The creep property of rock material is nonlinear obviously, one of the ways to solve nonlinear creep problem is to consider the parameters in creep model varying with stress and time. Some experiments have proved that the stress, time and outside conditions such as seepage will cause the change of some mechanical parameters of rock; so taking the creep parameters as variables accord with the essential attribute of rock material. The relation between stress, time and each creep parameter was investigated based on the Nishihara creep model. First of all, each creep parameter of different times under different stresses was figured out from experiment results by nonlinear least square method; and then the expressions of creep parameters vary with stress and time were put forward by nonlinear curve fitting of the creep parameters’ distribution; finally form the creep equation with variable parameters by these expressions. The variable creep parameters are reflections of nonlinear characters of rock creep, from the damage mechanics’ point of view, the changes of creep parameters reveal the accumulation of rock interior damage and the deteriorative process of material properties.

The comparative analysis on the diversity of water retention characteristics between Jingmen intact and lime-treated expansive soils is investigated by the pressure plate tests. The deformation and strength characteristics of unsaturated and saturated intact, lime-treated and compacted expansive soils are studied by unsaturated triaxial tests. The results show that the air-entry value decreases markedly, the residual water content increases notably and the slope between the two characteristic points is more gradual, which demonstrates that the water stability is improved after the lime-treated. Secondly, the types of stress-strain relation curves of intact and lime-treated expansive soils are all strain softening under the unsaturated and saturated conditions, the grade of strain softening is more gradual with increasing net confining pressure, and the peak stress increases with decreasing water content. The types of saturated and unsaturated compacted expansive soils are strain hardening and strain softening respectively, but the grade of strain softening of unsaturated compacted expansive soils is more gradual than the other soils. And far more important, the values of shear strength parameters are improved significantly after the lime-treated, lime-treated expansive soil can maintain the higher values of strength parameters and fairly stable mechanical properties even under the saturated condition. By contrast, the strength of intact and compacted expansive soils is very sensitive to wetting effect.

To explore the microelectric field effect of seepage(MEFES) in tiny-particle clay, consolidation experiments combined with analysis of particle surface potential are carried out. Five kinds of samples with different contents of kaolinite and bentonite are tested under the same experimental condition. The results show that the MEFES in micropore have great influence on seepage characteristic of tiny-particle clay. The permeability coefficient changes with the ion concentrations in pore water or with the surface potential on clay particles; and that the permeability coefficient decreases with the increasing relative content of bentonite under the same ion concentration in pore water. The same tests on Kuwait soil verify that the generation mechanism and regularity of MEFES in artificial soil can also be applied to natural soft soil. The conclusion shows that under the interaction of clay-water-electrolyte system, clay minerals influence the seepage characteristics in clay by bound water on the particle surface; and one of the intrinsic reasons for the change of the seepage characteristics in tiny-particle clay is the microelectric field effect produced by surface charges on clay particles.

Grain crushing occurs in granular materials when the materials are compressed at high stresses. On one hand, grain crushing induces the evolution of grain size distribution. The content of coarse grains decreases while the content of fine grains increases. On the other hand, the crushing of grains induces the conversion of energies. According to the law of the conservation of energy, one component of the work done by external forces is transferred into heat energy due to the friction between grains; and the other component is dissipated into grain crushing, which was estimated using the theory of surface physics in this study. A relationship between grain crushing amount ratio and void ratio was obtained based on the theories of fractal geometry. One- dimensional compression tests on sand were conducted and relevant test data were examined to verify the obtained relationship. It was indicated in this study that the obtained relationship can describe the influence of grain crushing on the compressibility of granular materials at high stresses.

The interior accelerated corrosion experiment is adopted to study the bond characteristics in mortar bolt anchoring body after mortar corroded. The relationship of interface bond behavior changing with the mortar corrosion level is achieved by means of testing the bond characteristics of bolt-mortar interface and mortar-matrix interface in mortar corroded anchoring body. The results show that: with the development of mortar corrosion, the bond strength of bolt-mortar interface and mortar-matrix interface decrease linearly; the shear stiffness in bolt-mortar interfaces reduces with the increasing of corrosion time; otherwise the corrosion time has little influence on the shear stiffness in mortar-matrix interface, but the chemical adhesion in mortar-matrix interfaces decreases with the rising of corrosion level.

The CT real-time tests were carried out to investigate the macro-mechanic properties and meso-damage mechanism of frozen silt at temperatures of -1℃, -2℃ and -4℃ under uniaxial compression. The compressive strength, stress-strain relationship, and the damage evolution characteristics of frozen silt were obtained. The test results show that the stress-strain curves of frozen silt mainly includes three parts: the linear elastic deformation part, the damage evolution part, and the post-peak strain softening part; the compressive strength of ice-rich frozen silt is sensitive to temperature; but the initial elastic moduli of frozen silt have little difference at different temperatures; with the temperature decreasing from -1℃ to -2℃, the strength could be enhanced about 63%, however, with the temperature further decreasing from -2℃ to -4℃, the strength could only be enhanced about 36%; the initial density damages at different slice of samples are different. The density in whole zone and medium ring zone of samples decreases with the increase of axial strain; but increases with increasing in axial strain in exterior zone.

With the integrated experiment apparatus of gas hydrate deposit syntheses and triaxial compression test, a series of ice, tetrahydrofuran(THF) hydrate, CO2 hydrate and methane hydrate(MH) in the skeleton of fine silty sand are synthesized; and then shear tests are carried out. The stress-strain and shear strength characteristics of these four kinds of deposits and the effects of gas hydrate and ice on the strength of deposit are analyzed and compared. It is shown that these four deposits behave as plastic failure. The larger the confined pressure is the higher the strength is. The deposits with the same saturation of gas hydrate have different strengths when the kinds of hydrates are different.

