Based on the framework of critical state soil mechanics，a new bounding surface constitutive model for sand, being applicable to cyclic loading, is proposed. No pure elastic region hypothesis is given in this model. Elastic region of sand reduces to a point. Reverse bullet-shaped yielding surface is adopted. No unique relationship between void ratio and the mean normal stress for sand prevents the direct coupling of yield surface size to void ratio. Incremental deviatoric strain is used as a hardening parameter, instead of adopted plastic volumetric strain as hardening parameter in Original Cam-clay model. The model combines the concept of state-dependent dilatancy by incorporating state parameter concept in Rowe’s stress dilatancy equation. Bounding surface magnitude ratio ? to loading surface gives plastic modulus evolvement. Formulation of d? is deducted. A single set of model constants, once calibrated, can simulate cyclic stress-strain response under different initial void ratios and different confining pressures.

Because ceramics is similar to rock in mechanism, ceramics is selected to precut the test specimens with artificial double initial disk-like cracks. The CT real-time scanning tests of the specimens are carried out to study the propagation and damage mechanism of the 3D crack under uniaxial compression. From the comparative analysis of CT values, CT variances and CT images in three different manifold areas, the different propagation laws in areas of up-crack, down-crack and rock bridge are obtained. Firstly, in the up-crack areas, compression and densification are dominant and growth is subordinate; so up-crack has little influence on the damage of the specimen. Secondly, the down-crack propagates greatly, visible wings appear and macro-cracks join together finally, which has great influence on the failure of the specimen. Thirdly, when the center distance between two cracks equals to the 4 times of the crack radius, the propagation process of the crack is related to its parameters; and the interaction between the dual cracks can be omitted.

Loess structure is an important physical property, which influences mechanical properties of loess with its particle size, density and humidity. Based on the structure potential of loess released by loading, remolding and saturating, the unconfined compressive strength of intact, remolded and saturated loess were measured by uniaxial compression test; and the structural index of loess was defined by comparing the stability and changeability of loess structure which determined respectively by the ratio of confined compression strength of loess and remolding soil and the ratio of confined compressive strength of saturating loess and loess. Through the unconfined uniaxial compression test of four kinds of loess adopted from different sites, the unconfined uniaxial compression stress-strain curves of intact, remolded and saturated loesses with different water contents were tested to reflect the uniaxial compression stress-strain property, as well as the law of unconfined compressive strength and loess structural index changing with the water content was analyzed for different kinds of loesses. When the particle size, density and humidity of loess being similar, the greater the structure index of loess, the smaller the compressibility and the greater the shear strength of loess. So the structure Index structure together with the particle size, density and humidity can be used to describe reasonably the fundamental physico-mechanical properties of intact soils.

The theory of isotropic double scalar damage variables was presented and developed based on the research work done by the predecessors firstly. Then, the elastic damage evolution equation described by the double scalar damage variables was deduced; and the finite element program for the coupled seepage and damage was written using the computer language Fortran90 based on the modified Biot’s theory. Finally, a simple roadbed foundation model was analyzed using the computer program written personally; and the typical node’s settlement, pore pressure, damage variables were analyzed and discussed. The results show that the double scalar damage variables model is more reasonable than the single scalar damage variable model in describing the constitutive relation of soils.

A series of triaxial shear tests on intact unsaturated Q2 loess were conducted using computerized tomography (CT)-multi-function triaxial apparatus developed in Logistical Engineering University. The distinct CT images and detailed CT data of the evolution of meso-structure were obtained during loading. A new method is proposed to identify the yield stress of intact Q2 loess using curves of CT-number versus deviatoric stress. A structure parameter and a structure evolution variable are defined based on CT data. The variable of structure evolution increases with the increase in net confining pressure under the same suction; while the variable of structure evolution decreases with the increase in suction under the same net confining pressure. An equation describing the evolution of structure is developed. In the equation, deviatoric strain and volumetric strain are included. The equation reflects the influences of net confining pressure and suction on the evolution of meso-structure during loading. The structure evolution equation successfully simulates the laboratory tests of unsaturated intact Q2 loess.

The rigid serve-controlled test machine and acoustic emission equipment are used to study the influence of space between 3D-cracks on the mechanical feature of mortar material; and the failure process of samples with pre-existing cracks is concluded. The analysis of complete stress-strain curves and AE data indicates that sample failure is due to the propagation and coalescence of cracks. Failure process of samples with pre-existing cracks could be divided into the following stages: microcrack initiation, initiation of pre-existing cracks, crack propagation and crack coalescence. The failure pattern is shear failure along single inclined plane. When the ratio of cracks space d and length of elliptic crack long axis 2c ranging from 0-1, as the ratio grows, the initiation stress and maximum stress of samples reduce. With the ratio d/2c growing from 1/3 to 2/3, the initiation stress and maximum stress fall suddenly, showing that this space scope is the sensitive range. When the ratio d/2c =1, the initiation stress and maximum stress of sample fall 22.48 % and 18.60 % respectively corresponding to the sample without pre-existing cracks. The ratio of initiation stress to maximum stress of all different samples ranges from 83.1 % to 78.9 %. As the ratio d/2c grows, the ratio of initiation stress to maximum stress declines, which indicates that as space d grows, the loading range between initiation stress and maximum stress increase.

The compression tests are conducted on Yangling and Qinghai structural loesses under different water contents. Based on the principle of equivalent deformation, the equivalent stress of structure fluid is defined by using compression stress difference between unsaturated and saturated loesses under the same consolidation void ratio . The effective stress principle of unsaturated structural loess is established under compression stress. Relations between equivalent stress of structure fluid and degree of saturation as well as stress are investigated. The relation between equivalent stress of structure fluid and stress is linear as the water content is lower. Based on the equivalent stress of structure fluid under lower water content, the formula of equivalent stress of structure fluid is proposed which can reflect coupling of stress and moisture. According to effective stress principle of unsaturated structural loess under compression stress and introducing equivalent stress of structure fluid reflecting the structure change, the formula of compression of structural loess is established. The compression curves of total stress and that of effective stress can be calculated under the coupling of stress and moisture by the formula. The calculating results are accord with the test results, so as to offer a new approach to evaluating unsaturated collapsibility.

