In the Western Sichuan area, settlement or deformation problems often occur in embankments consisting of the mixed soil containing sandy gravel and clay particles. The accumulated deformation under traffic loads could be described by the dynamic constitutive model under cyclic loading. The proposed model uses the mapping rule of mobile mapping origin and integrates the loading-collapse yield criterion within the framework of elastic-plastic bounding surface model. Modified Cambridge model was introduced to define plastic potential equation. Saturation and fine particle content are considered as two main influencing factors. The model parameters are obtained by fitting measured results. Comparisons between experimental results and model simulations show that the elaborated model is capable of describing the unsaturated loess behaviors under static loading and cyclic loading, and predicting the hysteretic properties during both loading and unloading. This model provides theoretical basis for settlement prediction of mixed soil subgrade in the Western Sichuan area.

The interfacial force of the precast pile with different roughness was measured by indoor direct shear test in clayey soil. The changes of the pore water pressure and soil pressure on the pile-soil interface were monitored by miniature piezo-resistive sensors. The influences of interfacial roughness on interface shear strength parameter, interface resistance-shearing displacement curves were qualitatively analyzed. The results show that the percentage of normal stress accounted by pore water stress on pile-soil interface is about 10%, which is supposed to be taken into consideration in practical projects. The concept of pile-soil interface resistance is presented and the resistance is contributed by adhesive force and friction force between clayey soil and concrete. the friction force is the product of the normal effective soil stress and friction coefficient on the interface. As the interfacial roughness of the concrete increases, the interfacial adhesive force increases and gradually closes to clayey soil’s inherent adhesive force. The interfacial roughness slightly impacts on interfacial friction coefficient and interface resistance: the ultimate interface resistance and shearing displacement increase with the increase of the roughness. The results provide references to the design, construction and detection of the pile foundation engineering.

Using a dynamic caustics blast loading system, we studied dynamic behavior of asymmetric Y-shaped cracks propagation under blasting loading. It was found that before two opposite moving cracks encountering, their tip singular fields affected each other, the shape of caustics spots distorted and stress fields of the crack tip changed. Moreover, two moving cracks propagated along the deviating horizontal direction, and the deviation angle gradually increased. However, after two opposite moving cracks encountering, the deviation angle gradually decreased, and two moving cracks propagated along the direction of the existing crack. It can be seen that two branched cracks intersected at the main crack, and the wing crack easily initiated from the branched crack with a smaller incident angle of stress wave and a longer length, and propagated along the vertical direction of the maximum tensile stress. However, this kind of branched crack may inhibit the propagation and the stress intensity factor of the branched crack with a larger incident angle and a shorter length. The average values of dynamic stress intensity factor of the branched crack decreased with the increase of the incident angle of stress wave. In addition, the propagation velocity of the branched wing crack presented oscillating change law. Therefore, the results provide a reliable basis for the analysis of crack propagation in practical engineering.

The shape of sliding surface has important influence on the active earth pressure of retaining wall. A new active earth pressure formulation is proposed based on horizontal differential element method assuming retaining wall backfilled with cohesionless soils is under horizontal translation model. The assumption of formulation is that the sliding surface is curved when backfill behind a retaining wall reaches limit equilibrium and that the soil arching is considered. First, the reliability of the formulation is verified based on the compared calculation results of the formulation, model test and classical theory. Second, the influences of the different internal frictional angles of soil and wall-soil friction angles on the distribution, resultant and loading position of active earth pressure are analyzed. The results show the regions of sliding wedge obtained from curved sliding surface assumption are slightly bigger than the regions of plane assumption. The results by the proposed formulation are more consistent with model test results for retaining walls of different heights. The distribution form and loading position of active earth pressure are close to Paik’s solutions in different inner friction angles and friction angles on the soil-wall interface. However, the magnitudes of active earth pressure are greater than Paik’s solutions slightly.

In this study, acoustic emission (AE) tests were conducted on altered granite gneiss specimens under uniaxial compression conditions. The evolution laws of AE events during the failure processes of specimens were further investigated. The results showed that for most specimens, the first occurrence of the high-energy level AE event indicated that the specimens were at the high-stress level. It is found that the stress level further increased when the intermediate-energy level AE events distribute throughly in specimens. The imminent rock failure was identified by the occurrence of the high-energy level AE event in the final through-going area. For brittle failure specimens, the through-going distribution phenomena of the intermediate-energy level AE events would not occur. For specimens contained weak-zones, the first high-energy level AE event took place at the low-stress level. In the meantime, the intermediate-energy level AE events gathered in a band shape around the high-energy level AE event. However, the density and energy level of AE events were low in the area far away from the high-energy level AE event. The research results can provide a testing basis for the identification of stress level and the evaluation of rock stability.