In order to understand the dynamic characteristics of the structured soft soil in Tianjin Binhai Area, dynamic triaxial test and mercury intrusion test are applied to measure microscopic features of structured clay. The microstructures of unloaded and loaded soft soils are studied by means of the mercury intrusion tests. The fractal theory is used and the fractal characteristics of pore distribution are studied through the data analysis. The method of pore classification is proposed; and the relationship between porosity feature and excellent frequency are formulated. The results indicate that the pore of structured clays under traffic loading is able to be divided into three types according to relation curve of pore diameter and volume of the structured clays. Menger sponge model can be applied to fractal research of the pore characteristics of structured clays under traffic loading. The porosity fractal dimension can be employed for predicting the excellent frequency and analyzing soil deformation mechanism under the embankment.

According to the results of previous tests the mesostructure of sand has been analyzed, which could provide theoretical foundation and further understand the mechanism of deformation characters. The relationship between and the principal stress ratio and also that of the void ratio were put forward through the analysis of the loading and deflection process of the particle unit. The results show that, there is the corresponding relation between the principal stress ratio and the void ratio, which is in accordance with the test result that the effect of stress path on plastic volumetric strain mainly depends on the stress ratio. And then the meso-scale study of evolution process of the pores of sand was made during the increasing of stress ratio. There are two kinds of pores, macro-pore and structural void of particle unit which are the major factors on deformation characters of sand. The macro-pore is independent of stress path, however, the structural void of particle unit which consists of two kinds of basic states depends on stress path (mainly on stress ratio). Finally, the peak stress ratio and phase transformation stress ratio were analyzed from the viewpoint of mesomechanics, As the results that, the smaller the initial void ratio is, the lower the peak stress ratio is; and however, the higher the phase transformation stress ratio is. It is consistent with the experiment observations of sand.

Compared with pure bentonite, bentonite-sand mixture can be used as buffer material in HLW geological disposal to provide low permeability, high thermal conductivity and good workability. Laboratory tests were conducted on compacted mixture of GMZ001 bentonite and quartz sand in different additions of 0, 10%, 20%, 30%, 40% and 50%. Test results show that the liquid limit and plastic limit of the mixture decrease linearly with the increase of sand addition percentage. The maximum swelling pressure of the mixture is exponential increase with initial dry density; but decreases slender with initial water content while the initial water content is higher. By introduction of the concept of effective clay density, an optimum model has been established to describe the relationship between swelling pressure with sand addition percentage and dry density under a certain water content, so as to provide a useful tool for predicting and controlling the swelling pressure of the GMZ001 bentonite and sand mixture in practice.

There are a large number of red clays of quaternary from alluvial-diluvial in Hanyang of Wuhan City. When meeting water, it will swell and soften; when losing water, it will shrink and crack. In order to reduce the harm to dirt road, road bed and anti-seepage engineering, ionic soil stabilizer (ISS) is taken to reinforce the red clay. The red clay is dried in the state of nitrogen and vacuum before and after treatment with ISS. Its specific surface area and pore diameter distribution were analyzed; its microstructure and fracture were observed. The results show that after treated by ISS, the adsorbed water film thins and attraction of clay particles increases, which make the specific density increase. In the connectivity of ISS, the structures of aggregate and stacked of red clay become more closely; the specific surface area, cumulative pore volume and average pore diameter decrease; thereby the unconfined compressive strength and shear strength of red clay were enhanced.

The strength parameters of the inferface between geosynthetics and soils are the key technical factors for the design of reinforced-soil engineering. The direct shear test and pullout test are widely used in characterizing interaction between geosynthetics and soils by experimental methods. The pullout tests of geotextile/geogrid buried in quartz sand and the direct shear test between geotextile/geogrid and sand were carried out; the attempt is made to explore the influence of shear rate and reinforcement material properties on the interface shear strength. The results indicate that the effect of shear rate on the interface direct shear strength could be ignored when the rate is not higher than a limited value ( such as 7.0 mm/min). The interface strength is influenced by the types and characteristics of reinforcement material; the internal friction angles of interface between geotextile/bidirectional polypropylene geogrid and sand are similar to that of clear sand; but a lower internal friction angle value between fiberglass geogrid and sand was gotten as its lower elongation rate and the smaller grid sizes.

In order to study the effect of cyclic temperatures on creep properties of marble, triaxial compression creep experiments of marble specimens were carried out by using rock servo-controlling rheology testing machine, which can consider coupled thermo-hydro-mechanical processes. In the experiments, different temperatures and cyclic temperatures were considered. Based on the experimental results, the axial strain variation pattern of marble with time under different temperatures and cyclic temperatures was investigated. Based on the knowledge of the triaxial creep properties of marble specimen under different temperatures, a modified Burgers model was developed with consideration of temperature change and cyclic temperatures. The results obtained from this model are very consistent with the experiments. It is concluded that the developed modified Burgers model is suitable to describe the viscoelastic creep behavior of marble, which brings important support for the analysis of long-term stability of rock slope under long-term exposures.

