Weathering is one of serious geological diseases that the Yungang grottos have been faced with. The changes of the temperature and water in the rock masses are the main causes of weathering，especially under the condition of freezing-thawing cycles. Therefore, to research the physico-mechanical characteristics under the condition of freezing-thawing cycles by laboratory test have important significance to the stability evaluation of the rock masses in Yungang grottos. The sandstone specimens taken from Yungang Grottos are separated into three groups：saturated, dry and control groups. Laboratory tests are conducted on saturated group and dry group which have experienced 35 cycles of freezing-thawing to simulate the weathering process of sandstone. Before freeze-thaw test and after every 5 cycles of freezing-thawing，the mass and volume of specimens are measured, the ultrasonic P-wave velocities of specimens are tested using ultrasonic testing instrument; and the uniaxial compression tests of sandstone specimens are performed by INSTRON－1346 rock mechanics test system. After freeze-thaw test, the microstructures of the sandstone specimens are seen by scanning electron microscope. Through above-mentioned tests,the failure forms of the specimens under different water contents and the changes of the mass and volume,ultrasonic velocities,the complete stress-strain curves,uniaxial compressive strengths,frost resisting coefficients and microstructures of the sandstone specimens after different freeze-thaw cycles are obtained. Consequently, the main physico-mechanical characteristics of sandstone under the condition of freezing-thawing cycles are summed up.

In order to establish a fitting approach for soil-water characteristic curves (SWCC) with clear physical meanings, a method is presented to directly calculate the fractal dimensions through the SWCC data based on the fractal theory, and a fractal model of SWCC is proposed. To verify the proposed fitting method, seven clay samples with different dry densities are prepared using hydraulic jacks, and the soil-water characteristic curves are measured by using the pressure plate apparatus. Based on the experimental results of SWCC, the fractal dimensions are calculated. On this basis, fitting analysis of the SWCC data is performed by using the presented method. The results show that, all the correlation coefficients of the seven samples range from 0.97 to 0.99, which indicates good fractal characteristics of SWCC as well as good fitting performance of the proposed method. In addition, it is found that the fractal dimensions and the air entry values increase almost linearly with the dry density. On this basis, a prediction method of SWCC at different compaction degrees is also proposed and tested. The prediction results are in good agreement with the measured values.

The dynamic impedance of pile groups in the frequency domain is computed by thin layer method. It is represented by the complex transfer function in the frequency domain as single input and single output system. The fitting of complex transfer function is proposed through the vector fitting method (VF method), so as to obtain the lumped-parameter model for pile groups in layered ground. The dynamic impedance of partial-fraction expansion type can be obtained by VF method; it fits over the whole frequency range, which is easily converted to the Wu-Lee model. It is shown that the lumped-parameter model by the VF method is accurately to match the dynamic impedance of pile groups in layered ground. Due to its partial-fraction expansion type，the expression can be conveniently transferred into the Wu-Lee model; and the fitting is numerically stable. The number of terms for the partial-fraction expansion is big when the dynamic impedance for the high frequency is needed to fit. The reduced order method called the Routh method is introduced to make the order reduced, and it is shown the result for the reduction is good.

This paper summarizes the research status of municipal solid waste (MSW) constitutive models, which is very important to study geotechnical problems in landfills. MSW consists of a variety of inorganic and organic components and has high compressibility and biodegradability; and its physico-mechanical properties gradually change over time. In these existing models, it can be seen that MSW instantaneous deformation, mechanical creep, biodegradation, fiber reinforcement are taken into account. Unfortunately, various influence factors are considered in some models, respectively, or only are simply added in other models. The coupling effects of these factors are not taken into consideration. Furthermore, the future studies and development trend of MSW constitutive models are proposed based on the study of the constitutive models of soils. A variety of factors that influence the stress-strain behavior of MSW should be considered. Meanwhile, a breakthrough should be sought by combining the theories of geotechnical engineering, environmental engineering, chemical engineering and biological engineering. Finally, the theoretical framework for biodegradation, mechanical deformation, fluid flow and contaminant transport in MSW can be established.

The glass fiber reinforced plastics(GFRP) anti-floating anchor is one kind of new materials which bonds by the resin and the glass fiber. Compared with the steel bar anchor rod, it has the high specific strength, nonelectric conductivity, nonmagnetic nature and corrosion resistance. Based on the full-scale drawing destructive field tests of six GFRP anti-floating anchor and four steel bolts, the load-bearing characteristics and interface bond properties of GFRP anti-floating anchor in moderately weathered granite are studied. By the test results, several conclusions are drawn: (1) There are two failure modes of anti-floating anchor as follows: shear failure between the anchorage rod and grout; and shear failure between the grout and surrounding rock mass. (2) Under the condition of M32.5 grout and the anchorage length with 2.0 m, ultimate anti-lifting bearing capacity of GFRP anti-floating anchor and steel bolt with diameter of 28 mm are 225 kN, ultimated anti-lifting bearing capacity of GFRP anti-floating anchors with diameter of 32 mm is 250 kN, which can be satisfied with engineering demands. (3) The average bond strength between GFRP anti-floating anchor and grout (the first interface) is 1.50－1.54 MPa; (4) The average bond strength between the grout and surrounding rock mass (the second interface) is 0.32－0.37 MPa, which is slightly lower than the average bond strength of the second interface of steel bolt; (5) The average bond strength of the second interface of GFRP anti-floating anchor with diameter of 32 mm is higher than GFRP anti-floating anchor with diameter of 28 mm. According to the test results, the probable failure form and mechanism of GFRP anti-floating anchor are further analyzed. The research results can provide theoretical basis for application of GFRP anti-floating anchor.