The existence of Kaiser effect was verified under Brazilian tests conducted on coarse-grained granite. Acoustic emission tests were respectively carried out after 2, 15 and 45 days time-delay since the preloading finished. Influence of time-delay on Kaiser effect were then discussed. The test results show that the closer the preloading stress to the ultimate strength, the less-pronounced the Kaiser effect is during reloading; and that the larger the time-delay, the faster the Kaiser effect decay. It is found from the Brazilain tests on granite specimens that Kaiser effect is still distinct after 15 days delay; and the effect disappears completely after time-delays of up to 45 days. The influence of friction contact between the specimen and apparatus on rock’s AE test results is also analyzed qualitatively.

The electrical resistivity of various lime-soil samples are studied indoor with four electrode resistivity measurement, the effects of different factors such as lime-soil ratio, water content, water saturation, soil structure and particle size on lime-soil samples were revealed. Under different water contents (about 15 %, 20 %, 25 % and 30 %), soil were mixed with lime at different lime-soil ratios (about pure soil, 1:10, 1:15 and 1:30). With light compaction test, the traverse and vertical resistivity of mixed soil samples were measured and the relationships between resistivity and physical properties of mixed soil samples with different lime-soil ratios are studied too. The electrical resistivity of mixed soil samples drops greatly with 15 %-20 % water contents, increases with about 20 % water content; and the resistivity reduces as the water content increased continuously. The electrical resistivity of lime-mixed soil sample larger than electrical resistivity of pure soil with 15 % water content, but the resistivity of lime-mixed soil samples is smaller than pure soil samples with 30 % water content. The resistivity is more lower as the lime mixing amount is larger. The electrical resistivity at transverse section is larger than at vertical section. The electrical resistivity increases from 0 to 50 ?•m as the unconfined compression strength increases. When the electrical resistivity larger than 50 ?•m, the resistivity decreases as unconfined compression strength increases. The relationship between water saturation and dry density is negative exponent; the relationship between porosity and void ratio is exponent reverse to the dry density. The resistivity is sensitive to the water content.

Experimental research on water retention characteristics of sand with different fine grains is carried out by pressure plate test to analyze the effect of fine grains on the soil water characteristic curve (SWCC). The results show that the water retention capacity of unsaturated sand enhanced with fine grains increase; while, the effect is varied in the regime of SWCC. The water retention capacity enhanced significantly when suction beyond air-entry value. is advanced to describe the SWCC of silty sand. Then, the effect of fine grain content of silty sand on the parameters of SWCC equation is analyzed; and the relationship of fine grain, suction and water content is described by .

Considering the practice of embankment construction ,an experimental method used to study moisture migration in unsaturated soil considering influence of the heat radiation of earth surface and rainfall is designed. According to the measurements of water content change in different depths and time under corresponding boundary condition, the rule of moisture migration of unsaturated soil is revealed due to influenced by different surface temperatures, compactness and rainfall intensities. Forthermore, the rule of moisture migration in embankment is discussed; and the conclusion that the higher compactness will reduce moisture migration rate greatly, is drawn.

Based on the true triaxial apparatus of Xi’an University of Technology, the failure modes, intermediate principal stress influence on shear strength parameters and strength surface characteristics on π plane of Q2 loess with different water contents was analyzed under the condition of different intermediate principal stress ratio b and different meaning normal stress. It was shown that the failure modes of Q2 loess cubic samples behaved four kinds of failure formation, including of lateral bulge failure, taper failure, trapezoid failure, irregular hexagon failure by true triaxial tests. The shear strength parameters ratio could be got by comparing the strength parameters measured by true triaxial tests with the results of triaxial tests. The coherence ratio changes between 0.9 and 1.9. The friction angle ratio varies between 0.7 and 1.5. The structure property and failure formation of Q2 loess influence the shape of failure criteria on π plane. The consolidation pressure influence the value of failure surface in π plane. The shapes of Q2 loess failure criteria on π plane under different water contents and different consolidation pressures include pear-shape and irregular hexagon. With the structure property of Q2 loess reducing, the shapes of failure surface on π plane changes from pear-shape into irregular hexagon.

The improved static and dynamic universal triaxial and torsional shear apparatus for unsaturated silty is employed to perform matric suction controlled cyclic triaxial tests under consolidated drained condition. Through a series of static and dynamic triaxial tests on unsaturated remoulded slity clay. The characteristics of static and dynamic strength of unsaturated silty clay are studied. The rules that static strength of silty clay changes with confining pressure and matric suction, and dynamic strength changes with confining pressure and matric suction and number of cycles are also analyzed. Moreover, it is verified that the correlation of strength between static and dynamic test of unsaturated silty clay is remarkable. Finally, some experience formulas of ascertaining dynamic strength curve according to static strength are presented by normalizating test data, so as to reduce the workload for analyzing of stability on unsaturated foundations.

The loading model of the static load and dynamic load being acted at the same time was established according to the superposition theory. The concepts, for example, combinatory load, combinatory stress and combinatory deformation, were put forward. At he same time, it provides the basis for continuing study the mechanical characteristics of layered subgrade under combinatory loads. Based on the similarity theory, through the resemble model test, the variation of the layered subgrade soil stress and deformation is discussed when the static load and dynamic load are acted at the same time. The variation of stress and deformation of the layered subgrade soil is discussed under keeping the dynamic invariable and changing the static load. The results show that: the combinatory stress and the combinatory deformation of layered subgrade linearly increase with the increasing amount of the combinatory load, the combinatory stress and the combinatory deformation of layered subgrade nonlinearly decrease with the increasing amount of the depth; the rule is exponential function. In conclusion, these results are instructive for the design, construction, operation and maintenance of layered subgrades.