In order to research the behaviors of green reinforced gabion retaining wall, tests including vertical soil pressure, lateral soil pressure, the deformation behaviors of reinforcement as well as the wall face were carried out. At the top of retaining wall, cyclic loading and unloading of six levels were imposed. The distributions of vertical soil and lateral soil pressure, the strain of reinforcement, and the lateral deformation and settlement behaviors of wall face under test loading were analyzed. Test results show as follows. Vertical soil pressure distributes along reinforcement uniformly, and lateral soil pressure shows nonlinear distribution along wall back. Test values of both vertical and lateral soil pressure are less than theoretical values. The strain of reinforcement in the third layer is single-peak distribution, and double-peak distribution in the fifth layer; the potential failure surface of retaining wall occurs behind that determined by 0.3H method and Rankine method. The deformation of wall face under test loading shows elastoplastic property. The largest lateral deformation occurs in the fifth layer.

Based on interface friction characteristics between geosynthetics installed on the side slope as liner system in the waste landfill, methods for evaluating tensile forces of geomembrane due to temperature variation and filling height, are proposed. A liner system composed of HDPE geomembrane and non-woven geotextile, the tests of tensile forces of geomembrane were conducted at the various filling height of soil. The results show that the tensile force creating at the shoulder of HDPE geomembrane is mainly temperature stress when the filling height of soil is low. When the difference in temperature becomes larger the tensile force increases. With increasing height of soil, the tensile force of HDPE geomembrane increases. The tensile forces creating at the shoulder of HDPE geomembrane due to temperature and filling height are analyzed by proposed methods. A comparison shows that the calculation results fairly close to the experiment values. Especially, when the calculation considering the interface friction force, the calculated tensile force of geomembrane has higher precision.

By analyzing the actual earth pressure of certain multistage gravity retaining walls, the horizontal earth pressure distributed situation can be described as “R”; the lower earth pressure is less than the bottom value, the bottom value is maximal and the middle is minimum. When the shelf-wall construction the actual earth pressure at the first and second layer is close to the resting earth pressure and more than the active earth pressure; while the third and forth layers is less than the active earth pressure; on the other hand, the pressure at all layers are less than the active earth pressure while the upper wall(s) and slope constructed. The coefficient of earth pressure changes with the filled increased, which is accordantly with the value of the earth pressure. Simultaneity, the position of the action point of the earth pressure is from 0.4H to 0.5H; and it is upper shift along with the earth fill depth; the smaller the platform width between each single wall, the bigger the upper wall influence on the subordinate wall; the higher earth pressure action point. This conclusion has good theoretical guiding sense to the multistage retaining wall designs.

The time-frequency histories of acceleration records on liquefied and non-liquefied sites are analyzed. The concept and the calculation method of frequency decreasing ratio are proposed; and the division between the liquefied and non-liquefied sites is presented. The zero-crossing method is employed to analyze the time-frequency curves of acceleration records. The non-liquefied sites include the soft sites and the ordinary non-liquefied sites. The results indicate: ① The concept and calculation method of frequency decreasing ratio proposed in this paper can describe the characteristics and regulations of time-frequency on liquefied and non-liquefied sites. ② Before PGA, the difference of the average frequencies of acceleration on liquefied and non-liquefied sites is not obvious; and the average frequency of acceleration on soft sites is smaller than that either on liquefied or non-liquefied sites. ③ After PGA, the average frequency of acceleration on ordinary non-liquefied sites is the highest of the three types of sites, that of soft sites is the middle and that of liquefied sites is the smallest. ④ If the absolute change of the time-frequency is used as the criteria, it will be confused between soft sites and liquefied sites. ⑤ The threshold of frequency decreasing ratio is 0.5 between liquefied and non-liquefied sites, which can distinguish the liquefied sites, non-liquefied sites and soft sites correctly.

Influenced by the material and natural environment, the wall paintings of Dunhuang Mogao grottoes have many diseases: flaking, disruption, detachment and loss; and many researches have proved that these diseases are caused by moving of salts; however the moisture is the main factor for the activation and moving of the salt. So, research on rock permeability of the Mogao Grottoes can explain regulations of water migrations and help us to learn the mechanism of wall painting deterioration. This article adopted the test of designated water level in situ to get the permeation coefficient of different groups of surrounding rocks, the test of high-intensively resistivity permeation monitoring in situ experiments; X-Ray CT account the void ratio to study the permeability of the surrounding rocks. We know that different rock strata of Mogao Grottoes have different permeabilities; even the rocks from the same stratum have very different permeability coefficients. Some stratum with good permeability makes it possible that the water permeates inside the cave through the rock layers. Due to the particularity of culture relics and some other reasons, high-density electric resistivity method and X-Ray CT scanning are efficient ways to learn the permeability of surrounding rocks under the situation that we can't measure it directly.

Monte Carlo search technique proposed by Greco is of the random walking type, and has been successfully used in the optimization calculation of the slope stability analysis. The method presented by Greco(1996) can provide solutions of the same quality as the best nonlinear programming methods, but the structure of the method is very simple. The Monte Carlo search technique can be easily programmed and implemented. In this paper, the Monte Carlo search technique presented by Greco(1996) is modified and improved to be applied to the optimization of the bearing capacity calculation by multi-block upper bound method. For this purpose, the following conditions must be taken into consideration, which are the kinematical admissibility requirement imposed by the upper bound method and the boundary conditions of the bearing capacity problems. Based on the above restrictions, the re-establishments have been done for the objective function, the geometrical constraints, and the generation of the starting slip surface and the criterion of arrest. After calculations, it has been found that, the search results tend to catch the local extremum due to the random characteristic of the Monte Carlo search technique and the more rigorous requirements imposed by the upper bound theorem. To solve this problem, many initial failure surfaces are generated to search respectively and the minimum value is selected as the final result. To examine the application quality of the Monte Carlo search technique, lots of calculations are done and comparisons are made. From the comparison, it is shown that the modified Monte Carlo search technique is efficient in optimization of bearing capacity calculation by upper bound. It should also be pointed out that the Monte Carlo search technique used here adopts the points on failure surface as the variables to optimize. So, it is convenient to optimize the failure mechanism employed which includes both the triangle blocks and quadrangle blocks in the multi-block upper bound method.

