Nuclear waste disposal and landfill engineering usually involve thermo-hydro-mechanical (THM) coupled issues. This paper reviews the current advancements of the thermo-hydro-mechanical coupled behaviors of clays from both experimental and theoretical aspects, which include the heat transferring behavior, the effects of temperature on seepage, Young‘s Modulus, strength, creep behavior, clay structural characteristic, and so on. Within this context, the applicability of the current moisture and heat transfer models and the coupled thermo-mechanical constitutive models is analyzed. Based on the review, an experimental study on the effect of temperature on strength, permeability, and creep behavior of Boom clay was conducted. The results show that as temperature increases, the strength of Boom clay decreases while its creep rate and hydraulic conductivity significantly increase. Then a coupled thermo-elasto-plastic-damage constitutive model for clay is developed. Finally, the weakness in the study of THM coupling problems is discussed, and the direction for the future research is identified.

As a fundamental parameter of soil, the shear wave velocity (denoted VS)offers a means to determine the seismic resistance of soil to liquefaction. The historical developments of VS and peak ground acceleration (denoted PGA)——based assessment method of soil liquefaction potential is reviewed. The basic principle to determine liquefaction triggering curve is given. The corresponding liquefaction triggering curve is proposed based on the database used by Kayen, Andrus, Saygili and Chu for a total of 49 earthquakes, 618 case histories. The position of liquefaction triggering curve is verified with respect to various factors based on the case history database, such as fines content, overburden stress and magnitude scales. In addition, the sensitivity of the database’s interpretation to a number of aspects and components of the analysis framework is examined, such as the shear stress reduction factor that accounts for the dynamic response of the soil profile, the magnitude scaling factor, the overburden correction factor for cyclic stress ratio. And the results show these factors have slight effects on the position of the proposed liquefaction triggering curve. At last, the relationship between nominal safety factor and probability of liquefaction as well as the probabilistic contours for the proposed liquefaction triggering curve are given based on Monte Carlo simulation, the weighted maximum likelihood method and weighted empirical probability data. The soil liquefaction triggering curves are proposed for the seismic design category Ⅰ、Ⅱ and Ⅲ of the structure, system and component of nuclear power plants, respectively. The presented assessment is provided with wide application prospects.

The failure hydraulic gradient is a crucial parameter for slope stability analysis and seepage control. Based on the experiment of seepage-induced deformation, the correlations among the critical hydraulic gradients of a coarse-grained soils, void ratios e, nonuniformity coefficients , and curvature coefficient of granular gradation are analyzed. By taking the advantage of Copula theory in constructing the joint distribution function of multiple non-independent variables, an optimal fitting Copula function of , e, and is proposed and used to estimate the critical hydraulic gradient. It is shown that the Nelsen No.6 function of the four-dimensional symmetric Archimedean Copula functions with single parameter is the optimal Copula function. By calculating the conditional probability for the optimal Copula function, the guarantee rates of estimated values can be obtained, or the critical hydraulic gradients with a certain guarantee rate can be calculated. Comparisons of the measured critical hydraulic gradient and the estimations of Copula theory, Terzaghi formulation, and Liu Jie’s formulation, the reliability of Copula theory is shown. These results lay a new foundation for developing the relationship among multiple factors including critical hydraulic gradient, void ratio and gradation characteristics and estimating the critical hydraulic gradient for coarse materials.

Probability distribution of rock strength parameters is the foundation of reliability analysis and design in rock engineering. Based on the linear yielding criterion (Mohr-Coulomb and Drucker-Prager), the probability density functions (PDF) of friction angle and cohesion are obtained through the theory of distribution for function of the random variable, on the condition that intact rock compression strength follows normal distribution. The PDFs of and show: the probability distributions of rock compression strength and , are not consistent, as do the probability distribution of and calculated under different yield criteria. Then, based on the characters of and ’s PDFs under different variation coefficients and correlation coefficients of yield criteria’s coefficients, the general forms of and ’s probability distributions are analyzed according to the skewness and kurtosis. The coordination problem between the distribution of rock compression strength and shear strength parameters is solved in theory. Finally, the correctness of PDF’s theoretical deduction and the analytical rationality of the method to determine probability distribution form for and are verified by large sample statistics and analysis for and which are obtained from the lots of marble conventional triaxial compression tests. It is believed that the research can provide a theoretical guidance to choose reasonable probability distributions of rock shear strength parameters in probability analysis of rock strength.

