The creep deformation of Zhanjiang clay is small in the range of low deviatoric stress; its isochronal curve of creep approximates to line without obvious yield characteristics, and demonstrates linear creep behavior. Whereas the deviatoric stress exceeds a critical value, the creep deformation increases to accelerating creep phase in a short time; and the soil mass failure occurs. Based on the creep deformation mechanism of each phase of Zhanjiang clay, the plastic components with variable parameters are introduced and assumed to be in absolute accordance with the plastic flow law of Mohr-Coulomb; the components are combined with the generalized Kelvin model; and the visco-elastoplastic model of Zhanjiang clay is put forward to describe the overall process of creep. In addition, the suggested model is developed in FLAC3D and compared with the Cvisc model; the results of numerical analysis indicate that the former is felicitous to characterize the each phases of creep deformation behavior of Zhanjiang clay.

The prestressed anchor cables are critical structural elements in ground anchors. Because of the widespread use of ground anchors in geotechnical engineering, the measurement of working stress of prestressed anchor cables in ground anchors becomes imperative. The lift-off test is currently practiced in China and many other countries for this purpose. However, the interpretation methods of testing results are different and country dependent. The interpretation method employed in China is examined by experiment and theoretical analysis that are presented in this paper. The experimental verifications are performed to apply a couple of lift-off tests on a anchor cable prestressed to its 75% ultimate strength. The results show that averaged load in the bending regime on the load-displacement curve recorded during lift-off tests can approximate the working stress of this anchor cable monitored with load cells installed. According to theoretical analysis the measuring principle of list-off tests is better understood.

Based on transfer function, the three procedures of spectral characteristics analysis, seismic response time-frequency estimation, and the spectral correction for input ground motion are proposed. Discussion and verification for these procedures are made based on the seismic analysis of Baihetan hydropower station underground power houses. The results indicate that the seismic input-output relation for underground engineering can be clearly expressed by transfer function. The results are well consistent with the conclusion made by the other methods. Generally the response of floor may be stronger than that of crown, and may contain different main frequency bands. However the response of floor is smaller than that of crown in the band of 3-4 Hz. The method of seismic response time-frequency estimation made with transfer function and based on white noise calculation is feasible. It is believed that this procedure can greatly reduce the time-consuming computation, and makes it possible to grasp the main seismic response characteristics of target project with limited amount of computation. Moreover, the correction of spectral characteristics for the input ground motion to correspond with the spectral reference points of carven bottom or the water level of valley can guarantee the reasonable mechanism of the input ground motion.

First, the influence factors on the stability of the mountain cut-and-fill roadbed slope are investigated, in which two categories can be generally identified: the packing physico-mechanical parameters and the fill regional geometric parameters. Secondly, based on the further research on the sensitivity analysis method of influence factors involved in the slope stability, it is concluded that the gray correlation analysis (GCA) is particularly applicable for the analysis and evaluation of stability of the mountain roadbed slope which is a complicated uncertainty problem, and then the deficiency of the traditional GCA is improved. By combining the advantages of the uniform design that can dramatically alleviate the test times and computational efforts, based on the improved GCA experimental analysis method for the stability of the mountain roadbed slope is then developed. Finally, the influence factors on the stability of the mountain cut-and-fill roadbed slope are analyzed by using the proposed method. Results show that the packing physico-mechanical and the fill regional geometric parameters are more sensitive for the cut-and-fill roadbed deformation, and for the roadbed stability the packing physico-mechanical parameters are more sensitive than the fill regional geometrical parameters. It is therefore reveal that the proposed method can offer important instruction on the precaution and control for the failure of the roadbed posed by the lack of strength as well as the fill excavation joint surface of differential settlement. Also, it can provide significant reference for the design, construction and reinforcement.

Study on the physical clogging of water source heat pump (WSHP) in recharge, and based on the mass balance equation to establish the mathematical model of transport and deposition of particulates. The suspended particle’s concentration dynamic changes with time and bring into the two variable quantity of and are introduced, and the size exclusion effect in model is considered fully. The occurrence of clogging is often caused by a particle that one particle plug a pore, and vice versa. The results of theoretical of the physical clogging of WSHP in recharge would directly bring into experiment research.

Stress variable is one of the key issues in constitutive modelling for unsaturated soil. Unfortunately, this issue is often ignored and may impede the further development of constitutive modelling. This article investigates the stress variables from the viewpoint of soil microstructure, conservation of energy and mechanical equilibrium, on which the selection principle of stress variables of unsaturated soil is put forward based. The difference between stress variables and stress state variables is highly focused. The study results show that some variables, like matric suction and net normal stress, which have the units of stress, are insufficient to qualify them as stress variables on the scale of the air-water-solid REV, but they are the essential stress state variables, and the effective stress and the suction stress could be the stress variables of unsaturated soil. Finally, we prefer using effective stress to simulate constitutive unsaturated soil behaviour, not only because it can obey the above principles but also it can smoothly switch to the theory of saturated soil. It is illustrated that the principle of stress variables selection for unsaturated soil is still immature, but the attempt to develop this theory is requisite.

