Based on the framework of damage mechanics for geological materials, a constitutive model is proposed for anisotropic structured sandy soils considering the micromechanism of the destructuring. The Lade-Duncan failure criterion is adopted to consider the effect of intermediate principal stress on the shear strength. An anisotropic state variable A considering the fabric of particle arrangement is employed to reflect the influence of the anisotropy on the mechanical behavior of structured soil. The influence of soil structure on the mechanical behaviors is considered by enlarging the structural yielding surface for reconstituted soils in geometry. The non-associated flow rule is applied to describe a reasonable plastic strain for the anisotropic structured soil. A damage law based on the debonding effect on microscale is used to model the soil destructuring in the hardening law for structured soils. The effect of both plastic volumetric strain and shear strain is considered in the hardening law. Thus, this model can properly describe the mechanical behaviors of soils from intact state to reconstituted state. The proposed model is preliminarily verified by predicting the mechanical behaviors of natural and artificially cemented sands in the triaxial tests.

a new ground improvement method is proposed to treat thick soft soil, which involves the use of concrete-cored sand-gravel piles with combined vacuum and surcharge preloading. In this method, the prefabricated inner piles are used to increase the bearing capacity of soft soil, and the outer sand piles are used to shorten drainage path, transmit vacuum pressures and accelerate consolidation of soft soil. According to the consolidation characteristics of the composite foundation improved by concrete-cored sand-gravel piles under combined vacuum and surcharge preloading, the analytical solutions of average degree of consolidation are derived by calculating the consolidation effects of the composite foundation under surcharge or vacuum preloading separately and then superposing them together. The effects of area replacement ratio of composite pile to soft soil, dimensions and permeability of the smear zone, length-diameter ratio of the concrete-cored sand-gravel column, and area ratio of the inner pile to the composite pile on the consolidation behaviors of the composite foundation are investigated by a parametric analysis based on the proposed solutions. The results show that the consolidation rate of the composite foundation increases with the increase of the area replacement ratio and the area ratio of the inner pile to the composite pile, and decreases with an increase of the diameter ratio of smear zone to composite pile, the permeability ratio of undisturbed zone to smear zone, the length-diameter ratio of the composite pile.

Based on the force equilibrium equations of the sliding mass behind the flexible supporting structure, a functional extreme value isoperimetric model is developed for calculating the active earth pressure with considering the point of resultant force. The problem of concern is cast into a functional extreme-value problem of two undetermined functions by means of Lagrange undetermined multiplier. According to Euler equations, logarithmic spiral sliding surface and normal stress function along the sliding surface are obtained. With combining the boundary conditions and transversality conditions, the conditional functional extremum problem of active earth pressure is changed equivalently into the problem of searching the minimum of unconstrained optimizations of function with two unknown Lagrange multipliers. Two special cases in which the slip faces are plan and arc surface are discussed. For a general soil, the active earth pressure resultant force is minimal when the point of resultant force is on the low limit of location; it increases nonlinearly as the point of resultant force moves up, and the slip face is changed from plan to logarithmic spiral face accordingly. For a sandy soil, the upper limit of location factor increases and the active earth pressure increases as the internal friction angle increases. For a soft clay, the active earth pressure is maximum when the point of resultant force is on the lower limit of location; it decreases nonlinearly as the point of resultant force moves up, and the slip face is arc face and moves away from pit accordingly.

Surface permeability of saturated porous half spaces can influence the presence of surface waves, i.e. Rayleigh and/or Stoneley waves, as well as behaviour of these waves. Rayleigh waves exist in the porous half space with permeable surface, while there are both Rayleigh waves and Stoneley waves for the case of the impermeable surface. Rayleigh and Stoneley waves play important roles in engineering prospecting and acoustic testing, respectively. Therefore, it is necessary to investigate effects of the surface permeability on behaviours of these waves. In this paper, the root searching algorithm of the frequency equations of surface waves is transformed into the eigenvalue problem using thin layer method. According to the behaviour of attenuation of the surface waves along depth direction, the eigenvalues and eigenvectors corresponding to the surface waves can be sifted from the calculated ones. The frequency behaviour i.e. dispersion and attenuation can be calculated from the sifted eigenvalues. The variations of the fluid pressure and skeleton displacements with the depth can be obtained from the corresponding eigenvectors. The influence depth and extent of Rayleigh and Stoneley waves are then analyzed based on those variations for the case of the impermeable surface.

