Deformation reinforcement theory (DRT) advances stability criterion for elastoplastic structures and suggests effective reinforcement to prevent instability. The core of DRT is the principle of minimum plastic complementary energy (PCE): elastoplastic structures deform trending to the state of minimum PCE, or to take full advantage of their bearing capacities while to minimize the required reinforcement. This principle is rederived and the principle of minimum complementary energy for stable states is given. It is shown that DRT promotes finite element method by revealing the physical meanings of the unbalanced force and the modified Newton-Raphson algorithm. By comparison with the rigid body limit equilibrium method, the engineering significance of DRT is illuminated: the traditional action-resistance system in engineering design is extended to action-resistance-reinforcement system, where reinforcement fully described the difference of action and resistance.

The stability of roof is the main factor to determine the roadway section size in the underhand slice stoping with cemented filling method. The failure modes, deformation characteristics of cemented tailings backfill roof and mechanical characteristics of reinforcement are studied by similarity simulation and in situ monitoring according to the actual conditions of Wushan copper mine. The experiment of similarity simulation indicates that the failure mode of roof is not affected by the arrangement of reinforcement in the cemented tailings backfill. And in comparison with the horizontal arrangement of reinforcement, the vertical arrangement is more helpful to enhance the overall stability of roof. In situ strain monitoring results show that the distribution of strain state of filling body roof is more complicated compared with the computation result of simply supported beam. In vertical direction, filling body roof is tensile strain. However, tensile and compression strains alternate with the mining process in horizontal and along roadway direction. Relationship between load on reinforcement and time is obtained by monitoring results of 24 reinforcement metres. According to the mechanical characteristics of reinforcement with the mining process, the process could be divided into four stages: i.e. initial tensile stage, relatively stable stage, alternant stage of tensile and compressive states and the bearing stage. In the bearing stage, reinforcements in the roof bear against the maximum compression before roadway is mined. And after the roadway under the roof has been mined out, reinforcements bear the maximum load of tension and show suspension action. The maximum tensional area lies in the crossing roadway roof.

In weak rock tunnel, elimination of systematic rock bolts is advanced, and the primary support structure is the combination of steel arch, shotcrete, reinforcing mesh, feet-lock rock bolt and longitudinal link steel bar. This paper is based on Baojiashan tunnel. Two test sections are chosen and field test is carried out. With systematic rock bolts replaced by feet-lock rock bolts, two models of systematic rock bolts and non-systematic rock bolts are established and analyzed comparatively. The content of comparative tests includes: the clearance convergence of tunnel primary support, surrounding rock pressure, steel arch stress, shotcrete stress, axial force of rock bolt and longitudinal link steel bar stress. The result shows that the deformation of primary support in the two test sections tends stable and the structure is safe, which shows that the elimination of systematic rock bolts does not affect the security and stability of primary support; some rock bolts in the arch part are subjected to tension; and some are subjected to compression; but the force is minor, and the maximum tensile stress is only 11.8% of ultimate strength of steel, so the support action of rock bolts in the arch part is not obvious; most feet-lock rock bolts are subjected to tension, and the maximum tensile stress is up to 191 MPa, so the feet-lock rock bolts play an important role in the support system. The elimination of systematic rock bolts will reduce construction process, lower engineering cost and shorten procedure cycle time, which is conductive to an early closure of surrounding rock to form a complete supporting structure. It will get a significant economic value and social benefits.

By using Lode angle, a shape function is proposed to describe the curve of strength criterion in octahedral plane, and then the Mohr-Coulomb criterion is revised to predict the influence of the intermediate principal stress ratio on the peak friction angle of soils correctly. The revised strength criterion is shown to be able to produce the same curve with Lade-Duncan’s criterion in octahedral plane, while it is suitable for predicting the strength of loose sands under true triaxial condition. In the loading process, the deformation of soil body often accompanies with strain localization, which makes the mobilized strength of soils to be reduced. The reducing effect on the strength of soils by strain localization is justified by bifurcation analysis. By comparing to the experimental results, it is shown that the mobilized strength of dense sands can be correctly predicted by the bifurcation analysis of non-coaxial plasticity under different intermediate principal stress ratio conditions.

Scanning electron microscope (SEM) was used to observe microstructure of soft clay before and after shearing under complex stress path, which analyzed microscopic nature on anisotropy of normalized shear strength of intact soft clay in three respects including changing characteristics of pore arrangement, changing characteristics of pore pattern and changing characteristics of pore scale. Test results revealed that the pore arrangement was disorder before and after shearing, and changes of pore orientation were very small, which influenced very little on macroscopic properties of clay. Changing characteristics of pore pattern contributed significantly to anisotropy of normalized shear strength of clay in coefficient of intermediate principal stress equal to 0. Changing characteristics of pore scale contributed significantly to anisotropy of normalized shear strength of clay in coefficient of intermediate principal stress equal to 0.5. Therefore, the micro-change factors which influenced anisotropy of normalized shear strength of clay after shearing were different in different coefficients of intermediate principal stress.

