The systematic study on the essence of creep strain has not been carried out at present. A method separating the viscoelastic-plastic strains and the techniques of data processing were proposed. The elasto-visco-plastic deformation characteristics of iherzolite at No.2 area in Jinchuan were studied. The instantaneous strain was decomposed into the instantaneous elastic and plastic strains. The instantaneous elastic response is nearly linear. The instantaneous plastic modulus increased with the increasing of stress. The creep strain was decomposed into the viscoelastic strain and the viscoplastic strain. The viscoelastic strain exhibited a creep reduction，while the viscoplastic strain exhibited the creep reduction，the steady creep，and even the accelerating creep. The viscoelastic strain，the viscoplastic strain and the steady creep rate are related to the deviatoric stress level nonlinearly. The visco-elasto-plastic strain characteristics of radial creep are similar to that of axial creep. But the radial creep strain is only 25%–30% of the axial creep strain. A new BNMC creep damage model was established by connecting the Burgers model with the nonlinear M-C plastic components in series. The accelerated creep was treated in the model as a stage that rock strength decreased rapidly and the viscoplastic deformation highly developed with the plastic instability. The BNMC creep damage model was written into FLAC3D via VC++ programming. The method of determining the unknown parameters in the creep damage constitutive model BNMC was proposed.

Rockburst process of mid-coarse grained granite specimens was simulated under the cyclic loading of low frequency combined with the static loading using the true triaxial rockburst system developed in-house. The influence of different loading factors on rockburst was studied. When the other load variables were fixed，the axial static stress，the third principal stress and the disturbance amplitude all have a threshold value for rockburst under the cyclic loading of low frequency. If these thresholds were exceeded，the possibility of rockburst increased rapidly and a slight fluctuation of these factors could cause the significant change of the kinetic ejecting energy of rock and the broken degree of fragments. When the other load variables were fixed and the frequency was in the range of 0–3 Hz，the kinetic ejection energy increased first then decreased with the frequency increasing. Enough elastic energy from the static load and suitable energy rate from the cyclic load continuously were the basic condition for the occurrence of this kind of rockburst. Small uprush of the elastic strain energy and the limit of elastic energy storage capacity declined rapidly，what is called the“two-way deviation effect”，is the energy mechanism of the occurrence of this kind of rockburst.

The dynamic fracture experiments to a single cleavage semi-circle(SCSC) specimen with the split Hopkinson pressure bar(SHPB) equipment were conducted in order to study the fracture behavior of pure mode I and mixed-model I/II cracks under dynamic loads. The crack propagation speed was measured with a crack propagation gauge system and a high speed photography system respectively. Several numerical models for the pure mode I and mixed mode I/II were established based on Drucker-Prager strength model and cumulative damage(CD) failure criterion. The crack propagation behavior was simulated with the code AUTODYN. The crack propagation paths predicated with the numerical simulation agreed well with the experimental results. The propagation speed was found not to be a constant. The crack propagation may stop，i.e. the phenomenon of crack arrest happened. The phenomenon was captured by the crack propagation gauge system and the high speed photography system. The results of the high speed photography system are visualized easily.

Laboratory experiments on the characteristics of acoustic emission(AE) in high and low frequency channels of granite specimens under different confining pressures of cyclic loading and unloading were carried out. The relationships of the time with stress and AE cumulative counts were analyzed. On the basis，the characteristics of AE irreversibility in rock were studied. Then inverse fast Fourier transform(IFFT) was used to denoise the AE signals at Kaiser points and the characteristics of spectrums of denoised signals were analyzed with fast Fourier transform(FFT). The characteristics before the major fracturing in rock were studied. The basic characteristics of AE counts，the Kaiser effect(KE) and the felicity effect(FE) are similar in two frequency channels. The main difference between the characteristics of cumulated AE counts in two frequency channels is the quantity. The dominant frequencies at Kaiser points mainly distribute in the range of 46.39–70.80 and 151.37–166.99 kHz. With the increasing of axial stress level，the dominant frequencies at Kaiser points shift from the lower frequencies to the higher ones in the low frequency channel and shift from the higher frequencies to lower ones in the high frequency channel before the major fracturing in rock. The upper limit of KE of the granite is about 65% of the ultimate compressive strength. The results of the dominant frequencies at Kaiser points provide evidence for the damage and failure of rock.

