Ground would settle while ground is subjected to surcharge loads. The deformation or break would happen in the walls of the pipelines in the ground due to the settlement. This paper focuses on the effects of ground surcharge on adjacent buried pipelines. A calculation model is established with the theory of Winkler elastic foundation short beam and Boussinesq basic formulas, taking into account the impact of subsoil deformation induced by ground surcharge on pipelines. The solution is derived with the finite difference method. Consequently, cases are performed under various loads, location of the load, geologic condition, pipeline depth, diameter and stiffness of pipeline as well as property of soil. Results show that: after increasing to a certain threshold, the pipeline diameter and the coefficients of foundation bed would have a relatively small impact on the pipeline maximum displacement. However, the buried pipeline deforms significantly as the burial depth decreases. As expected, the maximum displacement of pipeline decreases while the pipe stiffness increases and the location of ground surcharge loads pose large effect on buried pipelines. So it is necessary to consider the surcharge loads and make a reasonable protective measure for buried pipelines.

The naturally cemented calcareous soil is a carbonate soil or rock cemented by high-magnesium calcite or aragonite. It usually contains a large portion of coral and other tropical marine organism. Its unique engineering properties often result in troubles and difficulties in the geotechnical design and foundation construction. Its characteristics also attract research and experimental interests of many researchers. This paper presents state-of-the-art review of developments of the laboratory tests on both naturally and artificially cemented calcareous soils as well as the sample preparation techniques of artificially cemented soils. The general stress-strain behaviors of the cemented calcareous samples and factors that might affect its characteristics, such as confining pressure, initial sample density, and degree of cementation, are also summarized. The research work that could be improved is also proposed with an objective of providing a research guideline for the further studies of cemented calcareous soils.

The secondary consolidation of soft soil is very important for the deformation of soft soil. In the calculation of secondary consolidation of soft soil, the secondary consolidation coefficient is usually used as a calculation parameter, but this coefficient does not reflect the impact of variation for loading, and it can only apply to the normally consolidated clay. The over-consolidated clay is mostly encountered in many engineering projects. The laboratory experiments are conducted to study the secondary consolidation settlement of soft soil. The consolidation test is carried out on multiple sets of undisturbed soft clay samples. The test results show that for the calculation of secondary consolidation of soft soil, the secondary consolidation should be studied from the aspects of the strain and time; a hyperbolic form fitting is used; the strain parameters for the normally consolidated and over-consolidated soil are analyzed to establish a one-dimensional model of secondary consolidation of empirical formula. A secondary consolidation settlement calculation method is proposed considering the pressure effect on the secondary compression; the method is applied to the engineering project. It is validated that the method can be applied to the normally consolidated and over consolidated soil; it makes the consolidation of soft soil subsidence calculation more approaching the actual engineering problems.

Geotextile bag buried in subgrade can improve the bearing capacity of subgrade and also reduce or isolate vibrations. A series of horizontal cyclic shear tests are carried out to investigate the dynamic characters of piled geotextile bag. The test results indicate that geotextile bag is excellent materials for base vibration reduction and isolation as it has variable horizontal stiffness and large damping ratio. The damping ratio of geotextile bag decreases with increasing of vertical pressure, and increases with the increasing of maximum shear strain. Besides, the discrete element analysis is carried out on a geotextile bag under cyclic loading. The contact between soil particles in geotextile bag is modeled as a spring-dashpot system. The geotextile bag is modeled as coating of small particles with tension. The contact between the small particles in coating is also spring-dashpot system which has no tangential contact but only normal contact, and can only carry tension stress. The simulation results illustrate that the vibration reduction of geotextile bag is due to the energy dissipation mainly resulting from frictional and viscous forces among soil particles and the tension of bag. Moreover, in-situ tests are performed on a trench built with geotextile bag to validate the vibration reduction and isolation effect of geotextile bag.

In order to investigate the shear characteristics of salt rock in brine soak environment during the process of salt cavern building, an orthogonal experiment is designed to investigate the influences of brine soak time, temperature and loading rate on the shear properties of salt rock. The experimental results show that: brine soak weakens the shear strength of salt rock, and the longer the brine soak time is, the lower the shear strength of salt rock is, but the shear strength will be stabilized eventually; the increasing of brine temperature exacerbates internal damage of salt rock, which decreases shear strength; the shear strength of salt rock, soaked in a certain temperature brine, decreases with the increasing of loading rate. And the ductile characteristics of salt rock are gradually weakened with the increasing of soak time, temperature and loading rate. The binary linear regression is respectively conducted by any two factors, the relative importance ratio is used to build judgment matrix according to the standardized regression coefficients for salt rock’ shear strength, and weights of various factors are calculated by analytic hierarchy process. The weights of temperature, loading rate and soak time respectively are 0.397, 0.340, and 0.263. The results of range analysis and weights calculation show that the primary factor affecting the shear strength of rock salt is temperature, and the secondary factor is loading rate, followed by the soaking time.

This paper aims to study the development and distribution features of the force and earth pressure of cantilever fender pile. Data used in this paper are obtained from the field experiment on the construction site of Xining railway station; and an analysis is carried out on the basis of these data. The behavior of cantilever fender pile under different excavations and the development of internal force are presented. Experimental data obtained from the field test are different from the theoretical values, so it is necessary and feasible to adjust and optimize the reinforcement, concrete design and embedment depth. Strategies for optimization are put forward. The experimental earth pressure is less than the Rankine pressure of the classical earth pressure theory. Results of this paper can effectively optimize the pile design, and can also provide monitoring and controlling for the force and deformation of supporting structure in soft rock pit excavation.

