Tongji-1 (TJ-1) lunar soil simulant has been developed as a substitutive material of lunar mare for the purpose of engineering and scientific research. The moisture content and gradation are significant factors influencing the mechanical properties of TJ-1 lunar soil simulant. Their variation is hardly avoided if TJ-1 lunar simulant is manufactured in large quantities. This paper investigates the effects of moisture content and gradation on the mechanical properties (e.g. strength parameters, deformability) in TJ-1 lunar simulant. A series of mechanical tests were designed and performed for TJ-1 lunar soil simulant at different moisture contents and different gradations. The experimental results demonstrate: the upper limit of the moisture content is 3%; the relationship between strength parameters and moisture content and the acceptable range of gradation are obtained.

In offshore wind power project, pile is a commonly used foundation type and is commonly established in soft soil foundations and suffers complex loading combinations, while the bearing capacity and deformation of the foundation is with strict requirements for running of wind power generations. Therefore, studies of behavior and interaction mechanism of pile foundation under cyclic lateral loading have important significance. Centrifugal model tests for typical offshore pile foundation and saturated sand ground are conducted to study deformation characteristics under cyclic lateral loading. Test results show that: under cyclic lateral loading, settlement and horizontal deformation, which is mainly caused by extrusion or collapse, occurs in a limit extent of soil around pile; deformation gradually accumulates with increase of cycles; peak bending moment of pile appears in the 1/3 of burying depth; little change happens in distribution of bending moment with cycles increasing; different excess pore water pressure develops at different locations of soil surrounding pile, which has a certain influence on the foundation behavior

Through a series of stress-controlled bi-directional cyclic shear tests under different three-dimensional anisotropic consolidation stress conditions on the undisturbed saturated marine soft clay from the yellow river delta area, the effects of the initial orientation angle of the maximum principal stress ?0, the ratio of the two stress components R and the cyclic stress level (expressed by cyclic stress ratio Rc) on the characteristics of residual deformation of the saturated marine clay are examined. The test results show that the ?0 has remarkable effect on the residual axial strain ?r caused by cyclic loading, ?r at failure and the relation between ratio of residual axial strain ?r /?rmax and ratio of number of cycles N/Nf . Both ?r caused by cyclic loading and ?r at failure decrease with a decrease of R. At the same N/Nf , ?r /?rmax increases at first then decreases with a decrease of R. The relation curves of ?r /?rmax -N/Nf with different R concentrate in a narrow strip and can be expressed by a unified expression by normalizing the test data. At ?0 =0° and 90°, the differences of relation curves between residual shear strain ?r and cycle number N with different values of R are not remarkable. While at ?0 =30° and 60°, the R has significant influence on the relation curves between ?r and N. The differences of the variation regularities of ?r and ?r under low stress level and high stress level with an increase of N are obvious. The relational expressions between ?r /?rmax and N/Nf are proposed.

Loess plateau is a typical topography in loess areas; high steep slopes at plateau edge cause frequent geologic hazards of collapses and landslides. One of them is the south Jingyang plateau which is located at the south of Jing river in Shaanxi province of China. From southeast to northwest, frequently collapses and landslides form a 30 kilometers landslide group. Dongfeng landslide which occurred in recent years is one of the major landslides of the landslide group. Process and mechanism of high steep landslides were analyzed by field trips, in-situ measurement and physical and mechanical laboratory tests which were carried out on soil samples taken from leading edge and trailing edge of the landslide mass of Dongfeng landslide. Through grain size analysis and collapsibility test obtained collapsibility and liquefaction of mass loess. The influence of water content on strength parameters was studied by direct shear tests and triaxial tests on leading edge and trailing edge of the landslide mass. The structural properties of loess were studied by comparison of undisturbed loess and remolded loess. The consistency between remolded saturated loess stress-strain curves, volumetric strain-axial strain curves and Duncan-Chang model were certified by triaxial consolidated drained tests. The results of shear strength and deformation parameters of the landslide mass loess will benefit the parameter choices in the stability analysis of high and steep loess slopes.