The excavation-induced horizontal movement of soil behind retaining wall is analytically deduced based on displacement-displacement boundary problem under plane strain condition. With respect to two basic modes of wall movement, i.e. translation and rotation about toe, the exact theoretical solutions to horizontal movement of soil behind wall are provided. Specifically for incompressible soil, this theoretical solution has been validated by comparing to the classical Source-Sink theory. It has been indicated that horizontal movement of soil behind retaining wall depends essentially on the mode and magnitude of wall displacement and independent of Young’s modulus of soil. As for incompressible soil, the present theoretical solution may result in well consistent predictions with the classical Source-Sink method. However, Source-Sink method always provides an approximate solution, which tends to underestimate the horizontal movement of soil around the deep position with maximum wall displacement, and overestimate that of soil around the deep position with minimum wall displacement.

The probability integral method is an important approach to predicting mining subsidence, which can be used to calculate surface movement and deformation with normal distribution profile in the gently inclined and inclined coal seams. To overcome the shortcoming of the original method for arbitrary shape face, the integral regions of mining are defined by the strike and dip directions with different integral functions, and divided into several unstructured triangular elements as the basic unit of double integrals. By the double integral conversion method with coordinate rotation transformation, the integral of the basic unit can be converted into double integrals with two lines for the upper and lower limits. When the influence radius of rotation is given, the new double integrals can be calculated using the numerical compound Simpson method to obtain the subsidence at any point on the surface due to the mining of basic triangular element. Finally, the superposition calculation of all basic triangular elements is used to finish the probability integral at any point to predict mining subsidence for arbitrary shape face. The proposed algorithm is implemented in the GIS platform with good results in the case study, providing the support for “under three” coal mining with surface movement prediction.

The set surface perforation is the latest perforating technology which is proposed to improve fracture volume effect. Based on the theory of fluid-solid coupling and rock mechanics, a three-dimensional elastic-plastic fluid-solid coupling stress model for set surface perforation in stratums is developed. Based on the maximum tensile stress criterion, the crack rule of hydraulic fracture is obtained by numerical simulation. It can be seen from abundant calculations that under the condition of set surface perforation, crack first initiates in the perforation of the perforating plane, and then extends in the perforating surface to form a fan-shaped fracture surface, which increase the swept volume of hydraulic fracture and the wellbore connectivity. Both sides of the perforation produce additional stress in the middle perforation to reduce the principal stress of Y direction within the same plane and increase the principal stresses of the X and Z directions. Thus it is the reason that when set surface perforation is adopted for the normal fault, under a larger crack stress, the greater the perforation azimuth angle, the lower the crack pressure. Only when the perforating azimuth angle is greater than 60°, the set surface perforation crack pressure is lower than that of spiral perforation. For reverse fault, the smaller the perforation azimuth angle, the lower the crack pressure, and the crack pressure is lower than that of spiral perforation at any time. Reducing the angle between perforation and perforation, increasing the perforation diameter and depth can reduce the crack pressure effectively.

The indoor slope model tests were conducted to investigate the deformation, water infiltration and failure characteristics of an expansive rock slope under different types of precipitation. Significant horizontal displacement was found under the initial rainfall in continuous rainfall mode, whereas the later deformation was small and tended to be stable. The peak values of displacement and deep rock moisture content were reached at a period of time after rainfall ceased. With the increase of cycle number and rainfall, the slope deformation and the deformation rate increased significantly, and the rock fissures developed further, resulting in an increase in water infiltration depth. This was observed in the soil layer close to the ground surface, but not in the deep rock. The experimental results imply that, due to initial large swelling-induced deformation in the continuous rainfall mode, the drainage and protective measures should be enforced and improved; in the wet-dry cycles mode, the anti-seepage measures for slope surface should be improved to resist the infiltration of rain with the increase of cycle number. In additional, the typical circular sliding failure of purely expansive rock slope was not found in aforementioned two rainfall modes in the tests. However, the engineering slope failure often occurs in the weak interlayer. Therefore, further investigation into the weak interlayer in expansive rock slope should be conducted , and for the mudstone slope without weak interlayer, more attention should be paid to monitoring the shallow deformation characteristics.

To mitigate the erosion problem due to overtopping, the MICP (microbial induced carbonate precipitation) treatment method was applied to the levee surface so that its resistance to erosion was improved. By spraying the bacterial cells and nutrient solutions into the surface sand of levee, the gelation of calcium carbonate can precipitate rapidly in the interspaces, improving the mechanical properties of levee surface sand. To this end, the spray method was first used to treat the surface layer of levee model, and then the flume test was carried out to evaluate the ability of the model against erosion. After the flumes test, the engineering properties of the soil in the model were examined using an unconfined compressive test and hydraulic conductivity test. The experimental results show that the engineering properties of the model soil has been greatly improved. The UCS (unconfined compressive strength) reaches up to 9 MPa. The hydraulic conductivity of the bio-treated sand taken from the levee model is reduced from the initial value of 4.0×10?4 to 7.2×10?7 m/s. In short, the bio-grouting technology has a potential to be used in practice with a broad application prospect in erosion control of levees.