By using wave function expansion method and image method, scattering of a salient and a circular cavity with SH wave in an elastic quarter space is analyzed to obtain the steady state solution. The elastic quarter space which contains a salient and a circular cavity is divided into two media, while medium I is a quarter spaces which contain a circular cavity and a semi-circular canyon, medium II is a circular domain. Conjunction condition is introduced to force displacements and stresses of two media continued on the divided bound. Specific expressions of constructed displacement wave in medium I and medium II are determined by employing stress free condition on cavity bound and conjunction condition by using wave function expansion method and Fourier series expansion method. Simultaneously, the analytical solution is presented by solving truncated linear algebraic equations of definite boundary conditions. Numerical results are calculated to describe distribution of dynamic stress around the circular cavity and amplitude of displacement along the horizontal surface, then, effects of salient, cavity and stress free bounds of the quarter space to scattering and seismic ground motion are quantified.

Soil movement laws induced by shallow tunnel excavation had been covered by many researchers, but the research on the horizontal displacement induced by tunnel excavation is insufficient. Based on the summary and comparison of three formulas of soil layer’s settlement, a formula for calculating the horizontal displacements in the soil above the tunnel is derived by combining one of the soil settlement theories and the assumption that soil is incompressibility. Results of the formula are compared with the published data in relevant papers and verified by the finite-element simulation results. It is shown that the derived formula is capable enough for forecasting and describing the horizontal displacements of the soil induced by shallow tunnel. In addition, the vector angle’s formula of soil’s displacement is obtained based on the formulas of soil settlement and horizontal displacement; and it’s also compared with O’Reilly and New’s method. The comparison shows the agreement with some researchers’ published relevant conclusions, which verifies the applicability of this formula for soil displacement. The research results will provide theoretical references for calculating and controlling the horizontal displacements of soil in relevant practical projects.

Tests for time-dependent characteristics of cement grout are carried out, which find that cement grout of commonly used water-cement ratio conforms to Bingham fluid. Viscosities of grouts with different water-cement ratios increase greatly as grouting time increasing. According to the experimental results, considering the time-dependent characteristics of viscosity of cement grout, the diffusion law and model of pressure on segments of shield tunnel of backfilled cement grouting are found and derived respectively. A case is given. The results from theoretical calculation show that diffusion radius and pressure on the segments increase with the increase of grouting pressure when grouting time is constant on one hand. After considering viscosity variation of cement grout, diffusion radius and pressure on segment are smaller than the results obtained under fixed viscosity; and as the grouting pressure increases, the disturbance on pressure from viscosity of grout gets more obviously. On the other hand: when grouting pressure is constant, diffusion radius and pressure on the segments increase with the increase of grouting time. However, the values increase rapidly in the beginning and slow down later. The results can provide a guide to selecting appropriate techniques and parameters of cement grouting.

Desiccation shrinkage is one of the key factors which may lead to crack of clays. It’s significant to reveal the shrinkage mechanism to prevent disasters for geotechnical engineers. Free shrinkage tests have been carried out on the air-dried samples with different initial dry densities. There are four typical water content points on the shrinkage curves according to desiccation characteristic, which include saturated water content, mid water content in the scale shrinkage stage, shrinkage limited stage, mid water content in the residue stage separately. Specimens are air-dried from saturated water content to typical water content as above, and then drying up them immediately with liquid nitrogen freeze drying method, after that, the pore size distribution by the pores analyzer for acquiring relationship between micropore structure and macro volume shrinkage is determined. The results show that inter aggregate pores are prior to contract at the beginning of dehydration process, which show a large pore volume peak radius decreasing with the moisture content reduction. Meanwhile, small diameter pore volume increases. The intra aggregate pores will decrease at a residual phase showing that pore diameter of volume peak decreases. With moisture content further reducing, inter-aggregate and intra-aggregate pores will not change anymore at the zero contraction stage. The micropore structure is corresponding to macroscopic volume change during dehydration process.

Double-row stabilizing piles are employed commonly to stabilize large-scale landslides. The key in the design and calculation of practical engineering is to simply and reasonably determine thrust on the front and rear piles. The rock or soil mass in front of loading section of a pile is considered as the Winkler foundation. Using the elastic foundation beam model and fully considering the deformation continuity between loading segment and anchorage segment of the pile, slope resistance on the loading segment of the rear pile can be determined by iterative algorithm. Then, the thrust on the loading segment of the front pile can be figured out using transfer coefficient method for potential slide mass between the front and rear piles. The relative theoretical formulas are given. To verify the rationality of the proposed method, a laboratory model test is conducted. The results are acceptable. For a large-scale landslide example, design slide thrust on a rear or front pile is figured out in detail respectively. The proposed method can provide a reference for the simplified design of practical projects.