Combining large number of indoor consolidation and odeometer test data of Ningbo soft soil, using partial differential finite element software FLEXPDE, and taking into account complicated geometry and material nonlinearity of soil, the characteristic of soil consolidation is investigated. Under the conditions of different ratios of compression index to permeability index, analytical solutions and numerical solution as well as the distribution of effective stress and void ratio with height are obtained. The results showed that numerical solution fully taken into account the complex nonlinearity of soils; and results more in line with actual conditions when the ratio of compression index to permeability index is not equal to 1; the results are consistent with the results of Gibson’s in 1981 when ratio is 1; it’s more safe to forecast the effective stress and the consolidation degree when considering the complex nonlinearity of geometry and materials of soil.

he soils under the foundation of building or within the slope are usually in complex initial stress state before subjected to cyclic loading induced by earthquake or other dynamic loadings; after reforming the DTC-199 torsional cyclic load triaxial apparatus, the dynamic strength of compacted loess can be tested under this consolidation stress conditions. Results show that the initial angle α0 of principal stress has a considerable influence on the dynamic strength of compacted loess when other initial consolidation stress conditions are fixed; the initial coefficient b0 of intermediate principal stress has little influence on the dynamic strength of compacted loess; with the increase of α0, dynamic strength reduces gradually and it reaches minimum when α0 is 90o; maximum reduction range is about 40 % . The initial coefficient of intermediate principal stress has interval effects and amplification effect on the dynamic strength of compacted loess. When b0 increases from 0 to 0.5, the dynamic strength increases; and when b0 increases from 0.5 to 1, the dynamic strength decreases; the rate of increasing is less than rate reduction about 5 %.

Based on porous medium theory, the longitudinal coupled vibrations of saturated soil-pile is investigated with layer method by regarding soil around of the pile as saturated porous medium. A comparative analysis between the results of the three-dimensional model and Novak layer method is carried out; and validity of the results is shown. The influences of main mechanical parameters of pile and soil on dynamic behaviors of coupled system is analyzed; the results indicate that the length-diameter ratio and modulus ratio of pile and soil have a great effect on dynamic behaviors of the pile in saturated soil; while the influences of damping coefficient and coupling coefficient are smaller.

A great deal of factors evaluating the adjoining rock stability is uncertain. As the set pair system and connection entropy model can dispose the uncertain problem, a connection entropy model for stability evaluation of adjoining rock is presented. By calculating the connection entropy values at different safety gradation，the stability grade of adjoining rock could be obtained. The method could provide a new way to evaluate uncertain system like stability evaluation. The case study shows that the bigger the connection entropy value is, the worse the rock stability is, i.e. the more dangerous adjoining rock is.

Using four consolidation apparatus and triaxial instrument for unsaturated soils, they have advantages that could measure volume change and take into account effect of net mean stress that pressure plate apparatus could not. A seriers of tests with considering and without considering net normal pressure or net mean stress about generalized SWCC, are carried out. Test studies indicate that net normal pressure or net mean stress plays an important role in the SWCC. The test results are consistent with the theoretical formula. Combining unsaturated soils theories with practices, a formula of generalized SWCC under without considering and considering net normal pressure or net mean stress affect. Test results well agree with theoretical formula.

Based on anti-explosion model test, the explosion resisting performance of the tunnel which is reinforced by fully bonded rock bolts is studied under explosive stress waves produced by plane charging. The results show that test data are reliable by analyzing pressure temporal curves of free field; vault displacement of the anchored tunnel is reduced significantly; and the tunnels are damaged when the scale distance is 5.23 cm/g1/2; the surface strains of two tunnels are pressed under plane explosive stress waves，the most of which is on arch foot; with the reducing scale distance, the peak strains increase firstly; and then reduce, the maximal peak strains increase; the acceleration of roof is maximal, which is relatively reduced when anchored; and the acceleration of floor of the anchored tunnel is increased under the condition of small deformation which should be reduced as necessary by adopting some vibration-absorptive ways; the more the tunnel damages severally, the more the acceleration of ribs of the anchored tunnel reduce significantly, with the reducing scale distance, the acceleration of roof and ribs grow, especially when the scale distance is 5.23 cm/g1/2.

At same cement content there existed obviously strength difference between the stabilized soil samples formated from soil samples with different mineral components, which was adjusted manually. In order to find the reason of these experimental results, concentrations of main ions in the pore solutions squeezed from the stabilized soil samples were measured; and the concentrations of Ca(OH)2 in the pore solutions with many ions were calculated by the thermodynamic method. The result shows that ,at same cement content，when the mineral component of soil samples is montmorillonite, the concentration of Ca(OH)2 in the pore liquid of the stabilized soil can not reach to saturation; at this stage, the lower the content of montmorillonite is, the more the hydrates generated by cement hydration; therefore the higher the strength of the stabilized soil is; after the concentration of Ca(OH)2 reach saturation point, the hydrates will fully grow and the strength of the stabilized soil will reach maximum. On the basis of this, the concentration of Ca(OH)2 in the pore liquid of the stabilized soil was adjusted through alkaline matter; The result shows that alkaline matter can increase the concentration of Ca(OH)2 in the pore liquid, heighten the strength of the stabilized soil samples.