The shape of crushed rock particle greatly influences the shear behavior of crushed aggregate. However few quantitative evaluation indices were proposed. PFC2D (Particle flow code, 2D) was utilized in this paper to simulate the biaxial shear condition and the randomly shaped polygon particle generation method was studied based on clump logic. By comparing with the experimental results, the numerical model was validated and the parameters were determined. The angularity index was modified based on current research by dividing the clumped particles into polygons. The effect of particle shape on the shear behavior of open-graded crushed aggregate was analyzed. The results showed that, the AI (Angularity Index) was greatly influenced by the partition density, AI increased and became stable with partition density. The shear strength increased nonlinearly with the axial strain and the morphological characteristics of the curve was obviously affected by particle shape, except ball particle, all the aggregate showed shear hardening. The shear strength and friction angle increased slowly when AI was relatively small before pronouncedly increased with AI, the relationships can be fitted with power function.

To reveal the effect of freeze–thaw cycle on elastic parameters and uniaxial compressive strength of slate, uniaxial compression tests were conducted on slate specimens with seven types of bedding angles under six types of freeze–thaw cycle. The DX-40 low-temperature control box and DNS100 miniature control electronic universal testing machine were applied for tests. We analyzed evolution laws of five elastic parameters, uniaxial compressive strength, and failure forms. Experimental results showed that the elastic modulus, shear modulus, and uniaxial compressive strength decreased exponentially with increasing the number of freeze–thaw cycles. While Poisson’s ratio increased linearly with increasing the number of freeze–thaw cycles. Particularly, the uniaxial compressive strength firstly decreased and then increased with increasing bedding angle. It is found that there are three kinds of failure forms under uniaxial compressive stress. When the bedding angle was 0°≤?≤26.6°, shear failure occurred with a certain angle from the vertical axis. When the bedding angle was 26.6°≤?≤83.0°, shear failure occurred along the bedding plane. When the bedding angle was 83.0°≤?≤90°, splitting failure occurred along the vertical direction. On the basis of the single discontinuity theory proposed by Jaeger, an empirical formula of uniaxial compressive strength was established and further verified by experimental data, in which bedding angles and the number of freeze–thaw cycles were considered as control variables. Therefore, the effects of the number of freeze–thaw cycles and bedding angles on compressive strength of freeze–thawed transversely isotropic rock can be well simulated by the model.

By using a self-developed shear-seepage coupling experimental device for coal rock, experiments were carried out on sandstone samples to obtain shear-seepage coupled properties under the action of seepage water. The results show that with constant seepage water pressure, the larger normal stress was, the higher shear strength was, but the smaller normal deformation was. Moreover, the shear deformation process of sandstone can be divided into three stages: the linear growth stage, the unstable fracture stage and the friction sliding stage, respectively. In the case of the constant seepage water pressure, as the normal stress decreased, the peak values of normal and shear deformation of specimen increased, and meanwhile the fluctuation of shear section grew. Besides, the surface crack growth became more obvious and widely distributed, and the damage of sandstone was more serious. In the total shear process, there were several apparent value reductions of shear stress. Usually, the first stress reduction occurred at the end of the stage of elastic deformation, and water flowed out at the same time, which means the first stress reduction caused by the first macrocrack is spatial connected. Furthermore, the larger normal stress is, the narrower fracture is and the worse water transmitting ability is. During the whole experimental process, the lower mean flow rate is, the smaller total flow is.

Under natural conditions, geomaterials under gravity usually exhibit transversely isotropic properties. In this study, a new failure criterion for transversely isotropic brittle materials has been developed. The derivation of this failure criterion is driven by the strain energy density, rather than a completely phenomenological approach. So the form of the failure criterion can be coordinated with elastic strain energy density. This coordination explain the terms in the failure criterion as well as those in the elasticity theory. Obtained by series expansion this new failure criterion includes five independent material parameters and five terms which can be coordinated with those of the elastic energy. These material parameters can be determined by corresponding independent test, and are not just fitting parameters. The shapes of the failure surface in the stress space and in the π-plane of the proposed criterion are compared with Tsai-Wu criterion. Although the derivation of the criterion is totally different, the comparison results show this failure criterion is similar to Tsai-Wu criterion. In addition, this failure criterion can be degenerated into the criterion suggested by Christensen for isotropic materials. Comparisons with three sets of experimental data are compared to illustrate the proposed criterion. the results illustrated the prediction ability of the criterion.

A set of test devices were developed, and a series of full-scale uplift tests were carried out on a pipe segment buried in lumpy soft clay backfill. Focusing on the influence of shear strength of soil, depth-diameter ratio and loading mode, the pile-soil interaction, the failure mode and the uplift resistance were studied. The test results show that the deformation properties of lumpy soft clay backfill are different from uniform soft clay during uplifting. For the former, deformation is due to the position shift of soft clay blocks and the outflow of water in gaps between the blocks. For the latter, it is due to consolidation. When the depth-diameter ratio is equal to 1, the failure mode of lumpy soft clay backfill is more closed to ‘local’ flow-round. It is much less than DNV’s suggestion which is 3. It was suitable to use Palmer’s approach to calculate the uplift resistance of lumpy soft clay under long-term load if 1. The uplift resistance of pipeline in lumpy soft clay increases as the increase of and it is mainly linear increase with the increase of the shear strength. The consolidation rate of lumpy soft clay is much larger than uniform soft clay, so it may be taken into account of the effect of strength restoration of clay to the uplift resistance during design.

