The status quo of safety management in China?s underground projects construction was introduced. Based on the accidents statistics，the serious security situation of underground projects construction was certificated. The analysis of types and causes for accidents indicated that the responsibility and subjective reasons are the great challenges for security management. Combining with Hain?s safety pyramid theory，Heinrich?s safety rules and Johnson?s changes-errors model，the concept that accidents can be prevented by risk management measures was established，and some suggestions for accidents prevention were put forward. Besides，the mechanism and control measures for two typical geological hazards，i. e. water and mud outbursts and rockburst，were represented. For the study of water and mud outbursts，the laws of occurrence and development，the precursory information theory，the geological prediction methods and other incident countermeasures were introduced. For the control measures of rockburst，the definition and classification of rockbursts，the prevention mechanism，theoretical basis and engineering practice for monitoring and prediction，as well as the construction measures，were introduced. Some opinions and suggestions on technical methods and management tools were put forward for the accident prevention for underground projects construction.

A complex mechanical behavior of large squeezing deformation of tunnel weak rocks is discussed under high ground stress condition. The large squeezing deformation can be belonged to the scope of a kind of large deformation rate with slow convergence. On the basis of rheological squeezing deformation?s mechanism，a nonlinear 2D visco-elastoplastic constitutive model and a 3D elasto-viscoplastic constitutive model in case of large/small deformations are proposed respectively；and the corresponding secondary development special softwares are studied. The developed material subroutines are applied to analyzing the squeezing problem which occurred in rock excavation for the Wushaoling railway tunnel project.

The complicate earthquake dynamic response is simulated with FLAC3D that is much different with simple/homogeneous slope due to poor amplitude effect along the height. For the horizontal acceleration response，the front of the landslide has greater vibrating frequency and amplitude，that is easier to trigger the slide along the inclined layer. For the vertical acceleration response，the back of the landslide has greater amplitude of vibration，and as three times as the absolute value of the acceleration in the front，that is easier cracking，fragmenting or even throwing rock mass. In light of the earthquake dynamic response and movement，the landslide accumulation and source are zoned as follows：(1) the lower inclined bedding sliding accumulation，which distributed in the East and dammed a tributary named the Huangdongzi；(2) the upper avalanche accumulation，which distributed in the Northwest and the North that overlay the North margin of previous sliding accumulation with belt-like；(3) the back cliff and talus，in which lots of cracks in the cliffs shows the tensive failures during the vibration；and lots of talus masses show gravity processes after the earthquake；(4) inclined bedding sliding surface and striation，which distributed at the back of the lower inclined bedding landslide. Enormous large-scale striation belts show the moving direction to North that is as same as the tendency of the layer.

According to mechanism，characterization and law of rockburst evolution process，a three-step strategy to control rockburst was firstly proposed. It includes the first step to optimize excavation schemes to reduce concentration of stress and energy induced by the excavation；the second step to pre-release and transfer energy concentration；and the third step to absorb energy stored in rock mass by designing reasonable rockbolts and other support types. And then a dynamic control method of rockburst evolution process is proposed. During the construction，the real-time microseismicity monitoring is used to perform warning of rockburst. The feedback analysis and dynamic control strategy if needed can be conducted to perform the three-step control strategy of rockburst evolution process. The proposed method has been successfully used in Jinping II deep headrace and water drainage tunnels with depths of 1 900–2 525 m. The practice verified the applicability of the proposed method.

In each design phase，thorough studies were conducted to explore the key technical issues of rock engineering for the superhigh arch dam of Xiluodu hydropower project，allowing the physical shape and structural design of the arch dam to fit the geological conditions of the dam site. In view of changes in the geological conditions at the foundation of the dam on the riverbed，the designs of extending foundation surface excavation and dovetailing the dam body and foundation rock on both upstream and downstream sides were introduced，allowing the arch dam and foundation to fit each other and improving the stress conditions of the dam body and foundation. 3D geomechanics model test and finite element analysis results indicate that the Xiluodu superhigh arch dam and its foundation are in good conditions both in construction and operation periods. The monitoring data show that the behaviors of dam and foundation correspond with regular pattern. The“digital dam” initiative for the Xiluodu project，which is based on the theory of total life cycle，has lent strong support to construction process control and decision-making；this ensures all work conditions in the construction and operation stages meet design requirements，so as to assure the safety and reliability of the arch dam.

