bar(SHPB)，high-speed camera and discrete lattice spring method(DLSM). The stress wave propagation characteristics，stress-strain curve difference，energy dissipation law，damage evolution characteristics and the relationship between total kinetic energy and crack propagation of rock mass with six different combination dip angles were studied. The results show that the dynamic mechanical properties and energy dissipation law of the combined rock mass are related to the combined dip angle. When the combined dip angle increases from 0° to 75°，the transmitted wave amplitude，peak stress and dynamic elastic modulus of the specimen increase first and then decrease，while the reflected wave amplitude decreases first and then increases. When the combined dip angle is in the range of 45°–60°，the combined rock mass of hard and soft medium is easy to be destroyed. Combined dip angle will not only hinder the stress wave propagation but also affect the stress change of rock on both sides of the bonding surface，resulting in secondary loading phenomenon of rock on both sides of the bonding surface. The damage value of rock mass presents an inverted "V" shape with the increase of combination dip angle，and the damage value is the highest in the range of 45°–60°. The larger the combined dip angle is，the lower the total kinetic energy in the rock mass failure process，the less cracks，and the smaller the deformation and displacement of the specimen.

The main focus and challenge of landslide research is always the formation mechanism of bedding rock landslides. An ideal generalized model was created to investigate the progression and instability mechanism of bedding rock landslides. In addition to using the digital image correlation(DIC) approach，a freezing experiment was conducted for non-contact and real-time deformation observation throughout the experiment for the entire process of a bedding rock landslide. A method was proposed to finely describe the relative displacement evolution of the opening section of side slope rear edge and the shear slide section of the bedding rock landslide, based on the full-field deformation data derived by DIC. The findings indicate that there are four stages in the instability process that the bedding rock landslide goes through：early deformation, rear edge opening，shear sliding and overall instability. Prior to reaching the rear edge of the possible sliding zone，the strain localization band is initially produced at the shallow area of the rear edge opening section and subsequently proceeds to the deeper part. Following that，they keep going in the direction of the sliding zone?s front edge，finally passing through it and reaching the failure of overall instability. These occurrences demonstrate the characteristics of progression from shallow to deep，from the rear edge to the front edge and from local to global. Furthermore, the impact of the sliding zone dip angle on the instability of bedding rock side slope was investigated，and it was found that an increase in the sliding zone dip angle shortens the instability time. The research methodology based on DIC monitoring provides a new way to revealing the progression mechanism of bedding rock landslides through quantitative means.

The key of roof water inrush prevention and water resources protection of coal mine is to control the height of the water conducted fracture zone and reduce mining disturbance of the overlying aquifer. Based on the current research status of overburden damage control technology and pre-cracking weakening control of ground pressure in coal mine，a method to control overburden damage by actively weakening the hard rock layer is proposed. This method does not affect mining efficiency and coal resource recovery rate. Combined with similar simulation，theoretical analysis and numerical simulation analysis，the mechanism of pre-cracking weakening thick-hard roof to control the height of water conducted fracture zone was studied. According to the numerical simulation results，a method for determining the pre-cracking hard overburden under the aquifer is proposed. The results of the study indicate that：Due to the hard rock disintegrate into larger pieces during mining，and after mining，these broken pieces will be neatly piled up in goaf，therefore the bulking coefficient of hard roof after mining is smaller than normal roof. Pre-cracking can increase the bulking coefficient of hard stratum，reduce the subsidence of overlaying strata，and thus reduce the height of water conducted fractures zone. The response of the overlying strata to mining damage varies significantly under different pre-cracking for hard rock layers in different layer positions. Therefore，the selection of the pre-cracking position will directly determine whether pre-cracking weakening control of the water conducted fracture zone height is effective. The simulation results indicate that pre-cracking the middle thick hard rock layer and pre-cracking the middle and low level rock layers simultaneously can effectively control the height of water conducted fracture zone. The study results provide a new technical path for the safe，efficient，and green mining of coal resources under aquifer.