Taking the white strong expansive soil of Guangxi as the research object. Laboratory model test for evaporation- rainfall-evaporation is respectively carried out for expansive soil with vegetation covered or not, to explore the influence of rainfall and evaporation process on moisture-heat behavior and fissures development. The results show that, the values of radiation and surface temperature of soil sample with vegetation covered are smaller than the ones of soil sample without vegetation covered about 100 W/m2, 5-6 ℃ respectively. After rainfall process and under same evaporation conditions, the surface fissure ratio of soil samples without vegetation covered increases from 1.28% to 3.82%. Moisture content changes of surface soil increase from 3.42% to 11.17%. Drying rate of surface soil increases from 0.59%/d to 1.44%/d. The average temperature changes of surface soil increase from 13.1℃ to 14.9 ℃. Thus it can be seen, rainfall and evaporation process makes the changes of moisture content, temperature, and moisture migration rate increased. Soils tended to be broken. After rainfall process and under same evaporation conditions, obvious fissures in soil sample with vegetation covered don’t appear. Moisture content of surface soil changes from 3.16% to 2.36%. The drying rate of surface soil changes from 0.58%/d to 0.37%/d. The average temperature variation of surface soil changes from 0.58 ℃ to 0.37 ℃. Obviously, short-term rainfall and evaporation process has a low influence on the moisture holding capacity of expansive soil with vegetation covered.

In order to study the difference of the pore shape complexity among different loesses and the influence of stress path on the pore shape complexity, the pore fractal features are investigated on two kinds of loesses before and after stress path tests. Firstly, the reliabilities for calculating the fractal dimensions of pore by three fractal models are checked. Then the thermodynamic model is adopted to study the difference of pore fractal dimensions of two different kinds of loesses and the change of pore fractal dimensions after stress path according to the pore distributions of loess and filling loess around ground fissures, which are determined by mercury intrusion and withdrawal test. The change of pore shape is obtained based on the assumption that the pore is composed of sphere-shaped pore and tube-shaped pore. The results indicate that the pore fractal dimensions obtained by thermodynamic model are reasonable and reliability. The initial natural filling loess or initial remoulded filling loess has more complex pore structure compared with natural loess or remoulded loess. The void ratio decreases, the pore fractal dimensions increase and a part of sphere-shaped pores turn into tube-shaped pores after conventional triaxial compression tests. Compared with conventional triaxial compression test, the pore fractal dimensions of the sample and the ratio of the volume of tube-shaped pores to the total volume of pores after reduced confining pressure in triaxial compression test are smaller. In general, the tube-shaped pores possess larger fractal dimensions, the fractal dimensions are almost independent of stress path, compared with sphere-shaped pores, the ratio of the volume of tube-shaped pores to the total volume of pores increases with the decrease of void ratio.

Taking typical fault rockburst mine for example, using similar simulation test to analyze overlying strata movement and the stress variation rule of fault plane and dip abutment pressure after the coal seam of the giant thrust fault footwall has been exploited based on coupling disaster-causing mechanism between spatial structure instability of overlying strata and fault activation, and the rockburst characteristics of extra-thick hard roof and easy burst coal seam influenced by giant thrust fault are studied. The results show that there are three stages in rockburst catastrophe process of the giant thrust fault induced by mining ultra thick seam. The first stage, high stress concentration region forms under the influence of overlying strata movement when mining coal seam. The second stage, overlying strata spatial structures evolution induce fault activation, and fault activation leads to external rock mass of spatial structures rotation applying extraneous load to spatial structures, causing instability increased, stress increased and influence scope enlarged. The third stage is the fault slip with releasing energy and providing dynamic load . Ultimately, the scope of significantly affect areas of thrust fault is delimited combining with the stress observation data. The results provides reliable basis for the protection strategy and control design of rockburst for coal mining influenced by giant thrust fault.

Creep properties of Beishan granite under temperature effect are investigated by using the MTS815 rock mechanics test system. A rheological element with thermo-damage coupling effects is proposed by considering the temperature effect coupled with the damage evolution during the whole creep stage. By replacing the Newtonian dashpot in the classical Nishihara model of the coupled thermo-damage element, a new creep constitutive model for full creep process under different temperatures is set up. Based on a series of creep tests carried out at different temperatures under uniaxial loading condition, the parameters of the creep constitutive model and the variation laws of them along with temperature are determined by fitting to the experimental results of the time-dependent deformation of Beishan granite. A sensitivity study for the analytic solution of the creep model with thermo-damage effect is carried out, showing the effects of creep parameters (including elastic modulus, viscosity coefficient etc.) on a creep strain of granite. In addition, a simplified formula of the creep constitutive relation in the case of no temperature variation and damage influence is given. It is shown that the new creep constitutive model can be simplified to the Nishihara model in the absence of temperature and damage effects. Comparison between the predictive results and experimental data，it is shown that the creep model proposed is capable to provide a precise description of full creep process in granite. In particular, the accelerated process is also well reproduced by the proposed model. A bigger exponent ? in the viscosity coefficient leads to a shorter steady-state creep process and earlier onset of the tertiary process.