In view of geological origin, the formation of shallow gas in Hangzhou area was analyzed; and the original occurrence zonation characteristic of reservoir soil is investigated. It is shown that matric suction variation range of the gassy sand in enriched zone of scale gas reservoirs is not large, and its initial occurrence water content is close to its residual water content that means it is usually at the state of residual water content. Based on soil-water characteristic curve of the gassy sand described by Van Genuchten (VG) model, the indirectly engineering predictive methods to obtain unsaturated parameters of gassy soil are proposed. Results compared between the prediction and the experiment show that using Van Genuchten and Mualeum (VGM) model, Parker model and strength formula described by the power function, it is effective to predict the unsaturated parameters such as water and gas permeability coefficients, and shear strength of the reservoir soil, which can meet the need of preventive measures taken before metro construction to eliminate the shallow gas geological hazards

A series of pneumatic fracturing model tests are performed using a new developed laboratory apparatus to investigate the effect of air pressure and overburden load on pneumatic fracturing. The results indicate that the injection of high-pressure air into soil induces pneumatic fractures, which accelerate the dissipation rate of excess pore pressure. Before the air injection is stopped, the width of fracture reaches maximum and the fracture closes gradually when the air injection is stopped. The width of residual fracture is about one percent of the maximum width of fracture. The results also show that influence area of pneumatic fracturing and width of fractures are relating with air pressure and overburden load. Air pressure has more significant influence than overburden load. The influence area of pneumatic fracturing is related hyperbolically with air pressure; however, the width of fracture has a positive linear correlation with the air pressure, and has a negative linear correlation with the overburden load.

In order to investigate the bearing features of inflated anchors, a series of scaled physical model tests are done in a calibration chamber using dry sands and anchors of various inflation pressures, embedment depths, soil densities, membrane lengths and thicknesses; and the relevant load-displacement curves are obtained. The results show that the inflation pressure, soil density and anchor length are the dominant factors affecting the pullout capacity of the inflated anchor system in sands. The utmost displacement of inflated anchor is mainly from the elastoplastic deformation of the membrane, which reflects the mechanical properties of the membrane during the pullout test. By contrastive analysis with common anchors, it is indicated that the limit tensile load of inflated anchor is 4.3 times of that of the single-blade screw anchor, 1.9 times of that of the double-blade screw anchor. And its ultimate lateral resistance is 2 to 4 times of that of common anchors

Mixing of bentonite to a native soil is a convenient and economic means to make an impermeable earthen liner for landfills in a region where natural clay is deficient. In this investigation, laboratory permeability tests were conducted on the compacted specimens of loess and bentonite mixtures to study the feasibility of bentonite-modified loess as a landfill liner material. Two kinds of loess soils with different grain size compositions, the Lanzhou loess soil (LH) and Yulin loess soil (YH), were mixed with various contents of bentonite, and compacted to the maximum density for the measurement of permeability by a flexible-wall permeameter. The variation relationship between permeability coefficient and bentonite addition levels was analyzed; and the minimum addition of bentonite to loess soils was determined with respect to the regulations to MSW landfill liner. Scanning electronic microscopy (SEM) was conducted to observe the microstructure of the compacted loess soils with different contents of bentonite addition. It was found that the larger pores existed originally in loess soils were transformed into a larger number of small pores by bentonite addition, which is mainly responsible for the reduction of soil permeability. Based on the test data, a regression penetrative model governing the permeability and the bentonite addition was established for practical prediction.

The bearing capacity of pile tip is the main component of the pedestal pile; so it is the key of the pedestal pile design that how to evaluate the bearing mechanism qualitatively and quantitavely. By the model test of pedestal pile, we’ve done some discussion and analysis of the pile-tip bearing mechanism of the pedestal pile, and drawn some conclusion as follows. The value of the pedestal pile bearing capacity is determined by the exerting level of the pile-tip bearing capacity. The unsynchronized level of the pile-tip bearing capacity and shaft resistance of pedestal pile is much more obvious than that of the non-pedestal pile. The limit equilibrium zone of the pedestal pile tip is different from that of the non-pedestal pile tip; but is similar to that of contrary anchor-slab foundation. Because of the enlarged part, the foundation bearing capacity at pile tip is lower in some extent; so during the design and calculation of the pedestal pile tip bearing capacity, it is necessary to modify the pile tip bearing capacity lowered by the enlarged bottom.