At present, improving the engineering properties of soft soil by developing and using solidification materials is a worldwide pop topic. A new cement material (ALOFIX-MC) is used to solidify the soft soil; and the mechanism of soil reinforcement is researched based on indoor tests. Different percentages of MC, i.e. 0 %, 1 % , 2 %, 3 %, 4 % and 5 % by weight of cement were randomly put into the soil samples which included 15 % cement content and 2 % gypsum content. Six samples were prepared and subjected to unconfined compressive strength test. The results show that a low MC content can significantly improve the strength and stability of cement soil with 15 % cement content. The microstructural analysis using scanning electron microscopy (SEM) shows that MC can provide new cementations, and MC improves the hydration of cement, pore filling, and water sorption, which contribute to significant improvement on solidification effect. The results have provided a new way for cement soil engineering property improvement and reduction of cement content in conventional cement soil.

In order to research the salt expansion laws and moving patterns of water and solute migration after several freezing and thawing cycles, the crude coarse grain saline soil samples taken from China’s Gansu province were selected for experiment of freezing and thawing cycles. In addition, the effects of the microstructure of crude saline soil after the testing of freezing and thawing cycles was researched by using SEM. It is shown that salt expansion value of crude coarse grain saline soil is accumulated before the seventh freezing and thawing cycles; but soil body could be dented in the process of cooling; and collapsibility value is accumulated with increasing cycles; and one-dimensional soil column exhibits thermal sieve effect from the top to the lower; the moving patterns of moisture content and different ion content in soil column are different under many freezing-thawing cycles.

Strength and stability of reinforced soil depends on intercrossing and tensility of reinforced materials, and friction between reinforced material and soil. By means of SEM photos, it is observed that SH agent is infiltrated through the pore of wheat straw, and adhered to its surface. For studying its tensility, maximum tensile and elongation of wheat straw with one stem node and without stem node, is tested in the condition of original, soaked in sea water, marinated in SH agent, and soaked in sea water after marinating in SH agent. It has been certified that the maximum tensile and elongation of wheat straw without stem node is more than that of wheat straw with one stem node. Respectively comparison on the marinated in SH agent and original, and soaked in sea water after marinating in SH agent and soaked in sea water, the maximum tensile and elongation of wheat straw marinated in SH agent is more than that of original wheat straw. SH agent benefits to increase the tensility of wheat straw.

China has a large area with seasonally and perennially frozen soils. It is necessary to study mechanical properties of frozen soils for the sake of constructions in cold regions, so as to guarantee their stability. In this paper, the distribution of frozen soils in China and the main features of frozen soils differing from unfrozen soils, are briefly described firstly. Generally speaking, frozen soil mechanics consists of two main aspects, i.e. freeze-thaw related problems and mechanical properties of the already-frozen soils. Frost heave, thaw settlement and freeze-thaw induced changes in mechanical properties are freeze-thaw related problems. Frost heave has been extensively studied. Various theories have been put forward to describe the mechanism of ice segregation which is considered as the main cause of frost heave; and some theories have even been applied to quantitative analysis. The study of thaw settlement has a long history, while most of the previous studies still stay in empirical stage. Thaw consolidation has been studied; but it has considerable limitations so far. Therefore, we suggest that the artificial neural network could be used to improve the precision and applicability in estimating thaw settlement on the one side, large strain theory could be used to improve thaw consolidation theory. For the already-frozen soils, this paper summarizes the previous studies on strength, stress-strain relationship and dynamic properties. Study of the strength of frozen soil borrows strength theories for unfrozen soils; however, they can hardly reflect stress melting of frozen soils under high stresses. The previous studies of stress-strain relationship of frozen soils have been focusing on creep; and the empirical relationship directly obtained from testing data is the mainstream. Influence of temperature on dynamic parameters of frozen soils seems to be the only task in frozen soil dynamics for a long time; while influence of frozen layer in dynamic response of a site has attracted attentions in recent years. At last, physico-mechanical processes involved in deformation of constructions in permafrost regions are briefly analyzed.

Although prestressed anchor cables have been used to reinforce slopes widely, they can happen to fail at some time because they have bear high-tension stress in moist environment and been influenced greatly by many external factors. In order to make sure of failure effects of anchorage system well, failure mechanisms are put forward firstly according to monitor data of an actual slope engineering. Then, unloading test of a cable at site was performed to get the influence on tension-force of neighboring cables. By adopting the numerical simulation, the influence on anchorage force of neighboring cables and stability of slope because of cable failure is analyzed in detail. Finally, failure criterion for part slope is put forward.

Soft-hard alternant strata slopes formed by the interbedding of sandstone and mudstone or the mudstone imbedded in thick sandstones are distributed widely in the Three Gorges area. Cavities are formed by differential weathering between sandstone and mudstone and they can cause collapse of slopes. Firstly, mechanism of collapse of high slopes is studied from the aspects, such as the topographical features, lithologic characters, combination of structural surfaces, effects of rainfall and the weathering effects. Differential weathering is the main reason for the collapse of high slopes. Secondly, according to field surveys, failure mechanisms of high slope collapse are classified into toppling, sliding, creeping-tension, cantilever-tension and staggered breaking. Sketch maps of failure were generalized according to the failure mechanism. Forming process of collapse is determined by the numerical simulation. The failure process of collapse is mudstone spalling, cavity, sandstone crack opening, tilting of dangerous rock mass, toppling cillapse and rockfall deposite. Lastly, supporting measures were put forward against all the failure modes of high cutting slopes in the Three Gorges area. Research results are significant in the prevention and treatment of geo-hazards of the Three Gorges reservoir area.

The Tianhe Station horizontal frozen construction in Guangzhou metro No.3 line is the longest and biggest artificial ground freezing (AGF) project of the national metro construction currently. In the different phases of the construction; several parameters such as brine temperature, ground temperature, surface settlement/heave, swelling pressure, tunnel liner convergence and so on, are monitored dynamically. According to the data obtained from about 400 days in-situ monitoring, the features of propagation speed of the frozen soil wall and the brine temperature variation are discussed. The characteristics of ground temperature and the swelling pressure of soil are analyzed. The relationship between the ground pressure and the soil temperature is also achieved. Results show that the temperature gradient variation and soil temperature variance ratio decrease with the increasing of freezing time in the active freezing phase. The safety of frozen earth wall is also evaluated by different monitored data. Moreover, the environmental influence of the project is evaluated based on the surface frost heave and settlement data monitored in the process of construction. It is found that the pre-freezing time is too long which induces large surface frost heave and increases the project capital cost. The analytical results show that the pre-freezing time should be reduced.