Hydraulic fracturing is a frequent problem in petroleum extraction，dam safety monitoring，in-situ geostress testing，tunnel-groundwater inrush prevention，etc. Firstly，a one-dimensional model considering unsteady seepage is established and its analytical solutions are derived. Comparing the calculated key factors (water pressure and hydraulic gradient) of hydraulic fracturing with the simulated result by finite element method，accuracy of these theoretical solutions is proved. Secondly，in terms of comparison with the result only considering steady status，it is presented that hydraulic gradient gets maximum as soon as water pressure increases in unsteady process. By contrast，hydraulic gradient gradually decreases and tends to be stable when reaching steady seepage status. Finally，the effect of rock permeability on hydraulic fracturing is also studied. The probability that hydraulic fracturing happens grows higher while the permeability is lower. In summary，it is essential to consider unsteady seepage status in mechanism study of hydraulic fracturing.

Based on the entries retained for next working face in the multi-entry system in Jincheng mining district，and a large quantity of monitoring data collected in these entries，the characteristics and mechanisms of deformation and damage associated with these entries are analyzed. Numerical simulation code FLAC3D is utilized to analyze the effects of entry layout pattern，coal pillar size，and face width on the deformation and damage of the entries retained for next face；and the stress distribution around the entries and faces are calculated. The reinforcement patterns and parameters suitable for entries retained for next face are proposed based on above researches. Underground tests are carried out；the surrounding rock displacements，rock bolt and cable loads are monitored during the whole service period of the entries retained；and the reinforcement performance is evaluated. The research results show：when the entry retained is originally affected by the front abutment stress of the current face，the surrounding rock displacement increases moderately；when the current working face advances past the entry retained for a certain distance，the surrounding rock displacement increases sharply；the peak of displacement velocity appears when the working face is 50–200 m away；and then the displacement is tending towards stability；when the entry retained is affected by the front abutment stress of the next face，the surrounding rock displacement increases evidently again. The deformation of the entries retained is closely connected with entry layout patterns，coal pillar size and the parameters of working faces. The rock bolts and cables with high pretension and intensive strength，and the cable bolting set in full entry section are fit for the entries retained，which can reduce surrounding rock displacements greatly and keep the entries stable for a long time. Finally，the existing faults are also addressed and some improvement suggestions are provided.

Based on the meso-structure， the present paper employs the augmented virtual internal bond(AVIB) to model rock，thereafter to simulate fracture propagation in rock. The AVIB is a constitutive model that was developed based on the theory of virtual internal bond(VIB). It uses the Xu-Needleman potential function to describe the micro bond，which is very suitable for modeling the cohesive properties of mineral grain interface. For the constitutive model implicitly contains the micro bond rupture mechanism，it doesn?t need separate fracture criterion when simulating fracture propagation and coalescence. Moreover，by AVIB，the complex 3D fracture behaviors can trace back to the 1D micro bond rupture process. These features of AVIB make it powerful in analysis of rock failure. The purpose of the paper is to provide a new theory for multiscale modeling and fracture simulation method for rock.

By employing wave velocity test and deformation monitoring method，the use of checking different standards according to different zones，sections，layers and classification of rock masses，a re-evaluation of rock mass quality is carried out during construction period. Based on the nonlinear finite element method，the overall stability of the typical stage of the construction period of dam is simulated. The real mechanical parameters of rock mass are obtained by feedback analysis based on the geophysical results and monitoring data of field deformation and stress. The numerical results reflect the working condition of the dam in construction and operation periods，and also guide the construction process. The conclusions from this study have been applied to the design of Xiluodu project and are also beneficial to the design and construction of the similar projects.