In the classic strength reduction method (SRM), there is only one strength reduction parameter which can be proved to be equal to the definition of factor of safety (FOS) by strength reservation. Some double reduction methods (DRM), in which distinct reduction parameters are used for friction angle and cohesion force, have been presented by researchers. In this paper, a new basis is established to support the rationality of the double reduction methods, and also a specific definition of FOS is built for a recently presented DRM by the authors. A comparison is made between the DRM and the SRM through rigid mathematical proving, which shows that the FOS of the DRM is almost always smaller than that of the classic SRM. This conclusion is verified by four numerical examples. The research shows that the possibility that the classic strength reduction method (SRM) may overestimate the safety of a slope exists. It is advised that the presented DRM be adopted as an additional option in the slope stability evaluations although more application experience is expected.

A series of laboratory experiments is conducted to study the changes in soil particles and pores under freezing and thawing cycles. The results show that during cyclic freezing-thawing processes, grain breakages occur within the soil particles, leading to a progressive increase in plastic limit, plasticity index and specific surface area of the soil. Meanwhile, the pore size distribution, tested by mercury intrusion porosimetry (MIP), is also changed in the processes as macro pores increase, small pores reduce and micro pores almost remain unchanged. All the structural indexes, including particle composition, pore distribution specific surface area, tend towards stable after 15 freezing and thawing cycles. The intrinsic influence of soil’s three-phase components during freezing and thawing cycles is discussed; and it is considered as the fundamentals of the water phase change and moisture migration among soil particles. Correspondingly, the reaction of water phase change and migration on soil particles and pores is considered to be the primary cause of the change of soil structures.

The essence of shaft friction of jacked pile is friction at the pile-soil interface; but the mature tribology theory has not been used to study the mechanism of shaft friction yet. In this paper, friction mechanism of adhesion and deformation in tribology is introduced systematically. Using it to explain the sliding friction mechanism at the pile-soil interface of jacked pile, a good results is obtained. It provides a new approach to research the shaft friction of pile. The study suggests that unlubricated friction between jacked pile and soil is external friction, the sliding friction between jacked pile and soil is lubricated friction in mud that causes the shaft friction in the jacking process far less than that in load test. A pause during pile jacking can give rise to a sharp increase of pile jacking pressure. The principal cause for the increase of pressure is that the disappearance of the lubricating film of mud that brings the friction between jacked pile and soil from lubricated friction into unlubricated friction; the friction between jacked pile and soil in load test is unlubricated friction before failure; the strengthening of shaft friction near the tip of pile is due to the increase of tangential force caused by the improvement of soil strength underneath the pile that improves the coefficient of friction between piles and soil.

For a long time, the settlement of embankment body is a main research problem of highway and railway roadbeds. Embankment body is mainly composed of unsaturated soils, and its deformation includes three components, namely, the deformation resulting from the instantaneous compaction, the deformations of primary consolidation and secondary consolidation deformation. However, primary and secondary consolidations influencing each other are not two completely independent processes. So the deformations of embankment body are the results of unsaturated creep and consolidation coupling. Based on the results of uniaxial compression creep test on red layers, the theories of single variable of unsaturated soil and embankment settlement of unsaturated are put forward. And at the same time, through centrifuge tests and numerical simulation of centrifuge tests, relations between settlement and fill height, post-construction settlement and time, are studied for embankment body on various compaction coefficients, and final construction settlements are predicted. Results show that the simulated results are consistent with the predicted results by the centrifugal experimental data, indicating that the theories are correct.

The governing equations for miscible contaminant transport in saturated porous media with release effect are developed under the 1-D seepage condition, and an elementary solution is derived using the Laplace and Fourier transforms and their inverse transformation for the case of a point contaminant source which is instantaneously released from the surface of a half-space body. Then the analytical expression of the contaminant concentration in porous medium subjected to a circular contaminant source is derived from the elementary solution. A calculation example for cyclic contaminant source is analyzed. It is shown that the contaminant concentration in a porous medium varies in a cyclic manner under a cyclic contaminant source applied on the porous surface, and finally reaches a quasi-steady state with the same cyclic period as the contaminant source. However, the phase of concentration fluctuation at a given depth lags behind the contaminant source. At steady state, the cyclic period of contaminant concentration in the porous medium is the same as that of the contaminant source. In practice, as the contaminant source cyclically fluctuates at the surface of porous medium, the concentration of contaminant in a porous medium around the surface also increases or decreases alternately in the direction. On the other hand, the contaminant gradually penetrates towards depth and eventually reaches a definite depth away from the surface.