In order to improve the understanding of soil arching effect in the piled embankment, a series of three-dimensional model tests were carried out. The stress reduction ratio and the vertical stress distribution in the embankment fill were studied in detail. Based on the measured and the computed results, the applicability of Terzaghi method and Hewlett & Randolph method were verified. Three-dimensional finite element analysis was also performed in this research; the computed orientation of maximum principal stresses, the stress level and the settlement pattern were analyzed in detail. Based on the test and numerical results, it is found that the value of stress reduction ratio computed by Terzaghi method is closed to that of Hewlett & Randolph method; but the vertical stress distributions of the two methods are different considerably. If the failure surface observed from the numerical result is used, the prediction of vertical stresses using Terzaghi’s method is found to be coincident with the measured value

Through the statistical analysis of the pipe piles’ vertical bearing capacity tests in the soft soil area, according to the pipe pile foundation which mainly bears vertical load, we can find that more than 70% of the pipe piles’ actually vertical bearing capacity were less than 50% of the ultimate strength; and it failed to get full use of the high material strength of the pipe pile. The purpose of this study is to improve the work process of the pipe pile, in order to improve its bearing capacity. By the method of prototype test, this paper presents a kind of enlarged grouting pipe pile patent which is suitable for soft soil area.We can set the endplate’s diameter greater than the pile’s diameter, which can form a space surrounding the pile larger than the pile’s diameter while the pile was sinking, and we can use cementitious materials, such as the surplus grout, to jet grout into that space; then reaming grouting pipe pile is formed. Through thirteen test piles’ vertical compression tests, tension tests, and horizontal force full scale tests, it is shown that this process significantly increased the resistance of the piles’ tips and the soil surrounding the piles; and in this way the pipe piles’ vertical bearing capacity and lateral stiffness can be improved. And this type of pile has been applied to a practical project, and good social and economic benefits are achieved.

The failure damage of granite under cyclic load are caused by the propagation and coalescent of cracks at mesoscale; so it is helpful to understand the mechanical behaviours of rock by quantitatively investigating the meso-damage of granite. A great deal of mesostructural images of Changjiang granite in Hainan Province have been obtained by means of scanning electron microscopy(SEM). The mesostructural images of marble are processed by regional growing theory based on image processing technique. The meso-damage information of granite microcracks are obtained from SEM images. Then, the mesostructural information of microcracks is analyzed by statistical theory and the distribution regularities of microcrack parameters are proposed. Quantitative analyses of meso-damage characteristics under cyclic load are made from minerals and microcracks. It is shown that most of transgranular cracks are mainly concentrated within the feldspars and microcracks are initiated as boundary and intragranular cracks around micas. And the major meso-damage of fatigue damage is intragranular cracks. The energy of the development of transgranular cracks and intragranular cracks account for most of the micro-crack initiation energy consumption

Based on the rules of the loess distribution from northwest to southeast in the middle reaches of the Yellow River, the influence factors of solidified soil with the cement-based soil stabilizer were studied including physicochemical properties and minerals. The results show that with the clay content increase, the strength of solidified soil reduced and then increased of which the clay content of 17.0% is the cut-off points. The strength increased with the more alkalinity in soil. The impact of the montmorillonite is better than the illite. The strength increased as the content of the illite added in the illite soil. The strength increased as the cation exchangeable capacity added and the exchangeable sodium percent reduced. The study indicates that the main reason of soil suitability of based-cement soil stabilizer is the different physicochemical properties of soil; and the strength regularity of the solidified soil is that strength increased from northwest to southeast in the middle reaches of the Yellow River