Currently the less effort of research on the theory of space earth pressure behind retaining wall adjacent to existing basements exterior wall has been made. the existing plane strain state theories can’t satisfy the calculation requirement of the earth pressure behind retaining wall adjacent to existing basements exterior wall when the length height ratio B/H of retaining wall is smaller. In this paper, soil arching effects principle is introduced into the space earth pressure calculation model built by GU[8] and a model for calculating space earth pressure is developed considering soil arching effect and existing basements exterior wall. Based on the relationship between the failure space and the distance of two walls, the soil between the retaining wall and the existing basement exterior wall is divided into four districts, I, II, III, IV. Formulas for calculating the space active earth pressure in every district behind the retaining wall are derived by establishing horizontal and vertical static equilibrium differential equation of the horizontal differential element taken from every district. The Formulas can be applied to calculate the active earth pressure wherever behind the retaining wall. Furthermore, the method of resultant force of the space active earth pressure and its position are also put forward. The spatial distribution of active earth pressure behind the retaining wall can be seen visually through the calculation of the numerical examples. Two conclusions can be drawn as follows: When the spatial effect exists, the active earth pressure distribution considering the soil arching effect along the retaining wall is quite different from that when the retaining wall is in the plane strain state; that is, the active earth pressures behind both ends of the retaining wall are much smaller than that in the plane strain state. The position of the active earth pressure resultant force point considering spatial effect is higher than that in plane strain state; and when the B/H gets smaller，the influence of spatial effect on the distribution of active earth pressure along the retaining wall and the position of the resultant force point will increase.

The study of deformation behavior and damage characteristics under coupled thermal-mechanical loading is crucial to comprehensively understanding of the progressive failure law of rock mass in the high-level radioactive waste repository. The aim of this study is to investigate the macro-deformation behavior, damage evolution process, and failure characteristics of Beishan granite after thermal treatment. Granite samples are from Gansu Province a potential site for China's HLW disposal. Triaxial compression tests coupled with transmitted cross-polarized light and X-ray diffraction (XRD) micro-observation are performed on Beishan granite samples under different confining pressures. The mass, density, P-wave velocity and peak strength gradually decrease, while the volume and the peak axial strain slowly increase with the increase of temperature. Accordingly, the peak strengths decrease by 77.70%, 57.28%, 37.33% and 33.97% respectively, while peak strains increase by 196.37%, 115.27%, 105.13% and 90.38% at the 1,000 ℃ under different confining pressures. At the low temperatures and low confining pressures, the failure form of sample is characterized by tensile split, and a number of coalescent axial fissures around fracture surface are observed. The deformation pattern transforms from brittle fracture to plastic shear deformation with steep dip as the temperature and confining pressure increase.

It is great crucial for shale gas exploration and reservoir evaluation to investigate the rupture time and spatial position during the loading process of shale. Brazilian tests on shale were carried out under different angles between the loading direction and bedding planes to examine failure process. The digital image correlation (DIC) technique is adopted to track shale real-time deformation field evolution of crack initiation, propagation and coalescence during entire process, meanwhile, the force-displacement curve is recorded. Scanning electron microscopy (SEM) is applied to obtain fracture surface characteristics and microstructure of carbonaceous shale. Based on experimental data, the relationships between the loading direction and the micro fracture initiation time, spatial location, propagation rules and fracture mechanism of shale are explored. The results show that shale Brazilian disc split strength gradually increases with the increase of the angle between the loading direction and bedding plane. With the increase of the angle, the crack initiation time gradually increases, but the consumed time from crack initiation, propagation to damage decreases. The cracks basically produce from the ends of the specimen and propagate along the bedding plane. The cracks gradually develop from the middle of the specimen to the outside along with loading angle from 0° to 90° except the vertical main fracture of 90° sample. There exists a certain difference between main damage types of different shale specimen with loading directions. The fracture mode gradually transits from tension shear failure to shear sliding failure except the vertical main fracture of 90°sample with the increase of the angle between the loading direction and bedding plane.

In China, Gaomiaozi (GMZ) bentonite has been chosen as a potential buffer/backfill material for deeply buried geological disposal system to isolate the high-level radioactive wastes (HLW). A series of laboratory tests (including swelling pressure test, swelling deformation test and compression test) on two GMZ Na-bentonites (called as GMZ001 and GMZ07) is performed at different initial dry densities. The test results show that GMZ001 has larger swelling pressure than GMZ07 at the same void ratio and is harder to be compressed than GMZ07. On the other hand, the microstructural features of two GMZ Na-bentonites in saturated state are investigated by combining the mercury intrusion porosimetry (MIP) tests and scanning electronic microscope (SEM) observations. The test results reveal that GMZ07 has more inter-aggregate pores than GMZ001 at the same void ratio, and the aggregates of GMZ001 is characterized by more strong hydration compared to GMZ07. The difference in mechanical behavior of two GMZ Na-bentonites is due to differences in the grain size and montmorillonite content. Furthermore, based on the concept of the montmorillonite void ratio, the results of swelling test on two GMZ bentonites under fully saturated condition can be expressed by a unique line, and the predictions of the swelling pressure and deformation are conducted for two bentonites.