In order to calculate the active earth pressre or passive earth pressre under the inclined wall considering the soil arching effect, the two key factors, the coefficient of lateral earth pressure, and mean vertical pressure, which can decide the distribution of active earth pressure or passive earth pressure behind inclined wall and are derived based on the analysis of stress state behind the wall and the lateral differential elements method, are given as a unified formula. The unified solution of active earth pressure and passive earth pressure is used to calculate both the magnitude and point of application of total earth pressure. According to examples, the dip angle of inclined retaining wall has a different influences of soil arching effect on limit active earth pressure state and limit passive earth pressure state, as the dip angle increasing, the height of resultant active earth pressure would be decreasing due to that the influence of soil arching effect would be decreasing. On the contrary, as the dip angle increased, the height of resultant influence passive earth pressure would be increasing due to that the influence of soil arching effect would be increasing.

Some earth and rockfill dams have significant later stage deformations after constructions, which are closely related to the rheology of coarse-grained soils. The study of rheology for coarse-grained soils mainly focuses on mechanical tests and constitutive models. However, particle movement of coarse-grained soils in rheological test is not well evaluated. The CT triaxial rheological test of a single grading aluminite is conducted to investigate the particle movement of coarse-grained soils. The test results show that the rheological process is an adjustment process of particle position from unstable structure state to stable structure state for particles in coarse-grained soils. The rheological process will not stop until all particles reach the minimum energy state. No particles move, rotate, and break under the rheological steady state. The investigation of particle movement for coarse-grained soils contributes to the understanding of rheological behavior of coarse-grained soils, and also helps to provide reference to engineering application.

The mixed backfill paste for subsidence area is a kind of artificial compound granular media which has wide size fraction and is made of unclassified tailings and waste rock; its permeability performance directly affects the stability of backfill body for subsidence area and other secondary disasters occurrence. Based on homemade experimental apparatus of permeability, the effects of the content of waste rock, waste rock particle size on permeability coefficient of mixed backfill body, and the relevance between backfill paste’s inherent characteristic parameters (the content of particle size below 0.075 mm and 0.02 mm, non-uniform coefficient , mean particle size) and permeability coefficient are studied. Test results show that, with waste rock content and particle size increasing, the permeability coefficient of backfill paste increases; the fine particle effect is remarkable. The content of particle size below 0.075 mm and 0.02 mm in backfill paste has a crucial effect on permeability and has a negative exponent relation with the permeability coefficient. Permeability coefficient increases along with the values. When the value is less than 20, permeability coefficient increases sharply; and when the value is greater than 20, the increase in permeability tends to be stable. Then the quantitative equation of mixed backfill paste permeability coefficient is obtained, which is consistent with the test results.

The calculation expressions of seismic active earth pressure and modified earth pressure coefficient are derived based on the basic hypothesis of Coulomb’s earth pressure theory and a pseudo dynamic method. The formulas focus on a rigid retaining wall with cohesionless backfill and consider two kinds of conditions with vertical steady seepage. After the problem is solved by computer programs and parametric discussion is taken, the results indicate that the active earth pressure increases significantly with the increase of horizontal seismic acceleration; the effect of vertical seismic acceleration on earth pressure is relatively small, which can be ignored. The earth pressure decreases monotonously with the increase of soil friction angle when soil-wall friction angle is small; however, increasing soil friction angle makes the earth pressure initially decrease and then increase as soil-wall friction angle becomes larger. The seepage effect is also investigated, it is shown that the active earth pressure decreases with the increase of hydraulic gradient for downward seepage case, but increases for upward seepage case instead. Through comparison, the calculation results agree well with the existing methods so as to verify the validity of the proposed method.

Gradient ratio tests of two kinds of plastic vertical drain (PVD) filters (wrapped geotextile) are carried out under the condition of hydraulic gradient increased step by step in the environment of saturated soft clay. Combined with actual vacuum preloading working conditions of soft foundation treatment, the clogging characteristics of two kinds of PVD filters are analyzed. Experimental results show that, with increasing hydraulic gradient，gradient ratio of the anti-clogging effect of the new PVD filter with larger apparent opening size shows upward trend firstly, then downward trend, eventually stability, while gradient ratio of the traditional PVD filter shows upward all the time and is unable to stabilize. Research results show that different hydraulic gradients have a great influence on the clogging features of the PVD filters; and the new PVD filter is better than that of the traditional one in actual vacuum preloading working conditions (the hydraulic gradient is high). The clogging of PVD filters relates to the production technology, pore size of the filter and characteristic of soft clay; it is required to deepen the research of the clogging mechanism of filters.

Permeability-stress sensitivity of complex volcanic reservoir has been studied using the variable pore pressure-constant confining pressure method. Meanwhile, permeability stress-sensitivity obtained from two different experimental methods also has been compared. The experimental results indicate that the volcanic reservoir permeability declines with the decrease of reservoir pore pressure. Decrease of reservoir permeability mainly occurs in the pore pressure from 40 MPa to 25 MPa. There is no good relationship between rock initial permeability and its loss rate, which is different from that of the sedimentary sandstone reservoir. Permeability-stress sensitivity of tight volcanic gas reservoir obtained from variable pore pressure-constant confining pressure is much stronger than that obtained from constant pore pressure-variable confining pressure. And this difference becomes larger during the actual gas reservoir effective stress range. The gas well productivity equation has been mathematically derived taking permeability-stress sensitivity into consideration. Numerical results show that the absolute open flow potential(AOF) when considering the permeability-stress sensitivity is about 63.28% of that when the permeability is considered as constant during the gas reservoir production.