Wind erosion failure law of aeolian soils subgrade and the influence of the different subgrade design cross-sections on wind-blown sand are studied through interior wind erosion wind tunnel test. The wind-blown sand’s process of disturbance, accelerating, speed-down, and recovery in different subgrade cross-sections are studied; the characteristic of wind-blown sand field around subgrade are summarized for subgrade defect and subgrade non-defect. The influence factor on the wind erosion failure of aeolian soils subgrade is analyzed. The results indicate that the effect of subgrade height and slope gradient on the wind-blown sand field is obvious; while the change of subgrade’s width can’t affect the flow field notably. The disturbance to the flow field enhances with the increase of subgrade’s height, blow erosion on the top of the windward slope is severe; and heap erosion destroy is brought to the bottom of leeward slope. When subgrade model height is 250 mm compared with that of 60 mm, the wind speed on the top of windward slope increase 1.13 times and decrease 2.53 times at bottom of leeward slope for the certain side slope rate. So subgrade height should less than 2.5m to avoid the wind erosion failure of desert highway. Further, the influence of the different side slope rate on wind-blown sand is analyzed for the certain subgrade height. The change of the wind speed is unconspicuous when the side slope gradient is 1:1.75, the wind erosion failure of aeolian soils subgrade is neglectable.

A lot of on-site monitoring results show that the soil around many underground constructions is still in a state of small strain under working loads. It is important to consider the soil’s small strain stiffness and stress-path dependency in analyzing interaction between soil and structure. Hardening soil model can define loading-unloading characteristics, however, it can not accurately simulate nonlinear modulus because unloading-reloading modulus is not associated with stress and strain level. In this paper, unloading-reloading modulus of hardening soil model is modified so that it is related to both stress and strain levels; and unloading shear strength and scant stiffness of lateral unloading stress path are also considered specially. Finally, the model results are compared with soil stress-path test results to prove the reasonableness of the model.

A series of tests were done to study the influences and variation of strength of a single kind of expansive soil in the process of changing the soil state from nature and unsaturated and no cracks to saturated and no cracks to saturated and cracks fully developed by shear test and triaxial test. Test results show that water content and density and cracks influence the expansive soil strength; and water content and cracks influenc strength more than density does. It is concluded that cracks should be considered within the method of determining expansive soil strength. It is suggested that the strength of sample after 5 cycles of wet-dry should be used as the strength of cracks fully developed expansive soil. By residual strength tests, a conclusion is drawn that the residual strength of expansive soil was in proximity to the strength of cracks fully developed expansive soil; as a result, the residual strength could be used approximately as the strength of expensive soil in the region of cracks developed.

The asymptotic expansion method was combined with micro-based statistical model to develop a two-scale scheme for analyzing the behavior of brittle rock. The material properties were defined in micro-scale and the elastic-perfect brittle constitutive was adopted, the modified Mohr-Coulomb theory and the maximum tensile strength were selected as the fracture criterion. Through calculating in a global-local coupling way, the damage evolution of material in the micro-scale and its effects on the properties of rock in the macro-scale were derived. The scheme included three steps: determining material statistical parameters, determining representative volume element (RVE) and solving boundary equations. The numerical model was realized by the commercial software ABAQUS and its subroutine UMAT. This scheme can be used in the conditions that the rock is loaded with uniaxial compression or triaxial compression with low confining pressure. The regularization method is not used, so the result is mesh dependent after the rock is localized.

In many practical situations, for instance, in jointed rock mass, linear M-C yield criterion may not be justified and a nonlinear Hoek-Brown yield criterion would be more appropriate, so it is necessary to attempt to calculate deformation of tunnel by the criterion. The surrounding rock is divided into three zones: elastic zone, strain softening zone and plastic flow zone. Theoretical derivation on deformation is carried out by Hoek-Brown criterion and non-associated flow rule. Parameters of surrounding rock in strain softening zone are variable and they depend on the plastic deformation of this zone, so it’s difficult to derive the analytical solution for stress in this zone. Runge-Kutta method is used to carry out numerical calculation and the radiuses of strain softening zone and plastic flow zone are calculated. Finally, the deformations of tunnel are calculated. It is demonstrated by an example that the results calculated by the method in this paper and Carranza-Torres’s method are almost the same when strain softening zone and plastic flow zone are not be considered. Furthermore, it is demonstrated by the other example that dilation angle affects deformation more severely when in-situ stress becomes greater.

Two groups of parameters of ellipse-parabola double yield surface model from consolidated drained triaxial tests are used to study the influences of stress-strain relationship by changing one of parameters ? , KG, n, h, m, M1, M2 and pr (keeping other parameters constant). It is found that the volume strain is evidently sensitive to the parameters of h and m. On the other hand, ? , KG and n have significant influence on the volume strain for a dilative soil but little influence for a compressive soil. Parameters of ?, KG, n, h and m have no influence on shear strength that is reflected by the double yield surface model. The parameter pr has little influence on the volume strain and shear strength. In the opposite, parameters M1 and M2 affect the volume strain and shear strength dramatically; and the smaller one determines the strength in the double yield surface model. A parameter, called sensitivity which reflects the influence of model parameter on the stress-strain relation, is defined. It is found that different parameters give quite different sensitivities; and different soils also result in different sensitivities. It is pointed out that more attention should be paid to the parameters with high sensitivity to stress-strain of soil.