Coal seam and immediate roof ahead of the coal face are considered as an elastic foundation；and because of that the damage and fracture of tight roof start at the advanced position of the middle axis of working face，so unit width rock stratum structure at middle part of the working surface can be taken to study and then the indeterminate deflection simultaneous differential equations of tight roof which are under the combined action of uniform load，advanced swelling distributive supporting load and support resistance are established. On the basis of all natural boundary conditions and continuity conditions being satisfied，the expressions about tight roof?s deflection，bending moment are derived ahead of the coal face and over the gob before the periodic weighting. According to these expressions obtained above，using Matlab software?s calculation and drawing functions，tight roof?s deflection and bending moment with the change of load，strata rigidity，flexural rigidity，support resistance and gob span are analyzed. Both the obtained four-part bending moment and deflection curves connect smoothly above the investigation interval，the peak positions of the bending moments lie ahead of the coal face and the tight roof?s subsidence values are coincident with the field experimental data. The expressions of tight roof?s deflection and bending moment are only theoretical solutions under ideal roof model，which can be used to be aroused from the calculation example of the theoretical solutions and to obtain regularity understanding for the variation in the roof?s deflection and bending moment when the relational parameters are changed；and to make reasonable qualitative judgment on the changes of the mine roof status. The analytic solution can also offer basis for further study about the damage and fracture of tight roof before the periodic weighting，the releases of the roof strain energy and the energy source of rockburst caused by the fracture of tight roof.

The penetration resistivity of the homogeneous，layered and massive surrounding rocks anchored by crossing cable are researched by model tests based on the theory of similarity. The experimental results show that the type of (homogeneous，layered and massive) surrounding rock has little influence on the penetration depth. The higher quality of rock mass，the less increasing quantity of penetration resistivity. The largest penetration depth of the massive model rock，the least penetration depth of layered surrounding rock. In this article，the basic reasons which lead the penetration depth smaller between reinforced and unreinforced model rocks are analyzed；and the first condition to improve the penetration resistivity of model rocks is to improve the compression capacity of model rocks. The simulated rock mass containing lower rate of cable，though it can improve the simulation materials tensile strength，it fails to improve the bomb penetration ability of simulation rock mass. The results of the model tests are also simulated by LS-DYNA. The numerical simulation is in good agreement with the experimental results. The numerical simulations show that the change of angle and the space of anchors which influence on the penetration depth of rocks is small. Although the crossing cable fails to improve anti-bomb penetration of the simulated rock mass，the increase of the tensile strength and shearing capacity for material of rock mass can obviously reduce the deformation of the underground structure，conducive to the stability of the underground structure.

It is assumed that failure surface of backfill soil is composite curved one. Pseudo-dynamic method，in which time-history curves of acceleration was simulated by sinusoidal motions，was adopted to research the stability of the water front retaining wall subjected to seismic loads. The damping force and the inertial force acting on retaining wall and backfill soil were investigated. The closed-form solutions of passive earth pressure and dynamic factor of safety against sliding and rotation of the retaining wall during earthquake were obtained. Finally，effects of seismic acceleration，amplification factor，wall height，physico-mechanical parameters of backfill soil and hydrodynamic pressure acting on water front retaining wall on sliding displacement，dynamic factor of safety against sliding and rotation of the retaining wall were quantitatively analyzed. It is concluded that the stability of the water front retaining wall is getting worse when the earthquake speeds up，the water level gets higher and the internal friction angle gets smaller.