This article has accomplished the large model test for 1:20 loess slope, investigated the law of similitude, boundary condition treatment in the model test, studied the change rules of dynamic properties and dynamic response rules for loess slope in dynamic compaction, as well as the dynamic properties and dynamic response rules under the influence of the slope ratio. Results show that the amplitude of dynamic response increased with increasing slope ratio. The amplitude of dynamic response for loess slope in dynamic compaction fades out rapidly with the impact loading effect; the vibration cycle is less than 1s and the major frequency is between 25-45 Hz that no superimposed vibration will occur. The amplification effect on radial acceleration is more obvious for loess slope in dynamic compaction; the vertical vibration prevails at lower part of slope while radial vibration prevails at upper part of slope. There is amplification effect for response amplitude on impact vibration of on the ridge of loess slope. There is obvious amplification effect on slope for input acceleration along the slope, especially the most obvious amplification effect at the top of slope. The test results have favorable influence on revealing the rules of dynamic response for loess slope in dynamic compaction, so as to provide instructive reference for the engineering design and construction in loess regions.

Compacted expansive clay is widely used as impermeable material of liner in the garbage landfill and prevention fill of nuclear waste material treatment. The permeability characteristics of expansive clay will effect on anti-seepage effect of liner cushion clay. Due to the difficulty of measuring permeability coefficient directly, the parameter is also evaluated by indirect method which is hard to truly explain permeability characteristics of unsaturated soil and phenomenon of migration of water. This paper discusses measuring permeability coefficient directly by GDS system and quantitatively analyses the influence of structure by permeability test and the SEM test which show the micro and macro-structure characteristics in the permeability process. The results show that the volume deformation of unsaturated expansive soil in permeation process is due to pore air is compressed and changes in pore structure. The pore water permeability coefficient of unsaturated expansive soil is controlled by suction, cell pressure, dry density and degree of saturation of soil samples.

Usually, a negative slope of the stress-displacement curve characterizes the post-peak behavior, where the shear strength of a joint falls to a constant value that corresponds to the residual friction resistance of the joint; it means that the decay rate decreases until to ultimate strength. But for discontinuous joint, the curve follows a “S” shape; it means that strength decay rate increases at the initial stage, then decreases to zero; it means residual strength arrived. So, the constitutive model used by joints is not suitable for discontinuous joint. A new nonlinear normalized model is developed that takes a dimensionless form described by an exponential function. This function reflects the relationship between post-peak stress and displacement through normalized shear strength R and normalized displacement D. The post-peak shear strength reduction ? p-? normalized by shear reduction from the peak to residual ? p-? r is called normalized shear strength R: the post-peak shear displacement ? -? p normalized by the difference from residual shear displacement to peak shear displacement ? r -? p is called normalized shear displacement. At last, the model is used to fit experimental data for different types of discontinuous joints; and the high fitting accuracy shows its validity

Permeability variations of two types of soils (G1 soil with high dispersibility, G2 without) from debris flow source area in Jiangjiagou ravine (Yunnan province) due to fine particles transport were evaluated under constant head condition (the constant pressure head is 5 cm) in soils column. Boiled tap water and suspension of 1 g/L particles (the size range: 1.6－104.74 μm) was successively used as inflow water for both soil column experiments. During the stage of boiled tap water seepage flow, permeability coefficient of both the soil layers near the inlet of the column decrease, while that of both the soil layers near the outlet of the column first increased, then decreased. During the stage of particles suspension seepage flow, permeability coefficient of both the soil layers along the column decreased; and the most severe decreases of permeability occurred near the inlet of the columns. The permeability coefficient of soil G1 reduced by more than one order of magnitude; the permeability coefficient of soil G2 reduced by about two orders of magnitude; and the amount of time spent reaching those values in soil G2 was less than in soil G1. That is the rate of the decrease of permeability coefficient in soil G2 was more than in soil G1. Flow rate for both soils significantly decreased in this stage. The results show that the dispersion played a leading role in the seepage process. In other words, the process of itself particles release and transport can affect the pore concentration and offset the clogging effect induced by the deposition of the foreign particles. After the experiments, the pore space of both the soil layers near the inlet of the columns were almost filled by the foreign particles, and the filling rate gradually decreased along the column by observed with the naked eye, which was in agreement with the results of the permeability coefficient decrease of the soils along the column. In addition, the mass loss of particles only occurred in the first several tens of minutes, and the sizes of the loss particles from the two soils fell within the same range of 1–100 μm