On the basis of in situ measurements, it is necessary that the embankment only with crushed rock protective slopes in the warm permafrost regions along the Qinghai-Tibet Railway needs proactive mitigative measures to maintain the long-term stability. Thus, an ad hoc technique of the crushed-rock protective slopes and the awning combination (CPS-AC) was proposed. The cooling effect and mechanisms of the CPS-AC were explored on the basis of previous studies on the individual mitigative measures of the awning and the crushed-rock protective slopes, and of the current studies on the temperatures and velocities of the CPS-AC embankment configurations. The CPS-AC is further divided into two types, the closed and open systems. In the closed system, the airs between in the ambient environment and under the awning can not exchange freely. In reverse, the airs can do freely in the open system. The awning in the closed CPS-AC can shade the direct solar radiation on the protective slopes and protect the embankments from blowing sands and snow, as well as winds; and the crushed rock layer in the closed CPS-AC has the “thermal semi-conductor” effect and can shade the secondary radiation from warm awning. In the open CPS-AC system, the shading board shades sunlight and obstructs snow, and the crushed rock layer can shield the secondary radiation of the warmer awning, and protect warmer winds from entering the embankment, and also has a chimney effect for cooling the embankment. The cooling effect of the open channel between the awning and the crushed rock slope can be explained using the siphon, channeling and chimney cooling effects. The measurements and research on the effects and mechanisms have provided important evidences and application techniques for the CPS-AC practices in the Qinghai-Tibet Railway.

The vertical static load test is adopted to investigate 4 super-long bored piles in loess, in which the variation of axial force in piles is tested by vibrating wire strain gauge. Hence, the bearing capacity behavior, load transfer mechanism, the lateral friction and end bearing capacity are researched. With the increasing of vertical static load, the results indicate that: (1) shaft force distribution of bored pile is different from that of original cases; and this difference mainly concentrates on top of 1/3 pile length; (2) enhancing effect of static lateral friction and degradation effect of static lateral friction are obtained in sand soil; (3) the vertical static loading can induce decreasing of axial stiffness of single pile; and (4) axial stiffness of single pile reduces about 40 %-70 %.

For the Xi’an metro line No.2 passing through ground fissure active zones, the interaction mechanism between lining and surrounding rock was studied by the physical model test, stimulating the metro tunnel orthogonally crossing the ground fissure and being consistent with the settlement crack of lining structure, with geometrical proportion of 50:1. Test results show that the regularity of wall rock pressure, stress and uneven settlement of lining structure changing with the relatively vertical deformation are similar under the different stress fields for the case of the settlement crack being consistent with the orthogonal ground fissure in strata. The relative settlement between two sections of lining structure with deformation crack at ground fissure develops apparently with the relatively vertical displacement between upper strata above ground fissure and lower strata below ground fissure. The lining structure is of large settlement in the upper strata and small settlement in the lower strata. The additional stress of lining structure and increasing value of earth pressure acting on lining structure is small in the upper strata and large in the lower strata. The maximum value of additional stress and earth pressure locates at the section closing to the ground fissure. When the ground fissure being of largely vertical displacement, the wall rock pressure on the bottom of lining structure in the upper strata decreases obviously or equals to zero. It could point out that the research of physical model experiment has importantly theoretical and practical significance to the construction of underground engineering and maintenance operation in the area of ground fissure.

The dynamic triaxial test, resonance column test and other dynamic tests are carried out for the loesses which exist on subgrade and core wall of an earth-rock dam on deep loess foundation. The dynamic shear strength, dynamic stress-strain relation, dynamic pore water pressure curves and other dynamic parameters are obtained. Based on the dynamic test results and static analysis, the dynamic response analysis of the dam with foundation is calculated by 3D nonlinear effective stress FEM. The calculation results show that the loess foundation will be liquefied under the earthquake intensity Ⅶ. Therefore, an economical measure for overcoming the liquefying disaster is proposed. The effect of the resisting measure for earthquake destroying is discussed; and the optimum result is obtained at last.

The water-retaining structures built of dispersive clay are so easily destroyed to occur the safety accidents. Considering the safety, the dispersivity and treatment with lime of soil for the Majiashu dam are studied using double-hydrometer test, pore water salts test, pinhole test, crumb test and exchangeable sodium percent test. The results are that the dam soil belongs in the low liquid limited clay; and it has a lot of sodium ions in the easily soluble salt and the saturation pore water; and its pH is the stronger alkalescence or even the strongest alkalescence. Those soil samples had more illite and a few of kaolinite and chlorite and montmorillonoid. The soil samples are transition clays and dispersive clays; and the lime is the effective additive when the content of lime is the 0.25 % with mass ratio the dispersive clay becomes to the non-dispersive clay. It is shown that the key reasons of dispersivity are that the soil of dam has the more sodium ions and the pH is the stronger alkalescence. The lime is the effective additive of the dispersive soil.

The construction technology, implement mechanism, reinforcement efficiency of implementing method of backfill of abutment back with horizontal flexible-reinforced grouting technology were studied by in-situ experimental research combining with laboratory study. The in-situ test results show that the backfill of abutment back reinforced by the new horizontal flexible reinforced grouting technology has enormous advantages including easy processed, effectiveness, development and utilization value. On the processing of the in-situ test many valuable construction parameters and experimental data were obtained; and a lot of material resource could be used for changing the design and construction parameters so as to perfect the construction technology of the new technology. At the same time, a new engineering solution for the prevention and treatment of bridgehead jump-driving was offered.