Applied with a new professional apparatus, the 3D cycle mechanical behavior of a gravel-structure interface is investigated considering initial static shear stress. The tangential displacement in the direction of initial static shear stress is obviously observed due to the cyclic shear application; it has a linear relationship with its perpendicular shear distance. The angle between the line and the initial static shear stress behaves in quadratic polynomial manner with initial static shear stress level. The magnitude of initial static shear stress has little influence on the shear strength and the relation pattern between tangential shear stress and strain, but has significant effect on the peak perpendicular shear stress, volumetric change and the relationship between volumetric change and tangential displacement of the interface. As the initial static shear stress increases, the peak perpendicular shear stress and the corresponding tangential displacement of the interface decrease, the interface becomes more hardened due to cyclic shear application, and dilates more at the beginning of shear application while less during subsequent cyclic shearing.

The hardening soil model has become one of the most widely used constitutive models in numerical analysis of excavations. The key issue of numerical analysis using hardening soil model is determining parameters of this model. Soil samples of typical soil layers (②2, ③, ④ and ⑤3) in Shanghai soft deposit is got by using thin wall samplers. The stress-strain curves of soil is got through triaxial consolidated drained test and triaxial loading-unloading-reloading drained test based on GDS and the load-strain curve of soil is got through consolidation test. Parameters of the hardening soil model are determined according to the test results. At the same time, relationships between , , and are established. The parameters and these relationships are also compared with those of soils in other districts. The test results can be used as references for numerical analysis of excavations in Shanghai and other soft soil districts.

Tunneling in saturated soft rocks may induce serious environment problems. During the excavation of Beigang Tunnel, a railway tunnel in soft rock mass rich in water, a large volume of water and soil flowed into the tunnel and induced severe damage at several sites. At these sites, water table fell down, ground surface cracks occurred. Taking Beigang Tunnel as the prototype, model tests are conducted to study the pattern and law of ground subsidence and cracks when tunneling in soft rock with high water content. It was found that: (1) The transverse settlements curve of ground before collapse can be well described by the normal probability curve proposed by peck. (2) Water and soil flow is the main reason for severe damage in Beigang Tunnel. (3) Collapse happens firstly at the top of the tunnel and then develops upwards to form an arch shaped failure structure. (4) Main influenced area on surface by tunneling is limited in the region between the two largest cracks, which come into being in the early stage of collapse and located on the each side of the tunnel axis respectively.

A series of loading - unloading consolidation creep experiments are carried out on Nanning unsaturated expansive soils. Lots of stress-time curves of different moisture expansive soils and stress-strain isochronous curves are obtained under different stress levels. Through the various stages of creep deformation analyses, it is concluded that the creep deformation of expansive soil is a nonlinear creep, which contains viscoelastic deformation and viscoplastic deformation. Combined with empirical rheology and rheology model theory, the creep deformation of expansive soil is divided into two parts of linear and nonlinear ones. The creep compliances and the linear viscoelastic modulus decrease; while the linear viscoplastic modulus increase with time increasing. Considered linear viscoplastic model and nonlinear viscoplastic empirical model of expansive soil together, viscoplastic constitutive equation is proposed which can be used to describe the nonlinear rheologic characteristic of expansive soils. According to the experimental data, all parameters of this model under different stresses are determined by nonlinear fitting methods. It is shown that the regression curves calculated using this theory fit well with creep test results. The conclusions provide a reliable theoretical basis for the rheological model of expansive soils to further study.

The rheological behavior of rock at low temperature in a long time scale equal to that at high temperature in a short time scale is called time-temperature equivalence effect (TTEE). It is convenient to obtain the rheological data in a long time scale through increasing temperature. In order know about the TTEE of rock in nonlinear viscoelastic field, based on the single-integral nonlinear constitutive equation presented by Schapery, the equivalence equation of TTEE on the nonlinear viscoelastic creep property is put forward. According to the creep test data of granite at different stresses and temperatures, setting 20℃ as the reference temperature, the variation of the vertical shift factor with temperature and the modified compliance curves are obtained through considering the temperature influence on instantaneous creep compliance. The master curves at different pressures and the variation of the horizontal shift factor with temperature are obtained by shifting the modified curves horizontally to make the adjacent curves cross to a point. The coincidence of the master curves is good, which further confirm the existence of TTEE of granite. It is found that the nonlinear property of granite from 40 MPa to 64 MPa is not evident but reaching to 87MPa is distinct.

Based on structure parameters of soil established by the theory of comprehensive structure potential and the defects of structure parameters, a new structure parameter which is stress ratio structure parameter is proposed, it can reflect the coupling action of shear stress and spherical stress. Through theoretical analysis and triaxial test research, it is found that the stress ratio structure parameter can consider the influence of both of shear stress and spherical stress on soil structure, and its value no longer reach peak in the process of shearing which consist with the traditional recognition of soil structure. Namely, it can reflect the soil structure more accurately from the quantitative aspects.

