The collapsibility of loess is closely related with its microstructural character, which is directly affected by the stress state subjected and its moisture condition. The collapsible tests of the intact loess from Xi’an with various water contents and consolidation pressures were carried out. The differences and relations of collapsibility of loess under various conditions were analyzed based on the results of these tests. The scanning electron microscope (SEM) images were obtained both on loess samples of before and after collapsing; then corresponding microstructural parameters were obtained. Comparative analysis of simple microstructural parameters was made. The relationship among these parameters was discussed and the synthetic microstructural parameters were constructed as well. The results indicate that the proportion of particle and the first principal component increases with the increase of consolidated pressure; there is a linear relationship between collapsibility and the first principal component of loess. Based on this understanding, the calculation method of collapse coefficient is established. The collapsibility of loess can be evaluated objectively using the proposed method. The efficient exploration is made in quantificational studying the effects of microstructure on collapsibility of loess.

As a common waterproof material used in tunnel construction, nonwoven fabrics are widely used as a cushion in the waterproof layer. But the water pressure and structure stress distribution mechanism after using it hasn’t been studied thoroughly. Through the research of Xiang’an subsea tunnel, the effect of nonwoven fabrics has been studied with different proof-drainage patterns; i.e. whole block, block combined with drainage and drainage modes. The primary research method adopted is simulated model test with proportional scale of 1:38.88. Its test apparatus can apply both soil pressure and water pressure at the same time. According to the model test, the conclusion is as follow: under whether whole block or limited drainage condition, nonwoven fabrics have a good function of water collection and absorption; the nonwoven fabrics can strengthen the water fluxility and complementarity around the lining to make the water pressure distribution on it more well and also improve the stress condition around the lining structure.

In order to explore the stability evolution law, under water-rock interaction, of mudstone reservoir bank which has been located in Funing Port areas of Yunnan province, and then based on the rock samples, collected from the first-stage project field, the conventional triaxial compression tests were conducted with different numbers of drying and wetting cycles and the rock shear strength parameters were obtained. After engineering conversion of strength between rock and rock mass, it formulated the time-varying model of probability distribution of mudstone general shear strength parameters by regression analysis. Then combining with the limit equilibrium method and the reliability theory, the time-varying laws of mean safety factor, reliability and reliability safety factor were drawn. The results show that the reliability safety factor, coupling the safety factor and reliability, can analyze the time-variation of mudstone reservoir bank more reasonably, during the water level fluctuation repeatedly. Furthermore, it is nonlinearly that the characteristic of the whole stability of mudstone reservoir bank has changed. Besides, the failure model of the bank slope is gradual that the critical slip surface changes from inside to outside. The time-varying stability analysis methods of mudstone reservoir bank proposed by the paper based on the laboratory experiment can provide an effective approach for stability evolution rule of the reservoir bank, impacted on by the high water soaking and water level periodic fluctuation.

Granulated blast furnace slag (GBFS) is utilized to overcome or to limit the expansion of an expansive soil sample. GBFS is added to sample in proportions of 10%-20% by weight. The test studies of swelling-shrinkage and basic physico-mechanical characteristics of soil samples are taken, so as to determine the improvement effects. Compared with unmodified sample, the free swelling ratio, liquid limit and plastic index decrease obviously; and the particle size gradation, strength characteristics and hydrated properties of the treated expansive soil are improved by a wide range. After improvement, clay content decreases, while silt content increases. The change of dry density with water content decreases and the hydrated property of modified soil is enhanced. It is shown that adding GBFS can successfully improve the expansive soil.

Flexible uniform pressure loading is the premise to enhance the accuracy of geomechanical model test. A new flexible uniform pressure loading system is developed, which includes hydraulic automatic control system and flexible uniform pressure loading device. Hydraulic automatic control system can be operated easily and controls the 12-exact servo pressure loading with longtime stability or unloading automatically. Flexible uniform pressure loading device is composed of the hydraulic cylinder, rigid thruster and flexible transfer rubber pad etc.; the reasonable thickness of flexible transfer rubber pad is 50 mm determined by numerical method. The system is applied to the model test with uneven surface and compared with the rigid loading. The results show that the effect of flexible uniform pressure loading device is more significant to rigid loading. The model initial stress field depends on the Shore hardness of uniformity transmission rubber pads, loading stress and depth from the surface. The Shore hardness of rubber is lower, the model initial stress field is more even; and model initial stress field becomes uniform with the loading increasing and depth increasing. The model stress of depth 130 mm from surface is uniform using flexible uniform pressure loading. Test result shows that the flexible uniform pressure loading system improves the accuracy of pressure loading and can be applied to model test widely.

Most of multistorey buildings on loess areas encounter the ground treatment problems. It is common treatment methods to deal with the collapsibility of foundation with a variety of piles ( pure-soil pile, lime-soil pile, crushed-stone pile, etc.). In order to test the effect of the compaction pile in collapsible loess foundation, a field test was conducted. To consider the different factors (distance of two piles center, processing depth, processing area, pile hole filling), eight pilot sites were set up in the experimental field. First of all, the change of soil density at the five points equidistant between two piles and three piles were tested after pilot sites were set up; then, after the loading (200 kPa) on the every pilot site, the small area (small pit) immersion and the large area ( the entire location, 28 m×16 m) immersion were conducted; the every site’s collapse volume was measured respectively. From above experiment the effect and regularity of the treatment methods were obtained. The results show that: to ensure eliminating the collapsibility of all inter-area of compaction pile, the distance of two piles center must be controlled within 2.5 times of the pile diameter. The collapsibility still exists under layer exceeding compaction pile’s length. The settlement after small area immersion is loading collapse, exclusively the large area immersion the whole collapse is eliminated, and it is no matter with the processing depth. The lime-soil filling obviously surpasses the pure-soil filling. Within main bearing stratum the filling must be lime-soil. But it is unnecessary to use lime-soil filling under main bearing stratum and some light collapsibility location.