A proper degree of compactness is very important for reducing the dilatancy and collapsibility of sulfate saline soil foundation. To investigate the compaction characteristics, the microstructure characteristics of sodium sulfate saline soil with different preparation conditions were investigated using scanning electron microscope (SEM). It is found that the compaction characteristics and microstructure characteristics of sodium sulfate saline soil after compaction are related to the state of sodium sulfate in soil. As sodium sulfate solution possesses lubrication, the compaction characteristic of sodium sulfate saline soil is significantly improved as salt content increases. After the soil is compacted, the soil aggregates are mostly thin layers with smooth surface, and the soil has a rhyotaxitic mosaic structure. However, sodium sulfate decahydrate acts like a scaffold in the soil, the increase of salt content reduces significantly the compaction characteristics of sodium sulfate saline soil. After compaction, the soil aggregates are tiny and round, and the soil has a net-like open structure. The effect of sample pretreatment method and curing time on the compactness of sodium sulfate saline soil are analyzed, and the evaluation method for the compactness is suggested.

The use of cement stabilized marine clay (CSMC) as a filling material for land reclamation has received increasing attention and popularity in recent years. In tropical or subtropical areas, the actual curing temperature in the field can be much higher than the standard curing temperature of 20 ℃ in a laboratory, owing to the autogenous heat generated from cement hydration within the large casting volume as well as the relatively higher ambient temperature. This curing temperature difference is not taken into account in current design practice. Therefore, a series of laboratory tests is first conducted to acquire strength development curves of CSMC samples with different mixing proportions and different curing temperatures, and the influencing mechanism of curing temperature on qu development is then studied. The results indicate that the curing temperature has a significant influence on qu gain. A higher curing temperature gives rise to not only a higher short-term strength, but also higher long-term / ultimate strengths. This finding suggests that it is of practical importance, particularly in land reclamation projects where the volume used is often very large, to consider the curing temperature effect on the strength gain of CSMC. As a consequence, a procedure accounting for the curing temperature effect in the design of CSMC mixing proportion is proposed lastly.

The fracture of rock is the results of a comprehensive role in the process of energy conversion, and the release of the strain energy stored is the essence of rock abrupt failure. The energy characteristics of rock size effect under low / intermediate strain rates have been studied. It is found that the total energy U, the elastic energy Ue and the damage energy Ud at failure decrease with the increasing sample size. Rock strength is related to the stored energy, especially to the stored elastic energy, namely the more the elastic energy, the higher the strength. The stored elastic energy reduces gradually with the specimen length changing from 50 mm to 125 mm. Splitting is the main fracture mode for the short specimens while the shearing fracture mode dominates the longer specimens with evident strain localization. Energy is the inherent impetus which leads to differences of failure in micro, meso and macroscopic characteristics under different strain rates, which is also the intrinsic motivation of the size effect of rock strength.

With regard to the near-field environment of deep geological repositories of high-level radioactive wastes, this study formulated a semi-analytical method for calculating the displacement and stress in the 3D processes of water flow and heat transfer in saturated sparsely fractured rocks. Goodier’s thermo-elastic displacement potential and Laplace transform are employed to calculate the temperature-gradient induced displacement and stress. Considering the case of a rock mass containing one single fracture, Boussinesq’s solution and Cerruti’s solution in the classic theory of elasticity are utilized to obtain the constraint-induced displacement and stress for complying with the boundary conditions, which supplement the temperature-gradient induced displacement and stress to arrive at the total thermal displacement and stress. The fracture is discretized into a set of rectangular elements, on which the integrals involving singularities are evaluated using an analytical method with polar coordinates, whereas numerical integration is employed for non-singular integrals and for the integral concerning the distributed heat source. Comparison with an analytical solution, which assumes one-dimensional heat conduction normal to the fracture walls, indicates that the semi-analytical results are essentially agreeable with minor differences only in the region where the effect of 3D heat conduction tends to be more significant. For a hypothetical 3D water flow and heat transfer process in a rock containing one single fracture, the distributions of temperature gradient induced, the constraint displacement induced, and the total displacements and stresses are calculated and examined, which reveal, among other things, that water flow and heat transfer may exert significant influences on the spatiotemporal variations of the displacements and stresses; and that the compressive stresses may occur in the region that is close to the distributed heat source due to constrained thermal expansion, while tensile stresses may exist in the region that is relatively further away from the distributed heat source due to constrained compatible contraction.