On the basis of 182 gravelly soil samples taken from debris flow source area, the particle size distribution are obtained through laboratory test, fractal dimensions of samples are calculated by fractal theory. Analysis of calculated results show that the gravelly soil samples are mainly one dimension fractal; and it account for 88.46% of the total samples, the value of one dimension fractal is between 2.250－2.798. Based on the calculated fractal dimension, soil samples are configured; and self-made constant head device with controllable waterhead are used to conduct penetration experiment. The experimental results indicate that the correlation between permeability coefficient and fractal dimension is significant. When dry density equals 1.8 g/cm3, the correlation of permeability coefficient and fractal dimension is best; and the relationship between permeability coefficient and fractal dimension shows obvious power function using multiple regression analysis under different density conditions. Moreover, under same fractal dimension (condition), the permeability coefficient decreases with the increase of density; the power function relation between fractal dimension and permeability coefficient is obvious when fractal dimension ranges from 2.450 to 2.600. This study results can provide theory basis for future critical rainfall research; meanwhile, these can improve the universality and accuracy of the existing forecasting models.

Deep underground injection of carbon dioxide (CO2) into saline reservoir in China is in the stage of pilot project and field validation.The mechanical response of reservoir and fluid transportation induced by injection of supercritical CO2 are imperfect in theory and technology. In order to study the reservoir deformation and fluid transportation, the mass balance equations for both supercritical CO2 and saline are firstly presented based on two-phase flow model. The capillary pressure is introduced and served as the argument in the mass balance equations after some equation manipulations, with the help of relation between capillary pressure and saturation degree, which can facilitate consideration of the influence of fluid pressure on the reservoir formation. Secondly, a constitutive model is proposed to describe the mechanical behavior of dry rock of reservoir formation without fluid pressure, both the plastic deformation and damage mechanism can be considered. The coupling mechanism of fluid and reservoir formation is analyzed; the effective stress concept is used to consider the effect of fluid pressure on the reservoir formation, while the influence of reservoir deformation on fluid transportation is described by the variation of permeability of reservoir formation.

In order to simulate and study the effect process and mechanism of cemented soil by different sodium sulfate contents, a series of tests are conducted on the cemented soil samples, such as compression strength test, X-ray diffraction (XRD) phase test and scanning electron microscope (SEM) test, SEM pictures processed by Image-ProPlus6.0（IPP）software; the distribution of pore average diameter of SEM pictures at 200 magnified times is calculated. The test results show that the compressive strength of cemented soil increases with the increase of sodium sulfate content; and the value reaches its peak when the content is 9 g/kg. The distribution of cemented soil pore changes owe to sodium sulfate, and the porosity of SEM photo at 200 times decreases. From the SEM photos analyses show that the microscopic structure of cemented soil by sodium sulfate exhibits the granularity-inlay-cement. Chemical products are analyzed by means of XRD test. The testing results show that the chemical products become more such as Ca(OH)2, CaSO4, CaCO3 and C-A-S-H, after the sodium sulfate participated in chemical reactions. Those chemical products mainly play the role of crystallization action in the chemical reaction process, which is good for cemented soil strength when the chemical products in the sample with sodium sulfate content lower than 9 g/kg. With the sodium sulfate content increasing, the gel around soil particles is broken down, which make the strength of cement soil decrease.

Based on the two-dimension calculation approaches of soil deformation caused by ground loss in double-line parallel shield tunnel (DLPST) construction, the three-dimensional calculation approaches of soil deformation caused by DLPST are established. Altering equations of ground loss rate are established by choosing different longitudinal locations as variables. With consideration of the impact of the first shield construction on the second one’s, the total soil deformation induced by DLPST is obtained by calculating soil settlement caused by both the first and the second shield tunnel construction. The proposed method is able to calculate the deep soil settlement and horizontal soil displacement, which can reflex the three-dimension soil deformation relatively precisely. The result indicates that the calculated value by the proposed method almost coincides with measured value. As the distance to excavation face x increases, the soil settlement volume tends to increase, and remains stable when x=-40 m approximately in the end. The maximum of total settlement volume increases as the excavation distance between the first and the second shield shortens. With the depth of z increasing, the soil settlement increases slightly, but the settlement slot width slightly reduces. The maximum settlement tends to decrease along with two article tunnel axis level distance L increasing, and the settlement curve shape will slowly change from V-shape into W-shape which is not conform to the normal distribution.

A non-intrusive stochastic finite element method (NISFEM) based on Latin hypercube sampling (LHS) for reliability analysis of unsaturated slope considering the spatial variability of multiple soil parameters is proposed. The safety factor is explicitly expressed as a function of uncertain input parameters using the Hermite polynomial chaos expansion, the Latin hypercube sample points are selected as the collocation points for calculating the unknown coefficients of polynomial chaos expansion. The Karhunen-Loève (K-L) expansion method is used to discretize the random fields of soil hydraulic conductivity, effective cohesion and internal friction angle. A computer program named NISFEM-KL-LHS is developed. An example of reliability analysis of unsaturated slope stability under the steady-state seepage condition is presented to demonstrate the validity and capability of the proposed method. The results indicate that the proposed NISFEM can effectively evaluate the reliability of unsaturated slope considering the spatial variability of multiple soil parameters. Both the spatial variability of the soil hydraulic conductivity and the rainfall intensity have significant effects on the location of the groundwater table and the critical slip surface of slope. The probability of slope failure increases obviously when the ratio of the rainfall intensity to the saturated hydraulic conductivity is more than 0.01. In addition, if the spatial variability of soil properties is ignored, the probability of slope failure will be overestimated significantly when the coefficients of variation or the negative cross-correlation of soil parameters become larger.