Based on the finite-strain coupling model of primary-secondary consolidation proposed by Ding et al., a reduced small-strain coupling model is investigated with dimensionless analysis method. A new coupling coefficient of primary-secondary consolidation, , is introduced into the reduced model. For the case of , the model could be equivalent to classic Terzaghi’s consolidation model. Finite difference method is used to analyze the variation of excess pore pressure predicted with the proposed model. The results show that: (1) when is greater than zero, the excess pore pressure at early stage of consolidation increases with the development of time especially for higher values of , which is similar to Mandel effect; (2) values of excess pore pressure predicted by Terzaghi’s primary consolidation theory are generally less than those by the proposed coupling model. The mechanism of the above phenomenon lies in the coupling effect of primary and secondary consolidation, which is analogous to the viscous effect using EVP model by Yin et al. According to the concept firstly presented by Mesri & Godlewski, a method to determine the value of for a given soil is put forward as well as a modified small-strain coupling model utilizing the concept. The presented coupling model can provide new and good reference with its simplicity and convenience for further study of primary-secondary coupling mechanism with application to engineering practice.

The relationship between in-situ values of soil shear strength and laboratory experimental values is discussed. Based on consolidation theory of saturated soil, the consolidation of soil is the process effective stress increasing and pore water pressure dissipating under a certain pressure action. With the effective stress increasing, void ratio of soil decreases and shear strength increases. Compression curve and shear strength line have one-to-one correspondence relationship. Based on in-situ compression curves and indoor experimental curves, variation regularity of soil shear strength during loading and unloading processes is studied. Then, the relationship between cohesion and internal friction angle is derived based on the calculation method of soil unloading shear strength. Finally, the calculation method of shear strength for intact soil is obtained.

There are many 200-300 m high rockfill dams constructed in high earthquake areas located in western areas of China. The grain crushing of rockfill materials with high stress level has significant influence on the stress-strain properties under cyclic loading. Based on the theory of generalized plasticity, and by introducing state parameters, a new dynamic constitutive model for rockfill materials is formulated; and the determination of model parameters is provided as well. Finally the constitutive model is used to model the test results of rockfill materials at 400, 800, 1 500, 2 200 kPa consolidated pressures respectively, which verifies that the proposed constitutive model can simulate well the dynamic stress and dynamic strain responses of rockfill materials under cyclic loading considering grain crushing.

At present time the understanding of the physical nature of two kinds of compressional waves in saturated soils with extreme permeability is still not clear. For example the velocities of two compressional waves in case of infinite permeability given in different literatures are inconsistent. By using the dynamic basic formulations of saturated soils given by Zienkiewicz, the establishment of pore water motion equation is discussed. Then one-dimensional compression controlling equations and wave equations in u-w and u-W forms are derived, from which the compressional wave velocities in extreme cases of zero and infinite permeability are obtained; and their physical natures are also explained. The conception of inertial-coupling force is put forward; and it is emphasized that in dynamic analysis of saturated soils the interaction between soil skeleton and pore water consists of two parts: seepage force and inertial-coupling force. The parameter of measuring inertial-coupling-force is porosity; and its influence on compressional wave velocities is discussed.

It is necessary for stability analysis of high tailings dams to grasp the strength property of tailings material under high pressures. The theoretical derivation of a general power function based on the Mohr criterion must satisfy restrictions { , , }. The high stress traixial test results indicate that the power function of Mohr criterion reflects the strength characteristics of tailings material well under high pressures. The grain-size distribution curves of the pre- and post- test show that tailings material particles will crush in the cutting process when the confining pressure reaches or exceeds the threshold value. The threshold value for tailings silt of copper mine in Dexing is 1 200 kPa, and for tailings sub-silt of copper mine in Dexing is 1 600 kPa. Research results can provide the theoretical basis for the stability analysis of high tailings dams.

Soil structure is the intrinsic determinants of its strength and deformation. Loess structure is determined by the link structural strength and the friction structural strength. Based on this, some new and reasonable structural parameters of loess are suggested based on soil static strength, such as the link structural static strength potential parameters , the friction structural static strength potential parameters and the structural static strength potential parameters . The variation of the structure and the structural parameters based on the static strength conditions are studied with the triaxial compression tests of intact loess and artificial cement structural loess; and the impacts of moisture content, confining pressure and axial deformation on the structure of intact loess and artificial cement structural loess are revealed. The results show that the water content of loess is smaller; its structure is stronger; and the greater loss of soil mass strength will occur after the structural damage. Loess structure damage mainly occurs in the small strain stage. Finally, the rationality of these structural parameters based on the static strength conditions are discussed.