Dynamic triaxial tests are carried out to research the characteristics of fly ash soil improved by rubber particles such as the dynamic strength, dynamic modulus, cohesion and internal friction angle. Comparing with the normal fly ash soil, the experiment results demonstrate the conclusions as follows. Both of the dynamic strengths of the two soils are decreasing as the destruction cycles increasing under the same confining pressure. And the dynamic strengths of the two soils are increasing as the confining pressure increasing at the same destruction cycle. The cohesion is 203.73 kPa and the internal friction angle is 11° of the fly ash soil, at the same time the cohesion is 227.26 kPa and the internal friction angle is 17° of the improved soil. The cohesion increases 23.53 kPa, about 11.55%. The initial tangent modulus and the average dynamic modulus are higher than the data of the improved soil. The experimental result shows that the fly ash soil improved by rubber particles has high dynamic strength, cohesion and internal friction angle large. So that rubber particles of fly ash improved soil as subgrade freezing cold season blocking layer material.

At present, the Mohr-Coulomb criterion is usually used to calculate well casing collapse pressure in oil and gas wells. Since this criterion doesn’t take the impact of the intermediate stress in rock failure process into consideration, the calculated result is conservative and hence limits the development and application of low-density drilling fluid. For this situation, it is often advisable to apply the unified strength criterion. In this paper, the unified strength criterion is adopted and modified, based on the statistical damage theory and the damage condition during the process of rock failure. In addition, a new model of well casing collapse pressure calculation is established by using the modified unified strength criterion. It is indicated that the modified unified strength criterion is capable to simulate rock strength with higher accuracy. The calculated collapse pressure using the new model of well casing collapse pressure calculation is lower than that when applying conventional Mohr-Coulomb criterion and the accuracy is higher

Combined with engineering geological conditions of bridge foundation slope, deformation and failure process on the condition of natural state and loading is simulated and analyzed by floor-friction test method based on similarity principle qualitatively. The test results indicate that the rock masses of slopes at left and right banks are in stable state under the condition of natural state; under the condition of loading rock mass in left bank is in stable state; but the scattered earth-body in right bank is unstable; so that the right bank slope is in unstable state. A measure is suggested by pre-reinforcement or changing the location of bridge pier.

The high-modulus potassium silicate (PS) is used to protect the earthen ruins under arid weathering condition, of which protective effect is good. The earthen ruins reinforced by PS show good permeability. VJ-T and pressure plate apparatus are used to study coefficient of permeability of saturated clay and soil-water characteristic curve (SWCC) of unsaturated clay before and after reinforcement by PS. The coefficient of permeability of unsaturated clay is predicted by correlated model. The results show coefficient of permeability increases more or less under different saturated conditions after reinforcement by PS, particularly evident in sample reinforced by 7% PS. This is because that PS changes geometric figure of these particles and the degrees of roundness to a great degree, which increases effective porosity. The reaction between PS and particle surface leads to a large pore structure to some extent and particle morphology, which leads to the increase of coefficient of permeability. SEM is used to analyse the influence of clay mineral, pore structure on coefficient of permeability of unsaturated remolded clay reacting with PS. The results can validate the permeability test well.

It is imperative to study the engineering characteristics of residual soils which is weathered violently under large deformation. Making use of the test features of ring shear apparatus, the change law of shear strength of soils under large shear displacement can be studied. The experimental determination of residual strength and peak strength indexes of residual soil is conducted by ring shear tests. Test data are analyzed through arrangement and comparison. The relationship between water content and residual strength proved the existence of property of watering softening under large deformation. The character of strain softening of residual soil is analyzed by strain threshold, that is, various shear strengths should be different with various shear displacements. Specifically, the peak strength corresponding to the range of strain is between 0.02 and 0.06 while the residual strength corresponding to the range of strain is between 0.06 and 0.20. Besides, the results also indicate that the residual strength of residual soil is directly affected by the difference of mineral composition, which is the internal cause of inhomogeneity of residual soils