The expression of safety factor for slopes with cracks subjected to seismic forces is deduced through establishing an energy equation using upper bound limit analysis and pseudo-static analysis based on nonlinear Mohr-Coulomb failure criterion. Safety factors are calculated using mathematical programming method with combinations of different parameters. A detailed parametric study is performed to determine the influence of slope angle, upper slope angle, horizontal seismic coefficient, vertical seismic coefficient, crack depth, geotechnical parameters on slope stability based on nonlinear failure criterion. Results show that safety factor decreases as the nonlinear parameter and seismic forces increase. Cracks can significantly influence on slope stability under nonlinear failure criterion when crack depth is large, especially for steep slope. When the value of crack depth exceeds a certain value, the beginning of critical failure surface may not pass through the lowest end of crack, but cross at a middle part the crack. It is also observed that when slopes is subjected to seismic effect, the safety factor depends significantly on the nonlinear shear strength parameters. Research results perfect the contents of stability analysis of slopes with cracks and the charts provide an useful reference for design and the construction of slop parameters on stability of slopes with cracks.

Duncan-Chang constitutive model is commonly used in the numerical analysis of the geotechnical problems related to coarse-grained soils. To explore the applicability of this model under complex stress path conditions including axial loading, unloading and lateral loading, a series of triaxial tests is conducted on coarse-grained soils to determine their mechanical properties and constitutive parameters. Based on the principle of similarity, the centrifugal models of a rockfill dam are prepared, and the centrifuge model test of a rockfill dam under complex stress path conditions is performed using the coars-grained soil with the same gradation and particle size in triaxial tests. The tests are conducted by changing the centrifugal acceleration to simulate loading and unloading conditions, and using the upstream impoundment to simulate the lateral loading. A three-dimensional numerical analysis of the centrifuge model test is performed using software ABAQUS. The effects of the sidewall friction and the initial stress conditions are studied. It is shown that the initial elastic modulus of soil can significantly influence the calculated results and the initial stress should assume the stress under the action of gravity in numerical simulations. Duncan-Chang constitutive model can better describe the behavious of the coarse-grained soil under the loading stress path than under the unloading stage; and thus the unloading modulus need to be determined with a proper method.

Model soil design, as a vital component of shaking table test of soil-structure interaction, is introduced briefly. After analyzing drawbacks of existing design methods, the similarity indexes of dynamic characteristic between prototype soil and model soil is derived based on backbone curve equation of dynamic stress-strain of soil. Then, a new approach for model soil design is proposed in which treating the similarity of shear modulus ratio and shear stain with reference strain as controlling factors. Several dynamic triaxial tests are carried out to obtain the - and reference strain of model soil, and the data are compared with those of prototype soil. Then a juding system based on the degree of similarity of - between prototype soil and model soil is proposed. The evaluation indexes of juding system mainly include correlation coefficient, nonuniformity coefficient and coefficient of curvature. The research conclusions have great guiding significance on the design of model soil, which are particularly important for shaking table test.

Due to the difference in their longitudinal sections, foundation piles have significantly different shaft frictions and tip resistances under the vertical loading condition. Although the piles with a variable longitudinal section have extensively used in engineering, little research effort is made to investigating the failure modes of the surrounding soil or the end bearing soil under ultimate load. Based on transparent soil material and particle image velocimetry (PIV) technique, comparative model tests on the bearing capacities and the failure modes of belled wedge pile, tapered pile and uniform-section pile with an equivalent volume are carried out. The load-settlement curves of the pile top and the displacement field of the surrounding soil under different loads are measured; the failure modes under ultimate loading and the bearing capacities influenced by pile length are analyzed in details. The results show that the ultimate bearing capacity of a belled wedge pile is about 3.5 times that of the conventional tapered pile, and is approximately about 2.5 times that of the uniform-section pile under this model test condition; and the failure modes of soils around the pile tips of the variable longitudinal section piles are similar.

The hydro-mechanical behaviours of bentonite are prone to be affected by the wetting-drying cycle due to its swelling-shrinking deformation characteristics with the moisture changing. Vapor equilibrium method using saturated salt solution, is used to measure water-retention behaviour of compacted Gaomiaozi Calcium bentonite after wetting-drying cycles. The specimens compacted at the same initial condition, are subjected to one to six wetting-drying cycles, and then the original specimen and the specimens after three and six wetting-drying cycles are selected for measuring their water-retention curves(WRC). When every wetting-drying cycle finished, the pictures of the specimen surface are taken. The pictures are dealt by the digital image processing, and then the shrinkage and crack areas are extracted. The rates of shrinkage and crack to original specimen area are obtained. Test results show that, with increasing wetting-drying cycles (0→3), the WRC moves down, water retention capacity and average skeleton stress decrease. Void ratio, the rates of shrinkage and crack after oven dry increase obviously. But after three cycles (3→6), the changes in the above mentioned behaviour become stable with increasing wetting-drying circle.