Geogrid has been widely used in various practical reinforced soil structures, and are more or less in plane strain conditions. In order to describe the compound stress-strain behavior of geogrid reinforced soil under plane strain conditions and to improve the understanding of geogrid reinforcement mechanisms, large-scale biaxial compression tests were carried out on granular soil and geogrids with different numbers of transverse members. The influence of geogrid transverse members on the strength and deformation behavior of reinforced soil was investigated. The experimental results showed that the maximum vertical stresses of reinforced soil specimens were greatly improved using geogrid reinforcements. With increasing number of geogrid transverse members, the maximum vertical stress of reinforced soil specimen increased. Using the Digital Image Correlation (DIC) method, the displacements and rotations of soil particles in the unreinforced and reinforced specimens under the same confining stress were achieved to visualize the geogrid reinforcing effects. Moreover, the maximum longitudinal geogrid tensile strain in each reinforced specimen under biaxial compression loads occurred in the middle part of the geogrid and decreased gradually from the middle part to the side boundaries of the geogrid. Under the same vertical strain, the tensile strains within the upper geogrids were slightly larger than those within the lower geogrids. The longitudinal tensile strains decreased with increasing number of geogrid transverse members under the same vertical stress.

Permeability of mudstone interlayer is an important factor to evaluate the sealing property of salt cavern gas storage. The permeability of a certain mudstone interlayer in Jintan is relatively high according to pressure tests, and thus it is inappropriate for the sealing performance. Since the borehole cores of mudstone interlayer are easy to be broken, it is substantially difficult to carry out systematic permeability tests. To solve the problem, we proposed a new method for testing the permeability of brittle mudstone interlayer. The brittle interlayer cores tightly wrapped by epoxy resin were cut and polished to prepare standard samples for meeting the requirement of permeability tests. To observe the cement situation of the mudstone interlayer cores and the epoxy resin, the synthetic samples are carried out by scanning electron microscope (SEM). It is found that the pore of the interface is lower than that of rock and the interface cement as well, which shows that the interlayer core is the main seepage channel of synthetic samples. The results of permeability tests on synthetic samples by using a steady-state method are consistent with other results in the literature, which proves the reliability of this new method. The theoretical analysis also shows that the permeability results measured by the new method are consistent with the theory, and thus the feasibility of the method is verified theoretically. The new method of testing the permeability of mudstone interlayer proposed is feasible and reliable. This method has a certain reference value for the test of the permeability of the irregular brittle core.

Under the action of earthquake, the deformation and failure mode of the deposit slope depends on many factors. To study the influence of the inclination of slope surface and rock-soil boundary on the dynamic response of the deposit slope, a model test using a horizontal shaking table was conducted to simulate the failure process and dynamic response of the deposit slope under different inclination conditions. The results show that the failure mode of the deposit slope was controlled by both slope surface and rock-soil boundary. When the dip angle of the rock-soil boundary was in a certain extent (less than 20°), only local collapse in the slope occurred. As the dip angle of the rock-soil boundary increased, the failure mode of the deposit slope gradually turned from local collapse to entire sliding. Moreover, the inclination of slope surface controlled the extent of collapse.

According to the relative variable trend of slope displacement after its construction, this study declared the definitions of the relaxation zone and pre-compression zone, which are collectively referred to as the influenced zone. The construction process of the multi-stage slope was simulated through a large-scale model test. Meanwhile, the concept of the overlapping effect of influence zone was proposed. If the excavation relaxation zones (or pre-compression zones) of lower slope overlapped with pre-compression zones of the upper slope, it would produce relaxation (or reinforcement) effect on the soil and rock of the overlapped zone which belongs to the upper slope. As a result, the force of retaining structure in the overlap zone was influenced. Furthermore, it is found that the wider the overlapped region was, the stronger influence was. However, the overlapping phenomenon had no effect on retaining structures outside the overlapped region. Therefore, the reason for the force change of retaining structure was essentially caused by the overlapping effect in the influenced zone.