Tianjin coastal area (TCA), located at the coastal region on the west of the Bohai Gulf, has suffered severe land subsidence due to compaction of the huge thick unconsolidated sediments deposited since Late Cenozoic era. Several factors, including groundwater level decline, clayey soils natural consolidation and surface loading rapid increase are the primary causes of land subsidence in this region. A borehole with depth of 1 226 m is drilled at Tanggu in the TCA; and core samples are extracted at various depths. Through laboratory test of these undisturbed soil samples, the physical and mechanicanl properties and the engineering geological properties of all kinds of clayey soils are analyzed. Integrating estimation of total compaction of the under-consolidated clayey soils, the spatial characteristics of natural consolidation of the unconsolidated sediment layers are delineated; and the relation between consolidation characteristics and land subsidence is discussed. The results indicate distinct compaction characteristics of soil layers at different depths: clayey soils in depth less than 100 m show the states of low natural density, high porosity ratio, high moisture content and high compressibility of under-consolidated soft soil; clayey soils in depth of 100－550 m are in the states of over-consolidation or slightly over-consolidation, which is caused by long-term over-exploitation of groundwater in the past; clayey soils with depth greater than 550 m show the state of normal consolidation and include under-consolidated clayey soils interlayers. The total thickness of under-consolidated clayey soils in the borehoe core is about 218 m. These under-consolidated clayey layers are predicted to bring about cumulative compaction of 1 985 mm in a period of several decades to a century. The first and sixth aquifer groups are the primary contributors to this compaction, with predicted compaction of 614 mm and 665 mm respectively.

Previous researches on the hole-edge stress of rectangular roadway are summed up and the existing problems among them are presented. On this base, the general formulas of analytic functions are used to calculate the surrounding rock stresses around caverns with the function of complex variable, the hole-edge stresses are solved for rectangular roadways with variable span-depth ratios and lateral pressure coefficients through the calculating method for conformal mapping from exterior of unit circle to exterior of cavern with arbitrary excavation cross-section. Then distribution rules of hole-edge stresses influenced by variable span-depth ratios and lateral pressure coefficients are obtained. Stress concentration factors of midpoints in roofs and lateral walls are provided when vertical stress component and horizontal stress component are individually acted on the rectangular roadways; and their results are compared with those in literatures. It is showed that the calculated values of hole-edge stresses are dramatically affected by the boundary errors between the calculated cross-sections and the accordingly theoretical cross-sections. In this study, the calculated cross-sections obtained by the calculating method for conformal mapping approximate more to the accordingly theoretical cross sections, and accuracy loss will not be caused when surrounding rock stresses are solved by the general formulas of analytic functions. So these research results are much closer to the theoretical values for rectangular roadways; and they can be valuably employed in the stability analysis of surrounding rock and the designs on roadways theoretially.

It is one of the concern problems what’s the difference between the earth rockfill dynamic parameters determined in the laboratory and in situ and the real dynamic parameters of the dam materials. The earth-rockfill dynamic parameters back analysis approach based on earth-rockfill dam dynamic characteristics is presented. The material dynamic parameters of the hypothetical faced rockfill dam are back analyzed; and the results verify that the method is feasible, the calculation precision basically satisfies practical engineering requirements. Meanwhile, according to the Zipingpu concrete faced rockfill dam acceleration response information in the aftershock of Wenchuan earthquake, maximum dynamic shear modulus coefficient K and exponent n of the dam materials dynamic parameters are back analyzed. The results indicate that dynamic shear modulus coefficient K of the dam materials which obtained from laboratory dynamic triaxial test is smaller than true value; and it is suggested to adjust.

The effect of further downward excavation beneath an existing building on the pile foundation is different from the one encountered in a newly-created excavation case. Based on the finite-element parameters derived from a case history, a hardening-soil model and a contact-surface model are adopted to simulate the characteristics of soil and the pile-soil interaction, respectively. The three-dimensional finite element framework takes into account the interaction of piled raft foundation, ground and excavation, and is able to investigate the vertical bearing behavior of the existing pile groups after the excavation. The investigation accounts for the effects of end-bearing soil stiffness and excavation depth on the variation trends of pile-head rigidity, pile force, pile shaft resistance, ratio of pile base resistance and soil rebound. The results show that individual piles in an existing pile group subjected to further excavation behaved differently. Increasing the stiffness of the end-bearing soil is crucial to enhancing pile capacity and the critical ratio of pile base resistance. The excavation depth is a key factor that positively influences the mobilization degree of the shaft and base resistances of existing piles. The present results are possible to assist the deformation control of structure underpinning and the design of supplemented pile for further excavation under existing basement.