The limitations of expansion capacity calculating method in current existing standards are analyzed. Based on the testing results of load expansion ratio of expansive soils in Huai’an section of Ning-Huai expressway, the relationships between the load expansion ratio and initial moisture ratio, the upper load as well as degree of compaction are analyzed. The relationships between the load expansion ratio and the initial moisture ratio, the upper load and the degree of compaction of the compacted expansive soils are proposed, and have been used to calculate the possible expansive deformation if the embankment of Ning-Huai expressway is filled with the expansive soils directly. The influence of initial moisture ratio on expansion capacity is also analyzed.

A number of environmental and stability issues can be caused by a high leachate level in a landfill. Vertical pumping wells can be used to lower the high leachate level. Pumping tests were conducted at a municipal solid waste landfill. Finite element analyses were carried out to simulate the transient flow problem of leachate drawdown. The pumping test gives a hydraulic conductivity of 3.6×10-4cm/s and an influenced radius of about 20m. The numerical analyses show that radius of the pumping well has only a little impact on the pumping efficiency, whereas spacing of the wells is critical to the leachate drawdown. To design a drawdown scheme, spacing of the wells should be determined first considering the demand and time limit of the project. The pump should be selected based on the pumping rate. The radius of the pumping well is then determined by the size of the selected pump. Finally, filter, size of the borehole and type of borer should be determined in sequence.

Embankment body is composed mainly of unsaturated soils and its deformation included the three components, namely, deformation resulting from the instantaneous compaction, deformation of primary consolidation and secondary consolidation deformation,therefore, their theory should reflect the three-part deformation. Based on results of uniaxial compression creep test of red layers and unsaturated soil single variable, theory of unsaturated soil embankment settlement of red layers is put forward; through numerical simulation of embankment construction process of a worksite in Suining, railway line for passenger traffic from Chongqing to Suining, the deformation characteristics and predicted final settlements of numerical simulation are consistent with the field measurements，which shows that the theory is correct.

Based on the influence of Xi’an Metro Line 2 underneath crossing City Wall and Bell Tower in construction period and operation period, a new series of measures for protecting City Wall and Bell Tower have been studied. Many construction plans about protecting City Wall and Bell Tower are compared and analyzed. Finally, the construction plan that is bilateral around ancient buildings, foundation reinforcement about segregation of pile, and strengthening the ancient buildings structure is adopted. Finite element software have been used to analyze the effect of the protective measures; and it is shown that the influence on City Wall and Bell Tower is lower than the before reinforcement about 2/3. The monitoring data during construction is found that the, ancient buildings settlement displacement is lower than earlier forecast data; and it keep within the limits of design value. The data demonstrate that the protective measures are valid and reasonable. At the same time, metro vibration influence on City Wall in the operation period is analyzed; and vibration damping measures are put forward. Through scheme selection, numerical analysis, specific implementation procedures and real-time monitoring, a new series of protective measures for protecting ancient buildings due to tunnel underneath crossing have been put forward and demonstrated. And the series of protective measures is very practical.

In this paper, the geological conditions, regional tectonic activity and its distribution characteristics of Jiulongshan high loess slope located in high seismic intensity region were firstly analyzed, and then the dynamic stability of Jiulongshan high loess slope was evaluated by a new quasi-static method. Based on analyzing the sensibility of dynamic response and strength law of loess subjected by the cyclic loading and determining the earthquake the seismic inertia force along the slope height indicating the size of the earthquake, a finite difference based quasi-static strength reduction analysis method has been proposed by combining the strength reduction method and the finite difference method. Through the new method analyzing the Jiulongshan loess slope, the displacement and stress distributions of the slope, the relationship between the displacement at key points and the reduction coefficient as well as the dynamic stability safety factor of the high loess slope were obtained. The results agreed quite well with the solutions obtained by traditional two-dimensional limit equilibrium analysis method. It confirms the accuracy of the new quasi-static strength reduction method based on finite difference approach.

Zhengzhou-Xi'an Passenger Dedicated Line is the speed of loess area of China's first 300 ~ 350km / h without the laying of high-speed railway track ballast, subgrade settlement control is to ensure that high-speed railway operational safety an important factor. Zhengzhou-Xi'an Passenger Dedicated on-site through the settlement observation data analysis, we found a smaller settlement control of loess foundation required in the circumstances with a completion time is shorter, the settlement trends are consistent with hyperbolic analysis, laid on the roadbed over the central part of the settlement plates laid on the shoulder observation of pile settlement curve fitting is good, there are lots of cutting smaller settlement in its society,These results for high-speed passenger rail line Observation Design of Embankment Settlement great value.

The over-consolidated unified hardening model (UH model) proposed by Yao et al can describe many characteristics of clays well, including stress-strain relationships, stress dilatancy, strain hardening and softening, and path dependency behavior. Linear Hvorslev envelope has been substituted by a parabola Hvorslev. The parameters in the model are the same as those in the Cam-clay model. By using the UH model, numerical simulation of triaxial tests is performed. The difference of stress-strain curves predicted by using the Cam-clay model and the UH model is analyzed. To the test on rigid bearing plate, three-dimensional finite element analysis of foundation bearing capacity is carried out. The curves p-s are compared using the UH, the Cam-clay and the Mohr-Coulomb models. Stress-strain curves calculated by using the UH model in soil are analyzed. The stresses calculated by using the UH model and Boussinesq elastic theory solution are compared. In addition, numerical analysis of consolidation settlement is performed. The changes of pore pressure and settlement are analyzed and compared. It is shown that the UH model is better than the Cam-clay and Mohr-Coulomb models; and it is easy to be applied to the FEM from the comparisons of various calculation results in this paper.