To investigate macro-mechanical parameters of a rock mass slope in Jinping during unloading, a series of unloading experiments on sandstone is carried out in the laboratory. The results show that there is degradation effect on strength and deformation parameters of rocks in unloading process compared to loading failure, and there exist different deformation and failure characteristics under low and high confining pressure. Therefore, based on correction of slope mass rating (SMR) and conventional SMR (CSMR), an evaluation system of unloading rock mass-USMR (Unloading Slope Mass Rating) has been proposed. In this procedure, the excavation method, slope form and unloading damage are considered. Based on USMR, a dynamic analysis of macro-mechanical parameters (deformation modulus Em, compressive strength , tensile strength , and shear strength parameters cm and ) of unloading slope rock mass is made, the effects of different confining pressures and unloading damages (De) on deteriorating law of the parameters of rock mass are examined. The analysis results indicate that in the process of excavation unloading the macro parameters of rock mass degrade in different degrees. The degradation laws of rock mass parameters vary in tensile stress area, low stress area and high stress area. Mechanics parameters of rock mass are more sensitive to excavation unloading in the tensile stress area and low stress area. The results will benefit the stability analysis of slope unloading excavation.

The main control variables affecting the slope stability of stone masonry retaining wall are the verticality of retaining wall i, height of retaining wall h, angle of internal friction of filler , unit weight of slope soil behind the wall , friction coefficient between the soil and the retaining wall base , friction angle between the soil and retaining wall back . In this study, the optimal orthogonal experimental design is constructed, the safety factor of stone masonry retaining wall is calculated based on Coulomb theory and the force polygon method. The slope stability is further evaluated using the cusp catastrophe theory of catastrophe. The results show that six major factors controlling slope stability of retaining wall are in an order of h, , , , I, based on their importance. In analyzing slope stability of retaining wall, slope stability can be evaluated by the mutation progression method, minimizing the effect of uncertainty in employing the traditional minimum safety factor method to evaluate the slope stability.

Saturated sand foundation may be liquefied under explosive load. Structures on the foundation will suffer a dual influence of explosive load and sand liquefaction, which causes uneven settlement and destructive deformation. Based on a large-scale field test of liquefied foundation induced by embedded blast, the dynamic response of the shallow-buried reinforced concrete (RC) structures subjected to explosion and its deformations after liquefaction are examined. It is indicated that, obvious uneven settlement of the RC structure occurs; and the maximum settlement reaches 10% of the height of the RC structure; and differential settlement reaches 1/5 of the maximum settlement. The settlement comes to be stable in 15 hours after the explosion. There is no obvious crack appearing on the surface of the structure; and the dynamic tensile and compressive strains are both under 400 ??, which would not cause significant damage to the structure. The acceleration peak of the column is larger than that of the girder; however, the time required for the dynamic stability of column is shorter than that of the girder, i.e. column suffers a larger instantaneous impulse and has stronger ability to resist instantaneous impulse. The results provide references for the seismic design of shallow-buried RC structures in the liquefiable soils.

Four grade-scaling methods including scalping method, equivalent substitution method, similar grading method and hybrid method are adopted to model the site gradation of soil materials according to the code. 15 test gradations of coarse-grained materials from an engineering site have been simulated by using these grading scale methods, and the corresponding maximum particle diameters are 60 mm, 40 mm, 20 mm. The maximum dry density tests have also been conducted on the samples with test gradations and prototype gradation. The relationships among fractal dimension, grading scale methods and maximum dry density have been discussed by introducing the fractal dimension of particle diameters. It is found that the fractal dimension is a comprehensive evaluation index which can accurately reflects the test gradations by different grading scale methods. In addition, the grading scale methods significantly influence the maximum dry density, and the maximum dry density value of samples by the similar gradation methods is closest to that of prototype gradation, and the biggest disparity exists between equivalent substitution gradation method and prototype gradation. There exists a better linear normalization relationship between the fractal dimensions and the maximum dry density. Based on the normalization law, the maximum dry density of sample with prototype gradation could be calculated accurately.

Because the soil permeability coefficient can be changed while the soil is under loading, the change of soil permeability coefficient should be considered in the calculation of the segment load. Based on the experimental results of permeability tests, the simplified relationship between the permeability and the void ratio of soil is obtained. The coupled fluid-solid models for the segment and the soil are developed, including the seepage model and the mechanical model. The soil is divided into elastic zone and plastic zone in the mechanical model. The elastic zone can be farther divided into three zones according to the relationship of void ratio and permeability coefficient. So the effect of the change of soil permeability coefficient on the segment loading can be analyzed. The coupled mechanical and hydraulic calculation method is obtained through the radius of different zones; thus the seepage calculation and the stress calculation can be connected. The analysis results can be applied to design of bearing ability of the segment in shield tunneling.