The distribution of rock masses discontinuities is random and irregular; but in the statistical sense, the property of rock masses discontinuities distribution is self-similar. The three-dimensional network numerical modelling technique is used to establish the model of randomly distributed discontinuities in the statistical homogeneity of structure; the structure of jointed rock masses is regenerated on the screen of computer. Then the fractal dimension of the rock masses discontinuities distribution is computed applying fractals. The distribution of rock masses discontinuities has scale effects; and the fractal dimension of the rock masses structure decreases with the size of the rock masses specimen increasing; but when the specimen dimension increases to a certain value，the fractal dimension varies decreases no more. This certain fractal value is named "representative fractal dimension", and the value can be used for describing the distribution of discontinuities. By comparing "representative fractal dimension" calculated above with the rock masses grades classified by the traditional rock masses rating methods, a new method of rock masses quality classification, which takes "representative fractal dimension" of the discontinuity distribution as the classifying index, is proposed. The equivalent shear strength indexes of rock masses can be calculated, basing on the rock masses quality classification.

Filter tests on gravelly soil and a filter material under different stress states are conducted using a new large permeameter. The results show that: (1) In the case of confined compression, the permeability of the gravelly soil exhibits a negative exponential relationship with the increasing of compressive stress, which is consistent with a commonly used empirical relation. The critical hydraulic gradient of the gravelly soils increases nonlinearly with the increasing of compressive stress. (2) In the case of horizontal compression and free vertical deformation, the permeability of the soil sample decreases and reaches a minimum, then increases with increasing stress. The critical hydraulic gradient increases and reaches a maximum, then decreases with increasing stress. Before the peak, the critical hydraulic gradient of the soil sample with looser or finer filter increases more significantly with the increasing horizontal stress. After the peak, the critical hydraulic gradient of the soil sample with denser or finer filter decreases more quickly with the increasing horizontal stress.

This paper studies the influence of construction sequence of piles with steel sleeve on existing adjacent tunnels through theoretical research and numerical simulation. The results are tested and verified by the field testing data. Firstly, the stress conditions of soil plug column during the spinning down process of steel sleeve are analyzed through theoretical methods. Differential equations are established to calculate the bottom stress of the soil plug column as well as the suffered cutting torsion and the resistance shear torque of soil plug. As a result, the critical depth of shear failures and plugging effect of soil plug is obtained. Based on the study, the soil expansibility is studied in two cases according to whether the plugging effect happens. The influence on existing tunnels by construction sequence of group piles is then discussed through theoretical analysis and numerical simulation using the corresponding expansibility, resulting in a relatively optimal pile construction sequence scheme. The comparative analysis between field testing data and numerical simulation results indicates that the calculated results above are in good agreement with actual situation. This research provides theoretical guidance and practical reference for similar projects.

Based on the culvert-filling collaborative working mechanism, load reduction mechanism of culvert treated by imperfect ditch covered with geogrid is analyzed. A field experiment on a high embankment culvert treated by an imperfect ditch covered with geogrid is conducted to study the variations of vertical earth pressure on the crown of the culvert and on the surfaces below and above the geogrid. The distributions of earth pressures on the crown of the culvert and on the geogrid, as well as the coefficients of earth pressure are studied. The results show that the vertical earth pressure can be efficiently reduced by the imperfect ditch covered with geogrid, the vertical earth pressure is reduced by the “membrane effect” of geogrid and the frictions on the surfaces between the central soil prism and the lateral soil prisms, which transfer the vertical pressure from the central prism to the lateral prisms. Its load reduction efficiency is closely related to the height of the load reduction ditch, and a higher ditch results in a lower vertical earth pressure.

Suspended particles transport and deposition in porous media play an important role in pollutant purification, oil exploration, nuclear waste disposal, water- soil conservation. In order to study the effect of suspended particles concentration on the breakthrough curves, 4 different suspended particle concentrations have been studied under 3 flow velocities in columns of saturated porous media. The studies show that, under constant suspended particle concentration, the relative concentration is increase with the flow velocity. Meanwhile, under a constant flow velocity, there exists a critical concentration for suspended particles. Below the critical concentration, relative concentration in breakthrough curves is in creased with the suspended particles concentration; but the trend is inversely when the suspended particle concentration is more than the critical value. Besides, the critical concentration of suspended particles is related to the flow velocity; the critical value is increased with the flow velocity.

Colluvium is a natural deposit of soil and rock. The physico-mechanical properties of colluvium are controlled to a large extent by its structure. On the basis of ground investigation and laboratory grading analysis, large scale direct shear tests on remoulded colluvium samples are carried out in laboratory. The shear stress-strain curves and shear strengths of colluvium with different rock particle contents, rock particle shapes, soil types and stress states are obtained. In addition, studies of the deformation and strength characteristics of colluvium are performed and a nonlinear increasing trend in shear strength of colluvium with respect to an increase in rock particle contents is first proposed. The results indicate that the shear stress-strain curve of colluvium is different from that of homogeneous soil or rock. Colluvium samples exhibit shear dilatation characteristics at low normal stress levels and tend to have a transformation from shear contraction to dilatation at higher stress levels. Overall, the shear strength of colluvium increases with increasing content of rock particles, for which the trend of increase is slow at first, and then becomes rapid, and slow down finally. The increment of internal friction angle increases linearly with the increase of the rock particle contents (0-80% for cohesive colluvium and 40%-80% for cohesionless colluvium). With the same content of rock particles, the internal friction angle of colluvium containing rock particles with irregular shape is higher than that composed of rock particles with regular shape.