Lots of uncertain factors affect the time delay estimation precision of time-difference location method in rock acoustic estimation(AE) experiments. Aiming at this problem, the all phase phase-difference time delay estimation method is proposed. Time delay of AE signal is deduced through the phase-difference obtained by combining wavelet decomposition and all phase frequency analysis. AE sub-band signals with the same dominant frequency from different sensors are found with wavelet decomposition. Then the phases of middle sample of every sub-band signal are obtained with all phase frequency analysis method for those chosen sub-band signals, and the time-differences of AE signals’ reaching different sensors are computed according to the relationship between phase-difference and time-difference. Finally, the AE source is located by the method of time-difference location. Experiments are conducted on a 50 mm×100 mm×50 mm granite stone, and AE source is generated by broken lead at ten different points. Under the lab environment, the results from the proposed AE location method indicate that using phase-difference based on wavelet transform and all phase frequency analysis can effectively improve the accuracy of location of AE source. Compared to the results obtained by the PCI-2 acoustic emission instrument, the absolute error reduces by about 3 mm, so as to provide an effective way for AE source inversion.

This paper proposes an improved bounding surface model for remolded clay, which overcomes the defects that it is inconvenience to apply and not related with elastoplastic property in the unloading process of the bounding surface model, by considering elastoplastic loading and unloading processes under cyclic loading. The model uses a simple bounding surface formula, which significantly simplifies the derivation and calculation of the model; which also effectively reduces the empirical dependence in the application process of the improved bounding surface without predefining the bounding surface. It introduces bounding surface expansion and contraction rules, which makes the model consider the elastoplastic property of the soil in the unloading process and then reflects the hysteretic behavior of the soil. This improved bounding surface model is verified by comparison between numerical simulation of remolded clay cyclic triaxial test and the cyclic triaxial lab test. The results show that the improved bounding surface has following advantages: clear physical significance and simple form, parameters easy to determine, high precision of calculation and the calculation results fitting the real test results.

Strain softening problem in geotechnical engineering and the difficult solution problem of the finite element numerical calculation due to the negative tangent stiffness of strain softening model are studied. An elastoplastic strain softening constitutive model of rock is established based on the Drucker-Prager strength criteria. A fully implicit return mapping algorithm which has characteristics of the unconditional stability and precision is used to solve the constitutive equation, and how the programmed constitutive model to be solved is discussed in detail. Then, the shortcomings of low efficiency of the arc-length method in judging stiffness matrix is considered, Newton-Raphson scheme and arc-length method (NR-AL method) are combined to iteratively solve the calculation of elastoplastic incremental finite element equations. Namely Newton-Raphson scheme is used before the structure reaching the limit load, and when the structure is close to the limit load, turning to the arc-length method, so that the structure can go over the peak point into the softening phase until destruction. NR-AL method has the advantages in the iterative solution. A program of the built strain softening model and elastoplastic incremental finite element to solve the constitutive equation for the iterative process is compiled using C++ language. The program is applied to numerical calculation, and the stress-strain curves of the idealized elastoplastic model, strain softening and strain hardening model based on the Drucker-Prager strength criteria are comparatively analyzed. The results show that the strain softening constitutive model can simulate the characteristics the post-peak softening of rock material well, and it can reveal the features of the post-peak strain softening and failure mechanism. NR-AL method can solve the negative stiffness problem caused by strain softening and also overcome the shortcomings of low efficiency in judging stiffness matrix using the arc-length only.

Residual strength of rocks is an important parameter in rock mechanics, because it has a significant influence on accurately evaluating stability of underground excavations and optimizing design of rock mass support. Based on triaxial mechanical properties of the rock, an index, defined as the strength degradation coefficient, is proposed to describe the post-peak strength degradation of rock. In this paper, the index is in essence a brittle index for rocks. A power model is then proposed for the relationship between the strength degradation coefficient and the confinement stress. By fitting the data from 22 lab triaxial compression tests, it is found that the parameters in the model which are different in various rocks can be mainly related to the mineralogical composition and the structure of rocks. Furthermore, a strength degradation method based model is proposed for determining the residual strength of rocks. It is found that the proposed model fits triaxial compression test data of rocks better than the classical Mohr-Coulomb failure criterion does. Meanwhile, it can reflect the influence of structural properties on the residual strength of rocks.

Up to now horizontal vibration response of a single pile in unsaturated soil is analyzed theoretically. The unsaturated soil surrounding pile is described by three-phase poro-elastic theory, which takes into account the viscous and inertial coupling between solid skeleton and pore fluids as well as the matrix suction, while the pile embedded in unsaturated soil is end bearing and treated as a Timoshenko beam model to describe the shear deformation and rotational inertia effects. The Helmholtz decomposition and variable separation method are firstly adopted to decouple the governing equations of the unsaturated soil. And then a rigorous mathematical formulation of the pile-head frequency–response function is deduced by virtue of the three-dimensional continuum model proposed by Novak and the compatibility between the pile and soil. The influences of degree of saturation on the impedances of pile and soil together with the distribution of displacement and internal force along the pile are discussed in detail. Results indicate that both the complex impedance of soil and the dynamic impedance of pile top increase with the increasing degree of saturation of soil, while the deformation and the internal force of pile are reduced. The contribution of pore water to dynamic behavior is made only when the soil is close to the saturated condition. At low frequencies, short pile has a large stiffness factor. A longer pile will lead to a higher damping factor, but a low resonance frequency. The impedance at the top of pile would be approximately invariant as the pile’s slenderness ratio exceeds 10.