According to the particularity of porous structure and mineral composition in coastal energy storage shallow brackish aquifers, a controllable experiment of one-dimensional (1D) sand column infiltration was conducted. By combining with the mass transfer theory in porous media, this study probed into the internal connection at the porous scale that gave rise to the aquifer medium micro-nano particles detachment, transportation and attachment resulting from the particle morphology characteristics, and then explicated the induced mechanism of particles redistribution. The results indicate that, compared with another type of particle, the release rate of the spherical silica powder is the highest, and the accumulative weight of this particle in effluent liquid is up to 93.74 mg. However, the release rate of the brackish aquifer sand is the lowest, merely 0.62% when the hydrodynamics and physical-chemical properties of seepage solution is the same. Morover, the mechanical composition and porous structure of aquifer medium is also similar. After that, based on experimental results, the inversion of the adopted particle transport model with two kinetic retention sites is introduced. The results show that the brackish aquifer sand of the first-order attachment coefficient on the second kinetic site which is assumed to be irreversible and depth-dependent is 2 orders of magnitude higher than another two groups of the artificial aqueous medium column. Combined with experimental results from the SEM and the Zeta potential of particles, it is found that the seepage shear stress is directly proportional to the normal cross-sectional areas of particle. The diffuse electric double layer repulsion is obvious different from the change of particles morphology and mineral composition, which are based on the analysis of forces and force torque balance for the particles located on the internal grain surface of the aquifer medium. Therefore, the spherical silica powders usually detach in the form of monomer type from the grain surface of the porous media. However, regarding flake secondary clay mineral particles, the regular release type is a large size particle group which could enhance the probability of the attachment in matrix surface or the captured by the pore throat.

In this study, precast concrete blocks, #45 steel screw, mine chemical grout were used to simulate the surrounding rock and bolt. Shear tests of bolted jointed rock specimens were carried out to study characteristics of jointed shear stress and the cable deformation under three conditions of no-anchored, end-anchored and full-anchored specimens. The results show that obvious differences were found in curves of shear-jointed rock displacement with various anchoring ways. The no-anchor specimen was characterized as brittle. For the end-anchored specimen, a turning point was found in the slightly decreased shear when adjusting the shear strength of anchor. Compared with the above two specimens, the best matching was achieved by the full-anchored specimen with the joint, which indicates that the bolted specimen could bear the greatest shear force. For both the end-anchored bolt and the full-anchor bolt, their deformation characteristics can be divided into the tensile zone, shear-tension zone and compression zone. Under the combined action of shear and tension, the failure of the anchored bolt occurred in the shear-tension zone. With different anchorage modes, the distribution of axial force varied as well during the shear test. The axial force of full-anchored bolt was mainly distributed in the vicinity of the joint. Moreover, it decreased rapidly with the increase of the joint distance. While the distribution of axial force was relatively uniform in the end-anchored bolt.

Using a modified split Hopkinson pressure bar (SHPB), the tests were conducted on deep rocks under three-dimensional (3D) high-static load and frequently dynamic disturbance. Then dynamic stress-strain curves were obtained for describing general features, which can be divided into four stages, namely, steady development of microcracks, non-stable development of microcracks, fatigue damage, and fatigue destruction. Particularly, two stages after the peak value were in the dynamic stress unloading process. Based on the continuous divisor, strain equivalent principle and statistic damage principle, a fatigue variable of rock was defined and a damage evolution equation was deduced. Then, a combination model was adopted to establish a damage constitutive model. Compared with testing data, a damage evolution law of rock and the established damage constitutive model were verified. The damage variable was also calculated using the deduced damage evolution equation. Experimental results show that the relevant curves between the damage variable and dynamic strain conform to damage law of rock samples. It is also found that the established fitting curves of constitutive equations show comparatively good agreement with experimental curves. Hence, it indicates that the established damage constitutive model can be used to predict dynamic mechanical characteristics of deep rock under 3D high-static load and frequently dynamic disturbance.

Reconstructing the inner structure of rocks has been one of the critical problems in the field of experimental rock mechanics. In this paper, natural sandstone specimens were selected as research objects, and CT scanning and two different kinds of three-dimensional (3D) printing methods were adopted to reconstruct 3D-printed specimens. It turns out that the structures of 3D-printed specimens were in proximity to natural sandstone specimens. Uniaxial compression tests and Brazilian tests were carried out on these two kinds of specimens to obtain mechanical properties. Then the strength and deformation law of natural sandstone specimens and two kinds of 3D-printed specimens were compared. The results indicated that specimens made by different methods of 3D printing technology could highly reconstruct the complex inner structure of natural sandstone specimens. In the meantime, physical and mechanical properties of 3D-printed specimens were closer to natural sandstone specimens, and the dispersion of experimental results was relatively small. Therefore, this study provides a new promising way that can conduct experimental research, produce substitutes for materials and verify numerical simulation results.

As the increasingly harsh conditions of deep excavation in urban area, two or more different depths of excavation in one foundation pit are becoming more common. Ignoring the influences caused by two different asymmetric excavations, traditional method to solve this problem is simplifying the asymmetric excavation as symmetrical and using the deeper side in calculation. Given that, analytical solutions for the length of retaining structures in foundation pit considering the influences caused by two different asymmetric excavations have been deduced using the equivalent beam method. The influences on differences between retaining structures on two sides and their insertion ratio caused by two different asymmetric excavations have been investigated. The results show that, considering two different asymmetric excavations, insertion ratio of retaining structures located on the side of pit with shallower depth increases compared with calculating results without considering two different asymmetric excavation. This enhancing effect of insertion ratio becomes more obvious as the depth of deeper side of the excavation increases. Finally, a case study proved that the analytical solutions can improve the asymmetric excavation pit design method, and provide a useful and economic reference.