The jointed rock mass contains numerous embedded cracks，their propagation have significant impact on the stability of rock mass. However，it is very hard to study the embedded crack propagation through physical experiment. But when using the numerical method，i.e. finite element method，to numerically investigate this problem，the representation of 3D interface and mesh generation with consideration of setting up joint element has been a tough problem. To provide a simple and efficient method for failure analysis of jointed rock mass，the paper employs the 3D element partition method. The 3D element partition method actually develops a four-node contact element by taking advantage of the geometry character of the tetrahedron element. When a fracture cuts through a tetrahedron element，the nodes at different sides of fracture can construct 3 or 4 contact pairs，based on which the stiffness matrix of partitioned element is derived. When using this method，the cracked body can be directly meshed regardless of geometric integrity of jointed rock mass. Thereafter，many tetrahedron elements are intersected by pre-existing fracture. For those intersected element，the partitioned element stiffness matrix is adopted whereas for the rest，the normal element stiffness matrix is adopted. This makes the simulation of jointed rock mass highly simple and efficient. The comparison between the tested and the simulated results of elliptic crack propagation suggests that the present method can capture the features of 3D embedded crack propagation and is effective.

By improving the original constitutive relation of FLAC3D to the elastic-brittle model，as well as using superfine elements division，the failure process of the double-cracked rock specimen under uniaxial and biaxial compression are simulated and studied. The numerical results match well with the testing results obtained by early studies. This method is also used to simulate the failure process of rocks that contain four cracks (in two groups) of different inclinations or a single 3D crack；meanwhile，the numerical results of 3D crack propagation also match well with the testing results obtained by early studies. Finally，the model is applied to studying the crack propagation process and stability of a slope project；and it has a good effect.

Based on 1∶1 load test of the tunnel lining vault，the relationship between lining crack depth and lining stiffness is established；and a beam-spring model is put forward to calculate the stiffness of lining crack. Using the beam-spring model，the effects of crack location，crack depth and strata resistance on bearing capacity of lining structure are analyzed. The calculation results show that the tunnel vault safety factor reduces linearly with the increasing crack depth；when crack depth is 50% of lining thickness，the safety factor is reduced by 78%. Under the same crack depth，cracks in the vault are most disadvantageous；cracks in the arch of the waist，side wall or arch foot，the influence on safety factor is smaller. The effects of strata resistance on safety factor of the vault，side walls and arch waist are larger；but the effect on safety factor of the feet of arch is smaller.

Shandong Haiyang Nuclear Power Plant site contains multitudinous stratifications. On the basis of monitoring points? velocity of blasting vibration，the attenuation laws of blasting vibration in different directions to stratification are given out in the process of blasting excavation. It is concluded based on blasting experiment that the velocity of blasting vibration along the stratification strike is bigger than that perpendicular to the stratification strike with same distance and same excavation without considering the influence of blasting rear impact. What?s more，blasting vibration damped exponential increases when the angle between stratification strike and the line from monitoring points to explosive source makes larger. Therefore，the monitoring points need to be made sure on rational site in accordance with the site geological condition；and it is necessary to have several monitoring points when the site situation is complex.

The nonlinear behavior plays an important role in the stability of rock engineering. As an attempt to more accurately model the elastic response of porous or fractured rocks，a recently developed stress-strain relationship，called two-part Hooke?s model(TPHM)，is incorporated into a coupled reservoir-geomechanical simulator，TOUGH-FLAC3D code. TPHM is based on a macroscopic approximation that the natural strain (volume change divided by rock volume at the current stress state)，rather than the engineering strain(volume change divided by the unstressed rock volume)，should be used in Hooke?s law for accurate modeling of the elastic deformation except when mechanical deformation is very small. We first implement TPHM into a modified Mohr-Coulomb model providing by FLAC3D to demonstrate the numerical algorithm of TPHM in a geomechanical simulator. Then the nonlinear deformation behavior characterized by a shallow sloping stress-strain curve at low stress levels is numerically obtained with rock specimens under loading and unloading processes. Finally，based on the numerical simulation on the deformation of rock mass around an underground tunnel ED-B in Mont Terri laboratory，we show the usefulness of TPHM in light of its applicability to practical problems，and the importance of incorporating more accurate constitutive models for modeling mechanical response for field-scale problems related to rock engineering with unloading process.