Instability mode of soft rock slope in rainy condition is one of bases for slope disposal. In order to research the stability of soft rock slope under rainfall infiltration, this article put forward a new method which not only can consider the impact of seepage field on the slope stability but also can reflect the adverse effect on the slope instability caused by rock softening effect. Two-dimensional seepage numerical calculation method is used to simulate the slope pore water pressure size and the distribution of transient saturated zone area on space and time in rainy condition. Combined the seepage field calculation results with the value of physico-mechanical parameters of rock which are obtained from transient saturated zone area soften rocks test versus time, and strength reduction method is used to analysis the stability of soft rock slope under rainy infiltration condition. The research of example slope indicates that: in early rainfall period the representation of soft rock slope instability is the local layered collapsing of slope surface under rainy infiltration condition. With the growth of rainfall duration, the representation form of the instability is the combined local layered collapsing with whole sliding. After rainfall stopping, the recovery of slope negative pore water pressure has certain delayed effect for the continuous reduction of safety coefficient of soft rock slope.

Defining extensive patterns of nonstationary deformation by analyzing the physical significance and types of monitor time series, aiming at the lower reliability of landslide early-warning due to the key information data, reflected in stages, repeatability and mutability of landslide process, are limited or uncompleted observed. A method, added or imposed extensive pattern is identified according to current status of landslide, such as deformation stage analyzed use factors superposition technique and the types of time series, and the potential causative factors of prediction time into model of support vector machine (SVM) algorithm is presented. The efficiencies of new idea are tested by predicting two groups of displacement time series. All experimental results show that the project prior knowledge can be availably used to increase data message of nonstationary deformation and guide forecast modeling. In contrast to common SVM, the model based on extensive pattern is more reliable and accurate. Particularly, the average relative error is markedly cut down about 2 to 3 times.

In order to investigate the screening efficiency of open trenches to the train-induced ground vibration, a new analytical model is proposed based on existing researches. The ground is firstly modeled as a fully saturated poroelastic half-space in the research of vibration isolation to moving trains. The trenches are obtained by placing three rectangular elastic layers with appropriate widths on the poroelastic half-space. The middle elastic layer is treated as the embankment, upon which the rails and the sleepers are placed. The sleepers and the rails are modeled as transversely isotropic Kirchhoff plate and Euler-Bernoulli beams respectively. Biot’s theory is applied to characterize the poroelastic half-space. By Fourier transforms and Fourier series, the governing equations are solved in the transformed domain. The investigation reveals that, the screening effects of open trenches improve as the train speed increases. The effects of coupling between the soil skeleton and pore water on the screening efficiency is apparent, especially when the train speed exceeds the Rayleigh wave speed of the half-space; the screening efficiency of open trenches decreases obviously as the permeability of the ground increases. In addition, the screening efficiency of the trench on poroelastic half-space is much better than that on elastic half-space to the train-induced ground vibration for the supercritical-train-speed case.

The triaxial rheological tests are carried out on Suzhou lacustrine soft soil; according to the results of test, S-6, K-B and K-S rheological models are used to describe the rheological characteristics of the soil. In the inversion of model parameters, it is found that the fitting accuracy of initial deformation by S-6 model is not enough; and the fitting accuracy of medium-term deformation by K-B model is not enough; the fitting results of K-S model are the best. Therefore, K-S model is used to study the rheological properties of Suzhou lacustrine soft soil. In order to determine the parameters of model better, the concept of stress ratio is introduced in the practical application of the model, and it is found that, there are exponential relationship between stress ratio and model parameters; based on this, we can select the model parameters according to different engineering stress conditions. At last, the model is used for the settlement calculation of practical engineering; the results show that K-S model has high fitting precision, and it can be used to guide the region's project construction.

A simplified analytical approach is proposed to study the behavior of the piled raft foundation with flexible raft in layered soils. It is focused on the effect of the stiffness of the raft on the settlement of the piled raft foundation and the prediction of the long-term settlement of the piled raft foundation. The stiffness matrix of the raft is derived using the finite element method of Mindlin plate theory. The stiffness matrix includes the interaction effect of pile-pile, pile-soil and soil-soil, which are calculated through shear displacement method in layered soil and Burmister settlement solution. The long-term settlement of the piled raft foundation is deduced on the basis of the settlement of the piled raft foundation with the flexible raft in layered soils and the decay of the compression modulus because of the repeated loading. Comparison between the results of the existing analytical methods and the centrifuge tests shows the feasibility of the present method for analyzing the interaction of mechanism of flexible raft-piles.