Clump and cluster models based on two-dimensional particle flow code(PFC2D) were constructed through two different algorithms to explore the effects of micro parameters and microstructure(crystal grain size and distribution，pre-existing cracks) on the macro mechanical properties of specimen and to quantify the relationships between them. Meanwhile，the development of micro cracks and the mechanism of micro failure were studied. It was revealed that two algorithms had their own advantages. Macro mechanical properties of marked circular region algorithm changed with the variation of micro parameters nicely. The composition of crystalline gradation was better controlled by the searching algorithm. The uniaxial compressive strength(UCS) and the tensile strength(TS) are in exponential relationship with the clump radius and un-bonded ratio(random pre-existing cracks) and are in power relationship with the bond strength ratio. The elastic modulus and Poisson?s ratio are in linear relationship with the clump radius，bond strength ratio and un-bonded ratio. With the increase of the clump radius，bond strength ratio，bond strength ratio n of cluster and un-bonded ratio，the ratio of uniaxial compressive strength to tensile strength which is mostly affected by bond strength ratio increases a lot. The ratio of tensile cracks is mostly affected by the bond strength ratio，followed by the clump radius. Under the uniaxial compression，the failure of specimen is dominated by the tensile cracks which mainly extend along the axial direction. However，the angle between the dominant orientation of shear cracks and axis is 20 degree to 40 degree. Brazil test failure is dominated by tensile cracks across the center of specimen. The evolution of micro cracks and failure modes are different for cluster and clump models. Compared with the cluster model，the shear crack ratio of clump model is bigger and crack crushing zone is wider. Moreover，the fracture surface is more rough and uneven.

The real-time monitoring and analysis of the microseismic activities of the cave rocks of a large underground water-sealed oil storage cavern in Jinzhou during the disturbance caused by strong excavation were performed using the Canadian ESG monitoring system. The potential failure regions of the cave rocks within the scope of monitoring were identified. The initiation，development and agglomeration process of the rock micro-cracks during excavation were reproduced. The P wave velocity was determined to be 5 200 m/s with the error of source location less than 8 m within the scope of the sensor array. Micro-cracks of rocks within the scope were aggregated into two bands. One was located to the east of water curtain tunnel 6，in between the water curtain tunnels 1 and 2，and had a low angle with the horizontal plane. The other was located in 2+40-2+60 mileage between the oil storage grotto 1-North and 1-South，and shared the same distribution with the diabase dikes in the region. The microseismic monitoring system identified the condition of the weak structural surface like dikes. The strong excavation disturbance of the large section oil storage caverns and the release of large amount of energy led to the“over damage”of rock and resulted in a large number of micro-cracks. The research results proved the feasibility of applying the microseismic monitoring technology in the special rock mass structures like underground water-sealed oil storage caverns.

The large deformation disasters occurred during the construction of tunnels were discussed and summarized systematically from the perspectives of the definition，the type，the classification，the fundamental mechanisms，the standard of determination and the measure of control of the large deformation. The mechanical mechanism and the supporting philosophy of equilibrium transfer were illustrated. The key techniques and the important breakthrough were presented. The design method of structural frame core used in the super high-rise building was adopted to form a deformation control strategy of“release initially，resist then and become rigid at last”. A new style supporting system of the steel grids with concrete tube core were thus developed to be used in the weak and fractured stratum. The catalytic mechanism of bearing capacity of surrounding rock was explained. The characteristics of the multilevel transformation and load bearing were summarized. The results of field test verified the reliability of the support system.

The process of creep displacement of landslide is essentially a damage process of rock mass of slope. The interaction between the creep deformation and the stability coefficient and the quantitative relationships of the creep displacement，the damage parameters and the stability coefficient were therefore investigated based on the systematic analysis on the deformation characteristics and the failure mechanisms of different deformation stages of creep landslide. The method of determining the dynamic stability coefficient of slope based on the creep displacement parameter was established. According to the safety factor of slope from the limit equilibrium method and the variation of the tangent angular rate and acceleration rate parameters of displacement curve，the displacement monitoring and early warning criterion  and the early warning time points  before sliding based on the safety factor of slope stability were determined. The typical landslide at Jimingsi was studied as an example and the results were compared with the ones from the method of Saito Michitakanori. It was found that the results of the analysis were basically consistent with the measured variation of the landslide.