Highway rock slopes have the characteristics including spot distribution along the road, long interval, small scale and large quantity, little statistics and easy to be influenced by engineering and environment, lack of detailed rock mechanical parameters; and it is difficult to apply the current evaluation system. Based on the characteristics of highway rock slope, considering the systematicness and comprehensiveness, conciseness and scientificity, independence and operability, a reasonable slope stability evaluation index system has been set up; and the stability gradation model for highway rock slopes has been established by using the fuzzy comprehensive evaluation. This model has been applied to Changde-Jishou Highway in Hunan province to analyze the stability of 142 high rock slopes; and the results are reasonable and confirm to reality. Practical so as to provide for reference to other similar projects.

Landslide disaster analysis is a systems engineering, which not only reflects the status and dynamic characteristics accurately, but also embodies the safety and stable condition. It can provide reliable evidences for engineering treatment. Based on GIS and Surfer, various function modules are coupled; and the comprehensive evaluation decision system for landslide disaster is developed in order to realize status analysis, variation prediction and stability characteristics research. The system structure, global design, development foundation and integration of function modules are described in detail. Besides, the application aspacts of system function realization are studied emphatically, including terrain information treatment analysis, virtual landscape visualization, comprehensive decision analysis, deformation prediction and numerical analysis of stability. Then, the functional contents, theory foundation and application process are analyzed. Moreover, according to the problem of effect appraisal of landslide treatment, the fuzzy Markov chain model is used to make decision analysis. Based on the theory structure of model described in detail, a case study is introduced concretely. The results show that landslide treatment achieves good effect; and model analysis can objectively reflect the safety and stable state of landslide nowadays. Therefore, the system provides a feasible technical platform which can realize informatization, dynamic and decision-making for landslide disaster analysis and engineering treatment.

The collected data of integrity testing of pile by ultrasonic crosshole testing requires further calculation and analysis to find the defects along the pile length. For drilling piles, a new analysis method for the collected data based on the research work of test and calculation is proposed to reduce the subjective of tested results. The concept of “ultrasonic test line” is described; a new procedure which used to decide the critical velocity and the comprehensive system that constructed by the units of cross sections of pile is expounded. This method has been proved to be available and more impersonal and accepted by Technical code for testing of building foundation piles of Guangdong province in China.

Numerical methods are generally used for analyzing of laterally loaded piles when the nonlinear constitutive relations of soils around the pile are considered; the related analytical solutions are relatively few. Based on the Winkler foundation model and simplified elastoplastic constitutive relations of soils, the analytical solutions of the laterally loaded fixed-head long pile embedded in a homogenous soil are presented; and the unified dimensionless analytical expressions of the load-maximum deflection and load-maximum moment relationships are derived. Then the same method is used to calculating the maximum deflection of the high pile. The results show that the pile deflection and rotation on the soil surface under combined loads are not equal to the superposition value under each single load; so using the linear superposition method for combined loads will be on the unsafe side. The derived analytical solutions which can be calculated by a hand calculator are more easily applied to engineering calculations.

The problem of critical depth for plastic zone behind the retaining wall has not yet been solved well. The conventional calculation formula is only applicable for some special cases. This paper is based on the limit equilibrium theory, in which the backfill is treated as a perfectly elastoplastic material following the Mohr-Coulomb yield criterion; and it is assumed that a family of slip lines in the plastic zone are straight lines, i.e. the plane slip surfaces. The elastic overburden is put forward to replace the conventional tension crack; and a more reasonable slip wedge analysis model is established. The analytical solutions of the plastic critical pressure and critical depth and the possible maximum depth in plastic zone for active earth pressure on retaining wall in general case are deduced using limit equilibrium method. The calculation results show that the analytical solution of the plastic critical depth is identical with the result by iterative calculation in existing literatures and the conventional calculation formula is a special case of this analytical solution.

When detecting and evaluating the northern ports, some rubble-beddings were eroded by the high speed water-flow generated by tugs at startup, which consequently threatened the safe use of gravity quay. However, these cases were not covered in the previous design standard and the corresponding preventive measures were not provided. Based on a practical engineering, when the rubble bedding was eroded by water flow, the stability of the quay and limit value of the erosion depth are analyzed using standard method and finite element method respectively. It is shown that the results generated by the two methods are in good agreement. Moreover, sufficient attention should be paid by the design units and the quay management units to this newly discovered damage.

surface dynamic deformation of goaf surface is effected by a series of geological and mining conditions; in order to study the details of the process of dynamic deformation, based on information extraction technologies of the empirical mode decomposition (EMD) and phase space reconstruction technologies, and using the data of surface deformation monitored, the laws of surface deformation of dynamic time-varying are put forward. First, the EMD technology was applied to extract the law of the time-dependent deformations of goaf surface; then the phase planes of goaf surface are constructed by using phase space reconstruction technique for studying the evolution of surface deformation. The practice shows that the variation of time-dependent deformation of goaf deformation can be clearly found out by using the above method.