A series of direct shear experiments was performed to investigate the influences of pore fluid concentration on the liquid limit, plastic index and shear strength of remolded silty clay. The experimental results indicate that the liquid limit decreases with the increase of pore solution concentration, and the plastic index is similar to that of silt. It is found that the variation of the shear strength with the concentration depends upon the vertical stress applied. For a low vertical stress, the shear strength decreases slightly as the concentration increases; for a medium vertical stress, the shear strength first decreases and then increases as the concentration increases; for a high vertical stress, however, the strength constantly increases as the concentration increases. In addition, the internal friction angle increases with the pore fluid concentration and approaches toward a stable value, while the cohesion decreases rapidly in the early stage, and gradually increases again, remaining at a negative values all the time. These features of the soil behavior can be attributed to the combing effect of electric diffuse double layers, the intergranular stress variation and the void ratio change under coupled chemical and mechanical interactions. Based on the Terzaghi's effective stress principle, the shear strength parameters of the tested saturated silty clay are analyzed, suggesting that the osmotic pressure plays an important role in the occurrence of the negative cohesion of clayey soils.

Due to the advantages of the low cost and construction convenience, the geo-tubes are widely used in reclamation projects to build dikes on thick soft soil foundation. As the bearing capacity of soft foundation soil isn’t high enough,and usually the soil is in plastic flow state, the geo-tubes will penetrate into the foundation soils by squeezing out soft soil when geo-tubes dike is built on soft soils. With increasing penetration, the bilateral load applied on geo-tube dike become bigger. When the basal of geo-tube dike lands on the deep soil layers with higher bearing capacity, the weight of the dike approaches the bearing capacity of foundation soil, the penetration will stop, at this time, the soil attains limiting equilibrium condition. In the actual project, it is crucial to estimate the specified penetration at the design stage of constructing a geo-tube dike, and determine the quantity of the geo-tubes. Based on the limit equilibrium concept, in which the weight of dike and the bearing capacity of the foundation soil are balanced, a formula for caculating penetration depth of geo-tubes is deduced by considering the effect of the soil upheaval on the bearing capacity. The rationality and applicability of the formula is validated by model test results and the observed data from practical construction projects. The results can provide reference for the design of penetration of geo-tubes dike.

Traditional methods for the quantification of subgrade compaction uniformity are all based on the univariate parameters, such as the deviation coefficient. However, these parameters are unable to consider the spatial distribution of the collected data and evaluate the non-uniformity of the compaction state. The semivariogram is modeled to characterize the spatial variation of the compaction values(CV) based on the geostatistics. Then the exponential model is utilized to fit the calculated semivariogram curve. Finally the sill value C is obtained as the uniformity indicator to ensure the subgrade compaction quality. Both the suggested geostatistical method and traditional statistical method are employed to assess the compaction uniformity of the experimental subgrades in Zhijiang construction site of Shanghai-Kunming Passenger Dedicated Line. The results demonstrate that, different from the univariate parameter Cv, the proposed parameter C can not only eliminate the influence of the uncertain factors such as systematic error, but also provide a more objective evaluation on the spatial non-uniform distribution of the subgrade compaction state. The compaction uniformity evaluation specification can be significantly improved by the suggested method.

How to quantitatively describe and evaluate the mining-enhanced permeability for low-permeability coal seams has always been in a blind state, which results in the inadequacy of fracturing measurements and gas drainage during coal mining for local conditions. Mining-enhanced permeability can reflect the influence of mining or other measures on permeability enhancement and also quantitatively evaluate the effect of coal seam permeability enhancement, and its distribution and evolution can be used as a guide to the location of gas enriched area and the rational layout of gas drainage boreholes. The volumetric strain caused by mining is determined by simplifying the model of borehole with cracks. A single borehole algorithm is proposed for mining-enhanced permeability. A field test for detecting mining fracture network is carried out at mining face No.8212 of Datong coal mining group. According to the fracture data of each single borehole, the evolution of mining induced fracture network and pressure are studied, and the evolution of a single borehole mining-enhanced permeability is analyzed. The results show that the fracture network evolution presents a trend of growing out of nothing, growing from short to long, growing from narrow to wide and connecting continuously, respectively. The single borehole mining-enhanced permeability rises at first and then maintains steady as the mining face advances, thus providing a foundation for the design of gas drainage at the working face.