Blasting load and geostress transient unloading are important factors influencing the development of excavation damage zone(EDZ) in deep tunnels. The blasting load and geostress transient unloading of every blasting delays were analysed，and the damage extents of surrounding rocks induced by blasting excavation were compared based on the results from the theoretical model and numerical simulation. The damage mechanism of the blasting load was found to be mainly tension or tension-shear failure and the geostress transient unloading was mainly the compression-shear failure. On the excavation face，every blasting delays had an contribution to the final EDZ which reflected the repeated disturbance and the MS7 and MS9 were the main contributors to the EDZ. The EDZ induced by every delays is not only related to the load value，but also associated with the excavation radius. In addition，the higher the geostress level，the higher influence on the EDZ that caused by geo stress transient unloading. Under the same condition of blasting parameters，the geostress level is the decisive factor to the development of EDZ during deep tunnel excavation.

The triangle hanging plate is easily formed and hard to fall if the caving zone contains the thick and hard stratum，which produces high pressure to the gob-side entry retaining. The 8820 coalface mining without pillars with the thick and hard sandstone roof at Tangshangou in Datong was studied. The difference of cracked structural feature between ordinary filling entry retaining and joint-cutting gob-side entry retaining roof was analyzed. The deformation process of surrounding rock was investigated. The joint-cutting with the reasonable parameter of hard stratum roof in the caving zone resulted in the lost of the constraint of the direct roof and basic roof at the gob-side boundary in the range of the joint-cutting height. The hanging plate was sheared enough to fall off the roof along the structural surface of joint-cutting，and the impact load was reduced. The results of the numerical analysis with the software UDEC indicated that the joint-cutting was beneficial to the waste rock fall and supported the stratum covered above. The joint-cutting moved forward the touch point of the waste rock of the stratum covered above basic roof，limited the rotation of the basic roof and the pressure of surrounding rock caused by the sink action and reduced the deformation of the surrounding rock obviously. The test under the well suggested that the complex techniques of high constant resistance and large deformation anchor rope of roof，the dense pillar reinforced on the side of tunnel，the dense block rock point pillar and the technology of advanced focused power blast of joint-cutting could cut the roof on the gob-side effect and form a complete tunnel that every index could satisfy the requirement of working surface.

Prediction and early warning is one of the difficult issues of landslide. Currently，no enough attention was paid to the elapsed time and the critical deformation velocity of landslides in different deformation phases. In order to further explore the warning criterion of deformation velocity of landslides，the process of landslide was divided into four phases including an initial deformation phase，a uniform deformation phase，and an accelerated deformation phase and a sharp deformation phase. The landslide database was studied with the statistical method. The accelerated deformation phase lasted from 18 days to 1 080 days，and the elapsed time of nearly half of the landslides was within 30 days to 90 days. The sharp deformation phase of majority landslides lasted less than 30 days. The elapsed time of landslides in different deformation phases related to the failure mode，the landslide volume and the sliding surface type. The elapsed time and the sliding surface type are most closely related. When the slip surface is a rigid structure，the acceleration and sharp deformation phases are shorter. When the slip surface is a weak bedding surface，the acceleration and sharp deformation phases are longer. In the acceleration deformation phase，the maximum width of crack is 1–50 cm. In the sharp deformation phase，the maximum width of crack is 4–126 cm. The cracks of soil landslide and talus slide are wider，and the crack of rock landslide is relatively narrow. The critical deformation velocity of landslide entering into the sharp deformation phase is not more than 50 mm/d. The threshold of toppling landslide is relatively large，and the threshold of landslide with the weak sliding surface is larger than the landslide with rigid sliding surface. The critical deformation velocities of various landslides entering into the acceleration deformation phase are not large which are closely related to the failure mode. The threshold of sliding landslide is basically no more than 4 mm/d，and the threshold of toppling landslide or collapse landslide is slightly larger，generally larger than 4 mm/d.

In order to study the development of water and sand inrush across the overburden fissures due to coal mining，a simulation test system for water and sand inrush across overburden fissures due to coal mining was developed. The system consists of a load support bracket，a laboratory module，a confined water module，a coal mining simulator，a storage tank，a servo control system of hydraulic pressure and water yield，and a servo control system of displacement and stress. The system has the feature of large space for simulating，good visibility，good sealing，multiple loading methods and good precision. The coal strata in the western region of China were studied. New non-hydrophilic composite materials with the lower intensity were developed to simulate the coal strata. The excavation model reproduced the whole process of water and sand inrush across the overburden fissures due to coal mining. The deformation and failure of overburden，fissure extension of overburden，the formation of water and sand channels，and the parameters of water and sand inrush were obtained. Test results showed that the system was stable and reliable.