The non-stationary seismic motion for large underground cavern group located in alpine gorge is artificially simulated, based on the frequency analysis of near-site seismic log and bedrock response spectrum obtained by seismic hazard analysis. The trigonometric series superposition, under the control of two predominant frequencies by the Fourier transform from Panzhihua earthquake records, is used to simulate the seismic motion with consideration of depth modification, baseline modification and high frequency wave. The other earthquake log with similar geological background is also used to get the frequency spectrum if the near-site earthquake log is absent. The finished artificial seismic motions, as the numerical simulations show, fit the numerical analysis software such as FLAC and ABAQUS well.

In order to consider rock mass structures in slope hazard zoning, rough set theory and fuzzy pattern recognition was used to classify the slope units with different slope structures; and then, the slope units’ hazard was predicted by information value model. Above method was used to analyze slope hazard zoning of the New Badong county in Three Gorges reservoir area. It indicates that the main influencing factors of landslides include the relationship between slope aspect and strata tendency, the relationship between slope angle and strata inclination, tectonic condition. The slope units could be divides into three kinds that have different weight indices when predict the slope hazard zoning. The shoreline slope of the New Badong county is divided into four hazard ranks. The result of slope hazard is reasonable compared with landslides in New Badong county.

The research on fluid and stress coupling of fissured rock mass under seepage water has become a hot issure; but the calculation of rock considering intermediate principal stress is very few. By use of the unified strength theory and considering the intermediate principal stress, the tunnel surrounding rock to be placed in elasticity, soften, plasticity flow coupling, and give analytical solutiong of boundary radius in deformed district under the contain water to round a rock, lining stress and displacement. The acquisition result tunnel adjoining rock stability analysis and stress structure design's calculation to have the engineering practical meaning to the bottom of water tunnel.

Klinbenberg effect’s existence for gas flow in coal seam has been demonstrated by previous researches. It is a key issue for the numerical simulation of methane recovery to present the model of coupled gas flow and deformation process with Klinbenberg effect. The permeability’s dependence on gas pressure and confining stress in coal seams was studied through experiments. Experimental data’s fitting analysis shows that the fitting result of ZHAO YS formula is perfect, and Klinbenberg effect and the effect of confining stress on permeability can be better considered. The formula was coupled into the established seepage-stress coupled model; and the seepage-stress coupled model with Klinbenberg effect was presented. The corresponding code was developed; and the code was proved to be right with analytical solution. numerical cases with Klinbenberg effect and without Klinbenberg effect were studied. Our main findings are as follows: gas pressure drop with Klinbenberg effect is faster than that without Klinbenberg effect, which is conformable to the theoretical results; and the model with Klinbenberg effect is of marked theoretical and engineering value.

Gas enhanced coalbed methane recovery technology (ECBM), which has the win-win effects on reducing the greenhouse gas emissions and improving coalbed methane recovery ratio, is an emerging technology in recent years. Related research of ECBM has been paid the extensive attentions by major developed countries. Because of the pressure from greenhouse gas emissions reduction, up to now, the developed countries are focusing on studying the application of CO2-ECBM technology in high permeability and unminable coal, for the purpose of permanently storing CO2 as more as possible and enhancing CBM recovery ratio at the same time. Currently, research of this aspect is started just now in China. Most coal in China has the characteristics of low permeability and it is difficult to define unminable coal or minable coal, so it is questionable to apply CO2-ECBM in these coalbed. In view of the characteristics of coal and the present situation of coal mine gas drainage in China, the gas mixture enhanced coalbed methane (G-ECBM) technology has been suggested for the purpose of enhancing coalbed methane recovery ratio. The feasibility of G-ECBM in China has been analyzed by theoretical analysis, numerical simulation and field test study. The results show that G-ECBM technology is applicable to the low permeability and minable coal in China; and it can enhance the coalbed methane recovery ratio and single well production.

To quickly acquire the deformation distribution of underground powerhouse area during the process of construction, based on three-dimensional geological model, underground powerhouse model and monitoring model are appended to the geological model according to design information. In accordance with the characteristics of design information, illustration of three-dimensional monitoring instrument is designed; and a technique for quickly appending instrument model is proposed. Using the underground powerhouse monitoring model, together with three-dimensional spatial distribution based on monitoring instrument, three- dimensional geology and structure panel and deformation data obtained by monitoring instrument, deformation distribution of underground powerhouse is analyzed. Shepard interpolation is improved by the spatial information of stratigraphy and structure panel, which makes interpolation of deformation distribution more approach to reality. Taking Nuozhadu underground powerhouse for example, it is shown that the proposed method is feasible.

Through coupling the unified strength theory and the Lode stress parameters, a mathematical model is established for calculating the local safety and stability of high-cutting slopes along highway in mountainous area. Based on ArcGIS9.3, the high-cutting slope data are pre-processed and analyzed. And by using the finite element analysis software, the study profiles of high-cutting slope are numerically simulated. The relevant parameters of each node of the studied profiles are acquired. Then the stimulation results are further analyzed and visualized by ArcGIS9.3. Finally, the safety zoning maps of the study profiles are obtained. The K88+680 high-cutting slope of Wushan-Wuxi mountain road in Chongqing is taken as an example profile. The safety zoning maps of three different profiles at K88+660, K88+680 and K88+700 are stimulated respectively. And the safety zoning map of the mountain road from K88+660 to K88+700 is obtained by spatial interpolation. Overall, the study result coincides with the actual information very well. The result can be used to guide the excavation and control of the high-cutting slope mountain road. And the research method has an important reference value to the local high-cutting slope mountain road security research as well.