To overcome the shortcoming of the homogeneous and heterogeneous models that cannot successfully model the exfoliation or slabbing phenomenon of the surrounding rock, the rock is treated as an equivalent continuum, i.e. the granular assembly. The granular and interfaces are divided into square elements. The distribution of the shear strain increment, minimum principal stress and maximum principal stress in the surrounding rock of circular tunnel model at different lateral pressure coefficients are studied. It is found that the maximum induced tensile stresses within the model under compressive stress are closer to the applied maximum compressive stresses, while the maximum compressive stresses within the model are greatly higher than the applied maximum compressive stresses. Numerical results using FLAC suggest that the homogeneous and heterogeneous models give unsafe results. The contour maps of the shear strain increment and the minor principal stress show equidistant characteristics of their highest values zones, which is similar to the observed exfoliation phenomenon in the formation process of a V-shaped rockburst notch. Numerical results show that the reason for the exfoliation or slabbing of the surrounding rock is due to the high loop compressive stress and radial tensile stress.

Based on the self-balanced test technology, the size effect on the large diameter rock-socketed pile has been analyzed by using in-situ testing methods, including the change of diameter, the depth socketed in rock and size effect on tip resistance of pile and so on. From the result of test, it can be seen that it exit a certain phenomenon of the size effect on the large diameter rock-socketed pile. With the increasing of pile diameter, the side resistance is decreased while other conditions are invariable. From the socketed depth point of view, the side resistance of pile is not the same in the case of the same rock areas because of the difference of its socketed depth. The greater the depth embedded in rock, the smaller the side resistance of pile. The experimental results show that the character of the rock around the pile has the greatest impact on the pile side resistance. The higher the compressive strength of rock, the side resistance of pile is also greater. In addition, the effect of diameter change on the pile tip resistance is even more apparent. Therefore, the design of large diameter pile should pay attention to the size effect on the bearing capacity in rock areas.

To improve the understanding of the soil aching effect in the embankment fill, a parametrical study using finite element method is performed. In the analysis, the pile spacing, the fill height and the friction angle of embankment fill were varied. It is found that for low fill height relative to the net pile spacing, H/(s-a)≤1, the failure surface is vertical or slightly inclined which starts from the pile edge and goes through the whole fill height. For H/(s-a)≥1.5, the developed failure surface is similar to that assumed in the Terzaghi’s bearing capacity theory; there are triangular elastic zone, radial shear zone and passive zone in the embankment fill. By using the failure surface shape determined from the FEM, a two-dimensional simplified method to evaluate the soil arching effect is proposed. The computed stress reduction ratios are compared with FEM results and the experimental data collected from literatures; it is found that the present simplified method can predict reliable results.

Seismic load can bring serious damage to shield tunnel. Reasonable seismic analysis of tunnel can help to reduce or avoid potential seismic hazard. So it is necessary to establish efficient model for seismic response of shield tunnel. Segment connectors are simulated by embedded beam elements, and segments are simulated by thick shell elements. At the same time, noncontinuous contact is built between segments and between segment and surrounding soil, which can better simulate stress in thickness direction and the interaction between segments. Thereby, the thick shell-contact-infinite element model for dynamic analysis of shield tunnel is built. Actual seismic disaster data and project results prove that the model has good accuracy. Finally, the model is used to analyze grouting material parameters and contact nonlinearity on the impact of seismic response of segments. This model has a good popularization value for seismic disaster analysis of shield tunnels or tunnels constructed by TBM.

CO2 geological storage belongs to environmental protection projects, reservoirs and caprocks evaluation are the important base for CO2 sequestration safely for long period of time. Reservoirs geological evaluation contents include physical properties and CO2 injectivity, while caprocks geological evaluation contents include development characteristics and quantitative sealing capacity. In the different stages of planning and engineering site selection, contents and objects of reservoir and caprock evaluation should improve the precision and quantization degree according to the evaluation purposes. At the basis of CO2 geological storage engineering site selection stages division, combined with reservoirs and caprocks evaluation contents, suitable evaluation indexes and grading standard are established preliminary, which provides guidance for reservoirs and caprocks geological and suitable evaluation of CO2 geological storage engineering site selection in deep saline aquifers of China.

The extension criterion of fracture mechanics is introduced to analytical solutions of hydraulic tunnel, and the macroscopic load-bearing analysis of hydraulic tunnel and mesoscopic crack propagation research are combined. After classifying cracks in surrounding rock nearby tunnel into shear-tensile and shear-compressive types, analytical solutions of critical inner water pressure of hydraulic tunnel are derived when hydraulic fracture happens in the surrounding rock, according to extension mechanism of different variety of cracks. Based on the proposed analytical solutions, the influence on critical inner water pressure of trend, length, depth of cracks is researched. The results show that both shear-tensile type and shear-compressive type cracks may occur because of high inner water pressure or release of geostress; but the latter one has more probability. Under high inner water pressure, the crack will extend much more difficult than other conditions when the trend of crack is perpendicular to the normal of tunnel. The longer of crack length, the smaller of crack buried depth, the bigger of contact area between pore water and rock masses, the more easily cracks will extend.