Construction process of shield undercrossing the existing metro tunnel No.1 is monitored. Based on monitored data, the heave/subsidence, horizontal and convergence displacement of the existing tunnel structure are analyzed with the change of the relative position of the shield machine to the existing tunnel. Shield driving parameters have been recorded during the tunneling process. The parameters of shield machine are optimized further through the feedback of line 1 monitoring results, and the existing tunnel deformation is controlled within the permitted value according to the reasonable set of shield parameters. Based on the deformation of built tunnel, it is found that the displacement of existing tunnel is negligible when the cross tunneling is more than 20 meters away. The shield process had a major impact on the left side of the existing tunnel. The results indicate that the displacement process of the interaction of existing tunnel and new tunnel can be divided into five phases.

The dynamic behaviors of shield tunnel are influenced by the coupling interaction between the tunnel lining structure and soil behind lining wall. In order to analyze the tunnel-soil contact coupling mechanism, a shield tunnel in Shanghai metro is selected as study case; the Bucket method is used to analyze the modal characteristics of the tunnel structure under the two different types of contact couplings including node contact coupling and foundation contact coupling. The analysis results are compared to the tunnel modal characteristics extracting from the in-site vibration test data. The results show that constrained by soil coupling, the tunnel structure presents a low frequency characteristic, the first tenth order modal frequencies range are between 0 and 100 Hz, and the modal shape amplitudes are on the order of 10?4 m. And the most important is that there is a small error between the elastic foundation contact and the measured modal characteristics, which can be applied to simplifying the model of dynamic analysis of tunnel structure, and also provide a basis for tunnel structure damage identification based on the modal characteristics.

A general method for geometric morphological analysis of complex blocks is presented by using the Boolean operations; and the corresponding program with C++ is developed. The Boolean operations are conducted with the Boolean intersection, union or difference operation of master and slave blocks to obtain more complex blocks. The concept of degenerate shell vector is introduced into the data structures of blocks to describe the finite discontinuities inside blocks; and then hybrid-dimensional models can be described in a block. The intersecting lines are obtained by conducting intersections between faces in master and slave blocks; and then the separated faces can be obtained by loop analysis. The effective and ineffective faces can be determined according to the specific Boolean operation. The new shells and blocks can be obtained by searching the effective faces. Four examples including one actual project are selected to validate the method. The results show that the proposed method can generate the more complex block and conveniently describe the finite discontinuities, showing that the method is universally applicable to the actual engineering.

A combined method is developed to determine the cohesion and internal friction angle of a dual-pore-fracture medium and the microstructure-traceless tensor technique describing strength anisotropy of a material, which is further introduced into a three dimensional finite element program. Through the comparison of numerical and analytical solutions for a sample calculation example, the reliability of finite element program developed is validated. The elastoplastic numerical simulations of an assumed rectangular underground cave located in surrounding rock masses cut by three groups of orthogonal fractures are carried out by using Mohr-Coulomb yield criterion, and the states of displacement, stress and plastic zone of surrounding rock masses are analyzed. The computation results show that different distributions and combinations of fracture groups result in varied anisotropies in deformation and strength properties of rock masses, accordingly leading to significant changes in distribution and magnitude of the displacements, stresses and plastic zones in the surrounding rock mass.

This paper explores a modelling approach for two-dimensional (2D) and three-dimensional (3D) heterogeneous rock sample containing different types of inclusions base on the level set method (LSM). Taking the elliptical inclusion as an example, its distribution is considered as periodical and random, and the dimension is the same or random in the 2D finite element mesh. The interface between the matrix and inclusions is described by the functions suggested in this paper. Meanwhile, the modelling method for irregular inclusions is also provided using LSM for both 2D and 3D finite element mesh. In the 3D modelling, inclusions are assumed to be spheroid and the distribution also can be periodical or random. The main advantage of this modelling method is that the finite element mesh can remain the same without considering material distributions. In other words, the features of material distribution are separated from the mesh. But it should be pointed out that this method requires high computational resource. Finally, using LSM, the smeared crack model can be used to simulate the features of hydraulic fracture propagation in the heterogeneous rock materials with the same mesh.

The traditional numerical manifold method (NMM) is restricted to the cases of no structure damage when dealing with the discontinuous deformation problems. To overcome the limitation, a high-order NMM for modelling structure damage is further developed by adding the enriched displacement functions for modeling the stress singularity to the physical patches around the crack tips. Then it is applied to the simulation of the fracture process of the gravity dam from continuum to discontinuum. Firstly, sensitivity analysis of the gravity dam with a single crack is conducted; it is found that the crack growth paths are nearly the same as the results in the references, under the conditions of different crack growth lengths or mesh densities. Based on this, the analysis of the multiple cracks growth is conducted; the results indicate that only one dominant crack propagates, which again is quite the same as the result in the references. At last, it is used for the crack growth analysis of Koyna gravity dam, in which the changes of crack growth paths are studied by setting different overflow heights. The results show that the crack growth paths tend to propagate in the horizontal direction and the ability of the resistance to failure of the dam is gradually diminishing. In general, NMM has the good numerical stability and robustness in treating the real engineering problems.