Considering the external influences on rock deformation as instantaneous elastic damage defined with the reduction of instantaneous elastic modulus and long-term creep damage defined with the reduction of long-term creep modulus, kBurgers model with damage is presented. In addition, three-dimensional model considering the Poisson’s ratio and bulk modulus as the constant is established separately; and the transformational relations between the parameters are obtained. According to a case study, the damage evolution of model parameters considering water content changing under the assumption of constant bulk modulus is studied. The damage evolution equations of instantaneous elasticity and long-term creep under the assumption of constant bulk modulus are obtained, which prove that transformational relations between model parameters are reasonable.

The hydraulic parameters of unsaturated soils, including soil-water characteristic curve and permeability function, are very important to unsaturated soils. Because the traditional test method is time-consuming, one-step outflow method and dynamic multistep outflow method are proposed to get hydraulic parameters of unsaturated soils quickly; and the combined testing system is adopted to carry out the two flow tests. The results show that the differences of soil-water characteristic curves between the estimated and measured ones are small. The two methods also can avoid the problem of high-pressure gas through the water leaking in the back of the ceramic plate. The time of the one-step outflow method is shorter, but its accuracy is worse. So the dynamic multistep outflow method is superior to the one-step outflow method.

A number of conventional consolidated drained triaxial compression tests of cemented gravelly soil were performed; and the stress-strain relationships and strength behaviors of the soil were investigated at different cement mixing ratios. The test results show that as the cement mixing ratio increases, the stress-strain relationship of cemented gravelly soil exhibits various degrees of softening and dilatancy under different confining pressures; and especially under low confining pressure (200 kPa) and high cement mixing ratio (8%), the dilatancy of soil is more evident. Under the same mixing ratio of cement, the peak strength is nearly linearly increasing with the increase of confining pressure. Compared with gravelly soil without cement, friction angle φ of cemented gravelly soil increases in different degrees due to the different amounts of cement mixed into the gravelly soil. Cohesion c of cemented gravelly soil shows a growing tendency with cement mixing ratio increasing; and the tendency is more remarkable for cohesion c. The secant moduli of and increase with the increase of confining pressure and cement mixing ratio. Three dimensional finite element analysis results indicate that using cemented gravelly soil as the core will greatly decrease the settlement of earth-rock dam.

Natural rocks show highly heterogeneous character on the micro- and meso-scales due to the randomly distributed defects. Based on the continuum mechanics framework, a scalar damage model is presented for simulating the deformation and failure process of rock material on the meso-scale. A spatial correlation scale factor is developed into the conventional Weibull random distribution model such that the spatial correlation characters of the physico-mechanical indices of rock material can be considered in numerical model. A series of uniaxial tensile tests on sandstone are chosen for parametric analyses aiming for investigation into the influence of spatial correlation scale factor in the random field on the load-cut opening degree curves and failure behavior. The modeling results demonstrate that the value of the spatial correlation scale factor for physico-mechanical indices of rock material can significantly influence the evaluation of mechanical parameters as well as the damage and failure pattern.

Lateral soil movement induced by foundation pit excavation might adversely affect any nearby underground pipelines even damage. Based on displacement-controlled theory, the development of free soil movement induced by excavation with retaining walls is studied. By comparison with displacement-controlled finite element method, the displacement-controlled two-stage simplified method is verified. Secondly, the environment protection criterion for foundation pit in current technical code for excavation engineering is discussed; and a new deformation controlling criterion for excavation based on the protection for adjacent pipelines is introduced，in which the relationship between the excavation depth and the allowed maximum lateral deformation of the retaining wall is given. It is hoped that the above work could give theoretical support for the construction of environment protection estimation system in foundation pit excavation.

Based on the triaxial creep curves of silty mudstone, the linear Burgers model is selected to describe the characteristics of decaying creep and steady creep of the rock. When the nonlinear viscoplastic component is connected with the Burgers model in series, a new nonlinear viscoelasto-plastic constitutive model is obtained, namely nonlinear Burgers model, which can describe the accelerative creep of the rock well. The Levenberg-Marquardt algorithm is adopted to identify the model parameters, and the Burgers model parameters of the rock under different stress levels are obtained. Comparing testing curves with fitting curves, it is shown that the linear and nonlinear Burgers models are suitable to describe the three creep stages of rocks. The identification results show that the model parameters identified by the axial strain are different from those identified by the radial strain at the same stress level. Therefore, the creep model parameters of silty mudstone should be selected by considering the anisotropic characteristics and the differences of the creep strain and the creep rate between the axial and radial directions of the rock. Under the first seven stress levels, the Burgers model parameters identified by the axial strain should be chosen as the creep parameters of the rock. Under the eighth stress level, the Burgers model parameters identified by the radial strain should be chosen as the creep parameters of the rock. Under the failure stress level, the nonlinear Burgers model parameters identified by the radial strain should be chosen as the creep parameters of the rock.

Seepage characteristics of regional principal fratured rock mass are studied with the effect of stress. Using parallel plate model, elastic mechanics and electronics in single fracture, a new conception of equivalent seepage resistance is put forward. On the basis of the geometric construction of regional principal fracture, an equivalent seepage resistance model with seepage-stress coupling is established. With the model the relationships between equivalent seepage resistance, permeability and stress are obtained, which is helpful to the stress-seepage coupling characteristics of regional principal fractures in rock mass. Combining a case study with the model, the seepage laws of the herring-bone combined fracture are researched. Through further detail partition and consideration, this model can be used to study fracture seepage evolution law affected by in-situ stress in rock mass containing regional principal fracture.