Fly ash is a byproduct of thermal power generation that requires proper disposal. While it is abundant in western China，transportation and disposal costs can be significant. Furthermore，the regions of western Ningxia and Gansu are facing a severe desertification problem. This research aims to explore the potential of fly ash modified materials for sand fixation，while considering the balance between supply and demand. To develop reference and fixation standards based on the effect of sand fixation，the mechanical properties，hydration products，and microstructure of modified fly ash sand fixation materials were studied through various analytical methods，including uniaxial compressive strength test，water content test，scanning electron microscope test (SEM)，X-ray diffraction test(XRD)，and shear test. The results suggest a noteworthy enhancement in the uniaxial compressive strength and cementation effect of the modified fly ash materials. The hydrated calcium silicate gel formed after the hydration of the modified fly ash materials appears to be the key factor in explaining the difference in water retention. Additionally，the cohesive force of the 10% alkali exciter-modified fly ash cement increased to more than three times the original，and the shear strength of the 30% magnesium slag-modified fly ash cement was significantly improved. The article suggests considering the use of a low-dose alkali exciter，approximately 2.5%，or a high-dose magnesium slag modified fly ash，greater than 30%，while adjusting the ash-to-sand ratio accordingly to optimize both economic benefits and sand fixation effects.

The large error in the results of the maximum horizontal principal stress is a prominent problem in the in-situ stress measurement by hydraulic fracturing method. In this paper，the differences and applicability of several main formulas used to calculate the maximum horizontal principal stress are compared and analyzed on the basis of the domestic and foreign hydraulic fracturing in-situ stress measurements regulations or suggested methods. Taking the test system compliance as the main influencing factor，the error sources and physical mechanism that affect the calculation accuracy of the maximum horizontal principal stress are analyzed in detail and depth. On this basis，taking the measured hydraulic fracturing data of the deep-hole obtained from the granite borehole in Beishan，Gansu as an example，the fracture reopening process is numerically analyzed based on the KGD theoretical model, and the influence of system compliance on the calculation result of the maximum horizontal principal stress is quantitatively studied. Taking the theoretical calculation value of eliminating the influence factors of compliance as correction value，the measured data and heoretical correction valueof 6 testing intervals in the hole depth range of 18–930 m are given. The results show that the error of the maximum horizontal principal stress measurement results increases gradually with the increase of test depth due to the influence of the test system compliance. When the test depth is 930 m，the relative error of the measurement results is 24.55%. The research results can provide a reference for the error problem of the maximum horizontal principal stress measurement results in relevant engineering applications，also provide a new idea and technical approach for the error analysis and further improvement of the reliability of the hydraulic fracturing in-situ stress measurements.

In order to study the effect of internal flaw on rock energy dissipation and damage change law under impact loading，intact granite specimens and specimens with different flaw inclination are tested by a modified split Hopkinson pressure bar(SHPB). The results of experiment and theoretical analysis show that the elastic strain energy of 0° flaw decreases first and then increases，while 45° and 90° flaws increases first and then decreases with increasing the loading rate. According to the principle of energy conversion and distribution，a function model is constructed considering the variation of strain energy density，which can well reflect the energy dissipation characteristics of rock before peak stress. In this study，the ratio of dissipated energy to elastic energy is used as the energy indicator of rock failure precursor. During the absorption，storage，and release of energy before the peak stress，there exists self-control of energy. The damage variable of rock under different loading rates is divided into two stages，damage stable development and damage acceleration. Besides，the damage variable shows obvious rate effect，which decreases first and then increases with the increase of crack angle，and it has a good nonlinear relationship with the loading rate and the energy dissipation density，respectively. Based on the mathematical derivation method，the damage evolution equation of the fractured rock under impact loading is constructed，the influence of different fracture angles and loading rates on rock damage curve are also studied. The slope of the damage curve first increases and then decreases，while the damage factor m0 increases and F0 gradually decreases. These conclusions should provide scientific basis for the practical projects of deep rock engineering design and improve the efficiency of rock excavation and rock breakage to some extend.