This paper studies the influence of grain gradation on the undrained mechanical behavior of granular materials. A series of conventional undrained triaxial compression tests is carried out on two different materials (glass balls and Hostun sand), which have high degree of shape self-similarity. For each material, 6 samples with similar relative density and different gradations ( 1.1-20) are prepared, and then the samples are sheared. Test results show that the grain gradation has an obvious impact on the undrained mechanical behavior of granular material: both deviatoric stress level and undrained shear strength of two material samples decreases as the coefficient of uniformity ( ) of the material increases, their variations tend to converge as coefficient of uniformity surpasses 5. Based on the evolution of the value of the second-order work of the granular assembly during undrained triaxial loading, potential instability for the selected granular materials is also analyzed. The results demonstrate a significant influence of the grain gradation on stability: the higher of coefficient of uniformity ( ), the larger of the potential of static liquefaction and the unstabler of materials.

The seepage field monitoring of sandy soil is a necessary and basic work for disaster prevention and mitigation in geotechnical engineering. A distributed temperature system with the carbon coated heating optical fiber (C-DTS) is proposed on the basis of summarizing the advantages and disadvantages of the existing monitoring methods. The monitoring principle of the method is presented and the concept of the eigenvalue of temperature （ ）is introduced based on the thermal diffusion theory and Ohm’s Law. After that, a seepage field simulation device for sandy soil and monitoring program are designed as well. An indoor test of the seepage monitoring is run, the linear relationship of the eigenvalue of temperature ( ) and the seepage velocity (V) is defined at different seepage velocities in sandy soil. The temperature descends as the seepage velocity increases, and their relationship complies with the formula derivation. The experiment results show that C-DTS can effectively improve the sensitivity of DTS monitoring and realize fully-distributed monitoring of seepage velocity in geotechnical engineering. Finally, some related research work for further applying to geotechnical engineering practice has been analyzed.

A series of partially drained cyclic triaxial tests under different stress paths are carried out on typical Wenzhou saturated soft clay. The influence of cyclic confining pressure on the permanent deformation behavior of saturated soft clay in partially drained condition is studied. The experimental results show that: in partially drained condition, comparing the test results from conventional cyclic triaxial tests with a constant confining pressure and deviator stress cyclically shearing alone, cyclic confining pressure has great influence on both the permanent volumetric strain and permanent axial strain. Under the same cyclic stress ratio, for a given number of cycles, both the permanent volumetric strain and permanent axial strain increase with the increasing of the amplitude of cyclic confining pressure, which indicates that the conventional cyclic triaxial tests with a constant confining pressure may underestimate the settlement of subsoils induced by traffic load. Based on the permanent volumetric strain and permanent axial strain after 10 000 cycles, two empirical formulas are proposed. They can quantify the effects of cyclic confining pressure on the permanent volumetric strain and permanent axial strain during tests on saturated soft clay under the partly drained condition, and can be used to predict the permanent deformation induced by traffic load including any combination with varying deviator stresses and varying confining pressures.

As for the problem of ambiguous mechanism of crack initiation in inclined coal seam, it leads to a blind increase in water pressure or water injection rate to enhance the coal seam permeability during hydraulic fracturing in underground coal mines. In this paper, the stress state around the fracturing boreholes is analyzed using the in-situ stress coordinate conversion, then a model is established using the maximum tension stress (MTS) theory to calculate the initiation parameters of the borehole rocks. The influences of in-situ stress and coal seam inclination on the hydraulic fracturing initiation pressure and locations in underground coal mines are investigated using the model. The field test is conducted at Tonghua coal mine of Chongqing Songzao Coal and Electricity Co. Ltd. .The results show that: according to the stress state in fracturing area, the crack initiation pressure increases along with the increasing coal inclination. With the increase in the coal inclination, initiation location moves to the strike direction. The results in field test are consistent with the calculated result which is that initiation pressure increases along with increasing coal inclination. It verfies the feasibility of the calculation model.

A stability analysis model based on modified Morgenstern-Price method is established from both perspectives of design and check in order to assess the stability of pile stabilized slope, and the expressions of sliding thrust for stabilizing pile and factor of safety for slope are derived. In this model, an adaptive genetic algorithm is introduced to form the optimization model of slope stability analysis. The algorithm is used to search for the critical failure surface of pile stabilized slope. Then, the influence of the installing position of stabilizing pile on the slope stability is investigated under two situations: obtaining the sliding thrust as given factor of safety and determining the minimum factor of safety as given sliding thrust respectively. The results indicate that this approach can not only seek out the critical failure surface with non-circular shape which is more suitable for the reality, but also determine either the sliding thrust of stabilizing pile or the minimum safety of factor for slope as well. It can be concluded that under the same circumstances, stabilizing piles should be supposed to be installed in the middle part of the slope, where the reinforcement effect of stabilizing piles can be maximized.