Based on the gobi-filler test of testing for subgrade on the second double line of Lan-Xin Railway, the difference and relation between the ground coefficient K30 and the static modulus of deformation Ev2 were analyzed; and the curve feature of ground coefficient K30 and deformation modulus Ev of four different kinds of fillers were summed up; also, the correlation between K30 and Ev were analyzed. With more information of the laboratory test, the acting factors for K30 and Ev2 were summed up. The results show that: ① The compaction quality of the soil is the main factor for K30, Ev1 and Ev2/Ev1. ② The nature of the filler is the main acting factor for Ev2 and it also has a influence on Ev2/Ev1. ③ The Ev2 is the characteristic parameter for the filler; it reflect the rigidity of the subgrade. ④ The K30 is the controlling index for compaction quality. ⑤ The correlation between K30 and Ev1 is closer, while K30 and Ev2 is slight; and different kinds of fillers have different correlations between K30 and Ev; the results reveal that the correlation is little with the checking indices become more disperse.

Owing to many influencing factors for in-situ stress field of large underground powerhouse region under complex geological condition，reasonable analysis and evaluation of in-situ stress field is need to integrated study about multi-source information of project site. In view of this，analytical methods and ideas of multi-source information fusion for in-situ stress field of underground powerhouse region are proposed. The typical characteristics of these methods are three-level progressive and feedback analysis of information fusion including integration of basic information, identifying of feature information，decision-making and feedback of information fusion. With the methods and ideas, characteristics of in-situ stress field of the underground powerhouse region at Guandi hydropower station and its distribution are investigated. The above results are compared with unloading damage information and monitoring information of rock mass observed in the process of site excavation，related information of numerical simulation，as well as in-situ stress measurements; it is shown that the initial stress field of the project area is reasonable. And then, the reasonableness and feasibility of the above analytical methods of multi-source information fusion for in-situ stress field are demonstrated. Finally, the analytical results from stress field can provide a basis for decision-making to a number of key issues in the process of dynamic optimization design and information construction of the large underground powerhouses

Uniqueness research is one of the basic theories of displacement back analysis. The displacement analytic solution of a deep circular tunnel in transversely isotropic rock mass is deduced firstly; and then the uniqueness of displacement back analysis of a circular tunnel in transversely isotropic rock mass is discussed by means of identifiability conditions. The results indicate: all of 6 parameters can't be determined simultaneously no matter how many the measuring points are set; only when there are at least 3 known parameters, may the other parameters be determined simultaneously; whether the vertical ground stress component is equal to the horizontal one has obvious influence on the results；in the aspect of identifiability, two ground stress components have the best effect, elastic modulus and Poisson ratio on the isotropic plane take the second place, and elastic modulus and Poisson ratio in the direction vertical to the isotropic plane have the worst effect.

Density identification method of dam foundation deep overburden is put forward. The Weibull distribution model is established based on 8 holes, 106 points field pressuremeter tests in dam foundation deep overburden of Shuangjiangkou Hydropower Station. Parameters of the distribution are estimated by least-squares method based on the test results above; and the goodness-of-fit of Weibull distributions is tested. The corresponding relations among pressuremeter modulus, density and pressure are investigated by 20 sets of model tests using the given grading curve acquired in field exploration. The exponential relation of pressuremeter modulus and density is determined by model tests. Based on those above, the authors carry out randomly numerical simulation of the density of dam foundation deep overburden. The simulated density of second-overburden is obtained and its practicability is proved through comparing with exploration results

The full wave form acquisition of acoustic emission (AE) signal provides the possibility of source location based on waveform analysis. The time differences between several sensors are commonly used for AE source location; and the accuracy of time differences has a direct influence on the location accuracy. Based on the wavelet transform cross correlation, the time delay estimation of AE signal is studied. Firstly, through wavelet analysis, signals are decomposed into a series of time-domain signals, each of which covers a specific octave frequency band. Then, the frequency band of meaningful signals were ascertained, based on which the wavelet coefficients of corresponding frequency band after being decomposed were extracted. Finally, the method of cross correlation was applied to reconstruct the signals, to calculate the arrival time of AE waves and to locate the AE source. The results indicate that: compared with the AE monitoring experimental results, the newly proposed AE location method using cross correlation based on wavelet transform can effectively improve the location accuracy of AE source; so as to provide an effective way for AE source inversion.