The importances of evaluation indices are considered to be the same in the application process of distance discriminant analysis method commonly. But the importance of each factor is different in fact, so that weighting to each factor is necessary. It has a great influence to the final evaluation results for the reasonable weight values of the evaluation indices. Although there are a lot of methods to determine weights of influencing factors recently, these methods have some deficiencies. To solve these problems, weighted Mahalanobis distance formula is derived based on the conception of Mahalanobis distance; and the corresponding evaluation criterion of many collectivities is obtained according to the method of one to many. Based on optimization theory weight back analysis method is used to determine weights; it changes the directly given weights methods to back analyzing influence factors weights according to engineering samples. The method is fully derived by engineering samples, no experience is necessary, and it is very useful especially in the absence of expertise. The result by using this method in surrounding rock classification shows that this method is reliable. Weighted distance method improves the theory of distance discriminant analysis method. Weight back analysis method is universal, it shows a new idea and can be used in any weights problems.

There are three main reasons that caused the house inclined: ① The designer had a wrong understanding about the result of a large area fill on the highly compressible foundation of collapsible loess. ② The effects of circumstances around the house and the reaction of its change caused by constructions were neglected. ③ The investigator gave a wrong judgment on neo-loess as Q3eol ones. A problem that is often neglected by some designers in collapsible loess regions is pointed out. That is they always put all of their attention to the collapsible settlement which could only take place when its foundation is wetted. But the compression settlement which is inevitable is neglected in their design. Two related questions of the code are discussed: ① Un-rationalization of fixed loading in immersion test was verified by theory analysis and test data. ② The rationalization of coefficient β and ?0 in collapse settlement estimation according to the code was doubted. At last some suggestions are advanced. They are favorable to clear up the misunderstanding about collapsible coefficient and collapsible settlement for some engineers worked here.

Beijing-Kowloon Railway is a new main artery linking Beijing with Kowloon of Hongkong that has been finished and opened to traffic in June 1996. The Jianghuai Section is an interval of 306.1 km from the Huaihe River to the Yangtze River or from Huaibin railway station of Henan Province to Qichun railway station of Hubei Province. Because of complicated topography and heavy raining, collapsed disasters of the roadbeds have become the main damages. According to the statistics, 455 sites of collapsed disasters with 53 000 m of road damages are recorded from 1997 to 2007 along the Jianghuai Section. Basing on the geological background, all cases of collapsed disasters of the roadbeds and meteorological data of 10 meteorological stations from 1997 to 2007 along the Jianghuai Section of Beijing-Kowloon Railway, the rock situations are classified; the occurrence frequency and intensity of collapsed disasters of the roadbeds are graded; and the rainfall in 24-72 h preceding every case are analyzed in detail. Then the conditions of geological backgrounds and precipitation conditions in favor of the happening of collapsed disasters of the roadbeds are obtained and graded; the requirement for the conditions of precipitation especially heavy rain under different geological conditions are commented on; a map with the grades of the happening of collapsed disasters of the roadbeds around the Jianghuai Section of Beijing- Kowloon Railway are drawn out; and some countermeasure methods and a routing map of how to prevent and control collapsed disasters are given. It is clear that the combined action of the weak geological conditions with strong rainfall is the root causes of collapsed disasters of the some roadbeds.

Inshore saline soils have some engineering geological problems from salt expansion, dissolution and water absorption; without solidifying treatments, the saline soil cannot meet requirements in strength and deformation in construction. First on the basis of research results from reinforced soil with synthetic fiber and that with grass root, the type of reinforcement condition of wheat straw, including reinforced length, reinforced ratio, shape of wheat straw and added ratio of lime, were determined preliminarily. Then according to unconfined compressive strength test and Taguchi orthogonal design optimizing method, the best reinforcement condition is as follows: reinforced length of 10 mm, reinforced ratio of 0.25%, a quarter in shape of wheat straw, and added lime of 8%. It has been proved that compressive strength in air, anti-deformation and compressive strength in water of reinforced saline soil with wheat straw and lime is better than that of saline soil with lime and saline soil. The results will guide a direction for studying compressive strength, shear strength and deformation characteristics of reinforced saline soil with wheat straw.

Significant climatic warming is in progress in Northeast China permafrost regions and causes degradation of permafrost and influences the stability of structure. A finite-element heat conduction model with phase change was used to predict thermal regimes of foundations with various ice contents. MAAT (mean annual air temperature) of -2, -3, -4, -5 and -6℃ and medium climatic warming scenarios of 0.05℃/year were used as inputs to estimate the thermal response of frozen ground for the next fifty years. Based on results of ground thermal field FEM and experimental data of ground bearing capacity, the sensitivity of frozen ground bearing capacity to air temperature changes was analyzed and evaluated. The impact of climate change on the bearing capacity of frozen ground and stability of structure depends on the thermal response of the frozen ground thermal regimes to climatic warming and the sensitivity of frozen ground mechanical behavior to ground temperature changes. The results show that the sensitivity of frozen ground mechanical behavior to air temperature changes strongly depends on the ice content and the initial thermal regimes of frozen ground. The bearing capacity of frozen ground with ice layers is more sensitive to air temperature changes. The climate warming has significant influences on the bearing capacity of shallow foundation in high temperature permafrost and the adfreezing bond strengths between piles and permafrost with high temperature; while the temperature increase have less effect on the bearing capacity of deep foundation in permafrost regions.