The long-term stability of underground engineering is closely related to the time-dependent behavior in brittle rock. Jinping deep marble will appear initial damage when subjected to high stress unloading. The no damaged rock sample is obtained by sampling without damage and tested by acoustic emission. The effect of initial damage on test result is rejected. A series of long-term static-fatigue tests are carried out to test the time-dependent behavior of Jinping deep marble. The marble in Jinping shows the strength degradation with time. When the driving-stress ratio is rather lower, the failure time is longer. The static-fatigue limit is 0.48. The creep curve can also be divided into three phases when brittle rock under long-term loading and the strain ratio shows corresponding change trend. The deformation characteristics and failure mode in static-fatigue test are analyzed by dilatancy index. The stress relaxation zone and concentration zone caused by excavation are calculated by FLAC3D. The result indicates that the buried depth affects the test. When the rock samples contain joints, the strength is rather lower. Numerical test is performed by smooth joint model in the particle flow code (PFC). The numerical result meets well with the test. The existence of joints impacts the strength of rock. The rock will be compacted closely in initial loading stage and show the hardening effect and ductility behavior in residual stage.

To probe into the influencing law of clay on the deformation response characteristics of low-permeability sandstones, the study of the influencing law of rich-clay sandstones is carried out. Based on the concept of the effective stress coefficient for permeability (ESCK), it is found ESCK can reflect rock deformation and hence called as deformation response characteristic parameter. Meanwhile, According to the comparative analysis of the previous theoretical study, the relationship between ESCK and rock deformation response is constructed and one method diagnosing rock deformation is proposed. Besides, two samples’ permeability measurements under loading/unloading pore pressure with three different confining pressure cycles are made; data obtained with steady-state method are analyzed with the translation method and the ESCK are calculated accordingly. Results show that the values of ESCK are constant and greater than 1.0, the translation method is valid for calculating ESCK. In conclusion, the deformation characteristics of 31 rocks in present and previous papers are evaluated with diagnosing method; the diagnosing results illustrate that the type and content of clay mineral and rock microscopic pore structure are major factors affecting rock deformation.

Through analyzing the result of uniaxial and triaxial creep tests on rock salt from Yunying and Jintan salt mine and mudstone from Jintan salt mine, the effect of external conditions concluding stress state and confining pressure and internal construction on the creep characteristics of rock salt are studied. No matter under any confining pressure, the steady state creep rate of rock salt increases obviously following the accreting detective stress. Confining pressure, which plays a role of restricting creep deformation, however, has a little effect on the steady state creep rate more and more as confining pressure increases. Furthermore, larger grain size and more inclusions in the rock salt will result in weakening creep property. In this paper, the origin and the nature of this internal stress, which develops during inelastic deformation of the material, are discussed. It is shown that this internal stress, which reflects the microstructure evolution of the material under the competitive action of hardening and recovery mechanisms and bridges the gap between micro construction and macro experimental phenomenon，can serve as an internal state variable in the creep constitutive model of rock salt. Good agreement between the numerical results obtained from the model presented and experimental data of creep curves to triaxial multi-grade compression test is given.

When a drill machine is working, energy of broking rock is produced from the action of torque and propulsion. The torque is resulted from the rotation of the bit, on which the propulsion is acting. When drilling conditions are certain, physical mechanical properties of rocks can be reflected from the energy consumed to break the rocks per unit volume. Based on this theory, advance geological drilling experiment has been performed on fault FK4+375.5 around the subsea tunnel across Qingdao Jiaozhou bay and the drilling parameters of tuff stratum and the variation of drilling energy with the displacement of bit are obtained. Parameters of a drill have been monitored in drilling process and analyzed using energy theory. The results show that, there is a good correlation between the drilling parameters of a digital drill machine and rock lithology. When surrounding rocks are integrated, hard and in the absence of fracture water, the drilling parameters are high. Conversely, when surrounding rocks are fractured, or in the presence of faults, fracture water and intercalated gouge, there are abrupt changes in the drilling rate, propulsion, rotational speed, torque and hit energy. The values of these parameters decrease markedly. The obtained results are consistent with core-drilling and advance geological prediction using tunnel seismic prediction (TSP). The above method is used in the classification of surrounding rock. According to the relation between energy curves and classification of surrounding rock, faults or fractured zones will appear in tuff stratum when the value of drilling energy is less than 0.95 kJ.

Interface instability between high-density pdyethylene (HDPE) geomembrane and sand is a main reason for landfill structural failure on lining interface. A series of direct shear tests are carried out to investigate interfacial characteristics and specimen failure types of a novel geosynthetics-reinforced HDPE geomembrane and sandy soil interface. Based on the results of direct shear tests, the interaction mechanism of interface is analyzed. It is proposed that the total resistance of interface between reinforced geomembrane and sandy soil is made up of skin friction resistance, side frictional resistance and bearing resistance of reinforcement. Bearing resistance of reinforcement is given by using the theory of slip line field. Results also show that the interface shear strength is significantly enhanced by the bearing resistance of reinforcement, especially in the higher normal stress. The results show that the theoretical value and experimental value varies in the same trend. The analytic solutions can reasonably indicate the interface total resistance.