Judgement regarding the possibility of a dam-break is critical for deciding whether engineering measures should be taken. Fast access to final breach geometry parameters is also essential for peak-flow prediction. In this study，data from 49 landslide cases and natural dam-breaks from the year of 1654 to the present were collected. Then，the landslide dams after emergency response were regarded as “new dams” according to on-site disposal measures，and data about their upstream lake and dam characteristics were re-classified. Then，statistical and test analysis were combined to select factors that influenced dam-break possibilities and final breach shape from case characteristics，dam-break process and mechanical analysis；the rapid prediction method was summarized. Results showed that the dam-break possibility was related to upstream inflow，barrier lake volume，dam materials and the length-to-height ratio. The influence of length-to-height ratio on the dam-break possibility was only reflected on the dam composed of Class IV and V materials，and this influence was constrained by upstream inflow. The vertical dam-break degree was found to be mainly related to the material of the dam and length-to-height ratio. Based on the above factors，two quick-judgment methods met the needs of predicting dam-break possibility and vertical dam-break degree were proposed during the emergency response process. In addition，the prediction error of the vertical dam-break degree is caused by a vertically inhomogeneous dam structure，especially the binary and ternary stacked structures with “pseudo bedrock” at the bottom. They exerted a significant impact on the vertical dam-break degree. Therefore，such uneven distribution should be considered to reduce the error in prediction. Furthermore，breach width was influenced by the vertical dam-break degree；when one-half of a dam was washed away vertically，the breach width was limited to the river width. From the principles of sediment transport，empirical formulas for calculating top and bottom breach width were derived based on actual discharge storage capacities and vertical erosion depth data obtained from model tests and field cases(R2＞0.86). This research combined scientific，practical and systematic aspects of dam-break prediction；the resulting rapid assessment methods can provide effective references for field decision-makers in preparing emergency plans and preparing peak-flow predictions by assuming suitable breach parameters.

In order to investigate the motion instability of the hard roof in incline thick coal seam，a numerical model for mining covered rock in such seam was established using PFC2D discrete element particle flow analysis software. A hydraulic weakening program was designed to address the issue of large area hanging arch in the hard roof. The study analyzed the influence of different fracturing parameters on the effectiveness of hydraulic weakening and proposed an optimization method for selecting hydraulic weakening. parameters. The study revealed that the hard roof of incline thick coal seam undergoes a “Dam-shaped block” breakdown under initial weighting，and the vertical stress of overlying strata above the goaf exhibits asymmetric characteristics，resulting in stepped collapse in longitudinal direction as the working face advances；Four hydraulic weakening schemes with different fracturing angles and three different fracturing heights were proposed for large area hanging arch of incline thick coal seam. The results showed that the weakening scheme with a fracturing angle of “right angle” and a fracturing height of half of the thickness of the basic roof achieved the expected weakening effect. The weakening scheme reduced the hydraulic weakening influence area of the hard roof，resulting in an overall decrease in ground pressure strength，with a reduction of about 42% in peak pressure and 52% in weighting step distance；Considering the construction difficulty and cost，the hydraulic weakening parameters of the hard roof of incline thick coal seam was optimized. Based on the relationship between weakened degree and fracturing angle and height，a preferred method of non-fully oriented hydraulic weakening parameters of the hard roof of incline thick coal seam was proposed. An industrial test was conducted in the 1E201 working face，yielding a significant weakening effect on the roof.

The frost heave force is an important cause of rock mass failure in the cold region. The traditional analytical model cannot calculate the frost heave force after crack propagation. Considering the influence of crack propagation，it is of great significance to establish an analytical model of frost heave force in fractured rock mass. In this paper，an analytical model of frost heave force evolution in fractured rock mass is derived based on the theory of elastic mechanics，complex variable function and elastic-plastic fracture mechanics. The effects of crack size，freezing rate，water mobility and other factors on the evolution of frost heave force before fracture instability were analyzed. Combined with the estimation of frost heave force after fracture instability，the evolution mechanism and the whole process characteristics of frost heave force were studied. The analytical calculation results were compared with the experimental results. The results show that：(1) The analytical model of frost heave force proposed in this paper can calculate the frost heave force after crack propagation，rationally explain the mechanism of frost heave force fluctuation，and provide a basis for the evaluation of frost resistance of cracks to a certain extent. (2) Before fracture instability，the maximum frost heave force decreases with the increase of fracture length，and the time required to reach the maximum frost heave force increases with the increase of crack width. The maximum frost heave force may decrease with the increase of freezing rate. With the increase of water mobility，the maximum frost heaving force before fracture instability increases，and the time required to reach the maximum frost heave force also increases. (3) The variation of frost heave force can be caused by subcritical crack propagation and instability fracture，and the evolution of frost heave force in cracks is characterized by fluctuation. When there is no instability fracture in the freezing process，the frost heave force fluctuates and increases. When there is instability fracture in the freezing process，the frost heave force first increases and then decreases.