There are many mature methods to detect the bearing capacity of single pile, but for high-piled wharf piles, as they are parts of high-piled wharf, and complex structures are built on them, at this stage, for these non-free end piles, there are no effective and feasible bearing capacity detection methods. In this paper, regional heap load method to detect high-piled wharf piles capacity is proposed, and this method doesn’t destroy the original structure. The high-piled wharf piles capacity prototype testing is carried out, and the deformation displacement of while high-piled wharf, the displacement of piles, and the strain of structural elements are tested under grading loads. Also the numerical model is established to analysis the bearing capacity of high-piled wharf piles, and the numerical model is corrected by the experimental results, then the whole prototype test process is simulated using the modified mathematical model. The comparison between the numerical results and the experiment data shows a satisfactory agreement. Through comprehensive analysis, the vertical bearing capacity of high-piled wharf piles is finally determined as 1 400 kN, which could ensure the safety of the high-piled wharf, and the study results could provide experimental basis for the design of the wharf.

Continuous pile-plug structure is a new-type anti-sliding structure, with the combination of function of shear plug and slide-resistant pile. The FLAC2D numerical modeling program is used to model the relationship between continuous pile-plug structure and landslides. The result shows that, the internal anti-sliding mechanism of the structure can decrease shear deformation, reduce plastic zones, block slide displacement, mobilize rock-soil resistance; and the external mechanism is the reinforcement effect and retain function. In general, continuous pile-plug structure works under complex stress state with bending moment, shear force and axial force, and the internal force deformation distributes continuously and balanced corresponding to continuous rigid-frame under balanced force. Continuous pile-plug structure solves the limitation of monomer structure and behaves better in slide resistance and reinforcement of landslides. It improves the safety margin of mass movement stability significantly and has wider applicability in landslides management project. The continuous pile-plug structure is applied in Houzishi landslide control engineering, which is the most complex geological hazard control project in Three George reservoir, and obtains good governance effect.

Geological storage of carbon dioxide (CO2) into deep saline aquifers is a leading-edge technology of greenhouse gas emissions reduction. The paper investigates China's first full-chain carbon capture and storage (CCS) project, i.e. Shenhua CCS demonstration project. Combining actual operation condition, the site of demonstration project in Ordos Basin is selected for the study. The relevant parameters are extracted to establish the geological model that is used to simulate multilayer injection of CO2 into deep saline aquifers. In order to analyze migration and distribution of CO2 while and after injection, the relationship between injection capacity and storage mechanisms of CO2 is investigated in detail. Additionally, it is also investigated on changes of formation pressure, CO2 phase, CO2 mole fraction and pH value. The numerical simulation shows that when CO2 is injected into deep saline aquifers, it is almost sequestered into the top of the reservoir. When the injection capacity is stronger, CO2 is injected into more layer formations, and the injection volume of CO2 is relatively bigger. The injected CO2 bears a very complicated phase state in deep saline aquifers. It is mixed with a free gas, trapped and dissolved phases. Simultaneously, when an injection rate is different, main phase types of injected CO2 into deep saline aquifers are different and they change with time. The change pattern of pH values is also different because of strength of seepage effect caused by different injection rates. All exploratory studies are aiming at building a good foundation to optimize future schemes of the demonstration project.

With the rapid development of electronic information technology, scientific research and engineering practice, a wide range and a large quantity of data have been produced continuously. The big data phenomenon has emerged. It is attracting more and more attention and application in scientific data analysis, electronic commerce and banking industry, and taking a profound impact on human life, work and thinking. Traditional data storage methods, relational databases, data processing and data analysis methods can’t meet the current needs on big data gradually. The paper introduces the definitions, characteristics, methods involved, changes brought about and simple application examples of big data. A review on history, state of art and problems of geotechnical engineering monitoring is presented. The concepts of big data naturally agree well with the geotechnical engineering monitoring. Large-scale, comprehensive, multidirectional and multifield geotechnical monitoring will become a reality in the future. The in-depth analysis capabilities such as correlation analysis, cause analysis and decision support will become the core works for the monitoring projects in the era of big data. Furthermore, the site monitoring will be promoted to the same or even more important role as the experiment, theoretical analysis and numerical simulation. Thus, the geotechnical engineering workers should pay highly attention to big data research, enhancing the use of research results of big data from other disciplines. With the opportunities brought about by big data, a rapid development of geotechnical engineering monitoring will arise in the future.

In order to advance debris flow loss assessment from macroeconomic evaluation to service for civil engineering, the concept of engineering vulnerability based on structural devastation extent of civil engineering infrastructures is put forward. However, for those engineering harmed by debris flow hazards, such as bridges and tunnels, it is insufficient to determine the actual disaster loss merely according to structural devastation extent. When the engineering function is completely lost but structure slightly damaged, its vulnerability can be underestimated. Besides, when the engineering function is fairly workable but structure severely damaged, its vulnerability can be overestimated. Therefore, on the basis of the conventional assessment of structural devastation extent, the influencing factors for bridges and tunnels’ function is introduced, such as hazard-affected characteristics, railway/highway ranking and restoration cost. Thus, the engineering vulnerability assessment method for bridges and tunnels harmed by debris flow hazards is proposed, considering both structural devastation and function loss. In the case study, the assessing results show that the insufficiency of the conventional structural assessment can be overcome by this method. This method extends and develops the concept of engineering vulnerability, which makes the assessment more comprehensive and credible. Hence, it is concluded that this method is of great significance to correctly predict and verify the disaster situation of bridges and tunnels harmed by debris flow hazard, to properly prepare the emergency plans or to initiate a quick response.