A series of creep tests of high-density polyethylene uniaxial geogrids are performed under different environmental conditions, including the stress level, temperature, chemical reaction, installation damage and confined constraint in sand. The results show that: with the higher temperature or stress level, the creep of geogrid is bigger and the creep rate is faster; the creep critical stress level of uniaxial geogrid is unsuitable to exceed 40% under common conditions; chemical reaction can lead the creep deformation to increase about 10%; the influence of installation damage is obvious; the creep property under confined constraint in sand is related with the stress state of geogrid; the filling material and loading can reduce the creep deformation of geogrid greatly.

During the construction of south anchorage open caisson of Ma’anshan Yangtze-River Bridge, the settlement of the open caisson, the earth pressure under the cross wall, the stress of the bottom steel plate of cross wall were monitored. It is found that the super-large open caisson has the characteristics of both strip footing and block foundation. As large settlement is acceptable for the first lifts, the open caisson settlement control method is more suitable than the soil bearing capacity control method. The earth pressure under the common cross wall is smaller than the division cross wall; and the ultimate bearing capacity of soil under the common cross wall is also smaller. When the limit equilibrium state for soil under the common cross wall is reached, the load added during the following lifts is taken by the division cross wall (or the side wall). The stress in the bottom steel plate of cross wall is determined mainly by the concrete pouring of the very first lift, and it is less affected by other following lifts. The stress of the bottom steel plate of cross wall is smaller at the inner part, and bigger at the outer part. The tensile stress near the open caisson side wall can be reduced remarkably by sound compaction of soil backfilled outside.

Based on the theoretical model of dam-foundation interaction and the fluid-gas-solid coupling, the 3D FEM numerical simulation has been carried out for the experimental model of Jinping high arch dam with consideration of air-cushion isolation. According to the similarity principle of dynamic experiment and the uniaxial compressive strength tests as well as the ultrasonic detection, the basic physical parameters of the experimental model are obtained, which could guarantee the basic dynamic similarity of experimental model. To achieve the goal of the isolated effect of the whole air-cushion, the engineering plastics acrylonitrile butadiene styrene (ABS for short) is adopted for the air-cushion, which is used for covering on the upstream of the dam model evenly. The experimental and numerical results show that the hydrodynamic pressure is reduced by air-cushion significantly. Compared to the case without air-cushion, the hydrodynamic pressure can be reduced for more than 70%. The feasibility and the implying engineering value of the air-cushion isolation have been demonstrated through the results of numerical simulation and experimental research.

The soft interlayer under seafloor has great influence on the stability of subsea casing string for deepwater production. Especially, the earthquakes can cause a great bending moment and large shear force on the cross-section of casing string. An analytical model for the seismic response of subsea casing string is established on the basis of pile foundation theories and method of reverberation-ray matrix. The casing string is assumed to be a Timoshenko beam of variable cross-section. The bending moments and shear forces of different casing sections are discussed from the aspects of the shear wave velocity and thickness of soft interlayer. The result shows that while shear wave velocity of soft interlayer decreases or its thickness tends to the critical value hcr, the bending moment and shear force of casing string at interfaces of soft interlayer will increase accordingly. Therefore, influence of soft interlayer on seismic response of casing string should be fully taken into account in marine engineering.

By means of classic element combination modeling ideas, making fractional calculus soft-matter element and spring element in series and combining a visco-plastic body of power function, a new nonlinear viscoelasto-plastic rheological model with four elements is put forward. The constitutive equation and creep equation of the model are given and the creep curves in different stress conditions are obtained. It can be found that nonlinear gradual change process of steady creep phase and creep speed rate of accelerated creep stage of rock can be effectively simulated by adjusting creep parameters. In lower stress level, the model can describe the initial creep and steady creep of rocks. Moreover, if the stress level exceeds the long-term strength of rocks, the model can reflect the accelerated creep characteristics. The fitted results show that the nonlinear rheological model which contains soft-matter element and visco-plastic body of power function can effectively describe the creep properties of rocks and reduce the number of components and parameters of combination model.

According to the features of tunnel engineering, interaction between tunnel and wall rock is considered. Based on structural dynamics theory, interaction theory and the idea of equivalent radius, a dynamic equilibrium equation of tunnel structure is established. The equation takes into account the action of inertial force of the tunnel structure. As can be seen from the equation, classical displacement response method is a special case of the method. Factors effecting on longitudinal stress of tunnel lining have been studied. Those factors contain tunnel depth, strata shear wave velocity, shear wave direction, elastic foundation coefficient, elastic modulus and the characteristic period of the overlying strata. The case studies show that: (1) Interaction between structure and wall rock has a greater impact on lining. Without considering the interaction, the results are relatively conservative. (2) Inertial force has a great effect on the ultra shallow structure; but with the tunnel depth increases, the impact of inertial force can be neglected. (3) The method is actually an engineering algorithm for solving tunnel longitudinal stress. In the preliminary design of tunnel, the method could provide theoretical reference for seismic concept design of the overall tunnel.