Laxiwa Hydropower station is located in a high mountain valley and narrow valleys, where the regional geostress field is higher. Besides, local existence of tectonic fracture zone and size of large-scale excavation are common phenomena in this project. The surrounding rock of hydropower plant is mainly granite, which are hard and brittle rock, this kind of rock is very detrimental to the stability of the cavern. In order to judge the stability of surrounding rock after excavation and long-term security of support design, it is need for obtaining mechanical parameters of surrounding rock mass and the initial stress field. Based on the measured values of the initial stress in-situ, rock tectonic stress field distribution of large-scale rock mass is obtained through back analysis; then using displacement of the key point, measured at the top of stratified cave excavation disturbance, obtain the more accurate three-dimensional stress distribution results. For follow-up excavation of underground powerhouse, evaluation and prediction of stability of surrounding rock and long-term safety of support design, the basic data are provided for effectively guiding the following excavation of plant. Displacements of surrounding rock after the completion excavation obtained by using rock mass stress field parameters of the plant are consistent with the actual monitoring results of surrounding rock displacement; it is shown that the geostress field back analysis results are consistent with the actual values of the geostresses.

In order to analyze the shear behavior of sands, a numerical investigation was carried out on the shear band of ideal dense sand in direct shear test using PFC2D. The traditional band observation method is replaced by a new method , by which the sample is painted into square grid to observe sample deformation pattern. The discrete elements commercial software PFC2D is improved to visualize principal stresses and their inclinations in the sample. Averaged pure rotation rate(APR) and particle velocity are observed to describe the sample with aim to analyze the micro mechanism of the strain localization in dense sand. The study shows that in direct shear test, the strain is concentrated in a band near the shear plane, whose thickness is 10 to 15 times of d50. The particles in the shear band demonstrate significant rotation. Higher gradients are found in velocity and rotation fields on the edge of the shear band. The observation on the contact fabric and contact force shows that principal directions of contact points and contact forces rotate in the similar way with their inclination direction about 60° to the horizontal direction.

Numerical analysis has become the most important method for analyzing deep excavations in close proximity to sensitive properties. One of the key problems in a numerical analysis is to select proper soil constitutive models and their corresponding parameters. The possibilities and limitations of a limited number of soil constitutive models frequently used in geotechnical numerical simulations were discussed. The suitability of these constitutive models applied to numerical analysis of deep excavations in close proximity to sensitive properties was compared. As ground movement control is a key design consideration in excavations adjacent to sensitive properties, the constitutive model must be able to predict realistic distributions of movement around retaining structures. It was recommended to use strain hardening plastic constitutive models such as modified Cam clay (MCC) model and Plaxis Hardening Soil (HS) model to simulate excavations in close proximity to sensitive properties because they can reflect many important features of soil which are important in excavation simulations. These features include plasticity, strain hardening difference between loading and unloading stiffness, and stress dependent stiffness. The results of the simulation of a deep excavation illustrate the capabilities of the strain hardening plastic constitutive model in the numerical analysis of deep excavations.

How to simulate random distribution of cleats in coal rock is key technique for simulation of methane recovery. Monte Carlo simulation technique is adopted to simulate the randomness of cleats distribution; and the model with random cleats distribution for coal seams is presented. RFSS2D (Random Fracture Simulation System in two dimensions) is developed with Matlab. Based on spot data for coal and their statistical analysis, not only the virtual fractured coal seams in which there is the same fractured statistical law with real engineering rock can be generated, but also FEM grid can be performed automatically by RFSS 2D. As a numerical case, a gas production well in Liaoning is studied with the model. According to spot and statistical data the model of random fractured coal is set up; and gas pressure and stress evolution are simulated. The results are as follows: Cleats which are connected with gas well greatly effect on gas flow; and cleats which are not connected with gas well finitely effect on gas flow.

A linear transformed stress space method is proposed. The generalized nonlinear strength theory (GNST) is transformed into Mohr-Coulomb criterion in the new proposed stress space. Thus, the GNST can be regarded as Mohr-Coulomb criterion in new stress space. The strengths and stress-strain experimental results of two kinds of clay are collected and analyzed in the new linear transformed stress space. The consistency between the experimental results and the theoretical predictions shows that the transformed stress space method is effective.

Analysis of response of level ground subjected to earthquake is one of the most important problems in geotechnical engineering practice. By use of the bi-axial shaker installed on the geotechnical centrifuge at the Hong Kong University of Science and Technology, a centrifuge dynamic test was performed on a saturated sand ground model under a bi-axial earthquake loading. Based on definitions of stress and strain, and the D'Alembert's principle, stress and strain of soils at various depths were derived from the data of acceleration, displacement, as well as excess pore pressure measured in the test. The stress paths and stress-strain relationships of saturated sand during the shaking event, and their connection with development of excess pore pressure were revealed.

Stochastic medium theory was adopted to calculate the ground subsidence and horizontal displacement. The mechanism of displacement caused by gathering groundwater was analyzed and the compression of micro unit soil was calculated based on the effective stress theory. According to Theis formula of unsteady flow, the drawdown caused by the plane radium flow was calculated with well-flow supposed to be invariant, and parameters were determined by back analysis method using the data obtained from site observation. Due to the underwater boundary in the model changes constantly, a mathematic approximate method and numerical simulation were adopted respectively for different periods. On the basis of the above, a spatiotemporal coupling integral equation was suggested in the groundwater cone of depression and was solved under the cylindrical coordinates. The example indicates that the stochastic medium theory is suitable for calculating the ground deformation caused by gathering groundwater and can be used to calculate and predict the movements combined with unsteady flow theory and numerical simulation methods with a good precision.