Shield tunnelling in soft soils inevitably disturbs the surrounding environment and induces ground surface settlements. The serviceability and safety of the structures in the vicinity can be jeopardized in case that excess settlements are observed. A comprehensive understanding of the influencing factors of shield tunnelling induced ground settlements and an accurate settlement prediction are of great importance for minimizing the environment impacts of shield tunnelling. Taking the load of the shield into account, the Mindlin’s solution is introduced to calculate the additional stress in soils beneath the shield, and the layer-wise summation method is applied to calculate the final one-dimensional consolidation settlement. The duration of additional stress in soils relies on the shield advance rate and its halt time, and the corresponding consolidation settlement can be calculated using the Terzaghi’s one-dimensional consolidation theory. Finally, the relationship between consolidation settlements and ground surface settlements is established by Peck equation. The theory is verified by in-situ monitored ground surface settlements in construction of Hangzhou Qing-chun Road cross-river tunnel in China. These studies show that the shield advance rate and machine halt duration have a significant impact on the ground surface settlements, and the increase in shield advance rate and decrease in machine halt duration favors the settlement control.

More and more shield tunnels will crossing each other with very short distance with the rapid development of urban rail transit construction in China. There are four tunnels crossing each other between Hongshan Square Station and Zhongnan Road Station, which are the second line and the fourth line of Wuhan rail transit. The complicated multi-tunnels were simplified as four parallel tunnels and four perpendicular tunnels with different distances according to their practical characters. Three dimensional calculation models are established and their seismic responses are analyzed, in which the following aspects are considered: amplitudes seismic waves, tunnel net distance, tunnel space position, the difference of segment stiffness and the reinforced layer between tunnels. And then, their seismic capabilities are evaluated through two aspects: structure deformation and component internal forces. The analytical results show, (1) The net distances between tunnels have little influence on tunnel seismic responses; (2) The seismic capabilities of four perpendicular tunnels is superior to that of four parallel tunnels. (3) Adjacent overlapping multi-tunnels have good seismic capabilities and can satisfy seismic requirement. The research results can provide preliminary design for relevant practical engineering in future.

Considering the initial differential settlement of buildings as well as small strain characteristic of soil, the impact of the distance between the building and the excavation and the stiffness of the building on the differential settlement are analyzed. It is necessary to consider the initial differential settlement of the building. When the longitudinal walls of the building are perpendicular to the retaining wall and are located over the lowest point of the settlement trough, sagging deformation occurs and its trend is the same as the initial settlement. So the initial deflection increases the tensile strain. In this case, taking account of initial deflection is necessary. Especially for the building with low stiffness, the influence of the initial settlement on the tensile strain of the building is more obvious. When the longitudinal wall of building is perpendicular to the retaining wall and located over the hogging zone of the settlement trough, taking no account of initial deflection is conservative since the deflection trend is opposite to the initial settlement. When the longitudinal walls are located over the sagging and hogging zone, the initial deflection should be considered in the sagging zone.

The coupling relationship between structure field and property parameters field in geological space is not considered in current technology of 3D geological modeling, and this situation limits the reliability and the practicality of the computer modeling. Multifield coupled modeling in engineering geological space has become a bottleneck that restricts the development and application of 3D geological modeling. Based on the review of the present situation and development trends in 3D geological modeling, the general research framework and the primary working procedure for multifield coupled modeling in engineering geological space are introduced; and solving means of related scientific problems on multifield coupled modeling are given. The visualization effect of the multifield coupled model is realized inside the 3D geological modeling and visualization system; and the practical effect of those methods is shown in a case study. This research lays a foundation to build the theory and method system for multifield coupled modeling of geological bodies; and also is helpful to promote the deepening application of digital modeling and analytic techniques for engineering geology.

Aiming at the conventional back analysis method easily being limited in local optimization and back analysis data being not visualized, a new global intelligent optimization arithmetic–difference evolution (DE) is introduced and combined with stress return mapping nonlinear elastoplastic finite element method(FEM), realizing rapid elastoplastic parameters identification of surrounding rock. Displaying the element stress, element strain and node displacement by image based on visual class library, the visual platform with high performance of tunnel construction back analysis has been realized. After the introduction of arithmetic theory and program design, the engineering application of the platform is also introduced. The application displays that the platform has high computing precision and has visualized computing result, which provides scientific and high effect mean for tunnel back analysis.

Recently, increasing attention has been given to hydraulic fracturing phenomena in core wall of rockfill or soil dams. However, most of the studies are carried out from the macro prospective, and the fracturing mechanism is still disputable. In this paper, the hydraulic fracturing problem is analyzed using the particle flow code (PFC) from the micro prospective. The occurrence and development of hydraulic fracturing is simulated. Results show that the fracturing pressure Pf increases with the increasing of the vertical stress in an approximately linear way, which agrees well with experimental results. Under the high hydraulic gradient condition, the maximum principal stress near crack tip is decreased because of the wedge effect of water. Hydraulic fracturing will probably occur when the maximum principal stress is less than or close to the water pressure of upstream of core wall. In addition, it is also illustrated that the main reason of hydraulic fracturing in core wall is that the tension stress exceeds the tensile strength of the soil.