Based on the Hoek-Brown strength criterion, a calculation model of pile lateral normal stress and horizontal friction under small rotation is obtained. Using static equilibrium principle, a calculation formula for the rock-socketed depth of the highway bridge pile foundation under horizontal load is established. Furthermore, a new calculation method of rock-socketed depth is proposed. The analyses of parameter sensitivities and influence factors show that: (1) the torque caused by horizontal load, pile diameter d, strata overlying pressure , rock uniaxial compressive strength , rock mass category parameter and the rock geomechanical classification index RMR have certain influences on the rock-socketed depth. While , d are unchanged, the rock quality and rock uniaxial compressive strength are the most sensitive factor to determine of rock-socketed depth. (2) The worse the rock mass quality is, the greater the rock-socketed depth is; the better the rock mass quality is, the smaller the influence of overlying pressure on the rock-socketed depth is, vice versa. (3) The rock-socketed depth nonlinearly decreases slowly with the increasing of rock uniaxial compressive strength, and under the same uniaxial compressive strength ,the better the rock mass quality is, the smaller the rock-socketed depth is, vice versa.

Researches are carried out on the mechanical properties of red sandstones treated at 20 °C, 70 °C, 140 °C、200 °C, 300 °C, 400 °C, 600 °C and 800 °C, respectively. Based on the researches, the regular patterns of the pore structure and micro fracture of the heated red sandstones are investigated combined with mercury and scanning electron microscope analyses. It is concluded that: (1) the maximum uniaxial compressive strength of heated red sandstones at 300 °C is 1.4 times as much as that of red sandstones at room temperature. The uniaxial compressive strength decreases by 32.5% when red stones are heated to 600 °C. (2) The crack widths of heated red sandstones are mainly ranged from 0 to 0.01 μm, during which there are better correlation between the distribution ratio of cracks and the uniaxial compressive strength. (3) The main affecting factors of the deterioration of red sandstones are the transgranular cracks and heterogeneity of cracks.

Calculation methods for the critical placement height of gravel column reinforced soft soil foundations are not perfect at present. The traditional calculation methods do not take the improvement of composite foundation's strength and the enhancement of foundation's drainage consolidation ability into account. Based on the consolidation theory, the simplified method of consolidation calculation of gravel column composite foundation is introduced, and it modifies the formula of the critical placement height according to the deformation control. Analyzing the settlement deformation observation data of the soft ground distributed along the Suining-Ziyang expressway in Sichuan province, results show that the thickness of clay in the study area is within 6.5-11 m and the observation value of critical placement height ranges from 4.5 to 6.5 m. The difference between observation values and calculation values with modified formula is ±(0.1-0.4)m. It verifies that the formula deduced in this paper is applicable. Based on these, the factors influencing the critical placement height were discussed and it was found that the thickness of soft soil and the column spacing have more obvious influences on the critical placement height than other factors.

On the basis of catastrophic theory, taking bedding rock slope for example, a new catastrophic model on slope stability is established in consideration of elasto-brittle medium and strain-softening medium of the slip surface and the hydrostatic pressure of top splay fracture, then the mechanism of bedding rock slope stability is discussed. It is shown that: the stability of bedding rock slope is mainly affected by two factors, namely internal and external factors. The internal factors indicate that groundwater softens the rock mass of slip surface by physicochemical effect, so the rigidity ratio of rock mass is reduced, which plays a leading qualitative effect. The external factors refers to hydraulic pressure. It not only makes the sliding potential of the slope increasing, but also plays a role as a disturbance in the process of slope instability to speed up the landslide. On the basis of these, equations calculating the critical water height in the splay fracture and the critical rainfall intensity are derived, and then the bedding-slip failure hydraulic criterions for bedding rock slope are proposed. The displacement change rule of the rock mass of slip surface in the progressive softening is also given. The increasing of shear displacement is not uniform; it presents a leap which likes a ladder. Simultaneously, the physical model test is carried out (rigidity ratio ), which validates the rationality of instability mechanism and the displacement change rule of bedding rock slope with catastrophe theory. Furthermore, some suggestions of treatment technology and optimization methods for this kind of rock slope are proposed.

A lab model experiment of low-angled slope with interbedding of soft and hard rock is designed on the basis of geological analysis and similarity theory. The lab test is based on Peng Jiawan slope at Yi-Ba highway which has interbedding of soft and hard rocks with low dip angle. In the model tests, slope excavation tests are used to simulate the engineering excavation (or valley incision); and the water injection softening processes are used to simulate the rainfall infiltration. The results show: under both excavation and rainfall infiltration conditions, the deformation modes of the slope are sliding-tension at first and overall creep-slippage in the latter; and the failure mode is overall slip failure along the sliding zone of deep soft rock. Strictly speaking, the deformation of hard rock strata differs from the deformation of soft rock strata. Hard rock deforms mainly in sliding-tension but soft rock deforms mainly in overall creep-slippage. Changes of the condition of deep soft rock affect the total stability of the interbedding slope mostly. Both excavation and rainfall infiltration would lead to decline of stability of the slope. The free surfaces and micro-fissures induced by excavation are the basis triggering slope failure, and the rainfall provides incentives to the slope failure .

The Suoertou landslide, a giant old landslide with a volume of 72.85×106 m3 in Zhouqu county, Gansu province of China, has been reactivated with a small rate since 1970’s. The slow-moving character indicates the typical rheological behavior of the landslide. It is well known that mechanical characteristic of slip zone plays an important role in landslide activities. In order to clarify the creep behavior of slip zone and the relationship between long-term strength and residual strength, a series of directed creep shear tests under residual state is employed. It is found that the creep behavior of residual slip zone is strongly dependent on normal and shear stress, with two critical shear stresses and two critical initial strain rates. Moreover, it can be found that the critical shear stress and strain rate, when the creep develops into accelerated stage, have a linear relationship with normal stress separately. Based on the linear relationship between critical shear stress and normal stress, it can be speculated that the shear stress condition of the Suoertou landslide has been in accelerated creep state already. Meanwhile, the relationship between long-term strength and residual strength is analyzed and compared. It is found that long-term strength of the landslide’s slip zone is slightly greater than its residual strength, and the magnitude of their difference is negatively correlated with normal stress.