A database of blasts and microseismic events was established with the manual recognition methods based on the microseismic monitoring at Kaiyang phosphate mine. The source parameters including the seismic moment，the seismic energy，the P and S wave energy ratios，the event occurrence time，the static stress drop，the sensor triggers and the corner frequency were analyzed statistically. The probability density distributions of the first peak arrival time，the first peak amplitude，the maximum peak arrival time and the maximum peak amplitude were compared and analyzed. The frequency distributions of two kinds of event signals were statistically analyzed with the FFT transform. The logarithm of seismic moment，the seismic energy，the event occurrence time，the first peak arrival time，the maximum peak amplitude，the numbers of triggered sensors and the dominant frequency were finally selected as the characteristic parameters based on the probability density distribution of each parameter，the performance of recognition and the difficulty of acquisition. A mathematical model of automatic recognition was established on the application of Fisher discriminant analysis. Results show that the accuracy of training samples is 100% and that the accuracy of testing samples is 94%. The model was applied to the second time blasting crushing of bulky rock of the stope and the recognition results were consistent with the actual ones.

The permafrost on the Qinghai—Tibet plateau(QTP) is degrading at present under the influence of Global Warming，which will greatly affect the stability of engineering structures and the ecosystem on the QTP. The variation of the air temperature and the process of permafrost degradation based on the air temperature in the permafrost regions on the QTP from 1955 to 2011 from four weather stations along the Qinghai—Tibet railway (QTR) were studied. The continuous ground temperatures over 35 years from two boreholes including a 15-meter- deep borehole on the sunny slope and a 35-meter-deep borehole on the shady slope of the mountain，acquired from the permafrost observational station at Fenghuoshan were analyzed. The annual mean air temperature in the permafrost regions along the QTR started to rise gradually in late 1950s，went down during 1970s，ascended back in the middle of 1980s and increased rapidly after 2000，and the rate of increasing is rising conspicuously. From 1978 to 2014，the annual mean ground temperature of the permafrost on the sunny slope of the Fenghuoshan climbed up by 0.91 ℃，and that on the shady slope also increased by 0.58 ℃ from 1964 to 2014. The permafrost is degrading because of the rising temperature. With the degradation of the permafrost，the type of geothermal temperature curves has transformed. The geothermal temperature curve of the sunny slope was changed from the initial positive geothermal gradient type to zero geothermal gradient type，then to the current minus geothermal gradient type. The geothermal temperature curve of the shady slope was changed from the initial positive geothermal gradient type to the zero geothermal gradient type. The degradation on the sunny slope is far more severe than that on the shady slope，which is mainly caused by the difference of ground temperature in cold seasons. The permafrost table is sensitive to the change of the annual mean air temperature and fluctuates with the climate change.

In order to quantitatively analyze the dynamic shear modulus from the perspective of micro soil structure，relationships between the dynamic shear modulus and the intergranular void of remolded soft clay from Eastern Guangdong are studied from both macroscopic and microcosmic aspects using the resonant column test，the scanning electron microscope test and the microscopic-pore structure analysis method. According to the three-parameter Davidenkov model-based nonlinear regression analysis and the parameters analysis of microscopic-pore structure，the effective stress was found to increase and the wave velocity to accelerate after the consolidation process and thus maximum dynamic shear modulus became larger. The macro void ratio of soil decreased. The intergranular void layers grew and the fractal dimension of porous perimeter-area increased. The degree of void homogenization increased and the porous fractal dimension value decreased. The study demonstrates the correlation between the three parameters of Davidenkov model(initial parameter，range parameter and rate parameter) and the microscopic-pore structure parameters.

The initial shear modulus，modulus ratio and damping ratio of frozen soil at different negative temperatures were experimentally investigated with the low temperature resonant column apparatus(LTRCA). The test results showed that conventional resonant column testing applied to the low- temperature samples resulted in large errors. The test parameters such as the frozen duration and the confining medium were determined. The negative temperature was found to have significant impact on the initial modulus and shear modulus ratio which was sensitive between －4 ℃ to 0 ℃ and stayed stable when lower than －4 ℃. When the temperature decreased in the sensitive interval，the initial modulus increased rapidly obeying the Boltzmann function，while the reference strain decreased sharply obeying also the Boltzmann function. In the stable interval，they changed smoothly. Below a certain strain，the damping ratio at the normal temperature  was lower than that at low temperature. When the strain exceeded a certain strain，the damping ratio of normal test was larger than that of low temperature test. The negative temperature had significant influence on the maximum damping ratio，which decreased exponentially with the temperature decreasing.

