In stress-strain curve, the process of decline of uniaxial stress at increasing strain is defined as strain-softening. Many types of geomaterials behave in strain-softening way in the case of disturbance of engineering activities. When the stress-strain relationship is described in mathematical formulation, the matrix of tangential elastic moduli is no longer positive-definite. Thereby difficulties arise in finding the solution to strain-softening problem. Strain-softening process is simplified into a series of brittle-plastic behavior; and solving brittle-plastic problem comes down to obtaining a series of brittle-plastic solutions. On the basis of classic plasticity theory, the method for analyzing strain-softening behaviour is proposed; and the corresponding solution process is implemented in finite element code. Furthermore, the influences of different strength-weakening modes on the distribution of plastic zone in the surrounding rock mass of a circular tunnel are studied. The longitudinal deformation profile (LDP) obtained by strain-softening constitutive model is also analyzed; and it is compared with the measurements in a tunnel. The preliminary numerical analyses indicate that the presented results look reasonable.

Piping effect has serious hazards to river embankment engineering. The understanding of piping is gradually deeper and deeper to people. Nowadays, people know more about the beginning conditions of piping occurred and the consequences of piping channel completely penetrated the levee. However, because of the failure and development mechanism of piping is very complex, the study of the emission of sand and the flux after the piping effect is not deep enough. Three groups of cohesionless soils, in the same soil features, are used to make a series of tests by changing the thickness of overlying clay layer, using a self-designed equipment. A comparative analysis is made from the aspects such as piezometric head, scope of piping channel, sand production and flux. Furthermore the changing laws of the porosity, coefficient of permeability and flux are studied. It is found by the tests that cumulative amount of sand changing with time satisfies the Boltzmann model, a kind of nonlinear model. By using the relationship between permeability and porosity and the relationship between the porosity and cumulative amount of sand, a theoretical formula, from the changing flux over time, can be deduced and verified. The formula has a very important significance for the understanding of piping, the effective controlling of piping development, and the reducing or avoiding disasters of embankment collapsing.

To study difference for the work behavior of the composite foundation with rammed cement-soil column and tapered piles under cyclic load, based on the indoor model tests, and installing the miniature soil pressure boxes on the pile-top and the soil surface, the contrast model tests of working properties for the composite foundation with 4 rammed cement-soil column piles and with 4 rammed cement-soil tapered piles, and the soft foundation are performed in laboratory, respectively. The influence laws of the cyclic stress ratio and the number of cyclic load on the permanent settlement and the pile-soil stress ratio of the composite foundation with rammed cement-soil column and tapered piles are explored. The influence of the reinforcing methods on the permanent settlement and the pile-soil stress ratio are researched in the soft foundation. The relation of the cyclic stress ratio and the pile-soil stress ratio is revealed. The results of the study show that the critical cyclic stress ratio and the ability to resist cyclic load of the foundation may be enhanced by the composite foundation with rammed cement-soil piles. In the same loading conditions for the same number of cyclic load and the same cyclic stress ratio, the effect that the permanent settlement is decreased by the composite foundation with rammed cement-soil tapered piles is better than that by rammed cement-soil column piles. The greater the wedge angle is, the better the effect is. The greater the cyclic stress ratio is, the greater the pile-soil stress ratio is. The pile-soil stress ratio increases as the wedge angle of the tapered pile increasing; but that decreases as the number of cyclic load increasing. There is a critical number of cyclic load. When the number of loading cycle is less than the critical number of cyclic load, the pile-soil stress ratio decreases rapidly as the number of cyclic load increasing. When the number of loading cycle is more than the critical number of cyclic load, the pile-soil stress ratio almost has no change as the number of cyclic load increasing.

Split Hopkinson pressure bar (SHPB) was adopted to study the deformation behaviors and axial dynamic stress-strain relationship of artificial frozen clay in confining pressure state. Three kinds of artificial frozen clay with frozen temperatures of -8 ℃, -12 ℃ and -16 ℃ were investigated in SHPB test. And aluminum sleeve was chosen as confining pressure device. The results show that viscoplasticity failure is presented when artificial frozen soil in confining pressure state under high strain rate. When average strain rates are 410 s-1, 457 s-1, 525 s-1, 650 s-1 and 827 s-1, the maximum stresses of artificial frozen soil at -16 ℃ are 10.76 MPa, 12.18 MPa, 14.27 MPa, 20.24 MPa and 23.34 MPa respectively; and the maximum strains of artificial frozen soil at -16 ℃ are 0.081 7, 0.097 2, 0.105 0, 0.131 0 and 0.166 0 respectively. Besides, when average strain rate is 457 s-1, the maximum stress of artificial frozen soil at -12 ℃ is 8.28 MPa; and the maximum stress of artificial frozen soil at -16 ℃ is 12.18 MPa. When the strain rate is the same, the lower the frozen temperature, the larger the maximum stress of artificial frozen soil. Strong temperature correlation could be observed from artificial frozen soil in high strain rate. Research on dynamic mechanical behaviors of artificial frozen clay will provide some supports for frozen soil excavation.

The slope stability of waste dumps is controlled by the slope angle of waste dump and the shear strength of mining wastes. Triaxial tests are conducted to investigate the shear strength of a phyllite coarse grained material from a waste dump. The behavior of the coarse grained material is investigated from low to high confining pressures. Particle breakage of the coarse grained material increases with confining pressure. The increasing rate decreases as the confining pressure increases. An empirical equation is proposed to describe the relation between pressure and breakage rate. A new empirical strength criterion is proposed that can describe the strength change with confining pressure and particle breakage. The slope stability of waste dump is analyzed using the proposed strength criterion. The result is closer to the actual condition. But the safty factor of waste dump calculated by Mohr-Coulomb criterion is relatively large and has potential risk. The slope stability analysis of the waste dump indicates that the proposed strength criterion is reasonable for describing the strength of coarse grained materials from low to high confining pressures. It is strongly recommended that the present strength criterion should be used to analyze the slope stability of high waste dumps.