In order to decrease the blasting damage to tunnel surrounding rocks, a new charging structure and its mechanism are proposed based on the traditional smooth blasting charging structure. The PVC-U material is placed beside the burn-cut cavities to protect the surrounding rocks of the tunnel. The Φ100 mm Hopkinson test equipment is used for the purpose of researching the weakening level of the PVC-U pipe. The analysis is made on macroscopic damage of the test sample, attenuation of stress wave and dissipation of energy respectively. The test results show that: the stress state of rock is changed by the protective layer and the damage of the rock without protective layer is worse than that with the protective layer; and as increasing of the thickness of protective layer from 0 to 6.24 mm, the degree of rock damage decreases; the stress peak shows decreasing trend; and the reduction rate of peak stress value increases instantly. The ratio of dissipation of energy and the incident is reduced from 61.08% to 39.97%. Thus the conclusion can be drawn that the impact damage of rock is protected by the protective layer. Good results have been obtained in a roadway excavation project.

At the background of zonal disintegration was found in the model test, the strain field of the circular tunnel was studied by using the classical Fenner formula. The discontinuity of the radial strain and the concentration of elastic deformation energy were found at the ultimate balance boundary. The formation of the circular crack which is concentric to the opening is the rupture and separation between the ultimate balance zone and the elastic zone caused by the discontinuity of the strain field. Zonal disintegration is the result of ultimate balance zone expanding to deeper rock mass after the separation. The analysis results explain the non-monotonic under changing laws of the strain and displacement in surrounding rock mass with the distance to the cavity increasing; and the formula of radius of the fractured zones was got and it showed that there exist the equal ratio relations between the radiuses. The value of it was corresponding to the geostress state and the parameter of the surrounding rocks. Taking the parameters in the model test into the formula, it obtained that n =1.1. It matches well with the shape character of the fractured zones in the disassembled model after test.

Groundwater has mass corrosion pollutant because of environmental pollution that has a strong impact on the strength and durability of soil-cement subgrade. The soil-cement blocks has been soaked in different concentrations of vitriol solution for various ages in the laboratory. After testing electric resistivity and unconfined compression strength, the effects of vitriol pollution on soil-cement electric resistivity are presented. The results indicate that the electric resistivity of soil-cement and pore water are decreasing with the increment of vitriol solution concentration while increasing with the increment of age; the formation factor is increasing with the increment of vitriol solution concentration and age; the unconfined compression strength of soil-cement blocks is increasing with the increment of soil-cement electric resistivity. Finally, a formula is purposed to forecast soil-cement electric resistivity at any solution concentration and age.

To better understand the in-situ engineering conditions of frozen ground where the piers of Qinghai-Tibetan ±500kV Direct Current Transmission Line Project will be constructed; the direct shearing creep experiment for frozen silty clay, a kind of soil taken from Wudaoliang on the Qinghai-Tibetan Plateau and remodeled in different moisture contents and densities in laboratory at -2℃, was carried out. The study results show that most creep of the frozen silty clay appears as attenuation creep which has two phases: unsteady creep phase and steady creep phase; only several creeps of frozen silty clay takes on the third phases: accelerated creep phase. The long-term strength of frozen soil could be calculated by the long-term strength equation. The long-term strength of the frozen silty clay closely affected by the moisture content and density of the soil; the frozen soil with higher moisture content has higher long-term strength at low moisture circumstance; but it shows opposite trend at high moisture circumstance; the frozen soil with higher density has higher long-term strength with the same moisture content.

In recent years, with China's social and economic development, more and more cities began to plan and build metros. Meanwhile, the metro construction encountered the sandy pebble soil in some cities, especially the running tunnels of Chengdu Metro line 1 and 2 are almost both need to cross the sandy cobble soil. According to the design, Chengdu metro No.1 and No.2 lines will be constructed by mudding-type earth pressure balance shield. And during shield tunnelling, the face stability control that will be a key operation to ensure the construction can be carried through smoothly. Nowadays, the study of supporting earth pressure is mainly focused on sandy and clay soil; but the study involving the face movement and collapse of cobble-soil is seldom. So based on the heavily discrete characteristics of cobble-soil, the paper analyzes the shield tunnel face deformation and failure while the support pressure is lower than the limit pressure which constructed by using earth pressure balance method and the deformation and failure of excavated face by discrete element method. The results show that: (1) supporting earth pressure of tunnel face is lower than earth pressure at rest; (2) after the face loses stability, the slider ahead of the tunnel face is a surface body. The results will give reference to determine the face control pressure of shield tunnelling.

The causes of piping and sand boiling of shield launching are analyzed; a model that groundwater permeates from reinforced soil pervious underlying layer to wall is established. Using semi-confined aquifer seepage theory, an example is given to demonstrate that, supposing that the reinforced soil is impervious, the accident that water and sand inflows from tunnel portal is influenced by range of soil reinforcement, groundwater level and the gap of wall; the cost and safety of engineering have the positive correlation with the length of reinforced soil; the depth of reinforcement isn’t so deep but reasonable; the gap of wall also plays a key controlling role to shield launching’s safety. The factors are mutual constraint; construction parameters are influenced by security, economy and time limit for a project.