The assessment of the degree of deterioration of surrounding rock in a roadway is a critical issue for the prediction of roof disasters，which are essentially caused by the microstructural evolution inside the rock mass. In this paper，a combination of nuclear magnetic resonance technology，numerical simulation，and energy theory is employed to investigate the pore evolution laws from small，medium，and large aperture pores and cracks to macroscopic failure during rock loading，as well as the associated energy evolution laws. The unification relationship between the “pore evolution stage” and the “energy evolution stage，” which forms a “dual-stage” evolution process，is elucidated to establish a quantitative characterization of the microstructure of rock and the degree of deterioration of surrounding rock in a roadway. The results show that the distribution characteristics of porosity evolution during uniaxial loading of the specimens are obtained，and the porosity evolution is divided into four stages：pore compaction stage，elastic deformation stage，elastic-plastic deformation stage，and plastic yield stage. The mechanism of the differences in the characteristics of the pore evolution stages between laboratory tests and numerical simulations during the pore evolution process is revealed，which is caused by the elastic deformation recovery of the specimen during the unloading process of the laboratory test. The consistency between the “pore evolution stage” and the “energy evolution stage” during the synergistic evolution process is demonstrated，and the “dual-stage” synergistic evolution process curve shows a basic consistency in normalized values，indicating a micro-macro cross-scale unification relationship between the two. A roadway surrounding rock deterioration and failure warning method based on micro-macro cross-scale rock structure synergistic evolution is constructed to comprehensively evaluate the degree of rock deterioration，give corresponding warning levels for the rock strata in the relevant areas，and provide a theoretical basis for on-site safety hazard prevention and control work.

Sandy dolomite often has broken structure，with complex geological environment. It is prone to occur collapse，water inrush and sand gushing，induce the ground collapse and other disasters. Consequently，the construction of underground engineering in this stratum face several problems such as great excavation and supporting difficulties and high safety risk. There are five water conveyance tunnels passing through sandy dolomite strata in Yuxi section of central Yunnan water diversion project. In this paper，geological survey and analysis，microstructure testing and analysis were used to obtain the spatial distribution characteristics of sandy dolomite along the tunnels，with different sandy grades. Through geological survey in the construction period，case statistics of surrounding rock instability，theoretical analysis and induction，the influence factors of surrounding rock instability of sandy dolomite tunnel were summarized，the failure mechanism of surrounding rock was explored，and targeted prevention and controlling measures were put forward. The results show that：(1) The spatial distribution and sandification degree are closely related to the scale and distance of faults. In the vertical zonation，the sandification degree is gradually deepen from the surface to depth. Furthermore，strongly and severely sandy dolomite is the main surrounding rock mass in this project. (2) The influence factors of surrounding rock instability of sandy dolomite tunnel are mainly sandy grade，faults，groundwater condition and excavation disturbance. (3) Under anhydrous conditions，gravity-driven and stress-rock mass structure composite-driven surrounding rock collapse is prone to occur. In addition，under the condition of water-rich section，the failure modes are mainly water inrush and sand gushing，and the mechanism is mainly seepage instability. (4) Advanced geological prediction and dynamic risk evaluation of disaster occurrence are important measures for disaster prevention and controlling of sandy dolomite tunnels. The construction of slurry stop wall and consolidation grouting of surrounding rock are specific measures to deal with water and sand inrush. Construction experience still needs to be accumulated and summarized. The research results have certain guiding value for the disaster prevention and control of surrounding rock of sandy dolomite tunnel.

In order to study the influence of dolomite sandification on tunnel grouting reinforcement in the construction section of Yuxi construction section of Yunzhong Water Diversion Project，then reveal the law of slurry diffusion，a series of in-depth studies of scanning electron microscopy(SEM) experiments，theoretical analysis and multiphysics fluid-structure interaction numerical analysis were carried out. The results show that，dolomite sanded under dissolution and developed internal structure with multi-scale pore-fracture network distribution characteristics，during grouting injection，the slurry has a front surface during diffusion migration and produces obvious fingering phenomenon，fractures with different developmental configurations can lead to irregularity and instability of the diffusion morphology of cement slurry. Compared to traditional constant pressure grouting，variable pressure gradient grouting is more conducive to uniform filling of multi-scale fractures developed by complex strata after sanding，after the slurry solidifies，the cemented and broken rock mass reduces the stress distribution area of the surrounding rock，and alleviates the stress concentration phenomenon of the vault and arch bottom，it has a more significant effect on improving the stability of surrounding rock. The above studies can provide a theoretical reference for the actual grouting engineering design and construction of sanded dolomite strata tunnels.