This paper presents a solution of a rigid rectangular plate on transversely isotropic foundation. Firstly, the flexibility matrix of the subgrade is achieved based on the displacement solution of transversely isotropic multilayered foundation soils subjected to uniform rectangularly-distributed loading. Secondly, the governing equation of the interaction between the rigid rectangular plate and the layered transversely isotropic foundation soils is developed by using the compatibility conditions of the plate and the foundation, and the governing equation is solved for the reactional force of the foundation. This procedure is then implemented into a computer code with a proper meshing scheme. Finally, a case study is performed, and the effects of the properties of transversely isotropic foundation soils, the length-to-width ratio of the rigid rectangular plate, the thickness of the foundation soil and soil stratification on subgrade reactions are analyzed. The results indicate that the three factors mentioned above have significant influence on the subgrade reaction.

Due to the limitations of both the graphic method and the rectangular method in determining the pore structure eigenvalues of rock, an integral method is proposed, in which the pore radius is integrated to determine the eigenvalues. In applying the integral method, the pore radius is first determined through a capillary pressure model. Then a capillary pressure power function is derived and presented in the double logarithmic coordinate system, and the model parameters are acquired using the least square method. The proposed model is validated through comparing the calculations with the data provided in Sami’s paper. A connection between rectangular method and integral method is identified, showing that the pore structure eigenvalue can be calculated using the integral method. Finally, comparison of the proposed method with other two methods indicates that the results calculated by the integral method are closer to the real values. This study can help understand the characteristics of rock micro-pore structure.

In this study, a production method is proposed for making the similar material of sand and barite powder using cement and plaster as bonding agents. Three controlling factors including sand-blinder ratio, cement-plaster ratio and barite content are chosen to perform the orthogonal tests. The ratio schemes are obtained. A series of tests is carried out to determine the density, uniaxial compression strength and elasticity modulus of different similar materials. The extremum difference analysis is adopted to analyze the sensibilities of three factors to parameters of the similar material. It is found that the density is primarily controlled by the barite content, secondly by sand-blinder ratio, cement-plaster ratio; the uniaxial compression strength and the elasticity modulus are significantly affected by the sand-blinder ratio, next by the cement-plaster ratio and barite content. The density decreases as sand-blinder ratio increases, and increases with the cement-plaster ratio and barite content; the uniaxial compression strength and the elasticity modulus significantly decreases as the sand-blinder ratio increases, but gradually increases as cement-plaster ratio and barite content increase. Empirical equations for determining the similar material ratio are developed based on the multiple linear regressions of the test data using the program of MATLAB. The proposed method is validated through a practical case.

Tapered piles are a type of piles with a variable cross-section, which can effectively improve the skin friction of the piles. Thus far, however, little effort has been made to investigate the installation effect of the tapered piles. By using transparent soil materials and the particle image velocimetry (PIV) technique, a series of model tests is conducted to investigate the soil displacement of the surrounding soil in installing a tapered pile. The displacement field of the surrounding soil is determined by analyzing the distinctive laser speckle pattern generated by the interaction between the laser and transparent soil when the light goes through the transparent soil. The images of the laser speckle pattern is obtained by CCD (charge-coupled device) camera and analyzed using the PIV technique. For comparison, a model test on the installation of a constant cross-section pile is also carried out and analyzed. Finally, this result is compared with those of the model test on the installation of a variable cross-section pile and the cavity expansion theory, showing the accuracy and reliability of tapered pile installation model test using transparent soils. The results show that the model test on installing a tapered pile in transparent soil can effectively simulate the installation process of a tapered pile, and the radius of influence due to tapered pile installation is found to be about 1.2 times that of the equal section pile installation.

Based on the measurements of the spilt Hopkinson pressure bar (SHPB) dynamic tests on the jointed rock mass, we analyze the influence of various factors on the jointed rock mass, including the joint plane angle, penetration degree, thickness, crack group number, fillers and strain rate. By analyzing the mechanism of damage and the mode of failure for the jointed rock mass under high-strain rate, the general Bingham model is modified based on the theory of composite damage, and a constitutive model for modelling the dynamic response of the jointed rock mass under different strain rates is developed. Comparison of the theoretical simulations with the experimental results shows that the model can well describe the stress-strain relationship of the jointed rock mass in the early stage of elastic deformation, the steady stage of plastic deformation and the destruction stage of accelerating deformation under dynamic loading. The theoretical results agree well with the experimental data, showing the capability and good performance of the proposed constitutive model.

Distribution of earth pressure behind retaining wall is closely related with displacement of retaining wall and mode of rotation. For rigid retaining wall rotating outward around the base, based on analysis of forming mechanism of earth pressure and precious studies, a formulation of the relation between mobilized internal friction angle of soil behind the wall and displacement is developed, which reflects the process of progressive mobilization of soil internal friction angle as displacement of retaining wall increases. On the basis of it, a modified computational method for active earth pressure considering wall displacement of retaining wall is put forward. Computational results show that earth pressure behind retaining wall decreases gradually from at-rest earth pressure as the displacement increases; and when displacement of retaining wall reaches a critical value, all corresponding earth pressure values behind the wall converge to Coulomb’s active earth pressure values. Earth pressure behind the bottom of retaining wall also converges to Coulomb’s active earth pressure gradually as the movement of retaining wall increases. By comparing with model test results, it is shown that the value of theoretical computation is in good agreement with the measured experimental value.