It is of common occurrence that the flood scours the riverbed and the back-silting takes place immediately by turn, which inevitably influences the safety of shield tunnel through the Qiantang River. Hence, how to determine the thickness of covering layers reasonably is an urgent problem to be solved to ensure the safety of tunnel and the construction cost under control. According to the completed study that the riverbed thickness decreases extremely by nearly 16 m after the heaviest flood in 300 years, two embedding schemes of subway line are selected initially. That is, the minimum overburden layer thickness of tunnel is 3.5 m or 4.0 m. The results show that the two schemes are both safe for the tunnel considering the shearing effect of the soil around the tunnel and the one of the bolts between rings. However, in construction, the possibility of floating upward for shield tunnel increases greatly under the buoyant force action of back-filled grouting. More attention should be paid to construction management to minimize the disturbance of soil around the tunnel.

Recently, stabilization/solidification of heavy metals contaminated soils (HMCS) using lime, cement, and other binders has been widely adopted in geoenvironmental engineering practice. In this paper, the mechanisms of heavy metal-soil-binder interaction are overviewed based on literature studies. The performance of various leaching test standards for solidified HMCS is compared and discussed. The unconfined compression strength properties and influencing factors of solidified/stabilized heavy metal contaminated soils are also presented. The leaching properties, durability and long-term performance of HMCS from domestic and international studies are summarized. Finally, based on the current studies in China, it is suggested that the minimum strength requirement of HMCS should be given; and test specification of dynamic leaching tests should be built as the assessment criteria of contaminated lands remediation.

Based on the scheme of underground excavation of tunnel in Qiushui mountain, a finite element model of a shallow buried tunnel beneath an expressway in soft soil region is established, so as to evaluate the effect of tunnel excavation on the expressway above. Considering the minimum embedded depth of the tunnel which is only 4 m and vehicle load on the surface ground of the expressway, a method combined new Austrian tunneling method(NATM) and umbrella arch method(UAM) is put forward in the design. Analysis is performed using plane strain finite element model, which shows the characteristics of NATM by using stress release steps and tracing element. The UAM is simulated by using coupling constraint and spring element. The excavation sequence and support sequence are also taken into consideration in the analysis. As a result of this study, controlling the lateral deformation of the tunnel lining can reduce the settlements of ground surface effectively during excavation; and the method combined NATM and UAM is applicable to shallow buried tunneling especially in soft soil region.

As shield tunnelling method is applied widely, the longitudinal uneven settlement of shield tunnel has emerged because of the comparatively large settlement after construction, and the designing method has been emphasized gradually, which can consider the longitudinal structure characteristics of shield tunnel. For the purpose of determining the longitudinal equivalent bending stiffness, a 3D calculation model has been established, considering the longitudinal bolts’ characteristics and the ring seams’ true splaying states. The results show that some factors related to the ring seam, for example the amount of longitudinal bolts, the assembly pretightening force and segment ring width, influence the longitudinal bending stiffness largely, which increases linearly with the amount of longitudinal bolts and the segment ring width, and which nonlinearly increases with the assembly pretightening force. Other factors related to the longitudinal seam, for example the transverse effective rigidity ratio, influence it less. The results provide key parameters for the longitudinal design method of shield tunnel.

The increment of sodium montmorillonite crystalline interspace caused by tap water is greater than KCl, NaCl, CaCl2 solutions with different salinities; adding different types of salts into water can stabilize sodium montmorillonite clay mineral and inhibit the expansion of crystalline interspace. The increments of crystalline interspace affected by different salinities and types of solutions are different. Comparing three kinds of solution KCl, NaCl, CaCl2, the variation caused by KCl solution is the least; the crystalline interspace variation is only 1.32% under the saturated KCl solution. When sodium montmorillonite contacts with different types of solution, the crystalline interspace increment decreases and gradually tends to be stabilized with the increasing of solution dosage. The hydrate expansion capacity of sodium montmorillonite has no direct relationship with the total solution dosage; when the clay mineral is soaking in water, interspace will not expand unlimitedly as the increase of the total volume of water. When contacted with the same dosage but different types of solution, the crystalline interspace changes as complex exponential function with the increase of contact time; in shows the characteristic of mutation increasing in the initial stage and quickly tending to be stabilized.

The environmental effect of soil contamination recently has aroused considerable public concern since the increasing soil pollution, however, less attention was given to engineering properties of contamination laden soil. Therefore, the influences of sodium dodecyl benzene sulfonate on the mechanical characteristics of loess have been investigated by the authors. It has been proved that the pollution can weaken the loess, reducing cohesion, compression strain and permeability, as well as limiting collapsibility. Moreover, the contamination mechanism towards soil mechanical characteristics was discussed with the assistance of scanning electron microscope in junction with the soil water characteristic curve. It is necessary to prevent the deteriorated effect of anionic surfactants on the loess in the engineering in future. Simultaneously it could be applied to reducing the collapsibility of loess.