Several key issues in three-dimensional numerical analysis of slopes reinforced with anti-slide piles are systematically studied. A large finite element program considering the interaction of pile-soil-slope is used to achieve the factor of safety (FOS) and the critical slip surface (CSS) for the slopes stabilized by a row of piles, some key factors such as computational model scale, pile location, ratio of pile spacing to pile diameter, pile length and contact mode at the pile bottom are adequately discussed combined with a typical slope example. In addition, bending moments, shear force, horizontal displacement and lateral earth pressure for the stabilizing piles under four pile top constraints are also analyzed in detail. Some important conclusions are drawn according to the research results to guide the engineering practice and amend the design code for stabilizing piles, which include: (1) The FOS for a slope with reinforcing piles is the same under five computation model scales such as half pile, single pile, double of half piles, double piles, single pile and double of half piles. However, the computational cost under half pile condition is the least one. (2) The maximum FOS can be obtained when the piles are inserted in the middle of the slope, rather than the top or the toe of the slope. The relation between the FOS and pile location in a slope shows a parabolic curve. (3) The FOS for a slope with reinforcing piles will decrease with the increasing the ratio of pile spacing to pile diameter, the optimal ratio is S/D =2-6, because soil arching is formed between the piles. (4) The optimum stabilizing depth for the pile in homogeneous soils can be chosen to be 2/5 pile length.

In order to quantitatively describe the toughness and stability of a semi-infinite transversely isotropic medium including multiple rectangular cracks, the interaction between two coplanar or parallel rectangular cracks under a uniform distributed normal or tangential load is analyzed; and the corresponding stress intensity factor (SIF) is calculated. By employing dual boundary element method and based on the fundamental solutions for two joined transversely isotropic solids, the variation of the SIF with the distance between free surface and crack surface is investigated. And the influence of the side ratio of the rectangular crack, the free surface and the distance between two cracks on the interaction between two coplanar or parallel cracks is studied. Results show that the existence of the free surface causing the SIF of rectangular crack in semi-infinite extent is bigger than those in infinite medium. The side ratio and distance between two cracks exert an obvious influence on the interaction between two coplanar or parallel cracks, but the free surface has little influence on the interaction between two coplanar or parallel cracks.

Aiming at the difficulty developing large, complicated mechanics simulation program using the fast Lagrangian analysis of continua in three dimensions (FLAC3D) directly, the FLAC3D mechanical simulation program code generation system has been developed. Utilizing geological software Surpac, the programmable components formed by dividing the complicated excavating process according space position, order, structural function and attribution of engineering geological body are researched. The problem of the model unit centroid localization, unit capture, restructure, application variables, FLAC3D variables, function, sentence, the mapping between data structure etc are resolved. Developed by VC++, a particular excavation process simulation code generation FLAC3D mechanical system example is given. This application program uses the database of cell model as a data resource, through a series of steps, the process and parameters of excavation process necessary can be selected and confirmed, which can be transferred to the simulation code generation system, and then the FLAC3D codes will be generated by the application program. The FLAC3D mechanical simulation program code generation system builds a bridge between 3D geological software and 3D mechanics simulating software, can greatly improve the compiled 3D simulation code FLAC3D mechanical efficiency and reduce the programming of the error rate. It is favorable to use the FLAC3D to resolve problems in field of geotechnical engineering largely and deeply.

By treating the girder grillage supported by piles as a finite beam resting on an elastic foundation, regarding the vertical pile and the surrounding soil as springs with different rigidities, and with consideration of the interaction between the pile and the surrounding soil, a differential control equation for the capping beam is established on the base of the Winkler elastic foundation model. The semi analytical power series solutions for the vertical displacement, rotation, bending moment and shearing force of the capping beam under arbitrary loads such as concentrated load, added moment and distributed load are presented. The validity of the presented solutions is verified by the existing rigid-bar method and Newmark method. On the base of that, the influence factors such as the diversity of pile bearing capacity, the reaction of the surrounding soil, the diameter of pile and the load spreading properties on the behavior of the girder grillage supported by piles are discussed. The results indicate that the above factors significantly affect the behavior of the girder grillage supported by piles. With consideration of these above factors, the vertical deformation, bending moment and support reaction on the top of pile of the beam are different from that without consideration of these factors. So in the real engineering design of the capping pile beam, all those influence factors should be taken into account.

The control loads of jacket platform pile foundations are the wind load, wave load, seismic load and other lateral loads. A fundamental study of the soil response of piles subjected to lateral loads is conducted using the nonlinear finite element analysis. A finite element model is established to simulate the response of a pile subjected to lateral loads effectively. The effects of pile properties, i.e. stiffness and diameter and soil properties, i.e., coefficient of horizontal earth pressure, dilation angle on the response of a pile subjected to lateral loads are investigated. In addition, the response of pile groups under lateral loads is also analyzed. Finally, the results of finite element analysis are compared with API recommendations and the model test results. The results of the study show that the nonlinear finite element analysis is accurate in analyzing soil response of piles subjected to lateral loads. The calculation results can provide reference for the pile foundation design of jacket platform.