How to obtain the actual and reliable shear strength parameters of rock structural plane is the essential precondition for studying the strength of whole rock mass. The characteristics of one structural plane sample are quite different from those of another structural plane；and the mechanical tests also can?t be repeated easily. So it is very hard to obtain the reliable shear strength parameters only by mechanical test directly，or the test results are not available. Taking the rock structural plane samples with oriented deformation character for objective，a new method，which combines shear tests on rock structural planes，three-dimensional spatial analysis of rock discontinuities morphology and numerical simulation，was put forward. It was proved to be effective in obtaining actual and reliable shear strength parameters of structural plane. The advantages of this method can be described as follows：For rock structural plane，the two parts of friction angle，i.e. basic friction angle and climbing angle，can be separated completely；and three-dimensional morphology characteristic and shear deformation direction can be considered. Meanwhile，the combination of mechanical test and numerical test can solve the question that the shear mechanical test can?t be repeated.

With the application of 3D laser scanning technique，high density point cloud coordinate data of high steep slope was obtained；and a surface model of high slope was established. Information of structure of rock mass of high slope and data of dangerous rock mass were extracted based on point cloud data obtained from 3D laser scanning. Based on this，a method for identifying dangerous rock mass was proposed；grid of point cloud coordinate data of dangerous rock mass of high steep slope was constructed；block element was formed，then the block element was divided by surface of spatial structure，spatial block model was formed；and the spatial block model was classified according to slide types of dangerous rock masses. Based on the limit equilibrium theory，the failure mechanism of all kinds of dangerous rock masses and the load combination acting on the dangerous rock mass，a calculation method of dangerous rock mass anchor was established. This method was applied to the investigation and rehabilitation of dangerous rock mass of Dongping Baifoshan slope；the minimum numbers of anchors of different kinds of dangerous rock masses were calculated according to the main kinds of loads acting on the dangerous rock masses of Baifoshan slope(such as weights，fissure water pressures，seismic forces and so on) and the stability coefficients of different kinds of dangerous rock masses. The results of the study show that：(1) Spatial coordinate data of high steep slope can be quickly obtained at a far distance with 3D laser scanning technology；then the spatial information and attitudes of the structure of the rock masses can be obtained. (2) Based on the spatial coordinate data of dangerous rock masses，the spatial information of surface of structure and different kinds of load combinations，classification of dangerous rock masses and calculation of anchoring can be carried out；the numbers of anchor bolts and anchor cables needed in the dangerous rock mass anchoring were obtained；and the results can be referenced for rehabilitation and design of dangerous rock masses. Engineering example shows that this method has strong applicability and reliability；and it benefits to design and optimization of reinforcement scheme of dangerous rock masses of high steep slopes.

High in-situ stress and high water pressure are the main factors influencing the stability of rock mass and safety of lining structures for the deep diversion tunnels. Based on equivalent saturated porous media theory and considering rock mass and concrete of lining structures as permeable media，the seepage-stress coupling analysis of diversion tunnel at Jinping II hydropower station during its excavation and operation period were carried out. The results show that the drainage around tunnel boundary has great influence on forming excavation damaged zone during construction period；seepage in the reinforced concrete lining from inner tunnel to outer tunnel has little effect on water table and rock mass stability；but this phenomenon would influence the safety of lining structures near the excavation damaged zone，so as to lead tensile and compressive damage regions in the lining structure. Corresponding countermeasures for excavation damged zones should be taken.

Nanjing Yangtze River tunnel was constructed by slurry shield with diameter of 14.93 m. Along the 3 020 m tunnel，a highly permeable gravel stratum under water pressure of 0.65 MPa was passed through successfully. In the project，the most difficult tunnel with giant size across the Yangtze River，several construction difficulties were overcome，such as opening chamber under high pressure and under-passing the section of super shallow cover under the Yangtze River. Based on conditions of the site，difficulties faced with the project were analyzed and key technologies including filter cake formation and opening chamber under pressure were summarized systematically. These achievements would play a significant role in developing the technology of slurry shield with large size in China.