If acceleration of rock mass is too large, the surrounding rock of underground cavern is not stable. By analyzing time-history curves of acceleration obtained by model test, the acceleration response characteristics of surrounding rock with different anchorage parameters in underground cavern subjected to explosive loads are studied. The forms and peak values of the time-history curves of acceleration of underground cavern’s crown, floor and two sides are explained respectively. Because of the different reinforcing modes, the distinctions of the acceleration response of surrounding rock of underground cavern are compared emphatically. The results indicate that the time-history curves of the vertical acceleration of crown and the horizontal acceleration of floor right side are smooth enough; but the vibration of the time-history curves of the vertical acceleration of floor and the left side are larger than the others. The acceleration of the crown is the largest than the other positions. For the cavern of the smallest spacing of rock bolts in four underground caverns, the acceleration of its crown and two sides is smaller than the other caverns; but the acceleration of its floor is larger slightly than the others’. By means of comparing and analyzing above, reducing the spacing of the rock bolts can enhance the stabilization of underground cavern.

Computation of earth pressure acting on retaining structures constitutes an important research subject in the field of geotechnical engineering. In many engineering practices, the retaining wall displacement causing the backfill yield sufficiently cannot take place so that the earth pressure may fall anywhere between active and passive earth pressures. Besides, due to compaction, the backfill is always dense and its shear resistance will decrease from peak resistance to residual state during shear. However, classic Rankine and Coulomb earth pressure theories can only evaluate the earth pressure at the active and passive state. And they cannot consider the effect of reduction of post-peak shear soil resistance on earth pressure. The development of earth pressure at the passive side with wall displacement is studied. On the basis a new methodology is developed to evaluate earth pressures at the passive side under any boundary strain constraint for a rigid retaining structure with translational movement. It can take into account the effect of wall displacement and the strength characteristic of dense sand on earth pressure. The agreement of calculated results with the experimental ones confirms the correctness of the proposed method.

The researches on the quantitative analysis of ground settlement induced by the shield tunnelling workmanship are relatively less. In this paper, three workmanship parameters, i.e. grouting filling ratio, shield pitch ratio and support pressure ratio, are introduced into the gap parameters to make the quantitative analysis of ground settlement based on Loganathan expressions. The deep discussion about the equivalent circle zone which was proposed by some scholars is made to provide the basis of numerical analysis for the shield tunneling project. The back analysis of the Xi’an metro line-2 is carried out to validate the rationality of the method introduced in this paper. It is shown that the method can factually reflect the workmanship level and offer a certain reference to the control of the ground settlement during the shield tunneling.

Based on the Xi’an metro shield tunnel traversing old loess strata, dynamic tracking measurements of water pressure, earth pressure and structure internal force (axial force and bending moment) are carried out to analyze influences of the shield tail serum injection, cylinder thrust force, soil stress relaxation and water pressure on the distributions and varying laws of segment ring. Combining with field test data of internal force, the distribution mode and value of the load pressure on the segment lining in old loess strata are back analyzed by using orthogonal design method and defining target function. Internal force which are calculated by using optimized design parameters are quite close to measured value in magnitude and distribution. The results show that the analysis method proposed is feasible and reasonable; so it can be used for reference of similar projects.

Because of different compositions and depositional environments, the natures of dredger fills are different. In this paper, Tianjin marine soft soil is used as material to simulate site environment to study the strength growth in soft dredger fill. Experiments show that the different conditions of pressure and drainage affect the growth of soft dredger fill greatly. When conditions are conducive to the drainage of water in soil, the growth of strength is significant. The effect on soil strength growth by overburden pressure is through some possible drainage; when drainage conditions are bad, and the pressure increased, the strength grows slowly and little; on the contrary, it grows faster and absolute value is large.

The dynamic responses of a pile foundation under hammer impact are analyzed. The concrete pile in soil is modeled as a (standard linear solid) viscoelastic rod buried in a (Voigt-type) viscoelastic media. The upper end of the pile is subjected to a mass impact; and lower end is supported by a spring-dashpot foundation. Governing equations for the pile movement are given. Coupled boundary conditions at the upper and lower ends are deduced respectively using the dynamic equation for the hammer and the constraint equation for the foundation. The initial-boundary value problem is solved by using Laplace transform with respect to time variable to the equations. An exact solution for the stress distribution in the pile is obtained in the transformed domain. Using numerical inversion technique the stress-time curves at any sites of the pile can be calculated. Examples are given to show that the approach can be conveniently applied to analyzing the generation, propagation, reflection and interactions of the viscoelastic stress waves in the pile.

n view of old landslides, four kinds of indices including nine secondary factors, i.e. landform characters, slip surface characters, landslide body structures and recent activities signs, were chosen as the discrimination indices for potential landslides. According to discriminant analysis theories, distance discriminant analysis(DDA) models and Fisher liner discriminant analysis(FLDA) models were respectively built for potential landslides in the Three Gorges Reservoir and the upper Minjiang River areas based on the same number of training samples. The results show the error rates of DDA method were both 0% for testing and training samples, while the error rates of FLDA method were respectively 11.1% and 0% for testing samples and 5.56% and 11.11% for training sample in the two study areas. So, DDA method has much higher prediction accuracy than that of FLDA method for discrimination of potential landslides in the two study areas.