In recent years, the construction of electricity transmission systems that span from west to east China has been planned. Thus, the construction of foundations for overhead transmission towers is inevitable. Uplift loading often controls the design of transmission tower foundations. Belled piers have been used in loess area to satisfy the requirements for uplift resistance. At two places in Gansu province, twelve full-scale tests were carried out to investigate the uplift behavior of belled piers in loess. Based on the measured load-displacement curves, the ultimate bearing capacities and displacements were interpreted using the Chin hyperbolic model, the slope tangent, double line intersection and L1-L2 methods. A mean normalized load-displacement curve was obtained based on the statistical data of measured results. By fitting measured load-displacement data using a normalized hyperbolic model, normalized hyperbolic load-displacement curves were suggested at different confidence levels. The results show that the slope tangent and Chin methods represent the lower and upper bounds, respectively. The L1-L2 method is appropriate for interpreting the failure bearing capacity. Normalizing the measured load-displacement curves reduces the scatter in the curves. The mean curve more closely represents the actual test data. However, the field tests show a substantially stiffer load-displacement response than the curve at the 95% confidence limit.

There are many defects of the main soil swelling pressure measuring methods at present. So, an improved method is put forward which could measure the soil swelling pressure under approximately completely restricted swelling conditions. Taking compacted laterite as study object, the swelling pressures of specimens have been measured at different initial water contents and dry densities. Comparing with the test results which belong to swell-consolidation method, it is indicated that the former swelling pressure values are less than the later ones. Meanwhile, the restricted swelling method has three major advantages. Firstly, it accords well with the definition of swelling pressure owning to the soil un-deformation after soaking. Secondly, it takes less time and occupies smaller space. Thirdly, it can measure swelling pressure within wide range of water content. Furthermore, the samples mesoscopic pore size distribution features under different conditions have been measured by mercury intrusion method and nitrogen adsorption method. The results show that the influence of sample water content is significant on the pore distribution of compacted laterite at the same dry density. The compacted laterite occurs “irreversible” swelling due to the incursion of water molecule into laterite crystal and grain. The “irreversible” swelling degree of laterite is major reason which brings to difference swelling pressure values between the restricted swelling method and swell-consolidation method.

Failure modes of jointed rock mass with different joint dip angles, joint discontinuity degrees, joint sets, load strain ratios, joint filling thicknesses, joint filling types and slenderness ratios under split Hopkinson pressure bar(SHPB) tests are studied by means of similar material model tests. The results show that failure modes and dynamic strength of jointed rock mass are much related to joint configuration. For rock mass with single joint, its strength and failure characteristics are greatly controlled by the joint dip angle. The dynamic strength of the specimens with joint dip angles of 0° and 90°, whose failure modes are both tensile failure, is 90% and 71% of that of intact one, respectively. The dynamic strength of the specimen with joint dip angle of 60° is nearly zero. The dynamic strength of the specimens with joint dip angles of 30° and 45°, whose failure modes are mainly shear failure with partly tensile failure, is 50% and 18% of that of intact one, respectively. The peak strength of the specimens with 1/4, 1/2, 4/5 and 1 joint center continuity degree is 95%, 74%, 28% and 17% of that of intact one, respectively. With increase of joint discontinuity degree, the dynamic strength of specimen decreases. The dynamic strength of the specimens with 1, 2 and 3 groups of joints is 54%, 23% and 10% of that of intact one, respectively. Namely, with increase of joint group, the dynamic strength of specimen decreases greatly; but its failure mode does not change. With increase of joint filling thickness and strength reduction of joint fillings, the dynamic strength of specimen decreases gradually; but its failure mode does not change. The dynamic strength of the intact and jointed specimens both increase with increasing of load strain ratio; and the sensitivity to load strain ratio of the former is much higher than that of the latter, whose failure mode becomes more complicated accordingly. The dynamic strength of these two kinds of specimens both first increase then decrease with the slenderness ratio; that is to say, there exists a best slenderness ratio.

Based on the characteristics of loose organizational structure, high moisture content, poor physical mechanical properties and pore cementation contact, the basic physical properties tests on clastic sandstone were carried out first. It's considered that the rock which belongs to small porosity sandstone as micro-permeability is extremely complex microstructure and that internal structure is damage seriously. The main mineral compositions are quartz, feldspar, sericite and so on; mainly chemical constituent is SiO2 and the chemical erosion is not significant. Secondly, the hydrostatic pressure tests, uniaxial and triaxial compression tests were carried out for clastic sandstone to study the strength and deformation failure properties. Finally, the correlations between mechanical properties and physical properties are preliminary discussed. The results show that the internal micro-defect of rock is compaction completed when hydrostatic pressure reaches 2.6 MPa. The uniaxial compression curve shows the characteristics of six distinct stages; and that the peak stress is 0.98 MPa. Moreover, brittleness and ductility are shown. Under triaxial compression test, clastic rock shows significant characteristics of mainly compressed and ductility dilatancy failure. In the action of deviatoric stress, the axial and lateral strains of rock reach 6% and 4% respectively. The curve has no significant damage load, which shows the mechanical properties of nonlinear, plastic hardening, yield platform and volume strain from compression to ductility dilatancy and so on. And the volume dilatancy damage stress is almost the same as the yield stress. The dilatancy turning point increases with an increase of confining pressure, and moreover, the confining pressure enhances the rock resistance to deformation and failure. The results provide dependable reference for the establishment of rock constitutive model and stability analysis.