Anchorage foundation is a new structural foundation which can effectively improve its bearing capacity by increasing a small amount of material that due to the designability of itself. It is necessary to analyze the mechanical behavior of anchorage foundation due to the shortage of corresponding theoretical research. In-situ tests of an anchorage foundation of Huaihe Super Bridge are simulated by elastoplastic finite element method to demonstrate the effectiveness of numerical simulations and suitable selection of material parameters. The mechanical behaviour of anchorage foundations is then further studied by comparing that of a caisson without anchors. Meanwhile, the distribution of moment on anchor is analyzed; and the influence of anchors’ embedded depth on the bearing capacity is studied. The results show that the lateral bearing capacity of anchorage foundations can be effectively improved by a proper setting of anchors.

Stochastic medium method(SMM) is widely used in the field of surface movement induced by tunneling. And back analysis is the most useful method for determining key parameters. In the problem of twin tunnel back analysis the parameters of each tunnel is supposed same, so the problem can be solved for dual-parameters. But this way isn’t access truthfulness. For improvement, multiparameter back analysis method is presented, in which each tunnel should have different parameters. The case study shows that the back analysis result of 4 parameters is better than the dual-parameters. But 4 parameters back-analysis of twin tunnel is much more complex so that traditional pattern search method can’t solve the problem well. So simplex hybrid accelerating genetic algorithm(SHAGA) is introduced for solving this problem. The test of application shows that SHAGA can solve it accurately and stably.

foundation coefficient method is a common method for calculating internal forces of a elastic anti-sliding pile. Based on coefficient “m-k” method, the counterforce load method is presented to calculate the internal forces of a whole pile. The corresponding formula are derived in detail. The calculation program of internal forces for a whole pile is designed with Matlab. The pile can be analyzed as complete entity. It is not necessary to divide the anti-slide pile into loading segment and anchoring segment by the sliding surface like the tradition methods. Compared with the finite difference method, the presented method does not make use of the continuity condition at the sliding surface and the iteration and test calculation. An example shows that results coincidence well comparing the traditional method can be obtained. The results of figure treatments by the program can optimize the construction design of anti-sliding piles; and it demands very short time for the calculation and can improve the calculation efficiency.

The mechanism of blasting seism is complicated with numerous influencing factors. In order to find out the controlling factors of blasting seismic effect, the grey correlation theory of grey system is introduced. By conducting case analysis, the pecking order influencing blasting seismic effect is obtained; and it is pointed out that the super-deep drilling , pore network parameters are the controlling factors of the seismic effect. The most effective way for reducing the blasting seismic effect is to optimize these blasting parameters. The calculation of grey correlation analysis method is characterized by simplicity, reliable results and convenience for use; so it is of favorable value to the blasting engineering.

A portable real-time dynamic loading apparatus with support of medical CT is developed. This loading apparatus consists of loading host machine, actuator and digital monitoring; and the greatest pressure output of 100 kN, frequency of 5 Hz; the apparatus is available to perform the dynamic tension, compression test with impact, triangular ,sine wave. In addition, the CT test is conducted by the one graded concrete sample, in the sine wave compression load condition; under dynamic loading, the crack propagation, coalescence, through the whole process of CT images are obtained. The apparatus laid the foundation for dynamic CT test of brittle materials.

To simulate the complicated stress path, such as multi-directional stress and principal stress axis rotation induced by earthquake shaking, ocean wave or traffic loading, a hollow cylinder apparatus (HCA) with dynamic triaxial and torsional shear capability was designed cooperatively with GDS company. The working principle of the apparatus is introduced. Comparisons of the test results are made between the traditional dynamic triaxial device and the hollow cyclinder apparatus. Five series dynamic stress paths and a seismic record are designed and applied to evaluate the performing of the new apparatus. The deviation from the specified loading stress would be minimized as a sutiable parameter, which could be adjusted in the software, is chosen. The testing results show that the HCA is a good instrument to investigate dynamic constitutive model under complex stress conditions.

The advantages and disadvantages of some commonly used settlement prediction models are analyzed. comparatively An optimal method of settlement prediction by fitting precision and prediction accuracy is proposed. A better loess subgrade settlement prediction method is put forward based on the measured data of Zhengzhou-Xi’an passenger dedicated line.The fitting precision and the prediction accuracy of combination forecasting model are studied. It is concluded that the fitting precision and the prediction accuracy of combination forecasting model should be higher then any other prediction methods because of its comprehensive nature. But the members of combination forecasting model must be selected before prediction. Prediction accuracy and screening criteria are closely linked. How to choose better screening criteria which make square sum of error small in the prerequisite conditions of weight coefficient being greater than zero still need further study.

Using geotextile tubes to construct dikes for land reclamation has been a widely used technique. The tubes are usually filled with slurry of soils, such as sand, silt or clay. The tensile force developed in the geotextile during filling the tube is the dominant factor to construct a safe dike. The existing design methods are good for designing sausage shaped tubes but can not be directly applied to designing flat tubes, which are commonly used in dike construction. This paper presents a procedure that can determine the relationship among the tube size, the pumping pressure, the unit weight of the slurry and the tensile force developed in the geotextile during filing the tube. In the calculation model, the anisotropy of the filled slurry is put in consideration. The procedure has been programmed, which can help the designer to select material and determine the geometry and dimensions for the geotextile tube.

With the development of the global warming and human activities, the geology along the Qinghai-Tibet highway in permafrost regions appeared new changes. In order to inspect the influences of the changes on the stability of roadbed and take a long-term monitoring system study of early warning on roadbed diseases, the fuzzy math theory was introduced. In the warning system, some key factors including the annual average ground temperature, frozen soil type (ice content), the change of permafrost table, and drainage condition of the roadbed and the method of special adjustment were selected. Then linguistic variables and fuzzy membership function for describing the diseases and their intensity were installed. At last, 37 items of the logic rules for describing influencing factors of the diseases and their relationship with the disease intensity were put forward, combining the disease investigations and experience from experts. Matlab Fuzzy Logic Toolbox was adopted for building the early warning system on roadbed diseases of Qinghai-Tibet highway in permafrost regions.