In order to enlarge the usage extent of roadbed fillings of high-speed railway, the stress-strain relationship and failure shapes were studied on the cement- and lime-modified soil under different freeze-thaw cycles, cooling temperature and confining pressure. The results showed that stress-strain relationship of cement soil was work-softening. The stress-strain relationship of lime soil turned into work-hardening subjected to freeze-thaw cycles. Cement soil was mainly in a brittle failure state, and lime soil was in a ductile failure state. The effects of confining pressure on stress-strain curves of modified soils were not distinct, and the peak strength of modified soils increased with the confining pressure increasing. The cohesion decreased with increasing of the number of freeze-thaw cycles, but there was no changing law for the internal friction angle. The effect of cooling temperature on the cohesion was not obvious. The improvement effect of cement was superior to lime under repeated freezing and thawing.

The actual stress state of embankment installation slab-culvert was not accurately reflected by the calculation method of earth pressure in the prevailing Chinese General Code for Design of Highway Bridges and Culverts. So the deformation laws and stress characteristics of embankment installation slab-culvert under fill-load were studied based on field test and FEM numerical simulation. Meanwhile, the key influencing factors, such as the height of embankment fill, the characteristics of fill, the dimensions of the culvert and the elastic modulus of the ground on the structure deformation and stress characteristics were also discussed. It is shown that the bending unloading effects of the top slab, the bottom slab and the lateral walls of the culvert were generated under the fill load, the distributions of vertical earth pressure on the top slab and the bottom slab, as well as the lateral earth pressure on the walls are all nonlinear, they are significantly different form the results calculated by the code method. With the increasing of the embankment fill, the earth pressures on the mid-span of the top slab and the bottom slab, as well as the position near 7h/8 (h is the height of the culvert wall) of the walls has a trend of slow increase; however, they are rapidly increased away from the above- mentioned position. The influence of the factors on the stress state of embankment installation slab-culverts should be comprehensively considered in the design and construction procedure.

SHALTAB combines steady state hydrology assumptions and the infinite slope stability model to evaluate the distribution and the trend of shallow landslide. Taking Huachi county of Longdong in Gansu Loess Plateau region as study area, the availability and reliability of SHALSTAB for slope stability analysis of the loess gully area are evaluated. The degree distribution map of stability index is obtained by the digital elevation model constructed from 1:5 000 scale contour map, the slope of the terrain from DEM, physico-mechanical parameters of loess provided by field investigation and laboratory tests, and soil thickness data got from materials of boreholes and exploration trenches. By comparing the distribution of landslide from field surveys with model predictions, it is shown that the overall accuracy is 70.23%; landslide prediction accuracy is 72.33%; stability prediction accuracy is 67.51%. The simulation results are rational.

A new method of subsoil damping ratio identification based on law of conservation of energy is proposed. This method considers the whole time histories of vibration, differs from the traditional damping ratio identification method in the time domain which uses merely the amplitude to calculate damping ratio, and overcomes the defect of the traditional logarithmic decrement method for high accuracy requirement of amplitudes. The subsoil damping ratio of a massive concrete foundation is tested and calculated. The results of numerical simulation and actual test show that this method is of higher precision, stronger anti-noise ability and better stability compared with the traditional logarithmic decrement method. Even if the data acquisition is disturbed seriously by noise, the method proposed is effective and reliable.

JG(jet grouting) soil-cement-pile strengthened pile, simply called JPP pile, is a new sort of composite pile used in soft foundation. It may improve the vertical bearing capacity effectively; and it has been practically used in a considerable scale. In order to study the behaviors under lateral load, large-scale model test is carried out, using large test room made by Hohai University. It is shown that the JPP pile could improve horizontal bearing capacity by about 15% compared with bored concrete pile; and the biggest bending moment of JPP pile is located in the place 2 m below the pile tip; and lateral earth pressure is concentrated in the top 2 m soil. Meanwhile, with a cap added, JPP pile has a much higher horizontal bearing capacity. According to the formula for bored concrete pile based on m method, which standard remmends, horizontal bearing capacity of JPP pile has been calculated; and calculation results basically coincide with the experimental results. The results may be useful for the practical engineering and analysis of JPP pile in the similar soil layer.

Based on conditional probability evaluation method and systematic engineering theory, considering key block as the important part of blocks system, the evaluation method of reliability of key block was analyzed, then we discussed the inner-relationship between key block and secondary key block, and following the same thought, we knew the relationship between secondary key block and the following block easily, so it would be possible to establish the systematic blocks evaluation model if we had gotten the reliability result of each block. With the reliability evaluation formula of Series System, we could calculate the reliability of systematic block. The suggested method was applied to a hydropower project in Southwest China so as to test its reasonableness. The results demonstrated that it was more coincidence to practical situation of the engineering than traditional evaluation of key-block theory. It would have some extent reference for the research of systematic blocks theory.