Wrapping method is a effective method to expansive subgrade. Based on the condition of wrapping method, a wetting-drying cycle path was designed for the expansive soil and lime-treated expansive soil. The strength properties were studied and discussed for the samples experiencing 6 wetting-drying cycles with the systematic research of the shear strength before and after wetting-drying cycles. The results show that the shear strength increases with the increasing dry density for remolded and lime-treated expansive soils in the range of compactness between 90% and 96%. The variation of shear strength parameters are different for the soil samples before and after wetting-drying cycles. The cohesion after wetting-drying cycles increases with the increasing of dry density; but the influence on internal friction angle is small. The dry density restricts residual strength little for remolded and lime-treated expansive soils after wetting-drying cycles. The residual strength parameters of expansive soils are different for the samples before and after wetting-drying cycles; and it is larger before wetting-drying cycles. The strength parameters including peak strength parameters and residual strength parameters are influenced by the range of wetting-drying cycles. Based on the influence of wetting-drying cycles and repeated shearing on strength parameters, it is suggested that the difference of residual strength parameters before and after wetting-drying cycles and its range can be considered to analyze the safety factor of expansive clay slope. And lime-treated expansive soil is fit for wrapping in the expansive soil subgrade.

Based on amount of freeze-thaw tests and dynamic triaxial tests, the dynamic modulus and damping ratio properties of silty soil subjected to repeated freeze-thaw cycles were deeply researched and analyzed. The tests results are drawn as follows: At the same dynamic strain level, the relationships of dynamic stress and freeze-thaw cycles, water content present negative correlation, and the relationships of dynamic stress and confining pressure, frequency, compactness present positive correlation. The curves of dynamic stress vs. dynamic strain obviously present nonlinear relationship; and the dynamic modulus double decreases while the damping ratio double increases with the increasing of dynamic strain. The dynamic modulus sharply decreases while the damping ratio increases with the increasing of freeze-thaw cycles; and then the changes level off after 6 freeze-thaw cycles; while the mechanical properties after 6 freeze-thaw cycles are suggested for designing and calculating indexes. The soil particles contact area is improved by the increasing of confining pressure and compactness; and the dynamic modulus increases while the damping ratio decreases with the increasing of confining pressure and compactness. It is found that water content less affects damping ratio, but the dynamic modulus double decreases when the silty soil reaches saturation condition. The frequency is an important factor affecting on damping ratio, and damping ratio sharply decreases as the frequency increases.

Many researchers focus on deformation and strength of the soils experienced wetting and drying cycles. But few researches have been conducted on soil-water characteristic curve of the soils experienced wetting and drying cycles. Because the processing of suction equalization takes too long time, the studies of soil-water characteristic curve of the soils experienced drying and wetting cycles are mostly limited to a single wetting and drying cycle. But considering the variability of the actual climatic conditions encountered in geotechnical engineering and the complexity of natural environment, generally soils experience many drying and wetting cycles. Therefore the study of the soil-water characteristic curves of soils experienced many drying and wetting cycles is significant. On the basis of the existing experimental data about the variation of the drying and wetting curves with the numbers of drying and wetting cycles, a method is proposed by introducing a function of the number of drying and wetting cycle, which is capable of predicting the soil-water characteristic curve of soils experienced drying and wetting cycles. Once the first drying and wetting curves and plasticity index of the soil are given, the method can predict the soil-water characteristic curve of the soils experienced drying and wetting cycles.

PS, a certain modulus potassium silicate, is a kind of inorganic chemistry materials to protect and reinforce earthen relics. It is proved that PS material can enhance soil strength and the resistance of external environment damage by nearly twenty years of practice. However, the reinforcement mechanism and related improvement of macroscopic properties are not fully understood and invested until now. To contribute to this field of research, Liangzhu earthen relics soil specimens with initial water contents of 13%, 17%, 19%, 21% and 25% are reinforced by PS with 3% volume concentration through infiltration method. After that, scanning electron microscope (SEM), mercury intrusion porosimeter (MIP) and direct shear test are employed to compare the difference between unreinforced specimens and reinforced specimens respectively. Based on bimodal pore size distribution obtained by MIP and SEM, two sorts of microcosmic reinforcement mechanisms of PS, which are represented by indexes P1 and P2, are proposed to characterize the two mechanisms. Through the study, the above two indexes of specimens can characterize the variation of improved properties such as shear strength characteristic and soil-water characteristic curve very well at different reinforcement water contents. These conclusions provide a further research method and means for the application of PS material.

The basal stress of geotechnical triangular prism is studied. While it is impossible to get the analytical solution of basal stress distribution of geotechnical triangular prism, the approximate solution of basal stress distribution of geotechnical triangular prism is got with the Rayleigh-Ritz method. By comparison with different solutions of different slope ratios, different Poisson’s ratios, and different boundary conditions at the base, the results are drawn as follows. There is depression of basal normal stress on the base of geotechnical triangular prism. The steeper the slope is, the more depression of basal normal stress is. Much more depression occurs with the boundary condition of constraints on the base. Meanwhile, the value of Poisson’s ratio has little impact on the distribution of basal normal stress. The Poisson’s ratio mainly impacts the distribution of basal shear stress. The larger the value of Poisson’s ratio is, the larger the basal shear stress is. The slope ratio has large influence on the position and value of the maximum basal shear stress. The larger the slope ratio is, the larger the basal shear stress is, and the larger distance between the maximum basal shear stress and center of base is.