The in-situ stress measurements of 12 pits have been conducted within the depths of from -500 to -1 000 m in Huainan Coal Mine by using hydraulic fracturing technique and stress relief method by overcoring; and the measurement data of 19 effective measuring points have been obtained. The analyses of the measurement data indicate that: (1) The in-situ stress field in Huainan Coal Mine, in which the tectonic stress takes absolute predominance, is dominated by horizontal stress and belongs to typical tectonic stress field. (2) The magnitudes of the in-situ stresses are high stress level. (3) Vertical principal stress, maximum and minor horizontal principal stresses all show increasing trend with the increase of depth. (4) The ratio of maximum horizontal principal stress to vertical principal stress, , decreases with the increase of depth; the in-situ stress field has the changing tendency from dynamic to static. (5) The regression curve for the ratio of average horizontal principal stress to vertical principal stress, , distributes between the maximum and minimum envelopes of Hoek-Brown curve; and its change trend is similar with the Hoek-Brown curve, but compared with the Hoek-Brown’curve, the value of the regression curve is smaller. (6) The ratio of maximum to minimum horizontal principal stress ranges from 1.12 to 2.02, in which 68.42% of measuring points ranges from 1.67 to 2.02. (7) The orientation of maximum horizontal principal stress is about NEE-EW. At last, the relationship between in-situ stress and tectonics for Huainan mining area is discussed. The analysis suggests that the orientation of maximum principal stress is closely related with the tectonic movement, while the orientation of current tectonic stress field is roughly identical with that of the measured maximum horizontal principal stress of mining area.

The rate of penetration (ROP) of some oilfields in the western South China Sea is very slow in recent years, which restricts their exploration and development process. In order to increase the ROP and reduce the drilling costs, the mechanical properties of rock and the rock breaking mechanism should be known precisely. We identify the lithological characters of the complex formations (mostly pebble and interbed formations) by mineral composition identification device (X-ray diffractometer). Laboratory experiments of core uniaxial compressive strength (UCS), hardness, plasticity coefficient, drillability and abrasive property were done; and the prediction models of rock mechanical parameters were established. We plotted the continuous sections of rock mechanical parameters of 30 wells and three dimensional drillability planes using the log data to reveal the complex formations distribution and their rock mechanical properties. According to the complex formations breaking mechanism of the PDC bit, we studied the influence law of the tooth shape, weight on bit (WOB) and revolutions per minute (RPM) of PDC bit on penetrating efficiency of pebble and interbed formations. The results show that for the Northern Gulf Basin oilfields, the bit aggressivity should be improved and the downhole drilling motor with high rotary speed should be used; for the Pearl River Mouth Basin oilfields, the more wearlessness of the PDC bit under higher bit weight and lower rotary speed is suggested, which can reduce the drilling cost and improve the drilling efficiency.

Excess pore water pressure is generated during shield tunnelling, resulting in consolidation settlement. Assuming the disturbance range shape of shield tunnelling is circular arc, the distribution range of excess pore water pressure is determined. The formula of initial excess pore water pressure of soil around tunnel lining is deduced by stress relief theory; and the formula of initial excess pore water pressure of soil within the region of its distribution at any point is subsequently deduced by stress transfer theory. By comparing calculated and measured data, it is shown that they are in good agreement. Based on practical example, a conclusion is drawn that the distribution shape of initial excess pore water pressure of soil around shield tunnel circle is roughly circular (top of small, bottom of large). With the increase of distance from shield tunnel central axis, the initial excess pore water pressure of soil shows a concave curve shape. At the same time, the isopleths at the bottom of shield tunnel changes fastest. Above the top of the tunnel, the initial excess pore water pressure of soil gets the maximum at the tunnel axis in different depths, showing a similar Peck shape.

The main shock measured by stations of China strong motion networks center(CSMNC) around Zipingpu concrete face rockfill dam(CFRD) and the aftershock measured by Zipingpu stations are analyzed. The basic characteristics of strong ground motions are studied. Three-dimensional dynamic finite element analysis is adopted to analyze Zipingpu CFRD while the main shock measured by stations like Diban of Mao county(DBM), Zoushishan of Pi county(ZSP), Zhonghe of Chengdu(ZHC) and recorded aftershock of rock stations on dam site on Nov. 6, 2008 and artificial ground motion generated by standardized spectrum of specifications for seismic design of hydraulic structures as seismic input; and then comparison between the finite element data and the measured data is made. It is shown that the long period component (0.65 s later) of response spectrum of ground motion recorded by stations of ZSP and ZHC is much too rich as these far-field stations locate in the footwall of fault. As Zipingpu dam locates near the fault, main shock recorded by far-field stations can not be used as seismic input. The components in the range of about 1 Hz (base frequency of the dam) of the aftershock recorded by stations of Zipingpu dam are lower and the duration is less so that it is difficult to stimulate the dam. Compared with measured and calculated spectra on dam crest, ground motions measured by Diban station of Mao county and artificial ground motion generated by standardized spectrum are suggested to be used in dynamic analysis of Zipingpu dam during Wenchuan earthquake.

Due to the thick cylinder can give fully play to the compressive characteristic of materials, it is widely used in foundation pit engineering. The traditional design and calculation method is Lame solution of the thick cylinder which is mainly under the uniform pressure. In order to solve the eccentric load problem in practical engineering, an analytical solution of the thick cylinder under eccentric load is given. Combining with the engineering practice, the stress state of the cylinder supporting structure is simplified; the analytical solution is applied to calculating tensile stress of the thick cylinder supporting structure under eccentric load. Especially the effects of the uneven variety of groundwater level, ground uneven loading and the unbalanced excavation of the soil layer on the supporting structure are all discussed. The effects may cause large hoop tensile stress and vertical cracks on both internal and external surfaces of the cylinder. It has an important guiding role for cylinder section reinforcement design and excavation construction control.