Considering the broken status and the characters of strong nonlinear mechanical phenomenon of surrounding rocks at horizontal return airway in south of Gubei coal mine in Huainan mining area with a depth of 648m below, the deformation & damage process and nonlinear large deformation mechanism are studied by the universal distinct element code (UDEC). Based on the above research, the stepped combined support method is adopted. Through numerical simulation and field monitor measuring, the support method is analyzed and verificated. It is concluded that the deformation and damage process of broken surrounding rocks is gradual, after excavation. The main reason for nonlinear large deformation of roadway and destabilization of some parts is the collapse or sliding of local key blocks. Meanwhile, the long term stability of roadway can be ensured with the stepped combined support method. This support method is an effective method to control nonlinear large deformation of broken surrounding rocks of deep roadway.

The extended finite element method (XFEM) is a new numerical method for modeling strong as well as weak discontinuities within a standard finite element framework. The computation mesh in XFEM is independent of the discontinuities, such that re-meshing for moving discontinuities can be overcome. An extended finite element method for modeling three-dimensional crack problems is described. In order to model the crack discontinuity, a Heaviside step function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation for the local enrichment by using the framework of partition of unity. The crack is described with two level set functions. The nonlinear contact conditions between the crack faces are resolved with the linear complementary method; the iterative procedure is avoided. Stress intensity factors of crack front are obtained with two-point displacement extrapolation method. Three examples for three-dimensional elastostatic problems are given; the results show that the method can obtain high accurate stress intensity factors and effectively treat the contact problem between crack surfaces, and the combination of the XFEM and linear complementary method has wonderful practical merits for solving discontinuous problems.

The ground vibration of soft subgrade subjected to a non-uniformly distributed train load is investigated analytically. Based on field test data, 5 sleepers bear the dynamic loads transferred from rail, an expression of a non-uniformly distributed load is deduced by assuming that train load is distributed to sleepers with a certain proportion. Taking the ballast as elastic single-phase layer and the soft subgrade as water-saturated poroelastic half space governed by the Biot’s theory, the governing equations of motion are solved by employing the Helmholtz decomposition theorem and the Fourier transform technique. The exact analytical solutions of the displacements, stresses, and the pore pressure of the soft subgrade are obtained in the form of integral. By introducing fast Fourier transform algorithm, the numerical results are derived; and the influences of load distribution, the position of observation, the ballast parameters and the permeability coefficient on the responses are discussed in detail. It is shown that a moving load with a high speed will generate a larger response in soft subgrade than a lower speed load; and special attention should be paid to the pore pressure in the vicinity of soft subgrade surface.

According to flow characteristics of different flow area of rhombus inverted nine-spot fracturing well pattern in low permeability oil reservoirs, the three districts physical models that reflect physical nature of fracturing performance history have been built. Two-phase porous flow mathematical models of matrix non-Darcy flow with start-up pressure gradient, ellipse flow and fracture nonlinear flow in low permeability oil reservoirs are found. As the result indicates, the cumulative production and water content step up with the increase of fracture half length and flow conductivity; incremental scope of cumulative production decreases with the increase of flow conductivity; inclined angle of fracture and injection well row have a little influence on the cumulative production, and well row spacing influences cumulative production greatly. The major rational well row spacing are strongly recommended when put a hydraulic fracturing well into production.

The failure modes of stratified rock slopes are simulated by FLAC3D (fast Lagrangian analysis of continua), while the relationship between dip angles of structure planes and stability of slope is analyzed by shear strength reduction method at the same time. Calculation results show that; ① for horizontal layered slope, horizontal deformation failure at the top of slope occurs earlier than that on the surface and toe of slope, which leads to the tensile failure zones. For consequent slope, when dip angle of structure plane is small, the mainly failure mode is slippage; when dip angle is large, the failure is buckling. For vertical layered slope, the failure mode is bending-fissuring-slump. For anti-dip rock slope, the mainly failure mode is slippage for small dip angle of structural plane, and toppling failure for large dip angle of structural plane. ② for consequent slope, the total safety factor F of slope first increases then decreases with structural plane dip angle β; the outline of curve for the relationship between F and β is like shoulder which is higher on both side, and lower at the middle place. When β =30º, F reaches its minimum value. For anti-dip rock slope, the outline of curve for the relationship between F and β shows the trend of increase-decrease-increase. And the most parts of its curve are higher than that of consequent slope, which is in accordance with practical case. ③ the elastoplastic element with lower strength can reasonably simulate the deformation of weakness plane.

During the period of rainfall, groundwater level in the slope will rise; the matric suction and the temporary pore water pressure will change with time and rainfal1; after constructed the anti-slide piles, retaining wall or drainage structures, the change of the nature of slip zone and anti-slide structure settings whether affect the natural drainage channel of landslides, which lead to the groundwater table rising of landslide, then affect the effectiveness of landslide control. This paper discusses variable rule of volumetric water content and matric suction and seepage-field in the landslide under different conditions of rainfall infiltration and groundwater level change that on the saturated-unsaturated seepage model test and analysis of number value. On this basis, the contribution of matric suction to shear strength is considered. Studies have suggested: The matric suction in the landslide influenced by conditions such as the rainfall intensity, etc.; different change laws appear at different depths. So it should be considered that the anti-slide pile projects affect soil property in prevention and cure that soil landslide.

Based on the secondary development of ABAQUS by the object-oriented program language Python, the finite element method (FEM) with Hill’s stability condition is applied to analyze the bearing capacity of strip anchor in cemented calcareous soils; and the potentially instable regions in the soil are studied accordingly. When the local second order work is negative, some locally instable regions appear in soils; while the global second order work is negative, the system reaches limit state and becomes potentially instable. The limit bearing capacities predicted by the FEM with Hill’s stability condition are close to the theoretical solution. The FEM with Hill’s stability condition can also fairly simulate the potentially instable regions in soils. In general, the FEM with Hill’s stability condition, which has a clear mechanical background, is a convenient method to apply and deserves further study.