Based on the relationship among the coefficient of consolidation Cv, effective stress and void ratio, the equations considering the variation of Cv for consolidation under stage continuous loading are derived. According to analytical solutions of the above equations, a formula for settlement calculation under stage continuous loading is obtained. Combined with the construction of Yun-Gui high-speed railway, taking the stage loading of high embankment as the object of study, stage continuous loading oedometer test of intact expansive soil are carried out on geotechnical digital systems (GDS) triaxial apparatus. It is confirmed that the relationship between settlement and time can be fitted with broken line in loading stage and hyperbola in steady stage. The stress-strain curves of expansive soil can be described with ladder. The coefficient of consolidation increases firstly and then decreases with effective stress when ≤ ; however, it decreases continuously as wave while ＞ The calculated values of degree of consolidation are compared with test results. It is found that the degree of consolidation calculated by considering the variation of Cv is more accurate than constant Cv. The formula for settlement calculation under stage continuous loading can be used as a reference method to analyze the relationship between settlement and time of subgrade for high-speed railway.

To provide an insight into the effect of the nonlinear strain-softening phenomenon on the mechanical behavior of the surrounding rock mass, an elastoplastic softening model considering softening coefficient is proposed. The approach for calculating the stress and strain states in the surrounding rock of a circular tunnel is presented. Then, by comparing with Brown’s method and converted Mohr-Coulomb failure criterion method, the proposed model is proved to be reasonable. Finally, effects of softening coefficient on the deformation behavior of surrounding rock and the support pressure are studied. The results show that: when the softening coefficient is relatively large, the result by the elasto-brittle-plastic model is basically identical to that by elastoplastic softening model; it is the radius of the loose region that mainly controls the deformation and stability of surrounding rock; the critical support pressure that controls the appearance of plastic region is equal to the radial stress at the elasticplastic boundary quantitatively.

It was necessary to use the adaptive theory for computing the distribution of earth pressure behind the wall adjacent to existing basements and the height of total earth pressure, because it was inconsistent with the Rankine’s theory which was based on the semi-infinite half space state. It could be divided two parts of the deformation trends by considering soil arching effect. The upper soil parts slide down alongside the wall which is same with Terzaghi’s tarp door experiment. Also, the lower soil parts slide down as a triangle the soil wedge. So it is reliable that the earth pressure behind the retaining wall adjacent to existing basement should be analyzed based on the above deformation trends of the upper part and lower part. Assuming the arch in soil arching as circular, the lateral coefficients of earth pressure of retaining wall about both upper and lower parts are derived from the principal stress rotation. And the formula of distribution of lateral active earth pressure is given based on the soil static wedge equilibrium. Expressions of the total earth pressure and the height of acting point are derived by translation of coordinates. According to the examples, the results by proposed method are close to the simulation results. So it has a significant meaning for active earth pressure theory which considering the soil arching effect.

SWC-150 Fredlund soil water characteristic cell is used to test the soil-water characteristic curve (SWCC) of gravelly soils with different densities under different vertical stresses. The influence of the vertical stress and dry density on the SWCCs is investigated. The SWCCs are fitted based on Fredlund & Xing tri-parameter model using least-square method. The parameters of the model are determined and discussed. With the increase in the vertical stress and dry density, the model parameter n increases while m decreases. Except that the parameter a slightly decreases with the increase in the dry density during wetting process, it increases with the increase in the vertical stress and dry density. Based on the fitting results, the influence of the vertical stress and dry density on the air or water entry value and the slope of the SWCC are studied. The quantitative relationships between the air or water entry value, the slope of transition segment of the SWCC and the vertical stress, dry density are proposed. The results show that the air or water entry value has a positive linear relationship with the vertical stress and dry density. Nevertheless, the water entry value has little change with the change in the dry density. The slope of transition segment of the SWCC presents hyperbolic relationship with the vertical stress, while the relationship between the slope and the dry density is linear.

The fractal theory is used to study the microstructure of Hangzhou intact clay under wave loading by scanning electron microscope (SEM) and PCAS quantitative testing technology. The characteristics and variation of pores distribution under different cyclic stress ratios and different frequencies are investigated. The study results show that fewer cycles are required at higher stress ratio or lower frequency when the specimen approached failure. The levels of critical failure strain tend to increase with the increasing of cyclic stress ratio, but almost the same under different frequencies. The characteristics of pore distribution such as scale, arrangement and pattern would change regularly with the cyclic stress ratio; but no apparent regularity varies with frequency. Both contraction and dilatation exist on the shear band, caused by the pores which are broking while merging at the same time under cyclic shear stress; also, the pore’s orientation is consistent with the shear band’s direction. According to the variation of microstructure characteristic parameters before and after cyclic loading, the effects of cyclic stress ratio and frequency on microstructure of soft clay under wave loading are revealed; and the microscopic mechanism of wave loading is disclosed.

Grouting technology was an effective technical means to control the geological disasters in tunnel construction, including collapse and inrush of clay and water. As for the complex structure and advantage joint development of the water-rich fault, the grouting theory and control technology had not been mature yet. Based on the typical internal rock mass structure of water-rich fault zone, a model of grouting was established. Then concept of advantage-fracture grouting was proposed. Based on the assumption of generalized Bingham fluid and single plate model of advantage-fracture grouting diffusion, a control equation for calculating the diffusion distance was developed considering the rheology behaviors of grout. It showed that the grouting diffusion distance was mainly controlled by the grouting pressure, grouting rate and the rheological parameters of grout. And the influence laws of the three factors on the diffusion distance were discussed. On this basis, the method of controlled grouting was established. Three key technology of grouting which were the grouting rate gradient control, gradient control of grouting rate and dynamic regulation of control-fluid were concluded, which impelled grout constrained diffusion in the advantage of structure. The research results were successfully applied to the tunnel fracture zone collapse in Jiangxi province and played a positive role in promoting the theoretical research and engineering practice of geological disaster.