The critical filling height is an important index for the settlement and stability control of embankment on soft soils. A unified formula under the plane strain condition was firstly deduced for three true triaxial strength criteria，i.e.，the generalized M-N criterion，the generalized L-D criterion and the unified strength theory. Then，the unified solutions for both the critical load of foundation and the critical filling height of embankment were presented by considering the intermediate principal stress and the actual lateral pressure coefficient. The unified solutions were validated and their applicable conditions were also provided. Finally，the effect of strength theory was investigated and parametric studies about the influence of cohesion and inner friction angle on the critical filling height of embankment were discussed. It is found that the proposed unified solutions have good comparability. The effect of strength theory(i.e.，the intermediate principal stress effect) on the critical filling height of embankment is remarkable and the result of M-C criterion is too conservative. Moreover，the generalized M-N criterion，the generalized L-D criterion and the unified strength theory with parameter b =1/2 are recommended to be adopted. The influence of lateral pressure coefficient，cohesion and inner friction angle on the critical filling height is significant. A real lateral pressure coefficient should be determined in situ，and the variability of strength parameters of ground soils should be fully considered.

The water retention of soils with different particle sizes was investigated to analyze the influence of particle size on the soil water characteristic curve(SWCC). The test data were best-fitted using the D. G. Fredlund and A. Xing equations. The obtained fitting parameters and hysteretic behavior were discussed and correlated with grain-size distribution parameters. The results show that the fitting parameter，a，increases linearly with the increasing of the air-entry value of the SWCC and that the fitting parameters，m and n，decrease with the increasing of the residual suction and slope of the SWCC respectively. The coarse-grained soil has the lower air-entry value，residual matric suction and water-entry value and less hysteresis than a fine-grained soil. Moreover，the slope of the drying SWCC increases with the increasing of particle size of soil. The hysteresis decreases with the increasing of particle size together with the slope of the grain size distribution curve of the soils.

In the process of split grouting，the soil on both sides of the split channel is being compressed. The relationship between the stress and strain is nonlinear in the compression process of soil. A new model of relationship between the soil stress and strain was established to describe the nonlinear characteristics in the compression process of soil. The process of split grouting was simplified into the horizontal radiation circle. Based on the nonlinear model of compression and considering the coupling effect at the interface between soil and slurry，a theoretical model of split grouting was established. The spatial distribution equation of width of the split channel was derived，and the relationship among the grouting pressure，width of split channel and radius of grouting diffusion was obtained. After comparing with the result from the linear relationship of stress and strain，the nonlinear relationship of stress and strain was shown to be necessary. The model test of split grouting process was performed. The width of split channel attenuated along the diffusion radius. The calculated and measured the thickness of grouting vein are at the same order of magnitude and theory was thus proved reasonable.

Q3 loess is widely distributed in Northwest China and is markedly structural. In order to describe the stress-strain relationship of structural loess，a constitutive model of Q3 loess based on disturbed state concept(DSC) theory was put forward. The relationships of stress and deformation between Q3 loess and normal consolidation soil were incorporated in the constitutive model. New disturbance factors reflecting the influence of spherical and shear stress were used. The disturbance factors include the volumetric strain disturbance factor(Dv) and shear strain disturbance factor(Ds). The disturbed function based on theory and experiment was established. The disturbed function makes the constitutive model to accord with the actual stress path of soil. The physical meaning of the parameters of the constitutive model is clear. The model parameters are obtained from the isotropic test and triaxial shear test. Experimental results proved that the constitutive model described the deformation characteristics of Q3 loess reasonably.

To research the stress-strain behaviors of lignin stabilized silt during shearing process，the energy required to shear the stabilized soil during different stages was analyzed based on the energy conservation. A theoretical model was developed to depict the shear behaviors of stabilized soil，and the meaning and calculation method of parameters of the model were presented. The model was verified based on the laboratory testing results，and the limitations and applicability of the model were also discussed. The energy required to shear the stabilized soil with cementation is mainly made up of the energy required to break the inter-particle bonds，the energy required for a particle to roll and the energy required for a particle to slide. The cementation between particles，the shape of soil particles，the failure forms of shearing and other factors are considered in the proposed model. The proposed model depicts accurately the shear behaviors of stabilized soil from the direct shear tests on lignin treated silt.