Given the structural features and engineering geological conditions of north anchorage large cylindrical caisson of Wuhan Parrot Cay Yangtze River bridges, combining with in-situ monitored data of some key points, three dimensional calculation modes of FEM are established with software ADINA to analyze stress and deformation of caisson structures and its adjacent diaphragm wall. The stress distribution and deformation of the structures are studied during the caisson sinking and its bottom sealing. The effects of caisson sinking on adjacent high-rise buildings and bank structures are also analyzed comparatively. The research results show that: the principal stress of diaphragm wall increases with the increasing of sinking depth, and its deformation appears mainly in its top and bottom after the caisson bottom sealing, the tension stress would be higher at its structure cutting edge, the middle of cross wall, the joints of cross wall and inner face of caisson well. The corresponding settlement of adjacent soil around the caisson increases with the increasing of sinking length as well. Settlements of monitored points from calculation agree well with measured data after bottom sealing, and the former is generally less than the latter. The differences between them are from -1.22 mm to -0.88 mm at the key points of adjacent high-rise buildings, and those at the key points near the Yangtze River bank are from -1.27 mm to 0.64 mm. The calculation model will provide a guide for settlement control during the caisson sinking.

This paper proposes a method to calculate anchor force. It presumes the initial distribution of normal stresses over the slip surface is an interpolative function involving undetermined parameters. Using force equilibrium equations and moment equilibrium equations, an explicit solution to factor of safety for slope reinforced by anchors is derived, and an analytical solution to coefficient of anchor force given the requirement of safety factor of slope is also deduced. The method’s computation is quite straightforward to process. It is found that the distribution of normal stresses in this method is continuous and the internal stresses are reasonable. The method has been successfully applied to computing two engineering slope. Results show that the calculated precision is in range of limit equilibrium method satisfying all equilibriums. It overcomes the disadvantage of abrupt change in normal stresses on the slip surface, which is encountered when using conventional limit equilibrium methods. In addition, this method is verified with the results of slope in this paper agreeing with those obtained with dynamic method to the anchor slope.

The Urumqi-Yuli highway is an important channel connecting the north and south of the Tianshan Mountains. When the highway crosses the Tianshan Mountainsa, a lot of engineering slopes along the highway will be cut. How to quickly and accurately evaluate the stability of these existing slopes and access the influence on slopes by subsequent changes in the process of construction in the alpine region, would directly relate to the route selection, total engineering volume and the amount of investment estimation. Based on rock mass basic quality, a status quo slope quality evaluation system (TBQ) is established. In TBQ, the combining of rock mass discontinuity and slope free surface, the hydrologic condition are selected as the main factors to revise the existing rock mass quality evaluation system. On this basis, other several factors including freezing-thawing and weathering effect caused by the large temperature difference and hydrologic condition, the earthquake and excavation etc., are introduced, the prediction and evaluation system of rock slope stability(TFBQ) is established. Case application to a practical engineering shows that this system is applicable to evaluate and predict the slope stability in project area, and better results are obtained.

This paper presents a comprehensive study of the generation and distribution patterns of the temperature field within a large-diameter cup-shaped frozen soil wall used in shield construction of Nanjing Subway Line 10. Three dimensional finite element analyses are taken to elucidate various influential factors for the temperature field. It is found that, if the thicknesses of cup-shaped frozen soil walls can satisfy the designed amounts needed for the purpose of ground reinforcement, frozen wall forms in a clear sequence: firstly, in the outer tubes, then the intermediate tubes, and lastly, the inner tubes. The “closure time” of the frozen wall, which means the time period required for the full formation of the frozen soil wall, is heavily dependent on soil’s thermal conductivity as well as the original ground temperature. The closure time would decrease linearly with the increase of the thermal conductivity; it would increase linearly with the increase of original ground temperature of soil and volumetric heat capacity. For the concerned Nanjing shield tunneling site, it took around 12 days. This would have increased by approximate every one more day if the original ground temperature increases by every 5℃. The latent heat is found to be of no apparent influence in the cooling process of soil. Notwithstanding, the cooling speed varies much with different types of soil. Generally, the cooling speed of sandy cemented soil and sand is faster than that of clay cemented soil and clay respectively. However, they reach the phase-transitional-stage almost simultaneously. It is also noted that the frozen walls in sand are always formed 4 days earlier than those in clay regardless of whether the cement is in place or not. Results and conclusions from this research may play a useful role to aid designs of similar projects in the future.