Based on a slope located at the S214 Simao-Jiangcheng second class highway, the dynamic module of finite difference software FLAC3D is used to study the dynamic response of bolting shallow red clay slope under seismic loading. Based on the interaction and coordination of ground and supporting structure, a three-dimensional finite difference model which takes the damping and dynamic boundary into consideration is established. The dynamic response pattern of shallow red clay slope and the supporting effect of bolt under earthquake are analyzed. It is found that both the bolt axial force of each layer and the shear stress in mortar increase during earthquake. However, with variant increment in each layer of bolt axial force and uneven distribution along length direction, the axial force reaches maximum value at the junction of soil and bedrock. While the shear stress shows an overall increasing trend; and its peak value position approaches the slope surface. The minimum value positions of shear stress before and after earthquake are both located at the junction of soil and bedrock. Anchors’ support outstandingly constrains the deformation of slope and increases the ductility of ground under earthquake, which renders good aseismic behavior. Moreover, permanent displacement of slope is generated after the earthquake; and the seismic acceleration inside the slope increases with the raise of vertical elevation. While the platform setting weakens the increasing trend of slope surface acceleration, contributes in alleviating seismic effects. The research has certain reference value for seismic design and dynamic analysis of slope supported by anchor bolts.

It is necessary to obtain the critical slip surface in soil slope stability analysis. However, the existing analysis methods can not ensure the accuracy; and some analysis methods may fall into local minimum trap in the process of calculation. In order to obtain a non-spherical critical slip surface that is most similar with the actual slip surface, an alternating variable local gradient method is proposed based on univariate method and steepest descent method. This method can break through the bottleneck of optimization method applied to slope stability analysis. At first, the initial critical ellipsoidal slip surface of slope can be determined by Spencer limit equilibrium method and the grid search method (or any other method to determine the critical slip surface). Then, several nodes are arranged on the slip surface as variables; the objective function is an equation of safety factor Fs versus space node coordinates Zi; to make the value of objective function decrease fast, each node is optimized according to the negative gradient direction in every cycle. When the result meets the accuracy requirements, the non-spherical critical slip surface of the three-dimensional soil slope is obtained. Finally, this method is proved to be feasible and accurate by two examples.

The basic way to bury pipelines into ground in the municipal projects is: excavating a trench firstly, and throwing away the excavated soils as wastes; backfilling the expensive lime-ash soil into the trench after the pipelines are placed properly; tamping foundation and laying asphalt or concrete pavements. In consideration of recycling the excavated soils and reducing the use of lime-ash soil, soilbag technique is suggested in urban trench backfills so as to cut down the project costs. The mechanism of soilbag technique is briefly elucidated herein; and several field tests such as plate loading test, falling-weight deflection and vibration response measurements are then carried out respectively to evaluate the benefits of a soilbag-trench, with the strong support of the Rain and Sewage Diversion Project in Nanjing. The test results show that soilbag technique performances superbly in improving the bearing capacity of subgrade, decreasing the settlement of roadbed as well as in reducing and isolating the traffic-induced vibrations, compared with the common backfill scheme. It is also proved that backfilling the trench with soilbags is a new green, environment-friendly and economical approach for the municipal projects as a result of avoiding the removal of discarded soils and controlling the pollution of raised dust.

Movement of collapsed stones on the slopes is affected by many factors, therefore, its analysis and prediction is very difficult. Determining the damage range of collapsed stones is very important to the prevention of collapse disaster. Based on site measurement and statistical analysis of 399 sections of collapse induced by the Wenchuan earthquake, the movement characteristics and hazard range parameters of collapsed stones on slopes are studied. The main conclusions are drawn as follows. (1) Movement of collapsed stones on slopes can be divided into three stages, that is, initiating stage, movement stage and depositing stage. The limit between free falling and sliding-rolling model in initiating stage is 56º; the maximum slope angle of deposition zone is 39.6º; and the slope angle of deceleration zone is below 26º. (2) Ratio between moving distance and the height of slope, increases with the increase of earthquake intensity and rock strength; and a statistical formula is given. (3) We get good linear relationship between the maximum moving distance and height slope, as well as between slope angle in the steep sections and spread angle. According to the proportion of deposition area in the whole slope, the slope shape is divided into two kinds; and the statistical diagram of the relationship between the maximum moving distance and spread angle is given which may be useful for determining the damage scope of collapsed stones.

The strip coal pillar method is widely used in deep coal seams mining. The reasonable strip coal pillar size is of great significance to improve the coal recovery rate and protection of surface topography. Under the plane strain state, a unified formula is firstly summarized for five strength criteria, such as Wilson criterion, Mohr-Coulomb (M-C) criterion, generalized Matsuoka-Nakai (M-N) criterion, generalized Lade-Duncan (L-D) criterion and circumcircle Drucker-Prager (D-P) criterion. Then, the unified formula of limit strength, yielding width and remained width for strip coal pillar is presented. Finally, the effect of strength criterion is investigated and parametric studies are discussed. The results show that the obtained unified formula covers existing solutions in the literature and its application is very convenient; the effect of strength criterion on the strip coal pillar design is significant; the results of Wilson and M-C criteria are in too conservation, while the use of circumcircle D-P criterion is need to be cautious; moreover, the generalized M-N criterion or generalized L-D criterion is recommended to be adopted; the influence of changes in strength parameters (cohesion and inner friction angle) of coal seam on the strip coal pillar design is remarkable and should be fully considered. The obtained results can provide some theoretical guidance in reasonable design and construction of strip coal pillars.

As a result of underground engineering in a certain level of in-situ stress condition of surrounding rock, the stress environment is different from the surface slope. It directly relates to the block stability analysis results which the block boundary normal stress quantification is correct or not. Study of block boundaries normal stress by field measurement is not common. Based on stability analysis of a large underground powerhouse block, several different direct boreholes are placed in the block and adjacent areas; the method of preexisting fractures reopening tests is used to determinate block boundary normal stress firstly; and the normal stress state and rules of spatial change of preexisting fractures that occurrence similar to block boundary are successfully acquired. Research results show that, after the completion of excavation, distribution of block boundary stress is not uniform, but with a certain rule; the normal stress of structural surface increases from shallow to deep in the vertical direction, and increases with the excavation surface distance increasing in the horizontal direction. The measurement data of normal stress are less than the calculated values based on the method of surrounding rock stress; but the overall consensus. The results provide references for determining block boundary condition and simplifying stress model.