Based on the slope stability analysis method of normal stresses modification over 3D slip surface, a 3D back analysis model for shear strength parameters of slip soil is established. Firstly, the stability of slope mass is investigated and assessed to identify the safety factor of landslide and the geometrical dimensions of 3D slip surface. Then, through reasonable assumption and modification of the normal stress of slip surface, the equilibrium equations on the strength parameters are obtained; and the parameters would be solved out by using mathematic methods combining experimentation and experience. The presented model overcomes the defect that the 2D back analysis often overestimates the shear strength parameters of slip soil; and its calculation process is simpler with the help of programming. Two simple case studies show that the 3D back analysis model can take the space effect of 3D landslide mass into account; thus the shear strength parameters calculated is more reasonable and could be the reference for slope treatment.

Numerous impermeable underground structures exist in urban seepage field. Since the corner of the structure is singular point and the dimension of the structure is negligibly small compared with the whole urban seepage field, it is difficult to model seepage field in urban area with existing methods. Invoking the theory of complex potential, dipole, etc, pumping well and injection well are introduced to simulate structures. Different effects of resistivity water is formed by means of controlling the flow of wells. Furthermore, the size of element can be much bigger than traditional method; and then less nodes and elements are probably used to simulate underground structures. In a word, the proposed method is a simplified method which overlooks the local unrealistic flow field around structures but resolves the macroscopic seepage field reasonably well.

A large number of studies have shown that the differential settlement of embankment lead to the early damage of pavement under the repeat loading; so as to severely affect the service performance of the road. But the differential settlement of the embankment has not been taken into account in the pavement structure design. Based on the results of these studies, by using ABAQUS FEM program, pavement’s dynamic response under repeat vehicle loads, under which the subgrade has transverse differential settlement, has been analyzed in this thesis. The results show that the transverse differential settlement has serious impact on the typical asphalt pavement. The damage variable is used to describe the quantitative damage process of pavement; and also refer to the safety factor value of the subgrade slope stability. Then the limited transverse differential settlement of subgrade for typical asphalt pavement structure in mountain area, which is 2.2‰, is proposed and suggested to be considered in the pavement design. It should be effective to avoid the early damage of pavement as a result of the differential settlement of embankment, so as to improve the design and construction standards of mountainous highways.

At present, there are three kinds of slope instability criteria widely used in the strength reduction finite elements slope stability analysis method; namely the non-convergence of solution, the abruptness of the displacement or deformation at a certain characteristic location and the connectivity of plastic zone. Which one is better among three main criteria for evaluating slope instability were widely disputed. In fact they are consistent and uniform. The difference among three main criteria’s calculations is due to human misjudgment and finite element numerical calculation error. With enough accuracy the results of three main criteria are the same.

Geomechanical model test is an important research method to study the large underground caverns under complex conditions, this method can reflect the geological structure and powerhouse structure more truly, simulate the excavation of caverns which have influence on the stability of surrounding rock more precisely and reveal the failure characteristics of the rock. The 3D geomechanical model test of Shuangjiangkou large underground caverns is carried out. In the test, we choose the high precision FBG to measure the displacment of monitoring points and make a reservation pore and pour glue later to bury FBG. At the same time, we use the three-dimensional fast Lagrangian analysis of continua method to simulate the excavations, and make a comparison. The results show that: FBG solves the problem that the test has small deformation, but very high precision requirement. The results of the FBG agree well with numerical simulation results. In the test, it is successful to bury FBG . FGB measures the displacments of monitoring points effectively regardless of the excavation stage or the overload stage; the results reveal deformation mechanism and failure characteristics of the 3D geomechanical model.

A combined system for concurrently measuring the hydraulic properties of unsaturated soils is introduced in detail. The axis translation method and the Darcy’s law are adopted to determine the soil-water characteristic curve and the hydraulic conductivity function. By comparing the measured data, it is shown that the difference of the soil water characteristic curves determined by the laboratory combined system; and the adjusted method of weighing soil in the pressure plate extractor is small; but the residual water content determined by the combined system is less than that determined by the adjusted method of weighing outflow. In addition, it is shown that the measured value of the hydraulic conductivity is close to the computed value of that when the saturation is large. However, the difference between the measured value and the computed value is large when the saturation is small..

It is an important content for construction safety in tunnel to establish the deformation criterion. The land shallow-depth-excavation area of the Xiamen subsea tunnel was constructed by CRD method, its total length is 2 525 m and which holds higher water content and lower intensity. The indices about three-dimensional absolute displacement criterion of primary support are put forward according to the distribution rules of three-dimensional displacement by non-contact three dimensional deformation monitoring with total station. In addition, three dimensional absolute displacement criterion was put forward finally by analysis of normal displacement and abnormal or dangerous displacement about eighty six measurement sections. The study results indicate that the deformation indices of tunnel construction with CRD method are vertical displacement of arch crown on CRD1, 3 and horizontal displacement of middle wall. The ultimate vertical displacement of arch crown on CRD1, 3 is 200 mm, 130 mm and the deformation of CRD3, 1 is in proportion as 0.5-1.0. The ultimate horizontal displacement of middle wall between CRD1 and CRD3 is 100 mm while it is 15mm between CRD2 and CRD4. Fifty eight abnormal and dangerous things were found by applying this criterion to ninety seven sections in scene and ensure construction safety because of adopting some measures in time.