The movement distance of seismic-triggered landslide is one of the important assessment indexes for prevention and mitigation of landslides disaster, and it is not only controlled by landslide volume and drop, but also related to the topographical factor. Here the slope toe-type and turning-type landslides are analyzed and the influence of sliding volume V, drop , slope gradient and turning direction angle is studied on the maximum vertical movement distance H, transitional movement distance L, and transitional movement distance under the slope toe or after the turning . The results indicate that the apparent friction coefficient H/L of the turning-type landslide is jointly controlled by the gradient and turning direction, and less than that of slope toe-type landslide. The average value of of the toe-type landslide is equal to that of the turning landslide, showing that the influence of topography factor on the transitional movement distances of different types of landslides is similar. Analytical formulations for movement distances of the two types of landslide are developed with respect to the volume, drop and topographical factor of the slides. According to the formulations, it is found that the landslide volume affects trivially the maximum vertical movement distance H, showing the movement characteristics of the high slope-landslide; the drop is not the main factor influencing the horizontal distances under the slope toe or after the turning ; gradient significantly influences the movement distances , and of slope toe-type landslide; and turning direction angle is an important factor controlling the of turning-type landslide. These results can provide references for predicting landslide movement distance and controlling topographical factors, highlighting the importance of the slope gradient and the turning directional angle.

Based on a survey of the distribution of in situ structural planes and surface cracks and an analysis of surface deformation monitoring data, a case study is performed in Chengchao Iron Mine to investigate the influence of the structural planes on the surface deformation in the mining zone. The results show that, under a large horizontal stress condition, the structural planes of rock mass can change the surface tensile deformation distribution and the failure pattern, and intensify the deformation of rock mass. In areaⅰ(i.e., the area on the eastern of section Ⅲ), the toppling-sliding deformation is formed along NNW structural planes within the outermost crack, and the surface deformation is featured mainly with rapid deformation; the bedding deformation occurs along NNW structural planes outside the outermost crack, and a linearly stable development of surface deformation prevails; In the stage of toppling failure, the deformation in this area is mainly dominated by horizontal displacement of rock mass. In areaⅱ(i.e. the area on the western of section Ⅲ), under the north-south horizontal stresses caused by mining subsidence, the rock masses are separated into parallel blocks, resulting in rapid surface deformation. In some local regions, some parallel blocks mentioned above fails in a toppling way along NNW structure planes under the west-east horizontal stresses.

To resolve the stability control problem related to the fractured soft rock surrounding deep roadways, a case study is performed on the Xingdong Mine-980 roadway tunnel to investigate the characteristics and mechanism of the deformation and failure of the surrounding rock mass, with combining the procedures of field investigation, numerical simulation, in-situ testing and monitoring and so on. A bolt-shotcrete-net-grouting combined supporting system is developed, which is composed of densely distributed high-strength anchors, newly shotcrete protecting layer and time-lag grouting reinforcement. The controlling mechanism is explored for the surrounding rockmass stability with different types of supporting structures, and a numerical analysis is performed on the influence of bolt spacing and shotcrete layer thickness on the stress and displacement fields of the surrounding rockmass. It is shown that: 1) With the bolt spacing decreasing from 0.7 m to 0.3 m, the bearing capacities of anchor bearing arch and shotcrete layer structure increase following a power law, the compressive stress in the anchorage zone increases practically linearly and the displacement of surrounding rock decreases sharply; 2) When the shotcrete layer thickness increases, the bearing capacity of shotcrete layer structure increases linearly, similar to the compressive stress in anchorage zone; meanwhile, the displacement of surrounding rock decreases substantially; 3) When the layer thickness reaches 200 mm, compression prevails in most part of the surrounding rock without anchors, and the tensile stress zone shrinks significantly. Based on the above simulations, a supporting scheme is proposed and implemented for an experimental roadway with combining production and geological conditions. The field practice shows that bolt-shotcrete-net-grouting combined supporting technique can effectively control the large deformation of surrounding rock.