Reasonable rainfall threshold index is the key to ensure accuracy of debris flow forewarning. It is significant for the study of the formation mechanism of debris flow, the prediction of the future activities characteristics and the guidance of the prevention and controlling engineering. Most of the mountain areas have few rainfall and hazards data; therefore, both the traditional demonstration method and frequency calculated method can’t satisfied the debris flow forewarning. Through studying the characteristics of the forewarning regions, including the rainfall characteristics, hydrological characteristics, and underlying conditions, a method to calculate the rainfall threshold is put forward based on the initiation mechanism of hydraulic debris flow. Firstly, the critical water depth for the initiation of debris flows is calculated according to the topography conditions and physical characteristics of the loose solid materials. Then, the rainfall threshold is calculated combined with the mechanism of runoff yield and confluence, the change laws of rainfall with altitude, and the rainfall pattern. The results have been used in Shijia Gully in Ningnan city, Sichuan province; and it is shown that this method is reasonable and feasible. This method resolves the problem of debris flow forewarning in the data lack areas and provides a new thread for the debris flow forewarning in the mountain areas.

The loading/unloading response ratio theory is introduced to analyze the seismic response of underground rock cavern group. The response region is determined reasonably by taking the input seismic accelerations as loads and unloads and cavern accelerations as response. The numerical section model of No.13 unit of Baihetan hydropower station is established by FLAC3D. With Wenchuan earthquake as input wave, the seismic stability of underground rock cavern group is discussed. The result shows that the peak value of loading/unloading response ratio is about 4.05-11.52 under 2% exceeding probability in future 100 years. The rock mass around top arch of main powerhouse and interlayer C4 in upstream wall of tailrace surge chamber are under the state of nonlinear deformation, but the loading/unloading response ratio is not infinite during the whole process, with no stability failure of rock mass. The relative displacement of interlayer has adverse effect on the wall stability of tailrace surge chamber. This research method can be used for seismic stability study of common rock mass.

Blasting excavation damaged zone (EDZ) is regarded as a heterogeneous and unsteady three-dimensional disturbed field evolving with the excavation progress; and the mechanical parameters in EDZ are identified as a parameter field of time-space evolution characteristics. A displacement back analysis method is proposed for parameter field identification of the EDZ around openings in practical working state, considering the spatial effect of blasting disturbance and real deformation response of rock mass. Based on the spatial displacement field obtained by space interpolation of local monitoring displacements, by analyzing the deformation disturbance mechanism of the surrounding rock, a numerical model for parameter field of rock mass deformation modulus in EDZ is put forward; and the applicability and parameters sensibility are further analyzed. Taking the deformation modulus for instance and combining the measured displacement of surrounding rock, the dynamic implementation progress of the displacement back analysis for parameter field is introduced in detail. Finally, the method is applied to the parameter field identification and dynamic feedback analysis and prediction of stability assessment of the surrounding rock during construction of Xiluodu underground caverns. It is shown that the method is reasonable and effective and of significant engineering applicability and practicality for fast feedback analysis of monitoring and stability assessment during construction of large-scale underground caverns.

Based on Yangpoli tunnel in Wudu-Guanzigou expressway, both the interaction mechanism and the deformation and failure mode between tunnel and landslide in the condition of tunnel traversing landslide longitudinally are deeply discussed. On the basis of theoretical analysis, a relevant comprehensive controlling design is put forward. Furthermore, the strength reduction finite element method and limit equilibrium method are carried out to analyze the excavation reinforcement effect for the tunnel crossing landslide. The comparison analysis of stabilities before and after excavation illustrates that under the excavation, the landslide stability meets the design specifications of the code. So far, the engineering is under construction and the safety stability is in good condition. In addition, studies show that: the tunnel structure crossing landslide longitudinally works as a major “anti-sliding structure” in terms of landslide; due to the effect of landslide thrust, the principal stresses of tunnel lining suffer apparent deflection. When entering the stable bedrock, with the increasing of distance between tunnel vault crown and the interface of bedrock and alluvion covering, the principal stresses of tunnel lining gradually transform into normal state. The analysis of tunnel crossing landslide longitudinally and comprehensive controlling scheme will provide a guidance for similar engineering.

The instantaneous shut-in pressure ( ) is an important parameter in the hydraulic fracturing characteristic parameters. Not only is it assumed to be equal the minor horizontal stress, but also is an important factor to calculate the maximum horizontal stress. The accuracy and reliability of the determination of are directly related to that of the hydraulic fracturing results. The applicability and value features of four methods (the single tangent, dp/dt, lg(p)-t and dT/dP methods) frequently used to determine ps are analyzed combined with three examples of test records. The results reveal that the four methods are lack of general applicability at different forms of pressure records. Therefore, different methods chosen to determine the instantaneous shut-in pressure are various for different pressure records of hydraulic fracturing stress test. Aiming at the hydraulic fracturing segments with intact rock, undeveloped preexisting fissures or joints and compact structure, two or more than two kinds of four methods should be applied to determine the shut-in pressure. The methods of technique of single tangent and dp/dt should be suggested to obtain more reliable value of shut-in pressure directing at hydraulic fracturing segments with incomplete rock, more developed preexisting fissures or joints and incompact structure.