The semi-circular breakwater is a new light gravity type of structure suitable for soft foundation. It is necessary to establish a reasonable calculation and analysis method for stability and failure mode of the semi-circular breakwater under combined loads. Stability analysis method of the semi-circular breakwater under combined loads is developed by combining load mode with finite element method of the large coastal structures on soft foundation. Meanwhile, sliding failure along the bottom of the base plate and rubble-mound foundation, and vertical bearing capacity failure of the soil foundation are considered. Furthermore, stability failure mode and failure envelopes of structural bearing capacity are obtained. Finally, the effects of amount of filling sand in caisson, the width of rubble-mound foundation, and the reinforcement depth of soil foundation on stability of the semi-circular breakwater are analyzed. The calculating results show that the sliding surface and foundation bearing capacity failure lines of the semi-circular breakwater under combined loading divide the whole V-H loads space into four regions, namely stable region, slide-only failure region, region where only foundation bearing capacity failure happens and region where both sliding failure and foundation bearing capacity failure happen. The foundation bearing capacity failure line obtained by load and displacement composite load mode is outside the failure line obtained by Swipe load mode. But for each load mode, change trends of foundation bearing capacity failure lines are almost consistent. It can be seen that safety factors of stability against sliding along the bottom of caisson or rubble-mound foundation both increase with the height of filling sand in caisson, but safety factors of foundation bearing capacity decrease. Meanwhile, safety factors of foundation bearing capacity obviously increase with the increase of width of rubble-mound foundation or reinforcement depth of foundation.

According to roof collapse characteristics of large section roadway with thick top coal, a failure mechanism of roof collapse block, considering the influences of the stress of surrounding rock and supporting pressure, was constructed based on Hoek-Brown failure criterion and its associated flow law. Through upper bound limit analysis, the roof collapse mechanism of large section roadway with thick top coal was deduced with variational principle; and with one roadway in Zhaolou coal mine, for example, the influences of rock parameters on roof collapse mechanism were also analyzed. The calculation results show that: With the increasing of empirical parameter A, tensile strength, compressive strength and supporting pressure, the size of collapse block increases, while decreases with the increasing of empirical parameter B, the stress of surrounding rock and unit weight of rock mass. The size of collapse block represents the roof stability, larger size means more external work to expend, and the roof is more stable. The parameter B, the stress of surrounding rock and supporting pressure have significant impacts on roof collapse mechanism; and the parameter B determines the shape of failure curved surface; the curvature of failure surface will decrease with the increase of parameter B. Improving supporting pressure is an effective way to increase the roof stability, which provides theoretical basis for the support design of large section roadway with thick top coal.

The Shibeiyuan landslide is a typically large loess flow slide which was triggered by Haiyuan earthquake in 1920. Understanding its behavior and mechanism is very important to study liquefied slope failures with long travel distance in the loess area. The in-situ investigation of the Shibeiyuan landslide shows that the saturated loess or the loess with high water content has high liquefaction and destructive potential which could cause liquefaction or flow slide under strong earthquake. The dynamic triaxial shear tests are performed on seven intact soil specimens taken from three places at the landslide. In addition, the scanning electron microscope (SEM) microscopic characteristics of the soil specimens are used to clarify the shear behaviors of these soil specimens. According to the results, the relation between water pore pressure and strain, as well as the relations between liquefied stress ratio and particle size, microstructure parameter, and degree of saturation are analyzed. The analytical results reveal that the liquefied stress ratio decreases and pore pressure response is stronger with the increasing of clay content. Meanwhile, the specimens with greater porosity have greater fractal dimension and less liquefied stress ratio. Moreover, the liquefied specimens are denser and its fractal dimension is greater compared to that before the liquefaction. Additionally, the degree of saturation has great influence on the state of interparticle cement and the microstructure in loess. The saturating process shows that the ionic concentration of the pore water is greater and the rupture of the interparticle contacts is easier when the degree of saturation becomes greater. As a result, the structural strength of the specimens decreases, leading to the decrease of the liquefaction stress ratio.

Based on the joints random distribution characteristics of surrounding rock of the China's first large underground crude oil storage caverns, containment properties of underground crude oil storage caverns were assessed by using flow-solid coupling theory for discrete medium. Water seal principle and water seal standards of underground crude oil storage caverns are introduced. The structural plane parameters are obtained by the indoor structural plane shear test; and structural plane parameters are checked by using Barton-Bandis shear dilatancy model. According to the joint statistical results, a random joint network model of the surrounding rock is established. The groundwater pressure distribution, water inflow and surrounding rock deformation and stress distribution are analyzed after the excavation under the conditions of different water curtain pressures. The results show that groundwater pressure around caverns meets water seal standard when the water curtain pressure is greater than or equal to 75 kPa conditions. Under the water curtain pressure of 75 kPa, water inflow rates for the caverns range from 0.003 to 0.015 m3/d and crown settlements range from 16 to 32 mm. The results provide a theoretical basis for water seal evaluation of underground water seal oil caverns.

Composite bucket foundation which is wide and shallow is a new kind of foundation. The fluctuating pore water pressure around the foundation has bad influence on the safety of wind turbine under the wind, wave and current loads. In order to investigate the dynamic response of the foundation under the wind, wave and current loads, the numerical analysis is carried out. The combined effect among the wind, wave, current loads acted on the wind turbine structure and the subgrade is simulated reasonably based on the accurate simulation of various loads, and the model of the dynamic response of bucket foundation is presented with the three-dimensional finite element method. According to the numerical model, the dynamic response pattern of subgrade including the laws of the pore water pressure fluctuation and liquefaction locality around the bucket foundation are identified. It can be concluded that the liquefaction depth in the vicinity of composite bucket foundation increases with the growth of the saturation, permeability, wave period and water depth, and it decreases with the addition of the Poisson ratio.