Rainfall is an important factor inducing landslide deformation. Traditional displacement time series prediction models only consider historical displacement and do not consider the impact of rainfall to conduct landslide displacement prediction，resulting in significant errors in the medium to long term or long-term displacement prediction. Given that the Gaussian process regression(GPR) algorithm has the advantages of easy realization，adaptive acquisition of hyperparameter and probability significance of prediction output，a GPR prediction model of landslide displacement considering the previous accumulated rainfall by introducing the cumulative rainfall index is established in this study，which improves the long-term displacement prediction capability of the model. Taking the landslide in the southern mining area of Xichang as an example，the relationship curve of landslide displacement and daily cumulative rainfall was first analyzed，and the Pearson method was used to calculate the correlation coefficient between the landslide displacement and the previous cumulative rainfall days；Secondly，a GPR model was established，and trained and tested using existing monitoring data. The results showed that the prediction accuracy of the established model was significantly improved compared to the model without considering the previous accumulated rainfall. On this basis，a long-term displacement trend prediction was conducted for monitoring points S1–1 and S1–2，and a comparative analysis was performed on the displacement trend under the assumption of increasing rainfall by 10% and 20%. The results indicate that a 20% increase in rainfall leads to an increase in the deformation rate of the landslide to about 17 mm/d. Without taking control measures，the landslide will experience accelerated sliding to instability.

Aiming at the insufficiency of rockburst monitoring and prevention and control research in deep hard rock，a rockburst monitoring method for the pre-tightening force of bolt was proposed，the monitoring system of the pre-tightening force of bolt was developed，a biaxial compression test of anchor specimens was carried out，and the pre-tightening force of bolt and plate were analyzed，and the anchor spacing design methodology for rockburst prevention and control was determined. The results show that the pre-tightening force of bolt is highly sensitive to the micro-deformation of hard rock，and has a good correspondence with the evolution process of rockburst deformation，damage and fracture，and can be predicted by monitoring the pre-tightening force of bolt；compared with the instantaneous rockburst，time delayed rockburst is characterized by multiple obvious sudden increase peaks in the pre-tightening force of bolt. With the increase of depth of the anchored surrounding rock，the anchor prestress continues to decay and the influence range increases. With the increase of the pressure spread angle，the faster the anchor prestress decays with depth and the more obvious the increase of the influence range. The critical depth is defined，and the critical depth formula is given，and the optimized formula of the spacing of the anchor plate is derived based on the critical depth，and the anchor pre-stressing(tightening) force principle used for designing the spacing of the anchors is put forward to get the optimized spacing of the design of the anchor plate，and the design method highlights the control on the shallow part of the surrounding rock，and is particularly applicable to the design of the shallow control and prevention for the surrounding rock hazards such as the rockburst；The contact between the anchor plate and the surface of the surrounding rock affects the anchoring effect. It should be ensured that the anchor plate is in full contact with the surface of the surrounding rock，to ensure that the pre-tightening force of bolt is effectively transmitted and exerted effect to the surface of and the inner of the surrounding rock through the plate. The research results have good guidance and reference significance for prestressing anchor anchorage mechanism，rockburst monitoring，prediction and forecasting，prevention and control.

In the HLW repository，the strong alkaline solution precipitated by the corrosion of the lining concrete by the groundwater and the radiant heat released by the decay of the nuclide will affect the swelling performance of the buffer backfill material. The mixture of 70% bentonite and 30% quartz sand is used as the test object. Distilled water and KOH solution are selected for the pore solution，and the concentration of the solution is 0.1，0.3，1.0 mol/L. Set the test temperature to normal temperature and 90 ℃. Test the swelling pressure of samples with different initial dry densities. After the test was completed，X-ray diffraction(XRD) test was carried out on the sample. The test results confirmed that the high temperature increased the swelling pressure development rate and the swelling pressure value of the sample，and the final swelling pressure value increased by 19.3%. Under the action of KOH solution，the swelling pressure of the buffer backfill material decays over time，which is a typical feature of the alkali solution?s damage to the swelling performance. The final swelling pressure value is positively correlated with the KOH concentration and negatively correlated with the initial dry density. Under the action of 90 ℃ 1.0 mol/L KOH solution，the final swelling pressure value of the sample is higher than that of distilled water，and the attenuation degree reaches more than 52.3%. The attenuation of the sample is mainly related to the dissolution of montmorillonite and cation exchange. In the most severe case，the montmorillonite content is reduced to 43.2% of the initial.