This paper focuses on the way to get the value of rock resistant coefficient in high-speed railway tunnel. It runs the radial hydraulic pillow testing to measure the radial deformation during various pressures on Shanghai-Kunming high-speed railway tunnel. Based on field test data and combining different constitutive models, five theoretical calculation models for tunnel rock resistant coefficients are established. They are ideal elastic-plastic model, burst fissure elastic-plastic model, plastic softening rock model, Lade-Duncan criterion model and unified strength theory model respectively. Twenty tunnels are classified and the corresponding theoretical values of surrounding rock resistance coefficients are calculated respectively using the proposed models. To compensate the limitation of field test number, the numerical simulation of the research tunnel is carried out. Then the theoretical calculation values, field test values, numerical simulation values and standard values of rock resistant coefficients are compared and synthesized at different buried depths, rock grades and geological conditions. The recommended values of rock resistant coefficient of large section high-speed railway tunnel are proposed. The recommended value breaks through the limit of rock resistant coefficient standard values in ordinary high-speed railway tunnel based on elastic model. Also the recommended value can provide the theoretical basis for optimizing the design of the tunnel structure and making full use of the bearing capacity of the surrounding rock.

During drilling and blasting excavations of deep caverns, the transient unloading of in-situ stress on the excavation boundary can induce vibrations in surrounding rock mass. For circular tunnel excavation, the balance mechanism of strain energy, kinetic energy and work done by radical stress during the process of the transient unloading of in-situ stress is analyzed, then a new attenuation formula is established to analyze the attenuation law of vibrations induced by the transient unloading of in-situ stress based on the strain energy of excavated rock mass with the tool of unit analysis. Case studies of Jinping II and Pubugou hydropower stations are presented to show how to identify and separate the vibrations induced by the transient unloading of in-situ stress from the monitored vibration signals. Studies indicate that the amplitudes of vibrations induced by the transient unloading of in-situ stress are proportional to the square root of strain energy density of excavated rock mass, and the bigger volume of excavated rock mass is, the intenser vibrations are induced by the transient unloading of in-situ stress. Compared with the existing attenuation formula proposed by Lu and Hustrulid, the new attenuation formula has a wider range of application and higher precision.

During the reliability analysis of supporting structure in underground engineering, more reasonable reliability computing methods would like to be adopted because of large discreteness of parameters of soil-rock mass and high-degree of nonlinearity of performance function, as well as nearly manifesting as implicit function. While it is hard to satisfy the project requirement by traditional Monte Carlo simulation method with large amount of computation work, the finite element reliability program of joint computation including Matlab and Abaqus is developed. It combines the advantages of Matlab and Abaqus based on Latin hypercube sampling and has the outstanding feature of saving sample space and improving efficiency of sampling as well. It can easily converge and satisfies requirements of reliability analysis of supporting structure by exhibiting a case of a circular tunnel in underground engineering.

A coupling analysis model is proposed to study the hydro-mechanical response of the fluid flow in fractured rock mass with the method of discontinuous deformation analysis (DDA). A model of fractured rock mass is generated with the DDA method. Based on this model, the fracture water network is also generated with the matrix search method. In the fluid flow analysis, the cubic law is applied to study the steady flow along the fractures using the steady-state equilibrium iteration method. Hydraulic pressure is treated as a line loading in the DDA framework, and the aperture and hydraulic pressure in the fracture line are updated every iteration step, followed by the coupled motion equations expressed in the DDA framework, to study the interaction between the fluid flow along the fractures and the movement of the rock blocks. A real case of cavern excavation is selected to study the influence of fluid flow with water tunnel during the excavation and operation phases with the proposed DDA coupled 2D hydro-mechanical model. The results show that the DDA coupled hydro-mechanical model is suitable for the stability and seepage analysis of practical engineering problems.

A close distance coal seams in a coal mine is selected as a case. Deviatoric stress distribution under coal abandon pillars #8 is simulated with FLAC3D. Research results are as follows: (1) Deviatoric stress field in floor distributes as diffusion, the farther the distance is, the wider the range spreads; it transfers from border to floor in 45o direction; (2) When the width of pillar is narrow, the deviatoric stress influence depth at midline and border is shallow; with the width increasing; deviatoric stress at floor varies obviously and the influence depth is deeper; when the coal pillar width is wide enough, middle part is as stress of primary rock; (3) In the same horizontal plane, deviatoric stresses are distributed as saddle shape, with pillar width increasing, the pillar midline and border increase at first and then decrease; and the position of deviatoric stress peak at coal pillar border has little change; (4) as to a certain coal pillar width, deviatoric stress peak at border decreases in vertical direction and its tendency is slower; meanwhile, the peak is far away from coal pillar quickly and its tendency gets faster. Through vertical stress, horizontal stress and shear stress analytical solution, a floor deviatoric stress analytic formula is derived; the analytic solution is consistent with the simulated result. In this case, track roadway 9205 has a 20 m distance from coal pillar border (inboard-type); return airway 9205 is located in coal pillar border; transportation roadway 9205 is located in coal pillar midline, track roadway 9205 maintenance effect is the best of them, which proves that the inboard-type layout roadway with an enough distance from coal pillar bears a little deviatoric stress. Macrostress field is more suitable to the roadway surrounding rock self-stabilization.