When simulate slope sliding process by grid-based methods such as FEM, element distortion will happen. To solve such problems, a particle contact-based meshfree method (PCMM) is proposed; and a corresponding C++ code is implemented. In this method, the continuous media elements are created based on contact topology of particle DEM; and the elements will be deleted or recreated according to the movement and evolvement of the particle system. The elastoplastic analysis and sliding process simulation of slope are realized by intruducing the softening Mohr-Coulomb model and maximal tensile stress model into continuous media elements. PCMM is uesed to simulate the elastoplastic deformation of homogeneous slope, formation process of sand pile and failure process of soil slope through cases. The results show that the PCMM is an effective approach to simulate disaster range of slope; and it owns enough accuracy when simulating small deformation and large deformation problems.

Ground penetrating radar (GPR) has been widely used in tunnel karst detection as a main tunnel advance geological forecast mean. But its time profile obtained by the analysis software in GPR can only analyze karst qualitatively, and is difficult to determine the size, location, shape of karst cave. In this context, a single channel signal method is developed for calculating karst position and the size based on GPR data. First, analysis software in GPR are used to determine which signal channel a karst is located in, then the data of signal with regard to the karst is extracted by self-compiled program and is transformed using the Hilbert function so as to draw out the figure of instantaneous amplitude, instantaneous phase, instantaneous frequency of signal (denoted as three instantaneous figure). and then mutation point of "three instantaneous figure" of each signal is integrated to determine the starting point and the end point of a karst. At last, the caculated results of all channel signals are united to determine the karst position, size and shape. The proposed method is applied to judge the position, size and shape of the karst at the section of DK189 + 135, DK189 + 75 in Zhongfu tunnel of Gan-Long railway, which proved that the method is applicable.

Most tunnels in China have different degrees of diseases, such as lining cracking, imperfect, lining containing voids and lining water leakage, which seriously influence the traffic safety. Ground penetrating radar (GPR) is used to detect the tunnel lining diseases rapidly and nondestructively. However, the interpretations for lining diseases of GPR detection results strongly rely on the experience of GPR users, which to great extent leads to missing and even wrong judgments. In this study the tunnel lining diseases are classified, and the typical types of tunnel lining diseases are modeled. Finite-difference time-domain (FDTD) method is used to perform forward simulations of typical tunnel lining diseases. For special conditions of water leakage of lining and interference induced by steel reinforcement, the frequency spectrum analysis is used to quantitatively analyze these diseases. Interpretation rules of GPR detection for typical tunnel lining diseases are summarized and further applied to a real project example. The results show that the forward simulations and interpretation rules of GPR detection for typical tunnel lining diseases are reliable.

The borehole shear test (BST) is a direct shear test performed on the walls of a borehole in soil. The test is used to measure the cohesion and friction angle by destructing the soil along the circumference of the hole. The fundamental principle, testing method, and data processing method of the BST are introduced. To evaluate the applicability of this procedure to loess in Xi’an, tests were performed to determine the soil shear strength parameters of loess at several depths by using Iowa borehole shear tester. The results of the BSTs are presented along with the results of laboratory triaxial consolidated-undrained (CU) tests and direct shear tests on samples obtained from each testing depth. The BST results are compared with the results from laboratory shear strength tests. It is shown that there is a good linear correlation between shear strength and normal stress. The BST stress-strain curves of the testing loess show strain-softening behavior. The BSTs yield the cohesion values which are lower than those from the laboratory triaxial consolidated-undrained (CU) tests and direct shear tests, but higher friction angle values than those from the laboratory triaxial consolidated-undrained (CU) tests and direct shear tests. The BST results obtained in homogeneous stratum have little discreteness, and thus a “global failure envelope method” can be applied to the statistics analysis of shear strength parameters.

Foamed mixture lightweight soil (FMLS) is a new environmental protection geotechnical material. It has been applied to embankment filling. However, the issue of optimum casting thickness of each layer FMLS has not been solved yet until now. In this study, a self-developed instrument is used to measure the strength of the FMLS at different depths during construction. The testing principles and steps are given; and the judgment criterion of the optimum casting thickness is determined. Through an engineering case, a method is proposed for determining the optimum casting thickness for FMLS as embankment filling material. It is suggested that the optimum casting thickness should be controlled within 500 mm for test section. This procedure is beneficial to control construction quality of FMLS as embankment filling material.