Combined with a concrete arch dam and present design specifications for arch dams, a dynamic anti-sliding stability analysis method based on the safety index criterion for abutment fractured rock mass is presented. Taking comprehensive advantages of the finite element method and the rigid limit equilibrium method, and taking into account the uncertainties of different values of cohesion c and internal of friction coefficient f with large differences, this analysis method defines the anti-sliding stability safety index to evaluate anti-sliding stability safety degree of the abutment rock mass. And the anti-sliding stability safety index changes with the change of cohesive force’s and friction’s occupying weight. This method both considers coupling effect between the abutment rock mass and the dam body, and can reflect real behavior of the arch dam system. Based on a high concrete arch dam engineering, the aseismic stability of the abutment fractured rock mass is analyzed. The results show that the method has high practical value.

Settlement is the key point for safety monitoring of super-large pile group foundation built on thick bed overburden. According to the question existing in the settlement monitoring of pile group foundation in Sutong bridge, PSI (permanent scatterers interferometry) and CRI (corner reflectors interferometry) technologies are synthetically applied to the settlement monitoring for Sutong bridge foundation. Combining with the permanent scatterers characteristics of the bridge and corner reflectors set up in the key monitoring site at bridge region, by processing 20 scenes SLC (signal look complex) data of Envisat acquired in the construction period from 2003 to 2008, differential interferometry is analyzed by CTM module in EV-InSAR software. The permanent scatterers points in the bridge area are picked out and the deformations of the points in different construction periods are calculated by PSI and CRI joint algorithm. It reflects the settlement of Sutong bridge foundation in the construction process objectively and roundly. Comparing settlement values gained by PSI with finite element calculation, the relative error is 4.64%. The result indicates that PSI and CRI joint algorithm is a powerful technology to monitor the foundation settlement of huge bridge's foundation. Along with continuous accumulation of SAR (synthetic aperture radar) data in the monitoring area, high-precision settlements of Sutong bridge foundation in operation period will be gradually obtained.

The numerical manifold method is a new developed numerical method and has been used in many fields of geotechnical engineering. But there is no research on numerical manifold method in creep. In recent years, the study of high-order manifold method shows that using high-order cover function could improve accuracy of manifold method in complex geotechnical engineering. The research on high-order numerical manifold method in creep is presented. The “time step-initial strain” method is combined with high-order numerical manifold method to simulate the creep of rock. Based on generalized Kelvin model, some relation equations are given; and a new code is developed. Some examples are used to check the feasibility and rationality of the method. The result shows that the high-order numerical manifold method could simulate the creep of viscoelastic rock very well combining with “time step-initial strain”. It can improve accuracy of the solution only by using high-order cover function but without changing the mesh density.

Shear deformation gradient near the interfaces of the layered rock mass structure face is very obvious under compression and shear loading. The interfaces boundary layer effect of layered rock mass is studied based on couple stress theory. Numerical calculation is implemented by using the finite element method. The results of the couple stress theory and the classical elasticity theory are compared. The interpolation type functions and displacement interpolation formulae are derived for Serendipity element (S-element). The pre-treatment is put into practice by ANSYS. The computing and the post-treatment programs are writen by Matlab for the typical elasticity theory and the couple stress theory. The results show that the influence of couple stress on the shear strain near interfaces of layered rock mass is remarkable. The scale effect is distinct. Compared with the classical elasticity theory, in couple stress theory, strains decrease and the transition region of shear strain emerges near interfaces boundary layer. The abrupt change of the shear strain is also improved but the shear stress is no longer continuous. The characteristic length affects the size of the transition zone. The second shear modulus, Poisson’s ratio and elastic modulus don’t affect the size of the transition zone.

Regarding the seismic liquefied field deposit as being composed of a non-liquefied crust layer at the ground surface, non-liquefied base layer and a sandwiched liquefied layer, based on the nonlinear Winkler model for pile-soil interaction and taking both the nonlinear bending moment-curvature constitutive relationship and geometric nonlinearity of the pile, the fundamental governing equations for nonlinear large deflection deformation of the pile undergoing soil layer’s lateral spreading are formulated and are solved numerically with the shooting method. At the same time, the analytical solutions of the pile are presented for the case of small deformation and linear elasticity. The validity and reliability of the shooting method presented in the paper are verified by comparing the results of the shooting method with those of the nonlinear finite element method and analytical solutions. The influence of the lateral spreading of the soil layer on the mechanical behavior of the pile is investigated numerically. The results show that the effects of nonlinear interaction between the pile and soil as well as material nonlinearity of the pile are much stronger than that of the geometric nonlinearity of the pile. The effect of the geometric nonlinearity is increased with the lateral spreading increasing of the liquefied soil layer. And it’s necessary to analyze the mechanical behavior of the pile with fully nonlinear model.

The key block theory is widely used in stability evaluation of engineering fractured rock mass. The searching method of key block should be of pertinence and flexibility due to large amount of joints and huge calculations caused by the searching of very few occasional blocks. Firstly, the researching region is decomposed into convex sub-regions; and all closed loops on free surfaces of research region are found out. Then the primary joints that form the closed loop and relevant joints that intersect with the primary ones are regarded as infinite plane to cut the region into convex blocks, among which the key block associated to closed loop will be identified. With better pertinence and programmability, this method can fit some artificial conditions very well such as wedge searching and limitation of trailing cutting. It can also search concave block successfully. Finally, an example of top pillar is presented to show the effectiveness of the above-mentioned searching method.