Based on mesoscopic damage mechanics, dynamic numerical code RFPA2D is developed to simulate the dynamic failure process and dynamic properties of inhomogeneous medium in large diameter split Hopkinson pressure bar (SHPB); the influence of waveform loaded to incidence bar and inhomogeneous medium on test results including stress-time curve, strain-time curve, stress-strain curve and strain rate-time are analyzed. The results of numerical analysis indicate that, when the diameter of SHPB is large, the geometric dispersion effects due to radial inertia become very important; and when the appropriate waveform is loaded, the dispersion effects in wave propagation can be reduced so that the more exact results is obtained; for example, triangle wave which may reduce dispersion effects is the appropriate loading waveform in dynamic test of inhomogeneous medium such as rock by using SHPB. Moreover, the influence of inhomogeneity of medium on dispersion is not obvious; and the change of test curve of inhomogeneous medium is larger than that of homogeneous medium after wave crest; it is caused by different distributions of failure unit in inhomogeneous medium, not dispersion of wave.

The rheological property of anchorage interface is one of important problems of anchorage time-effect in underground engineering. Aiming at the defects of hard contact formulation in normal direction and discontinuity from bond to slip in tangential direction when analyzing long-term stability of underground engineering, a contact formulation which is an exponential softened pressure-overclosure relationship in normal direction and a continuous nonlinear constitutive model in tangential direction are proposed. The model solves the problem of converging hardly and reflects the process of shear rheological behavior truly and reasonably because of its consideration of normal stress. By the further development of ABAQUS code, the nonlinear rheological model of anchorage interface is applied to analyzing time-effect of anchorage in underground engineering. The main achievements are conducted as follows: anchor stress will increase with shear rheology of anchorage interface, the location of anchorage peak stress will change and move towards the end of anchor with the lapse of time. The research results provide the theoretical basis for deeply researching the reliability of anchorage in underground engineering.

Diffraction of plane P waves around a local fault is presented in frequency domain using IBEM，in which, the dynamic stiffness matrix and Green’s function for distributed loads acting on inclined line by Wolf are used. The paper discusses emphatically the dynamic response to the surrounding rock of the narrow fracture zone and the effect of the dynamic characteristics of layered site on the diffraction. It is shown that a local fault has great effect on wave diffraction. Even if the local fault is very narrow, significant amplification may appear. The dynamic characteristics of layered site also play an important role in the wave amplification.

The three-dimensional (3D) transient dynamic response of transversely isotropic saturated soils due to surface loads is studied. First, based on Biot’s 3D wave theory for fluid-saturated porous media, the governing differential equations in cylindrical coordinate are presented by Laplace transform. Then, according to operator theory, the general solutions of soil skeleton and fluid displacements and pore pressure as well as the total stresses for saturated soils are presented by means of Fourier expanding and Hankel integral transform. Furthermore, using general solutions, the transient solutions for Lamb’ problem of transversely isotropic saturated half-space to impulsive concentrated loading are presented. Numerical results show the obvious difference between the model of isotropic saturated poroelastic media and that of transversely isotropic saturated poroelastic media.

A method to calculate the time-history of safety factor of slopes subjected to seismic load is given. At every moment, the stress field got from dynamic finite element analysis, and the critical slip surface is searched by genetic algorithm. So, the time-history of factor of safety is derived and has definite physical meaning. By inputing sine wave acceleration with different periods from the bed rock, the relation between the period and the factor of safety is studied. The results show that as the period of input becomes longer, the factor of safety becomes lower. The natural period and mode shape of the slope are investigated; and one can find the amplification of dynamic response cause by the coupling of the load period and the natural period of slope not only depends on the coupling of the period, but also the mode shape of the slope. Only when the mode shape is a vibration of the slope itself, the dynamic response will be amplified and the factor of safety will decrease.

According to a big karst cave in highway tunnel engineering of Qing-Lian Expressway in Baixugong, a three-dimensional element software (ANSYS) was employed to simulate the interaction between tunnel excavation and treatment structure in Baixugong tunnel. Stability of treatment structure and surrounding rock during tunnel excavation is studied in order to analyze the mechanical characteristics of treatment structure and the displacement of surrounding rock during tunnel excavation. According to analysis of calculation results, the pre-support effect of treatment structure in karst tunnels is evaluated. Treatment mode using pile-pile cap-one-wall support wall-connection beam, is safe and reliable. In the process of tunnel excavation, the pile strain and support wall stress all increased largely during the advance of excavation face, then gradually stabilized; and the treatment structure bears a part of surrounding rock pressure, it plays a support action role in karst tunnel excavation. The results are in good agreement with the field test data, so as to offer for reference in design and construction of tunnels crossing a big karst cave.

A double media mathematical model is established according to the feature of the Xinjiang carboniferous volcanic rock gas reservoir; the cross flow among the matrix pore-fracture-borehole is studied by means of the numerical simulation; and how the interporosity flow coefficient λ influenced on the rate maintenance capability is analyzed quantitatively. Results indicate that there are two periods in the process of cross flow: transition period and stabilization period. In the transition period, the cross flow amount is smaller than the bottom hole inflow, and the bottom hole pressure drops quickly; in the stabilization period, the cross flow amount is equivalent to the bottom hole inflow, and the bottom hole pressure flattens out. The time needed from transition period to stabilization period is depended on the interporosity flow coefficient ?; the greater the ? , the shorter the time is need. If ? >10-7, interporosity flow has little influence on gas well production. If ? <10-8, stable yields is greatly influenced by the interporosity flow, and it is important to fix production according to the interporosity flow coefficient ?. Finally, an example is given to verify the correctness of these results.