The layered soft rock is widely distributed in Western China, such as slate, carbonaceous slate, phyllite, and so forth. During the tunnel excavation, geotechnical problems frequently occur in the surrounding rock, such as excessive overbreak and intense deformation associated with asymmetric squeezing, because of low strength, poor self-stability and intense anisotropy of structural strength in layered surrounding rock. Large deformation can result in intense damage to the primary support, and even splitting of secondary support, significantly influencing the construction and security of tunnels. At the site of Liangshui tunnel in Lanzhou-Chongqing railway, a series of real-time contact pressure monitoring tests is conducted at different positions in section between surrounding rock and support system. Mechanical responses of the support system are analyzed in time and spatial domains using the monitored contact pressure. In-situ monitoring and numerical inversion analyses of displacement are also performed. The results indicate that the contact pressure of support system shows irregular distribution in space, which agrees with the concentrated deformation position of the surrounding rock; and its variation often lasts for a long period of time due to the influence of excavation method. The failure of the steel arch frame takes place in the weak axis plane because of its smaller lateral anti-bending rigidity. Meanwhile, the monitoring data show that their occurrence significantly lags behind the stabilization of convergence deformation. Based on the force characteristics of the support system, a more reasonable design scheme is proposed for tunneling in such a kind of rock.

A field monitoring program is performed to measure the earth pressures acting on the linings and the internal forces in segments of a slurry shield tunnel of Yangtze River tunnel project in Nanjing. The magnitude and distribution of the earth pressure are analyzed around the tunnel deeply buried in a silty sand stratum with high pore water pressure. The internal forces in the segments of concern are calculated under three different vertical loading combinations(i.e. effective overlying soil pressure plus water pressure, Terzaghi’s soil pressure plus water pressure, and water pressure only ), and the results are compared to the ones measured in the field. The results show that: 1) the water pressure acting on the shield tunnel lining is almost equal to the theoretical hydrostatic pressure; 2) the observed vertical earth pressure on the crown of shield tunnel accounts for about 80% of that yield by the Terzaghi’s soil pressure plus water pressure formulation, showing soil arching effect exists above the tunnel; 3) the observed bending moments are smaller than theoretical results of the three combination methods, and the measured axial forces are approximately twice as much as the theoretical results. In addition, the influence of the ground reaction on the internal force in the segments is also discussed. The insights provided from this study can contribute to the improvement of large-section shield lining design.

In application of the current Terrestrial Laser Scanning (TLS) technique suffers several limitations, such as its 1-D nature in monitoring the deformation and insensitivity to infinitesimal deformation. Here a new approach based on the data obtained from repeatedly scanning is proposed for monitoring the slope deformation. The new approach includes three main steps: sampling the raw TLS data, registering the obtained TLS data, and computing the deformation based on the subareas matching method. Central to the proposed procedure is a 3D matching algorithm (a generalized concept of the least-squares 2D image matching). Taking advantage of the high redundancy of TLS data, the procedure can be used to monitor the full 3-D deformations with high resolution, yielding the transitional and rotational displacements of the monitored objects, while possessing high flexibility in application. The performance and advantage of the approach are illustrated through a designed simulation experiment. In addition, a case study is performed based on the proposed approach, further confirming the result of the simulation experiment. This procedure is applicable to the deformation monitoring, especially for the remote areas, helping promote the transition of the current deformation monitoring method from pointwise to morphological monitoring.

A new method for dynamic reliability analysis of slope stability is proposed with considering the energy-time distribution. In this method, the dynamic critical slip surfaces and their factors of safety (FOS) are described as time series. The slope reliability evaluation criteria including dynamic fuzzy failure probability, dynamic reliability index and dynamic FOS, are obtained utilizing the statistical windows of duration that are extracted according to the characteristics of energy distribution of slope dynamic response. To validate the proposed method, a soil slope stability standard testing problem issued by Australian Association for Computer Aided Design (ACADS) is analyzed under the conditions of the Lushan Ms =7.0 earthquake. The differences of analysis results, which are controlled by the selection of statistical windows of duration, are studied in detail. The case study shows that: （1）The new method can yield good results by emphasizing the most significant time period.（2）The fuzzy discrimination for slope failure state significantly improves the reliability evaluation, which avoids the problem of insufficient discrimination of the traditional methods. （3）The guaranteed-probability-based dynamic FOS of slope has great potential of application and inherent the advantages for reliability analysis. Formally it is compatible with the definition of static stability FOS; quantitatively it is the conservative estimate of instantaneous FOS; and practically it compares well with the pseudo-static method in existing design specifications.（4）In this case, the locations of dynamic critical slip surfaces tend to approach the static critical slip surface. It is illustrated that a reinforcement design under a static or pseudo-static method framework still has a positive meaning in dynamic seismic conditions.（5）The new method provides a way to quantitatively determine the optimal redundancy of seismic design specifications. In summary, the new method provides new ideas, techniques and a reference example for slope seismic analysis.