Soil grouting has become an important technology for deformation recovery of existing tunnels，in order to explore the formation mechanism and influencing factors of slurry diffusion and additional soil pressure during grouting，a unit test for ground grouting has been designed.The grout with different water contents has been injected into sandy soil and rubber particle formations respectively，to explore the diffusion mode of slurry and the formation law of additional soil pressure during the grouting process using model experiments.The test results are as follows. (1) Pore water pressure dissipation will occur after the grout is injected into the formation soil，and the larger the soil porosity is，the faster the water pressure dissipation rate will be. (2) During grouting，the diffusion mode of grout in the stratum soil is closely related to the soil porosity and water content of grout. (3) When the slurry is still，the static water pressure will dissipate，the slurry volume will gradually reduce，and the additional earth pressure value will also gradually decrease. (4) During deformation recovery grouting，the change of additional earth pressure shall be monitored in real time，and multi-point grouting technology shall be adopted when injecting grout with low water content into sandy soil layer.

Artificial freezing method has been widely because of its good water sealing property，wide adaptability and small impact on the environment. However，groundwater seepage will seriously affect the freezing effect，and the influence of seepage on artificial freezing has not been considered in the design code. In order to study the characteristics of artificial freezing under seepage，indoor model tests of artificial freezing process under different seepage velocity and temperature gradient were carried out based on the self-developed double pipe freezing physical model test system. Through the model tests，the development laws of the temperature difference of inlet and outlet water，the cooling capacity exchange rate and temperature field changing with the initial temperature of the ground layer，the temperature of the refrigerant and the seepage velocity are revealed. The intersection time and the critical seepage velocity under different temperature gradients and seepage velocities are determined. The critical flow velocities of the three tests are 16.81，10.22 and 13.33 m/d. Furthermore，the changes of the shape，thickness and average temperature of the frozen wall with the temperature gradients and the seepage velocity of groundwater are analyzed. The research results can provide reference for the application and design of artificial freezing technology under seepage conditions.

In order to further study the dynamic characteristics and deformation characteristics of a new type of long-short pile composite foundation with part-screw pile + cement soil compaction pile under long-term train load，the indoor dynamic model test of long-short pile composite foundation was carried out. The time-frequency domain characteristics，sub-band energy distribution and energy attenuation law of vibration response signal were analyzed，and the spatial transmission characteristics of vibration energy of long-short pile composite foundation were revealed. Based on the method of wavelet packet energy analysis，a vulnerability evaluation index ?ERMS was established，and the identification effect of ?ERMS index was verified by the dynamic strain response of piles and the displacement response of the soil between piles. The results show that：(1) The frequency of the vibration signal of the composite foundation of part-screw pile + cement soil compaction pile is mainly distributed in the range of 0–25 Hz，and the characteristic frequency causing the peak vibration response is mainly concentrated near the natural frequency of the train. (2) During the propagation of the vibration wave along the soil medium between the piles，part of the high frequencies are filtered out and the low frequency part continues to propagate，at a distance from the surface of the foundation the vibration energy is mainly concentrated in the low frequencies. (3) The vibration energy of the pile and the soil between the piles decays faster at the shallow level of the foundation but slows down as the depth of the foundation increases. (4) The ?ERMS index value has a good identification effect on the vulnerability of the pile. The vulnerability of the middle part of the long pile and the short pile is the largest，which belongs to the weak part of the vibration resistance. (5) The displacement of soil between piles increases gradually with the increase of vibration times. The value of ?ERMS index cannot effectively distinguish the damage and deformation degree of soil. The research results have certain reference significance for the engineering design of long-short pile composite foundation under train load.