Pre-stressed anchor cables are widely used in tunnels, slopes and foundation pits. The loss of anchorage force affects the anchoring of pre-stressed anchor cable. The engineering accidents of anchorage failure often occur owing to the loss of anchorage force of pre-stressed anchor cable. The stress state of pre-stressed cable anchor is easily changed and anchor failure leads to engineering accident in water-affluent region. Based on the deformation data, this paper establishes a coupling constitutive model considering soil creep, anchorage force loss of pre-stressed anchor cable and seepage force. Then, the three-dimensional creep equation of soil and relaxation equation of anchoring force loss of pre-stressed anchor cables are deduced. Based on FLAC3D software, the corresponding procedure is developed to calculate and analyze the soil creep and anchoring force characteristics loss of the above mentioned foundation pit in coastal region. Combined with monitoring data, the above constitutive model is feasible and correct for analyzing anchoring force loss characteristics of pre-stressed anchor cables under seepage condition. The research results provide meaningful theoretical and practical guide for other similar projects.

According to the history and current situation of ground caving-in in the eastern Chengchao Iron Mine, a 3D surface model of ground caving-in was reconstructed with the help of a 3D laser scanning technology. Furthermore, the ground subsidence contour map and the accumulative subsidence basin were obtained by combing with Surfer program. It showed that the initial ground caving-in points were mostly distributed in the marble area and the wall rock alteration zone. It is found that the ground caving-in area was a zonal distribution from east to west. Moreover, the situation of ground caving-in in the north was more severe than in the south. The terrain and landform of the ground caving-in area show similar glacier landscape features, such as the horn and blade ridge. According to geological conditions, underground mining situations and monitoring data of cracks and ground surface deformation by the 3D laser scanning technology, it is considered that underground mining is an internal cause and geological condition is an external cause for ground caving-in. The combined effect of these two factors led ground caving-in to appear mostly in the marble and surrounding rock alteration zone area for the first time. After the emergence of ground caving-in, a high level horizontal tectonic stress was released. As a result, rock mass, which was cut into a cantilever beam-plate by NE-trending joints, was broken. Through the analysis of the mechanical model of a cantilever beam-plate, the scope of fractured rock mass reached up to 172 meters wide. The fractured rock mass produced toppling-sliding failure along the sliding surface. Therefore, this mechanism of mechanical expansion makes the scope of ground caving-in wider, and finally forms a large ground caving-in basin in the eastern Chengchao Iron Mine.

The floor water inrush coefficient of No.2222 mining face is close to the critical value and a high possibility of floor water inrush occurs due to insidious faults in Xingdong coal mine. This paper aims at solving the above problem, and ESG micro-seismic monitoring system was applied to monitor the forming process of water inrush pathway. Besides, the space location of water inrush pathway was obtained by a developed micro-seismic analysis system CMMA-3D. Hence, this provides significant guidance for targeted grouting and safe mining above the confined aquifer. The mechanism of water inrush through insidious faults was analyzed based on fracture mechanics and then a formula was deduced to calculate insidious fault propagation length. The propagation laws of different types of faults, including normal fault and reverse fault, were achieved. When the insidious fault is a normal fault, its propagation length ?l is positively correlated with confined water pressure p and lateral pressure coefficient . When the insidious fault is a reverse fault, its propagation length ?l presents the variation tendency of decrease-increase with the increase of confined water pressure p. The permeability of floor fractured zone decreases with the increase of compaction degree of caving rocks, which reveals the reason for water irruption reduction of a later stage in No.2222 mining face.

In high-level radioactive waste (HLW) disposal engineering, structure in rock mass is a key parameters in rock mass quality assessment which may provide potential pathway for nuclide migration. Under the consideration of the great importance of joints on the long-term safety requirements for HLW disposal, a multi-dimension and multi-scale comprehensive index-SCE is proposed to conduct rock mass quality assessment. The index-SCE is applied to assess the quality of Tianhu rock mass, the pre-selected area of high radioactive waste repository using the structure date from borehole and outcrop. Results show that the SCE is more effective than conventional rock mass assessment method (single parameter method). The research could provide scientific understanding for quality assessment of rock mass, which help understand more properties such as the permeability of rock mass and the migration of nuclide. In a word, this index will provide meaningful reference for site selection and quality assessment for high-radioactive waste repository.