Using numerical simulation by PFC2D (particle flow code in two dimensions), the group piles effect of pile tip resistance of under-reamed piles on uplift loading is studied. The increase of tip resistance with uplift displacement and the variations of soil displacement around pile tip are observed in the simulation. The differences between single pile (pier) and group piles (piers) in uplift loading are shown and the development of tip resistance with uplift displacement for group piers in different spaces is compared. It is shown that the uplift characteristics are similar for single pile (pier) and group piles (piers) when the normalized uplift displacement s/D is smaller than 0.1. With the development of uplift displacement, the tip resistance of single pile (pier) is larger than that in group piles (piers) and the interaction of soil particles around tip emerges. When the normalized uplift displacement s/D is smaller than 0.5, the tip resistance of central pile (pier) is larger than that of side pile (pier) in the group piles (piers). When the normalized uplift displacement s/D is larger than 0.5, the tip resistance of side pile is larger than that of center pile in the group piles and that is reverse in the group piers, which embodied the effects of side restriction of pile shaft on the mobilization of tip resistance. The characteristics of group piers had obvious difference with single pier only in larger displacement with the increase of pier distance.

Through applying horizontal loads on pile top in model test, the displacement distributions of soils on the upper-surface and around piles are analyzed by the non-target digital photography deformation measure system. The surface horizontal displacement of sand around dual-piles is observed. The effect of space between piles on the interaction of piles is studied combining the relationship between displacement of pile top and horizontal load. Particle flow code in two dimensions (PFC2D) is introduced to simulate the displacement of sand at some given depth. The particle flowing behavior of sand around active pile and the effect of space between piles on the pile-soil interaction are revealed. The results show that the displacement field of sand around piles seems two fusiform bodies; the deformation region of sand in front of pile extends with the increasing of compactness of sand; the effect of interaction between piles is obvious with small pile space.

The failure pattern of embankment under explosive load is of great importance to the national defence as well as engineering application. In order to study the failure formations of embankments under different explosion conditions, the constitutive model which can well describe the dynamic property of soil is proposed in the frame of LS-DYNA. Meanwhile, by means of multi-material arbitrary Lagrange-Euler method (ALE method), the simulations are implemented for homogeneous earthfill dams under explosive load; the crater formations are obtained with different buried depths of explosive and different pore water pressure developments of soil. The numerical results reveal that the crater size increases with the increasing of buried depth of explosive, while crater can’t develop if the buried depth beyond a certain range. In addition, the pore water pressure development of moist soils is significant to the formation of blasting craters; with the increasing of pore pressure development, the crater tends to grow bigger. These analysis results can provide references for the design of embankments safety and for engineering application such as blasting demolition of barrier dams.

In numerical calculation and analysis, the inhomogeneity of rock is reflected by giving different and random physical and mechanical parameters without considering the rocks’ structural characters—the contents of mineral composition in the rock. So a new parameter assignment method is provided considering the inhomogeneity of the rock materials—the random parameter assignment method of the rock mineral cell unit. The sort intervals of the minerals cell units are defined based on the sorts and contents of the rock minerals. For each unit, content judgment is dealt with by Monte Carlo mothod; and the corresponding value of the physico- mechanical parameters are given to the cell unit. Then the inhomogeneity of rocks can be described according to the random and uniform assembly of mineral cell units of the model. The method not only takes into account the contents(sorts and ratios)of mineral composition in the rock, but also considers the random distribution characteristic of the mineral. In the light of the random distribution characteristic of the mineral, choosing two minerals and three minerals for parameter assignment respectively; a series of numerical experiments are taken to research the influence of the random distribution characteristic of the mineral on macro mechanical parameters of the model. The study results indicate that the random parameter assignment method of the rock mineral cell unit has dual characteristics of structure and randomness; and the random characteristic is independent of statistical parameter. The randomness has little or no influence on the macro mechanical parameters of the model.

Landslide is easy to occur at the tunnel portal section due to the surrounding rock is weak, and besides, many of the tunnels portal section are shallow and under unsymmetrical pressure. The surrounding rock of Ruipo tunnel in Guizhou province of Xiamen-Chengdu expressway is instability when the tunnel excavated shortly. Analysis of three-dimensional simulation in the excavation process of portal section of Ruipo tunnel is conducted by using the fast Lagrangian analysis of continua in three dimensions (FLAC3D). Based on the results of plastic zones in surround rocks, deformations in rock and actual situation on site, the causes of tunnel collapse and support deformation are analyzed. Actual tunnel excavation sequence is optimized by numerical simulation. Then the effective remedy measures are proposed and good results are achieved. The analysis results can provide reference for similar engineering.

Considering the effect of grouting pressure on soil porosity, the grout flowing law is analysed and deduced from continuity equation in porous medium. The simple approximate formula of diffusion radius is obtained. Then two-phase theory is applied to grouting research. With the hypothesis that soil pores are filled with water and grout and they are immiscible, unsteady flow model of grout driving water is established. The solving key lies in getting the relations between relative permeability, capillary pressure and porosity. Two-phase flow module in FLAC software is used to simulate grouting process of a certain dam; and the results are compared with the deduced expression. These two results are approaching in the initial stage. But because of considering capillary pressure, the diffusing rate using two-phase theory decreases faster. The simulation results show that there is a transitive area between grout and water. Grout saturation is varied with time and space. As the time passing, grout permeates farther, but the rate becomes slow gradually. Diffusion radius is not only related with permeability coefficient but also with porosity; and porosity has more influence than permeability coefficient. The greater permeability coefficient makes grout flow faster and the larger porosity lets grout flow farther. Two-phase theory is better to analyse the permeating regularity.