The soft foundation earth-rock dam in the Chengmen lake in Chengmenshan copper mine of Jiangxi province was selected as a case study. Based on the characteristics of impact force during the silt flowing process, FLAC3D program was used to simulate and analyze the dynamic response of earth-rock dam, such as the horizontal velocity, displacement and shear strain, under the impact-squeezing action of silt. The research results are drawn as follows: (1) The variation law of the dam velocity is basically identical with the period of the impact-squeezing action. The monitoring point velocity and motion region in dam increase with the time. The monitoring point velocity reaches the maximum at about 0.3 s (1/2 period); while the motion region reaches the maximum at about 0.45 s (3/4 period). Afterwards, the dam tends to be static with the attenuation of the impact force. (2) Permanent displacement happens in the dam under the impact-squeezing action of silt. The average displacement is 30 mm, which can be seen that the whole dam moves 30 mm towards the downstream. (3) An obvious coalescence zone of shear strain increment generated in the dam is located in the upper soft foundation of the dam, which indicates that the dam will probably slide and damage along this coalescence zone.

Single safety factors are used for most stability assessments of tailings slopes which can not reflect the whole evolutions of stabilities of tailings slopes subjected to variations of external condition. A method of time-varying analysis of tailings slopes was proposed to solve this problem and the time-history of safety factor was used to evaluate the stabilities of tailings slopes. A time-varying model was established to analyze a tailings pond. Conditions of rainfall infiltration, water level fluctuation and the associative action of both of them were simulated by numerical method to study the variation of safety factor with time. The results show that after 6 hours the rates of decrease in safety factor under different rainfall intensities are similar. But within 6 hours the greater the rainfall intensity is, the faster it decreases safety factor. The rain types will affect the trajectory of the variation of the safety factor; and the constant rain which is widely studied is not the most critical rain type. The variation of the safety factor lags behind the water level fluctuation. And the hysteretic effect is weakened by the declination of rising rate, the increasing of descending rate and the decreasing of the varying range of the water level. It is of important significance for the designation and operation of tailings ponds.

Based on engineering tests of muck foundation treatment project, a model of the reasonable thickness of overburden on muck foundation (including the original covering and artificial filling soil) is established using static-dynamic drainage consolidation method under impact loading. The basic considerations of the model are the bearing stratum capacity of muck foundation and the adaptive relations among static loading, dynamic loading and drainage system. Further analysis is made of the model parameters including foundation pressure diffusion angle , bearing capacity eigenvalues of muck foundation and maximum allowable stress ratio R. The parameter R in the model visually and quantitatively reflects the mutual adaptation relationships among impact loading, distribution of drainage system and thickness of overburden. In addition, the parameter R can be used as evaluation parameter for muck foundation reinforcement effects. And the results of relevant tests also show that parameter has a larger value under actual tamping than the 23°-30° in the Code for Design of Building Foundation of China. Engineering applications indicate that the model is in good agreement with the reality; and the quantitative relation also provides convenience in design and application for general engineering staff, which can be used for reference or guidance in similar soft foundation treatment projects.

The approach of searching the most dangerous slip surface is always a hot area for research. However, the other secondary potential slip surfaces, which do not meet the requirement of safety, should also receive attentions. The shear strength parameters of the whole area are reduced in the conventional strength reduction method; but only the minimum safety factor and the most dangerous slip surface can be obtained through this approach. An analysis method of slope multi-slip surfaces, which is based on local strength reduction method, is proposed. Firstly, the safety factor of each element is defined and calculated; different element sets with the safety factors falling in various specific scopes are found out automatically. And then the shear strength parameters of those element sets are reduced respectively; the slip surfaces corresponding to different safety factors are located. The feasibility of this approach is verified through a slope with single step and a slope with double steps. The results show that the depth of the secondary slip surface and the slip area enlarge with the increase of the safety factor of the slope. At last, this method is applied to stability analysis of a slope located at the entrance of a tunnel; and the multi-slip surfaces acquired from the proposed method can agree well with the field data.

To explore the variation process of seepage field of a three dimensions slope due to rainfall infiltration, routines for improvement of the capability of unsaturated seepage calculation of FLAC3D software were programmed by using FISH language after the analysis of unsaturated seepage module and seepage calculation algorithm used in FLAC3D platform. Based on the analysis of infiltration mechanism of rainfall, some FISH routines for simulation of rainfall infiltration and oozing of pore water in the slope after raining stop were programmed. The variation process of saturated and unsaturated seepage field of an engineering slope under the rainfall condition was simulated by employing FLAC3D software and the developed routines. The variation law of transient saturated area in the slope due to rainfall infiltration was explored and compared to the results in references cited in the paper. The distribution of transient saturated area in the slope obtained by calculation is same as the results presented in the cited references. It shows that the simulation of rainfall infiltration and unsaturated seepage analysis could be fulfilled corrected by employing FLAC3D platform with the relevant routines developed by users. The proposed method for the calculation of unsaturated seepage process provides a significance way for the simulation of seepage field of three-dimensional slope.