Offshore wind power structure is the system of superstructure-foundation-infinite domain soil. Dynamic response of structure system is directly affected by transmitting boundary of the model and seismic motion input mode. Firstly, finite element models of tower tubes-foundation-soil-transmitting boundary and tower tubes-foundation-soil-fixed boundary are established. Then, the reason why force instead of acceleration, velocity and displacement is used for seismic input in the model while transmitting boundary is briefly clarified. At last, the following modes are analyzed, i.e. (1) seismic input of fixed boundary; (2) external source wave motion is considered only; (3) external source wave motion and scattering force caused by endogenous oscillation are both considered. Analysis results show that: (1) the reason why force is used for seismic motion input in the model with transmitting boundary is clarified; and the method of seismic motion input is in accord with the actual situation; (2) a convenient method of the generation of stiffness force and damping force is proposed for the foundation of circular cross-section; and it can greatly reduce the workload; (3) the reason that dynamic response of offshore wind power structure is smaller using transmitting boundary than using fixed boundary is explained from the viewpoint of vibration characteristics of model and the damping; (4) the indispensability of endogenous oscillation in seismic response and failure modes of structure using transmitting boundary is pointed out.

The effect of underlying tunneling on existing tunnel is of great concern because the newly built tunnel can induce longitudinal deformation of existing tunnels. A prediction model based on the method of beam on Kerr elastic foundation is proposed. The existing tunnel is simplified as Euler-Bernoulli beam and Timoshenko beam, respectively, to consider the effect of the tunnel shear stiffness on the longitudinal settlement caused by the underlying tunneling. The impact of underlying tunneling on the existing tunnel is taken as Gauss-distributed loading. The proposed prediction method is then verified with the centrifuge results from the reference. The effects of volume loss, load distribution, relative bending rigidity between shield tunnel and ground and tunnel shear strength on the longitudinal settlement of existing tunnel caused by underlying tunneling are investigated, respectively. The results of Timoshenko beam are consistent with those of Euler-Bernoulli beam when the tunnel shear strength is big enough. The proposed method is more feasible for the tunnel with the bending rigidity greater than 7.54×106kN?m2. The effect of tunnel shear strength is very significant when the equivalent shear strength ratio is less than 1/4. The proposed method is finally validated using the field monitoring in Shanghai.

To analyze the feasibility of coastal soft soil foundation treatment using vacuum well-point dewatering, along the Bohai Sea region in the south of Tianjin Hangu district, a certain power plant construction site, a consolidation experiment is made by use of vacuum well-point pumping on site. In order to analyze the effect of consolidation test, groundwater level observation and pore water pressure test are all arranged and different depths of soil are tested before and after the test. After the comparative analysis of the data of static cone penetration test, vane shear test and soil test before and after dewatering, the results show that the consolidation effect is remarkable; a short period of time after the start of the pumping test (within 75 d), the foundation can be reinforced to achieve the consolidation of stability; specific penetration resistance increased from 200 to 300 kPa; and average of vane shear strength increased from 30 to 50 kPa; foundation bearing capacity can be increased to 120 kPa. The consolidation tests show that, it is feasible in soft soil foundation treatment with vacuum well-point.

In order to investigate the zonal disintergration of surrounding rock in deep tunnel, a 3D linear elastic model is built based on linear elastic theory of thick-walled cylinder. The internal wall of model is subjected to decreasing uniform pressure to simulate the processes of cavern static excavation. The end of model is subjected to increasing uniform pressure to simulate the stress concentration effect which causes by cavern static excavation. The external wall of model is subjected to increasing pressure to simulate the stress concentration effect and stress redistribution which caused by cavern static excavation. Based on the elasticity theory and boundary conditions, the stress field, strain field and displacement field around circular opening induced by excavation are determined. We address the following features of the model: tension-compression region, strain gradient, elastic energy of compression and tension from decreasing uniform internal pressure, increasing stress redistribution and increasing uniform external pressure and axial pressure. The results show that the relative change between elastic energy of tension and elastic energy of compression would like to reflect energy release rate and quantity during the processes of cavern static excavation. The stress redistribution and axial pressure are the main factors leading to zonal disintegration. The model provides theoretical basis to study failure of surrounding rock in deep tunnel.

The foundation pile in the slope soil has the dual function of load-bearing and slip resistance. The horizontal force character of it is more complex than the pile in the flat ground. Numerical experiments and model tests are used to study bearing characters and influence factor. Results of the model test show that the distance from the top of the slope has a great impact on horizontal bearing deformation properties of the pile. Under the same level of the load, the horizontal displacement of the pile with a bigger distance is less than that of the pile with a smaller distance. The critical load and ultimate bearing capacity of the pile with a bigger distance is larger than that of the pile with a smaller distance. The result of numerical simulation shows that the horizontal ultimate bearing capacity decreases with the increase of the slope ratio and increases with the growth of the distance from the top of the slope, which is same as the result of model tests. Differences between horizontal bearing deformation properties of piles in the slope and piles in the flat ground are discussed and the calculation method of horizontal bearing capacity of pile in the slope is developed, which can provide a reference to specification revision and engineering design.