The self-healing behavior of mudstone is an important topic, which has to be addressed in site assessment and stability analysis for the nuclear waste repository. With a high-level radioactive waste repository in mudstone as background, the laboratory experiments and field tests are performed, and the distribution model and self-healing model of permeability are developed with introducing a decaying exponential function. Based the long-term field monitoring data of excavation-disturbed zones, a hydromechanical (HM) coupling model, which can describe construction and excavation processes, is developed and implemented into a finite element code for the optimization analysis of the permeability coefficient, with combining a new exact penalty function and the Nelder-Mead algorithm. The permeability coefficients of the excavation-disturbed zone around a waste repository are studied using the proposed procedure. The results show that the permeability coefficients from both the inversion analysis and the measurements have the same magnitude of 10-12 m/s, and the calculated pore pressures are also very close to the measured data. The vertical permeability coefficient is disturbed by excavation more significantly compared to the horizontal permeability coefficient with regard to both the intensity and the extent, and indeed the magnitude of the vertical permeability coefficient is increased by 2 orders, while the disturbed area is about 25 m. The self-healing time is about 5 years.

In the 3-D finite element analysis of complex geotechnical structures such as earth-rockfill dams, the hexahedral elements with a high precision are generally adopted with being supplemented by some degradation elements as transition. Because of their poor geometric properties, the degradation elements could degrade the precision of the finite element method. One way to overcome such a problem is to adopt transitional isoparametric elements. Here the interpolation functions, integral coordinates and weighting coefficients are summarized for some common transitional elements such as 3D wedge, tetrahedron and pyramid elements and implemented into a finite element program. By comparing the finite element analysis results of an ideal earth dam using hexahedron elements and pyramid elements, respectively, it is shown that the pyramid elements are sufficient with regard to the precision. The three kinds of transitional elements are then used in analyzing a real earth-rockfill dam, and the numerical results show that use of transitional isoparametric elements can improve the computional accuracy to some extent. Finally, the quadratic isoparametric elements are analyzed and adopted in a dynamic analysis of the elastoplasticity problem. Use of the quadratic isoparametric elements can substantially improve the precision in calculating the excess pore pressure.

Although the limit equilibrium method for rigid bodies and the nonlinear finite element method are commonly used to analyze the deep anti-sliding stability of gravity dams, the limit equilibrium method does not capture the feature of progressive failure of gravity dam, and the nonlinear finite element method cannot effectively simulate the behavior of discontinuous rock masses. In addition, a unified failure criterion has yet to be developed for the finite element analysis. Using the calculated boundary stresses based on the discrete block method, a formulation is derived for calculating the factor of safety with regard to the deep anti-sliding stability of gravity dams with multiple sliding planes, and the physical meaning of the dam foundation failure criterion based on the energy mutation of the dam-foundation system is clarified. By comparing the calculated results of the finite element method and the limit equilibrium method, the proposed method and criterion are validated. A case study is performed on the 12th section of Xiangjiaba Gravity Dam, and the results indicate that the instability zone of dam foundation is composed of a yield zone of rock mass foundation and a sliding zone of structural planes. This implies that the proposed method and criterion is capable of addressing the deep anti-sliding stability of gravity dams, and yielding a reasonable factor of safety for dam design.

Pulsating hydro-fracturing (PHF) is a new technique on substantially increasing permeability in coal seam. However, few studies have considered the stress propagation and distribution of PHF in real formation. Combining with perfectly matched layer (PML) absorptive boundary and quasi-static confining loading technique, staggered-grid high-order difference numerical method is used to establish a dynamic and static response numerical model in infinite elastic formation with confining pressure. The peak value distribution of minor principal stress is investigated with different loading styles, confining pressures, frequencies, and amplitudes. Numerical results indicate that the transmission and interference effect of stress wave are the dominant factors which make the permeability-enhanced area of PHF is much larger than that of conventional fracturing. The frequency and amplitude are directly proportional to the PHF effect, but only the amplitude overtops a threshold value controlled by confining pressure, the permeability-enhanced area can be brought; the confining pressure is inversely proportional to the PHF effect, and the second principal stress is the dominant factor. When the second principal stress decreases from 3.5 MPa to 2.0 MPa, the permeability-enhanced area will increase 600% at most. Based on this numerical model, the dynamic and static stress response of PHF and conventional fracturing can be investigated, and its results will provide guidance to optimize the PHF technological parameters.