The aim of this study is to resolve the present control problems and the corresponding high-strength anchor cable control technology in deep large section roadways. This study was based on the Hoek-Brown criterion and the upper bound theorem of the limit analysis and also considered the stress of surrounding rock in the roof and the effect of supporting the load. On the above basis, the roof caving mechanism of large-section roadways was acquired. Furthermore, a design method for roofs was put forward for the minimum length and the pre-tightening force of an anchor cable. Since the design parameters of anchor cables was affected by established sensitivity indexes, it is important to investigate the effects of established sensitivity indexes on factors, such as the roadway’s width, the specific weight of the rock mass, the stress in the surrounding rock, the compressive strength and the tensile strength of the rock mass, anchor cable layout spacing and vertex anchor cable laying angle. According to the actual field conditions, engineering suggestions are proposed for controlling surrounding rocks in the deep large-section roadway. Finally, this design method was applied to determine the roof anchor parameters of transport gateway of 1305 Island Coal Face in the Kilometer Deep Well Zhaolou coal mine, which effectively controlled the deformation of surrounding rock. From research results, only when the roof anchor cable was anchored in stable rock and enough pre-tightening force was exerted, the roof rock caving and damage can be effectively controlled in high-stress large-section mining roadways. It is found that roof pre-tightening force for anchor cable decreased with the increase of tensile strength, compressive strength and empirical parameter A of rock mass. Besides, this roof pre-tightening force increased with increasing the width of the roadway, the specific weight of rock mass, the stress in the surrounding rock, the compressive strength and the tensile strength of rock mass, anchor cable layout spacing, vertex anchor cable laying angle and empirical parameter B of rock mass. Moreover, the highest sensitivity of all the influencing factors turned out to be the surrounding rock stress. This indicates that special attention should be paid to the influence of in-situ stress of the surrounding rock when designing the deep high-stress roadways. Therefore, the effective release of the surrounding rock stress can be achieved by using the high strength, high elongation anchor cable and adding the yieldable device. Meanwhile, the integrity of the surrounding rock can be improved by applying high pre-tightening force and grouting reinforcement, resulting in better control performance of surrounding rock.

In southwestern of China, the stability problem of the complex high slopes subjected to excavation has become one of the key technical problems in the hydropower project construction. Based on the geomorphic conditions, characteristics of geologic framework and stress measurement data of the left bank slope of Baihetan hydropower station, by using the discrete element analysis procedure UDEC, a calculation model was established to study the stability of the left bank slope during excavation unloading. The principal stress field, deformation field and plastic yielded zones distribution law were studied under the condition of excavation, then the deformation mechanism of the left bank bedding rock slope has been declared. Meanwhile, the potential damage zone and critical sliding surface in deep rock mass were identified and delineated, by combination with the microseismic activity at the left bank slope during the periods of excavation and stress redistribution. The comprehensive studies indicated that the deformation of the left bank slope is mainly affected by multiple factors, such as tectonic stress, geological structure and unloading. The weak structure planes, such as LS3318, LS3319, LS331, LS337 and F17, play a decisive role in the excavation deformation of the left bank slope. The research results can provide valuable references for excavation and reinforcement of similar bedding rock slope projects.

The reinforcing and restraining effect of pile groups and the soil deformation under the pile tips are the key problems in settlement calculation of pile groups. However, the research on pile groups settlement is insufficient and needs to be continued. The reinforcing and restraining effect of pile groups was analyzed using the shear displacement method. The relations of settlement and axial force between bottom and top of each pile in layered soils were deduced by the load transfer method, respectively. Based on virtual soil-pile model, the calculation formula of virtual soil-pile length was provided. The relations of settlement and axial force between top and bottom of each virtual soil-pile in layered soils were obtained. Flexibility coefficient matrix was ascertained by the boundary conditions and the balance equations of pile section and virtual soil-pile section. Pile groups settlement was obtained based on different pile cap types. Lastly, case study indicated that settlement predicted by the present method agrees well with those measured from real test of engineering cases. The proposed method has high accuracy. The research played a complementary and promoting role on the development of settlement theory of pile groups.

The deformation of roadway roof is considered as an important index for evaluating the stability of roadway roof. In addition, the spacing fractal dimension of the fissures is a significant parameter of comprehensively reflecting the development and distribution characteristics of the fissures in roadway roof. In this study, a mathematical relationship between these two indexes was established. The multiple-point displacement meter was used to monitor the roof deformation of the mining induced roadway in Shuanghe Coal Mine. Meanwhile, the mine bore TV imager was employed to observe the development and distribution characteristics of the fissures in roadway roof. Thus, the spacing fractal dimension of the fissures was calculated. The monitoring results show that the most developed fissures were found in the range of 0~2 m of the roof. In this range, the linear density of fissures followed the same change law with the spacing fractal dimension of the fissures, and a linear relationship was found between them. The same change trend exists both in the roof deformation of the roadway and the associated spacing fractal dimension of fissures. The corresponding roof deformation increased with increasing the spacing fractal dimension of fissures, furthermore they increased linearly. This study indicates that the spacing fractal dimension of fissures in roadway roof is an indicator that can comprehensively reflect the stability of roadway roof. Hence, this study provides a reliable basis for evaluating the stability of roadway roof and designing the supporting.