Marine sandy sediments containing pore-filling type methane hydrate particles can be considered as a class of special granular materials which present apparent discontinuity characteristics. In order to investigate the mechanical characteristics of methane hydrate-bearing sediment (MHBS), the paper preliminarily explores the simulation method about the load mode of methane hydrate under the different temperatures and confining pressures. To numerically simulate such materials, the distinct element method (DEM) can be used by modeling methane hydrate particles as groups of spheres cemented together and filled into the pores of soil skeleton. The back pressure is converted into inter-particle cementation, and it is rational to choose appropriate parameters of inter-particle bond model to realize the role of back pressure. The macro-micro parameter relation among macro-strength, macro-stiffness parameters, microscopic cementation strength and stiffness parameters of parallel bond model is established, based on existing indoor triaxial compression test of methane hydrate. The cementation parameters of parallel bond are determined under the condition of a given temperature and pressure state. The deviator stress obtained from the stress-strain behavior of methane hydrate uniaxial tests in DEM simulation is in line with that of the laboratory triaxial compressional tests. The relationship between macro-micro parameters can be used to realize the simulation about the load mode of methane hydrate by DEM. This study lays foundation to further propose a technique for generating pore-filling methane hydrate-bearing sediments and to study the mechanics and deformation characteristics of MHBS.

Owing to the mesh-independent crack modeling, the extended finite element method (XFEM) is up to now most effective approach for modeling crack problem. In order to consider small cracks in the analysis of large structure or improve the accuracy around the cracks at a low cost, the fine-scale mesh is generally required around the cracks, whereas the coarse-scale mesh is used outside the cracks. A multiscale XFEM for three-dimensional crack modeling is proposed, which enables one to use a refined mesh only where it is required. The arbitrary-node hexahedron element is developed based on the point interpolation method. The eight-node hexahedron element is used for any scale element; thus the arbitrary-node hexahedron element can conveniently and effectively connect elements with different scales. The three-dimensional stress intensity factors are evaluated with the interaction integral method. Examples including an edge-crack problem and a central circle crack problem are given to illustrate the correctness and efficiency of the proposed method.

Detailed knowledge of crushability evolution and particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This study reports original results of the particle development, energy input/dissipation and shear band formation of idealized crushable sands using 2D discrete elements simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary discs. Simulation results show that the particle crushability strongly affect the mechanical response in macroscopic level and energy allocation in particle-scale level of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the inter-particle friction dissipation. At large strains where particle breakage is greatly reduced, a steady energy dissipation by inter-particle friction and mechanical damping is observed. Furthermore, it is found that the amount of particle breakage keeps increasing during the whole shearing process; but the rate of particle breakage decreases gradually with the applied axial strain. And a clear shear band can be found in low-crushable soil and the anisotropy of the broken bonds becomes weaker and weaker as the development of shearing.

The coupling method of finite- discrete element method(FDEM) by Munjiza is an effective procedure for simulating rock failure. In order to overcome the mesh dependency, it is necessary to partition the rock mass into very small triangular elements; and the elements do not share the nodes, creating a vast number of variables, therefore, the calculation is very time consuming. The method overcomes competition among the existing data in the parallelization and balances loads in a parallel program. A set of strategies for parallelizing serial programs are proposed, determining the hot zones of the serial program, then parallelizing the hot zones as far as possible and using as many private variable as possible to circumvent competition. If there are still data competition among the treads, dynamic lists can be used to store these competitive data. Finally, the data stored in the various dynamic lists are merged outside the parallel zones. Data competition is accordingly avoided with no use of critical section or lock; and the effect of the program parallelization is hence increased. By the proposed method, the parallel version of the FDEM program is developed, which can be used to solve large-scale problem. A numerical example about cliffs collapse shows the effectiveness of the proposed method.

Multi-interlayer and large amount of unsolvable materials are the China’s salt rock’s specialties, so that the current software is not able to simulate the process that how domestic layered salt rock cavity built clearly .By using the theory of hydrodynamics and chemical kinetics, a mathematical model which has excellent ability to describe the cavity building process of salt rock, and a criterion of interlayer collapse are proposed. Then by combining the specificity of the domestic washing techniques , an improved simulation software: Salt Cavern Builder V1.0 is developed. This software has the ability to simulate the cavity building process of pure salt rock and multi-layered salt rock. This software has outstanding capability to present the result in every step for designing cavity-building scheme. By testing the process of similar cavity-building experiments for large-size molded salt rock, the cavity-expansion processes for both none-layered and simple-layered salt rock are simulated successfully. Based on similar theory, this cavity-building simulation software can obtain satisfactory result under the condition of the cavity-building technique in the field. The result is very closed to the one produced by real experiment, so as to verify the practicality of this software.

Sections of the image information of soil-rock mixture are obtained by CT scanning, the point cloud data of gravel surface are extracted by technology of image binarization and boundary recognition. By using Geomagic Studio, a reverse engineering software, three-dimensional geometric model of the gravel is reconstructed and the geometric model of gravels of the soil-rock mixture imported to ANSYS is quickly obtained. With the features of powerful and flexible function of mesh dividing, ANSYS ICEM CFD is adopted to mesh and generate orderly tetrahedral elements to obtain 3D numerical model of the soil-rock mixture. The gridding along the boundary of the soil and the gravels is densified. By using the interface code, 3D numerical model is imported into FLAC3D for numerical simulation. Comparison with the results of nongravel model, it is shown that the established fine 3D model can reflect the structure characteristic of the soil-rock mixture. Especially, it can precisely describe the stress and the deformation of the soil, as well as the boundary behavior of soil and gravel. The method presented can reduce the error caused by model simplification and improve the accuracy and reliability of numerical simulation.