In studying the deformation and failure mechanism associated with tunneling, it is very important to consider the transient excavation-induced unloading effect and analyze the dynamic response of surrounding rock. Based on the dynamic unloading model of a circular tunnel under hydrostatic pressure, a procedure for simulating dynamic unloading response of tunnel excavation is developed by using Fish language in FLAC3D. A numerical example is analyzed and the results are compared to the theoretical results, showing the validity to the proposed procedure. It is shown that the stress and volumetric strain of the surrounding rock vary in a wavy manner and the proposed procedure can be effectively used to simulate the dynamic unloading response of the surrounding rock. Based on the calculated damage range using the Griffith strength criterion, it is found that surrounding rock damage area is larger than that of the static analysis with considering the dynamic unloading effect. The proposed procedure is applied to analyze the dynamic response of the surrounding rock under different unloading conditions including unloading time, unloading path, tunnel shape, tunnel diameter and ground stress and so on. It is shown that as the unloading time decreases, the unloading path increases in a way gradually to drastically, and the tunnel diameter increases, and that with the increase of geostress and its difference, the difference between the maximum and minimum principal stresses increases. The proposed instant unloading analysis procedure can provide new insights into the deformation and failure mechanism of the surrounding rock of deep buried tunnels.

The limit equilibrium method plays a dominate role in the slope stability analysis, but the method is usually based on certain hypotheses, without considering the nonlinear stress-strain relationship of soil, so it can’t be used to analyze the stability of slopes which fail to reach the limit state or are reinforced. To solve the problem, combining the finite element analysis with multi-population genetic algorithm (MPGA), a general numerical model about the stability analysis of slope under complex stress conditions is proposed. The model can solve safety factor by numerical stress field, and construct fitness function for MPGA, and then use MPGA to provide the slip surface for the safety factor calculation. To ensure the analysis efficiency and rationality, the initial slip surface is generated dynamically according to its development trend and a constraint condition is also added to the slip surface. Finally, by the stability analysis of the homogeneous slope and the slope with weak interlayers, the method is verified to be rational. It’s also proved that the method can be applied in reinforced slopes under complex stress conditions by analyzing the stability of soil-nailed slope.

Hydro-mechanical coupling triaxial tests and acoustic emission monitoring experiments are performed on a sandstone, and the stress-strain relationship and acoustic emission (AE) data of sandstone are obtained under hydro-mechanical coupling conditions. Based on the experimental conditions and results, a HM coupling biaxial model is developed using the 2-dimensional particle flow code (PFC2D) to study the AE characteristics and energy dissipation of sandstone. By its very definition, the incremental dissipation energy can be effectively used to interpret the evolution of AE characteristics. AE source can be traced according to micro cracks, and then the spatial distribution of AE signals and the types of the micro cracks are determined. The results show that: 1) The average contact force between particles is weakened by the dragging force induced by pore water pressure so that the overall strength of sandstone is reduced. 2) The pore water pressure variation reflects the repeated “storage and depletion” nature of the elastic strain energy, which leads to the relatively scattering of AE energy and stress fluctuation after its peak value. 3) The existence of the osmotic pressure promotes the dissipation efficiency of the total input energy, while lessening the total input energy and elastic strain energy. It is necessary to consider the total input energy (elastic strain energy) and dissipation efficiency in determining the total dissipation energy. 4) Crack distribution shows a possible occurrence of an associated crack zone, which is at a certain angel to the main shear zone. Influenced by the hydraulic gradient, the cracks become denser in inlet for water than outlet. 5) The ratio of the tensile crack number to the shear crack number increases sharply at the peak stress then tends to be constant afterwards.

The creep parameters of rockmass are essential data of geotechnical engineering design. To accurately determine the creep mechanical parameters of rockmass, considering the advantages of the analytical inversion method and intelligent inversion method, the analytical intelligence inversion method coupling the analytical inversion and the intelligent inversion is developed. The proposed method is applied to the Dagangshan hydropower station project to obtain the compressive creep parameters of rockmass in dam zone. The results show that analytical intelligence inversion creep curves are more coincident with experimental creep curves than the analytical inversion creep curves, proving that the creep parameters obtained through the analytical intelligence inversion method to be more accurate and reliable, and hence the validity and rationality of this inversion method are also verified. The method provides an important theoretical guidance for efficient rheological parameters inversion of rockmass in dam area.

In the three-dimensional space, the conventional strain state is expressed by three normal strains and three shear strains. Therefore, six strain gauges at least are required to determine the strain state of a point. Based on the strain state theory, a contacting three-dimensional strain rosette that can measure strain in concrete or geomaterials is developed. The device is made up of six strain gauges, and the layout of strain gauges must meet a special condition. According to the relations of components of strain between representations for the conventional strain and the linear strain in an arbitrary direction, transition matrix is built to bridge relationships between the test results and the traditional strain state. Subsequently, the solution qualification is derived and expatiated in order to illustrate the layout of the six strain gauges. The two schemes, namely the orthogonal tetrahedron and the normal tetrahedron, are studied in detail after considering the construction convenience, rational and logical methods are constructed. The tests on the device itself and further on a rectangular shaped sample made of mortar show that the two three-dimensional strain rosette is reasonable and convenient to measure the strain state of concrete, rock and soil in engineering.