Currently, most of studies on the mechanisms of driving and pulling for Benoto pile sleeve are focused on sleeve driving process. Yet, pulling by high-frequency vibration are deficient. Using the ALE (Arbitrary Lagrangian-Eulerian) method, the finite element-infinite element coupling model is developed to explore the pulling mechanism and influence of parameters on sleeve pulling. The results of numerical analysis show that the process of sleeve pulling by high-frequency vibration can be divided into two stages: the slow and the fast pulling stages. During sleeve pulling, the soil displacements, stresses, void ratio and excess pore water pressure all mutate near the sleeve end, and the change is more significant as approaching to the sleeve center. Therefore, the influence of soil parameters (including soil young’s modulus and soil-sleeve friction coefficient) and vibration hammer parameters (such as vibration frequency and vibration force) on sleeve pulling are investigated. When the soil is soft and the friction of the sleeve-soil is strong, the change of soil displacements and stresses variety are obvious. The parameters of the vibrating hammer only have influence on sleeve pulling speed and soil particle velocity, and hardly have any effect on soil displacements and stresses. When the vibration frequency is close to the natural frequency of soil layers, the pulling resistance is the small. The larger the vibration frequency is, the smaller the influence range of vibration.

Analytic solutions and numerical solutions were employed to analyze the effect of the crack face contacting on the Mode-II stress intensity factors (SIFs). The crack face of the centrally cracked Brazilian disk (CCBD) specimen was subjected to both the confining pressure and diametrical force. Through the theoretical study, the stress field inside the CCBD specimen was analyzed under different loading conditions when the crack surface contacted. Then, an analytical formula was obtained for calculating the Mode-II SIFs in CCBD specimen under different loading conditions by using the weight function method. Meanwhile, a numerical modeling by ANSYS software is used to calculate the corresponding SIFs. By comparing numerical results and theoretical solutions, it is found that they are in good agreement, which indicates that the reliability of the theoretical analysis is valid. Even if the crack is closing, the SIFs can be obtained explicitly and easily for any arbitrary relative crack length, loading angle, confining pressure and friction coefficient. Finally, the effect of the coefficient of friction on SIFs in a CCBD specimen was investigated. The results show that the Mode-II SIF decreased significantly with the increase of friction coefficient, while the Mode-I SIF was constant. In addition, more complex secondary cracks were produced on the crack surface when the load angle was larger. Hence, the recommended loading angle range is 30°~50° for compression-shear fracture tests.

Soil-rock mixture deserves special attentions from engineers as one type of general geotechnical material. The numerical simulation of soil-rock mixture provides direct consultation for engineering practices. The mesoscale model of soil-rock mixture was reconstructed first and appropriate numerical method was selected afterwards. Establishing mesoscale model in two-dimension can be summarized as filling the model area with randomly generated rock inclusions obeying known size distribution and meanwhile avoiding overlaps. In this paper, the background Mesh-EAB algorithm is proposed to replace the widely adopted random sequential addition algorithm. In the latter algorithm, a random position for the newly added rock inclusion needs to be repeatedly generated if overlap between this inclusion and previous added rock inclusions can be detected. Thus, it is based on trial-and-test. In the Background Mesh-EAB algorithm, a prior knowledge about overlap can be obtained and thus eliminate the necessity of trial-and-test and improve the efficiency. In the stage of numerical method, the numeric manifold method is adopted. Furthermore, the original numerical manifold method with uniform mathematical cover generator is modified adaptively. Due to the difference in the magnitude of deformations, individual mathematic cover is generated for each rock inclusions while uniform and denser mathematical cover is generated for soil. The revised numeric manifold method can reproduce the interaction between discrete blocks and continuous medium. Finally, the confined compression test of soil-rock mixture is simulated to unveil the influences of confining stress and dislocations between soil and rock on the compressive strength of soil-rock mixture.

In this paper, the diffraction of Rayleigh waves around a circular cavity in poroelastic half-space was investigated by indirect boundary integral equation method based on the Biot’s two-phase medium theory. The impacts of incident wave frequencies, porosities, drainage boundary conditions and depths of cavity on the displacement and pore pressure responses were discussed in detail. The results show that the existence of circular cavity amplifies the surface displacement and pore pressure in poroelastic half-space. The peak values of horizontal and vertical surface displacement were enlarged by 10.1 times and 11.2 times respectively for drained boundary, and enlarged by 12.0 times and 9.6 times respectively for undrained boundary. The peak value of surface pore pressure increases by 2.1 to 3.0 times compared with the free field responses. The peak values of displacement and pore pressure responses were both found at the cavity boundary close to the incident wave. With the increase of incident wave frequency or cavity depth, the amplification effect was weakened. The maximum pore pressure around cavity was found at the top of the cavity. For constant porosity, the pore pressure around cavity will reach the highest level when the incident frequency is 1.0 and reach the lowest level when the incident frequency is 2.0.