With the development of foundation pit scale toward larger and deeper, the traditional single pile, the pile anchor supporting structure, pile brace are subject to certain restrictions, in the case of higher control requirements in the deformation and which should not be used within support and anchor, double-row piles can play a better role. Double-row piles consist of two rows of parallel retaining piles, top beam and connecting beam formed a space envelope system. High stiffness, good stability, small deformation and benefit for erect excavation are the strengths, so double-row piles are widely used in deep foundation pit engineering. In the new specification Technical Specification for Engineering of Foundation Excavation (DB42/T159-2012) increases the foundation retaining structure with double-row piles in related chapters. On the basis of the double-row piles calculation model proposed in the new pit specification of Hubei province, a simple, practical design and calculation software of double-row piles for foundation pit (hereinafter referred DESDROP) has been developed by VB.NET. The research and development of this software is to cooperate with new rules for implementation. The displacement, internal force and stability of the double-row piles are analyzed by the software; and the soil pressure, displacement, bending moment, shear force diagram also can be seen through the query result under any working conditions. The software has been applied to Jindimingjun foundation pit engineering. The results show that the operation speed of DESDROP software is fast, calculation results can meet the needs of the double-row piles supporting design.

In light of the collapse of an expansive soil tunnel owing to rainfall infiltration, swelling stress field caused by the change in the moisture content distribution of surrounding soil was taken into consideration to solve the problem. At first, due to the similarity of continuum heat conduction energy-balance equation and seepage continuity equation, an alternative expansive equation is derived based on the theory of heat conduction expansive to simulate water-increased expansion of expansive soil, and then determine the swelling force and seepage parameters by laboratory test and engineering simulation. Finally, considering the proper geologic factors, a numerical model of tunnel is established by means of thermal-mechanical coupling of FLAC3D. And by the simulations of tunnel with different swelling forces under water-increased state, relation curves are acquired between liner deformation and moisture content, swelling force. According to the above analysis, turning points of moisture content and swelling force to prevent liner from failure are proposed, which can effectively guide the design and deformation controlling of tunnel liner in expansive soil.

The viscoelastic B-K anchorage model can be computed efficiently. However, this rheological model is limited in application of mining engineering because it cannot well describe the mechanical characteristics of rock mass into plastic stage. In order to improve the Bolt-Kewin (B-K) model, a new viscoelasto-plastic anchorage model called BK-MC was proposed by introducing a modified Mohr-Coulomb (M-C) yield criterion. The increment iterative calculation scheme of BK-MC model was deduced in finite differential method first. Then, based on UDM interface program of FLAC3D, the corresponding calculation process was compiled by the VC++ programming language and called by DLL of Microsoft Visual Studio 2010. Finally, the BK-MC model was verified by the numerical simulation of uniaxial compressive test and applied to the stability analysis of deep roadway’s surrounding rock in Kouzidong mining area. The results show that the simulation displacement evolution process of roadway surface tends to be uniform with the regularity of field test data, which further verifies the validity and applicability of the BK-MC model. And it is necessary to consider mechanical properties of rock into plastic stage when studying the rheological problems of mining engineering.

Yielding bolt has been widely used for rock reinforcement in mining and civil engineering in high stress conditions. However, the interaction mechanism of the yielding bolt and the rockmass is still not clear at present; and no model is available to predict its reinforcement effect quantitatively. According to the mechanical and deformation characteristics of yielding bolt, an interaction model is proposed to account for the coupling action between the bolt and rockmass. Based on the plane strain axial symmetry assumption and the incremental theory of plasticity, equilibrium equations and compatibility equations of rockmass, and also the response of yielding rock bolt are deduced theoretically. The proposed method has been programmed in the Visual Basic development environment; and a semi-analytical solution for the coupling model is achieved using Runge-Kutta method. The reinforcement mechanism of yielding bolt is demonstrated through an illustrative case study. The distribution of shear stress and axial force along the bolt are presented; and the reinforcement effect of yielding bolt is estimated quantitatively. In addition, the validity of the proposed method is verified by numerical simulations. The reinforced ground reaction curve and the yielding bolt reaction curve can also be constructed systematically by the proposed method, which could help the support system design in conventional tunnelling.

A new laser convergence monitoring method is proposed, combining with the advantages of the current two measurement methods, i.e. traditional convergence measurement and total station measurement. For the traditional convergence measurement method and total station measurement method, both have some disadvantages, such as high operation requirements, the construction disturbance and difficult to long-term monitoring, etc. risen from by the former, and lower accuracy raised by the latter. Laser ranging technology used by total station measurement has been adopted, at the same time direct-measure strategy used by traditional convergence measurement also has been followed. By virtue of the existing laser ranging products, the measuring apparatus required by the new method has been designed and processed out. The apparatus consists of five parts which are laser rangefinder, rangefinder base, connecting rod, connecting sleeve and measuring base. According to the specific implementation steps, the measurement precision in on-site engineering environment has been tested and estimated in the tunnel of Chengchao Iron. The test results show that the new method is low-cost, simple operation, good stability, and the measurement precision can reach 0.7 mm. Therefore it is useful for universal application of convergence monitoring to the process of construction of underground engineering.

In high arch dam abutment stability geomechanical model test, the relative displacement of weak structural plane is the important reference to determine dam abutment instability and analyze whole dam abutment safety degree. But the current measuring instruments, such as resistance strain gage, surface displacement meter just can measure the strain of dam body and displacement of surface dam abutment; for the relative displacement of weak structural plane which in dam abutment is difficult to obtain. So in light of this problem, based on the resistance strain gage technology, a new type of inbuilt displacement system has been developed and installed on the structural planes to obtain the relative displacement of structure. This system are composed by signal acquisition instrument, Wheatstone bridge and displacement sensor. In model test, strain changing process is got using the inbuilt displacement system; and displacement value is got through the strain-displacement curve. In integral stability geomechanical model test of Jinping high arch dam, installing this system in weak structural plane, the relative displacement is obtained efficiently during the loading process. Comparing with the strain and the abutment surface displacement monitoring results, the feasibility of inbuilt displacement system is proved. The results can provide reliable data to determine the overall stability of the dam and foundation.