Based on the non-Darcy flow described by non-Newtonian index, the theory of one-dimensional consolidation is modified to consider a linear variation in the additional stress with depth and the effect of time-dependent loading. The numerical solutions are derived in detail by FDM for pore water pressure and the average degree of consolidation. The influence of various parameters on consolidation behavior is investigated. The results show that the rate of consolidation is reduced when non-Darcy flow is considered; furthermore, the greater the non-Newtonian index, the slower the rate of consolidation. The greater the thickness of a soil layer, the slower the rate of consolidation. Thus, the classical similitude with non-Darcy flow between laboratory samples and field layers is no longer satisfied. The greater the value of the additional stress in a foundation, the faster the rate of consolidation. The distribution of additional stress has a great influence on the rate of consolidation for the case of single drainage condition; on the contrary, the rate of consolidation is independent of the distribution of additional stress for the case of double drainage condition. The faster the loading rate, the faster the consolidation rate. Finally, applicability of Darcy’s flow to consolidation deformation is discussed.

The bearing performances of the composite foundation improved by single-flexible-pile or multi-flexible-pile are calculated by using the FEM software ANSYS. Factors such as load, pile area replacement ratio, pile’s length-diameter ratio and pile’s distance-diameter ratio, have been taken into the consideration. Results show that in the composite foundation improved by single-flexible-pile, the distance of pile’s axial stress peak point to the pile’s top is about 0.1 time of pile’s length with the increasing of load and pile’s length-diameter ratio, while, the settlement tendency both pile and soil are similar. The pile’s bearing performance is increased with the increasing of pile area replacement ratio; but the settlement tendency both pile and soil are opposite, which affects the composite foundation’s settlement. In the composite foundation improved by multi-flexible-pile, the changes of load and pile’s distance-diameter ratio have no influence on loads shared by piles and result in the same tendency for the pile and soil’s settlement. The change of pile’s distance-diameter ratio has more influence on loads shared by piles and results in the soil’s settlement more than the piles’ one, which has the obvious influence on the composite foundation’s bearing performances.

An improved Hvorslev envelope-based three-dimensional elastoplastic model for overconsolidated clay was proposed by Yao et al (2009). The return mapping algorithm is adopted in order to implement the model into a finite element analysis software ABAQUS through the user material subroutine (UMAT) interface. By coupling the model with Biot’s consolidation theory, three dimensional coupled analyses of an overconsolidated clay specimen in triaxial compression and extension and plane strain stresses are performed. The numerical results show that, different stress paths are seen inside and outside the shear band. The elements in the vicinities of the shear band take on volume contraction, dilatancy and contraction due to being sucked, while the elements inside the shear band keep the dilatancy during shearing. Dilatancy is accompanied by the development of the shear band, so the negative pore pressure appears inside the shear band and their vicinities. The changes in the pore pressure and volumetric strain in plane strain are between triaxial compression and extension stresses and depend on the shear velocity, but the shear bands early occur in plane strain condition. The migration of the pore water controls the formation and development of the shear band. The confining pressure and location of the weak element also play an important effect on the formation of shear bands.

The plastic characteristics of the coal seam floor has been explored with the finite element strength reduction software of ANSYS; and its plastic area perforation process is given; and that the slip lines given by this methods are much close to theoretical solution; the plastic failure fields depth of the coal seam floor similar to Prandtl type; some parameters are compared with that by theoretical solution; the error is less than 10% so as to show that used the finite element intensity reduction method to solve floor damage situation is feasible. The scope of its plastic area can be used to reserve the safe thickness in water inrush from coal seam floor and the maximum effective spacing of liberated seam; then further utilizes in liberated seam to obtain its plastic area and slip lines.

An analytical solution is derived for seepage flow into a lined tunnel in a semi-infinite aquifer by assuming the soil and lining are saturated, homogeneous and isotropic media. Using the conformal mapping, the soil region is transferred into a cirque, and the flow in the soil region, as well as in the lining region, can be described by Laplace equation in a ring domain. The seepage inflow volume and hydraulic head along the tunnel circumference are solved by Fourier method for the Dirichlet problem. The influence of radius, hydraulic conductivity and internal water pressure on the seepage inflow volume and hydraulic head along the tunnel circumference is discussed and compared with numerical simulation. The comparison shows the analytical solution is a simple, convenient and practical calculation for shallow tunnels.

An apparatus for specimen preparation and test on contact behaviour of idealized bonded granules is designed, which can be applied into the verification of contact model and parameter rationality for natural structured sand in the discrete element method (DEM). By using the specimen preparation devices, two aluminum rods with the same size are glued together by adhesive in a pre-defined mode. By using the auxiliary loading devices, the mechanical behaviours of contact between the bonded rods are obtained under simple and complicated conditions. The results show that the apparatus can be used effectively in test on contact behaviour of the bonded rods. The mechanical behaviours of contact between bonded rods agree well with the bonded materials contact model implemented by the discrete element method. The peak shear and rotational strength of the bonds increase with the increasing of normal force. The strength envelope in the normal-torsion-shear stress space is an elliptic paraboloid shell.