Currently many researchers studied size effect on the crushing strengths of rock particles, but they rarely considered the complex shapes and internal structures of heterogeneity. By the stochastic granular discontinuous deformation method (SGDD), numerical was employed to simulate the single particle compression tests for rock particles with five different sizes. Particle crushing is simulated by introducing zero-thickness interface element and cohesive zone in SGDD model. Then we studied the influence of interface strength on particle crushing, and analysed size effect on the crushing strengths of rock particles using Weibull model. Comparing with single grain compression test indoor, the SGDD method makes the crushing process of single particle compression very realistic. Every compressive curve shows the same trend, that is, the curves increase sharply before reaching the peak force and followed by a sharp drop at fatal breakage. The peak stress is the strength of particle crushing. Crushing strengths in every group of particles satisfy the Weibull distribution well with an average Weibull modulus of 2.48. In addition, the crushing strengths among different groups of particles shows that the characteristic strengths decrease with the increase of particle size. The characteristic strengths and particle sizes obey a power law with an exponent of -0.163, less than the prediction of Weibull model.

Currently, there are few studies on inclined pile field test. Four piles at the position of 40 # and 41 # fans (two vertical piles, two inclined pile) were tested for their vertical bearing capacity in Donghai Bridge Wind Farm Phase II project. Prior to testing, the ABAQUS was used for preliminary analysis on vertical piles and inclined piles under reasonable conditions and selected soil parameters. it found that the calculated results and post-test results are close, and after comparing calculated results and the results of test piles, it showed: 1) at the project site conditions, finite element analysis and experimental results showed that the vertical ultimate bearing capacity of inclined pile was less than vertical ultimate bearing capacity of vertical pile. 2) when the inclined pile was under axial load, the settlement and the settlement value range on the anticline side of the soil were significantly greater than that on the oblique side; 3) the finite element analysis and the parameter value were more reasonable, which could provide reference for similar project preliminary analysis; 4) ultimate bearing capacity of the two vertical piles was less than design value: ultimate bearing capacity of the two inclined piles was greater than the design value; the proportion of pile side resistance of the two inclined piles was higher than that of two vertical piles; the proportion of pile side resistance was lower than two vertical piles.

Based on BOTDR technology, Brillouin strain monitoring technology has been applied preliminarily in the field of geotechnical engineering. However, a series of experiments and engineering applications reveal that there are large differences induced by using different types of fiber optic cables, due to the sheath effect. In this study, three kinds of cables were selected to comparably investigate the engineering performance, namely new strain sensing fiber optical cable, suit fiber optical cable and armored fiber optical cable. Based on BOTDR fiber optic strain monitoring technology, a number of experiments, including precise positioning (temperature stimulation), strain measurement range (drift) and temperature measurement, were carried out. As a result, the effect of fiber optic sheath on tunnel monitoring was obtained. Finally, a suitable fiber optic cable type was identified for different engineering applications, and monitoring results show good agreements with the actual deformation and temperature change. Therefore, this study initially solves the problem of fiber selection in tunnel monitoring technology based on BOTDR technology and further provides the theoretical basis for engineering applications.

The middle stream and upstream of main rivers in western Taiwan exists serious subsidence situation. The changes in the real-time water level and scour depth during flood and typhoon seasons influence the safety of bridges significantly. Bridge management unit often use water level elevation as a bridge closure decision basis. Although simple, but this is lack of a strong technical support. Therefore, scour depth monitoring system capable of functioning in the floods impact is very important. Among existing automatic observation methods for scour, the instruments and equipments are limited to the river course silting form, high sand content, high salinity, difficult device installation and conflict between onsite laying and construction. They may not reflect local scour behavior of submerged bridge foundation in a timely manner. Therefore, this study cited the Sutong Bridge scour monitoring technology, through the sunk piezometer under riverbed and water level real-time measurement to comparison of the head difference to find the scour depth. However, the Sutong Bridge is a sandy riverbed. In this study, the bridge is a gravel riverbed. Due to the long and narrow terrain of Taiwan, the river is steep and fast. For the construction and preservation of monitoring equipment is more difficult to measure than the Sutong Bridge. This study has considered the safety monitoring of civil engineering suitable for the harsh environment. The use of a sturdy and sealed steel hoop helped the piezometer not only maintain a high degree of reliability and stability in the long-term monitoring process, but also can be operation in the harsh environment.

Since serious environmental pollution problems are caused by the continuous development of fossil energy industry and releasing huge combustion products, shale gas is gradually becoming the key element of the green revolution. The Longmaxi shale formations in the Sichuan basin are the main mining layers of shale gas in China. In the process of exploiting shale gas, monitoring the stress and strain of the shale gas reservoir is helpful to guide programs in exploitation of shale gas and provide management of security risk and other works. Fiber Bragg grating (FBG) strain sensor system is a widely-used advanced technique to monitor real-time strain in recent years. In this paper, the FBG system was employed to measure the strain of shale surface in uniaxial compression tests using the MTS 815 machine. The results show that the strain variation of shale surface was well recorded by FBG, and axial strain transferring was more effective than that of the radial strain. It is found that the strains measured by FBG sensors were superior to those from strain gage rosettes, but the axial strain variation was susceptible to the development of surface cracks, resulting in lower strain transmission efficiency. The strain transfer ratio was mainly influenced by the grating itself, the properties and thickness of the bonding layer. According to experimental results from two kinds of epoxy resins, it can be seen that the new 555 viscose was better than DP100.