In order to solve the surrounding rock control problems in deep gob-side entry retaining, the working face 1126 with large mining height of Xingdong mine (850 m occurrence depth) was taken as research subject. Then, by means of UDEC simulation, we analyze surrounding rock response character with different subsidence amounts of key block B. Analysis result shows that: ①the deviatoric stress peak value of coal sides and its position have linear relationship with subsidence amount of key block B, and they transfer to deep part; ②deformation in deep part of coal sides has weak response to subsidence amount of key block B, and the closer to coal side surface, the more sensibility the coal sides has, therefore, there is an obvious inflection between the deep and shallow surrounding rock displacement; ③the roof subsidence amount and sides deformation amount have positive exponential relationship with the subsidence of key block B; ④along with key block B settling, broken form of coal sides experiences the following progress: unstable triangular block slide →X conjugate broken →double X conjugate broken. Therefore, some conclusions are made as follows: ①the roadside gob backfilling in can effectively limit the driving effect from key block C to block B; ②steel-concrete support can adapt subsidence feature of key block B well and has strong compression resistance and bending character; ③the high performance and high pre-stressed anchor can better improve the load capacity and deformation resistance ability of anchoring body; ④the roof truss anchor cable can be anchored in key block B that has solid and reliable anchoring basis, and, side cable can be anchored the area within the displacement inflection by passing through potential slip surface in order to restrict the side structural slip. Based on the above analysis, a collaborative control program was put forward which consists of roadside gob backfilling, steel-concrete support, roof truss anchor cable, side cable and high strength and high pre-stressed anchor. Thirty days after the entry retained, surrounding rock deformation tends to be stable. In addition, the relative displacement amount of roof and floor is 613 mm, and the other one of two sides is 374 mm, which achieves the effective control of gob-side retaining entry surrounding rock in deep mining with large mining height.

Using the theory of upper bound limit analysis method and the volume force increment method, considering the defects of limit analysis model of a single sliding surface, an arbitrary block model considering the dislocation effects of multiple rock layers with structural joints is established. When the rock mass reaches the limit state (destruction) under external load, the work that is done by external loads is equal to the work that rock mass absorbs. Based on this premise, relevant equation can be established; thereby the calculation formula of slope stability coefficient can be derived. After analyzing typical numerical examples of slope and comparing to results of discrete element numerical simulation, the feasibility and applicability of this method are verified. A calculation of bedding rock slope located in Puli-Xuanwei highway in Yunnan province is achieved, the result shows that the stability coefficient is close to the result obtained from discrete element numerical simulation. The coefficient is slightly larger, but the slope is stable. It provides a new calculation method for evaluating the stability of this kind of slope.

In order to implement the seepage monitoring with temperature in embankment dam with the popular distributed fiber optic temperature sensor system (DTS), it’s necessary to study the background characteristics of temperature field. Herein, a saturated-unsaturated seepage field and temperature field coupling model (thermal-hydro coupling, i.e. T-H) is established. The model considers the heat convection-conduction-diffusion, as well as the boundary periodically fluctuation with atmosphere temperature. Some parameters are considered nonlinearly so that the result of simulation is closer to the true state of dam temperature field. For instance, the fluid viscosity is influenced by temperature and thermal conductivity is influenced by moisture, and so on. A clay core embankment dam is taken as a case study. It is shown that the temperature field within the dam has the characteristics of seasonal fluctuation, which is controlled by seepage and atmospheric temperature. Specifically, the heat from the reservoir controls the temperature variation of the saturated zone and the heat from atmosphere controls that of the unsaturated zone. If the core wall leaks, the temperature nearby will reduce as cold reservoir water flowing into. In this case, the distributed fiber sensors lying on the core wall can be used to detect spatial and temporal distributions of leakage. The conclusions are drawn as follows that the seepage monitoring with temperature is effective in theory. In the data analysis, particular attention should be paid to the temperature anomalies caused by atmosphere temperature.

A series of consolidated drained (CD) triaxial compression tests on sand with dilatancy is conducted to obtain mechanical parameters. The behaviors of large diameter monopile foundation in offshore under horizontal loading are analyzed using a three-dimensional finite element model with the finite element software ABAQUS. A lot of parameters, like stress path, friction angle, dilatancy angle and the characteristics of soil-pile surface, are taken into consideration to study the soil structure behavior, which is verified with the centrifuge modeling. Then, a reasonable finite element computational model of large diameter monopile foundation under horizontal loading including the parameter selection method of this model is established. Besides, the deformation is proposed as the control criterion to determine the horizontal bearing capacity of monopile foundation for the offshore wind turbine. With that, the pros and cons of existing methods for analyzing horizontal bearing capacity and deformation of pile foundation are discussed. Finally, it is suggested to determine the critical embedded length of monopile foundation by numerical analysis.

Internal crack in rock slope may grow under seismic loading, which would have an adverse effect on slope stability. By taking advantage of extended finite element method (XFEM), the development of cracks in a rock slope located in the southwest China under seismic loading is simulated. An analysis of the potential sliding surface is carried out according to the crack after extension, and the factors of safety are calculated with vector sum analysis method (VSAM) before, during and after earthquake. The result shows, under the loading of Wenchuan seismic waves, both crack LLT1 and crack LLT2 grow. The angle between growth-direction and the horizontal is nearly 45 degree, and the crack LLT1 grows to the slope surface. The factors of safety before and after earthquake are 1.75 and 1.05 respectively, and the minimum factor of safety during the earthquake is 1.01. This illustrates that the slope is stable before earthquake, but the anti-sliding force and the slope stability are both reduced because of the growth of crack under the seismic loading. Even if the slope is stable in the process of the earthquake, it may collapse subjected to other forces after earthquake.