The study of the interface coupling between the optical fiber and sand is highly significant for the application of optical fiber in rock and soil monitoring. In this study，we proposed a new elastic-plastic model to evaluate the coupling of the fiber-soil interface and conducted an indoor optical fiber pull-out test that took into account moisture content，fiber type，pull-out rate，and overlying load，using optical frequency domain reflection(OFDR). The results demonstrate that the model is straightforward to calculate and accurately describes the stress process between the optical fiber and the soil. The critical strain reference value for optical fiber monitoring soil deformation failure was obtained. The coupling coefficient ζ，which represents the coupling capacity of fiber-soil，can effectively evaluate the coupling performance of the fiber-soil. Furthermore，the sensitivity analysis of model parameters clarifies the interaction mechanism of optical fiber and soil，providing an essential reference for the application of distributed optical fiber in soil monitoring.

In order to study the effects of dry density and initial water content on water retention of coral sand，soil-water characteristic curves of samples with different dry densities and initial water contents were tested and analyzed by pressure plate apparatus test，and the pore water distribution characteristics of samples under different suction forces were obtained by nuclear magnetic resonance technology. The results show that the air entry value of coral sand increases with the increase of dry density and decreases with the increase of initial water content. The residual water content increases with the increase of dry density and initial water content. In general，the samples with high dry density and initial water content have better water retention. The F‐X model has good applicability to soil-water characteristic curves of coral sand samples under different conditions. Dry density and initial water content have important effects on pore size distribution and water retention of compacted coral sand samples，but their effects on water retention gradually weaken with the increase of matric suction. At different suction stages，the effects of dry density and initial water content on water retention of coral sand were different. At 0–10 kPa，the initial water content was the main factor，while at 10–70 kPa，the dry density had a greater effect，and at 70–300 kPa，neither of them had a major effect on water retention of coral sand. The poor connectivity of coral sand pores results in large pores that can still store water under high suction，which enhances the water retention of coral sand to a certain extent.

This study focuses on Tamusu mudstone，an argillaceous rock from the preselected area for high-level radioactive waste(HLW) underground disposal in China. Based on the previous work on the evaluation of argillaceous rock for the HLW geological disposal repositories，a systematic experimental and theoretical study is conducted on the creep characteristics of Tamusu mudstone under complex conditions. Creep tests show a positive correlation between deviatoric stress and creep deformation under the same confining pressure. The elastic modulus shows a trend of first increasing and then decreasing during the creep process. The creep deformation of Tamusu mudstone results from the combined effect of strengthening and structural degradation. Based on the creep behavior of Tamusu mudstone，creep hardening variables and creep damage variables were introduced，and further the creep yield surface and creep potential function were constructed based on Perzyna?s overstress theory. A creep constitutive model for Tamusu mudstone was established，and it was numerically implemented and verified by the software ABAQUS and its UMAT subroutine. This study comprehensively and systematically interprets the creep deformation law and deformation mechanism of Tamusu mudstone in the HLW disposal environment，providing an important theoretical basis for the safety，feasibility，and suitability evaluation of China?s argillaceous rock HLW geological disposal repository. The research work has important practical value for the development and long-term safety of China?s nuclear industry.

It is very important for evaluating the instability of geotechnical structures to investigate soil deformation and the spatial evolution of shear bands. For this aim，this paper employs the distinct element method(DEM) to simulate conventional triaxial tests on sand with flexible boundaries，analyzes the evolution of macroscopic and microscopic characteristics within and outside the shear bands，and tries to establish an upscale association between the macro and micro behaviors. Firstly，the DEM employed a complete microscopic contact model that accounts for the effect of particle shape on the macro-mechanical response by incorporating rolling and twisting resistances. Secondly，a flexible membrane boundary was used in the simulations of triaxial compression tests to enable the complete development of the shear band. Finally，the DEM simulation results were compared with the experimental results available，and analyzed from the macro and micro viewpoints. The DEM results indicate that the employment of the complete contact model and flexible boundaries is able to accurately reproduces stress-strain and volume responses of the sand sample and capture the evolution of the shear band in the simulations. There are significant differences in the average particle rotation rate(APR)，porosity，mechanical average coordination numbers，and anisotropy coefficients within and outside shear bands. With the increase of axial strain，the APR and porosity inside the shear band are larger than the outside，on the contrary，the mechanical average coordination number outside the shear band is greater than the inside. In addition，the local porosity and anisotropy within the shear band have significant influences on the global evolution of void and anisotropy in the sand sample.