Unloading of foundation pit excavation will no doubt induce the soil deformation and have result in uneven settlements of adjacent metro tunnels. The excessive settlements may induce the crack of tunnel segments and eventually may affect the safety use of metro trains. Two-stage method is presented for determining the longitudinal deformation of metro tunnels caused by adjacent foundation pit excavation. The soil unloading effects of the bottom plan and the surrounding walls induced by the foundation pit excavation can be considered by this method. Firstly the additional stress due to adjacent foundation pit excavation is calculated. Secondly the governing differential equation is built up based on Winkler model. Then the differential equation is deduced to the finite element equation by the Galerkin method; and vertical displacement and internal forces along longitudinal axis are obtained. Furthermore, the parametric analysis of existing tunnels is carried out; such as, the different depths, the distance from the excavation site, the different geologic conditions and the different outer diameter of the tunnel. Finally, the results from present approach are compared with that from 3D numerical simulation and measured data; good agreement is obtained. It may provide certain basis to draw up correctly protective measures of metro tunnels influenced by adjacent excavation

During the process of the percolation, muddy water seepage can form a sediment deposit layer of weak hydraulic permeability to reduce the water leakage, which is different from the clear water seepage. According to the above muddy water seepage theory, the present study proposes that diversion of the muddy water from the Yellow River to the reservoir and then let the water to form the sediment deposit on the bottom to reduce leakage. Firstly, based on the analysis of characteristics of the silt of muddy Yellow River water, the research discusses the influence of the sediment deposit formed by the muddy Yellow River water on the leakage for the plain reservoir. Secondly, through the laboratory test, we get the correlation between the leakage and the sediment deposit formed by different water heads, and finally obtain the certain thickness of the deposit layer with the best impervious effect. Finally, the research results are applied to the seepage control of the plain reservoir; the theoretical calculation and the operation of the project evaluation show that the theory has satisfied effect and can be applied to other similar projects.

An artificial intelligence reasoning and similar case retrieval methodology for tunnel projects characteristics, such as geographic region, monitor position, depth-width ratio, levels of surrounding rock mass and embedded depth of tunnel, and time series of arch-top deformation, is presented aimed at universality of prediction model and extrapolative accuracy. The similar case is searched and analyzed; and a forecast model is further built based on prior resource with LPG new kernel of support vector machine. The efficiencies of method are tested by predicting arch-top subsidence of a tunnel project example. Experimental results show that the approached method is suitable for the study of different tunnels or different sections of same tunnel. The average relative error of regression is 1.36% and the accuracy of extrapolation prediction is up to 97.28% within 8 steps proved case-based reasoning could achieve good prior resource and greatly help to enhance the ability of generalization of support vector machine. The better accuracy and reliability for extrapolative assessment of arch-top deformation can be utilized to server tunnel monitoring measurement

The analytical solutions of the equivalent deformation modulus and equivalent Poisson’s ratio of composite foundation on the stage of elastic deformation are developed according to the deformation consistent principle and considering boundary constraint conditions based on the unit cell model. The research results indicate that the equivalent elastic constants of composite foundation are related to the lateral restraint condition of the unit cell. The equivalent deformation modulus increases as the lateral restraint enhances, and the equivalent Poisson’s ratio has a reverse trend. The equivalent deformation modulus are respectively the upper and lower limit values; and the equivalent Poisson’s ratio varies with area replacement ratio greatly when the lateral restraint condition is strong. The results also show that the deformation modulus calculated by area-weighted method leans to small; and the compression modulus leans to large. Comparing with area-weighted method, the difference value of the equivalent compression modulus varies with area replacement ratio and increases as the oedometric modulus ratio enhances; the difference is up to 20%-30%

Acoustic emission tests of coal-rock specimens under uniaxial compression were carried out; then the long-range correlation and multifractal characteristics of acoustic emission strength sequence were analyzed by multifractal detrended fluctuation analysis method (MF-DFA). On this basis, the trend of long-range correlation exponent H of AE strength sequence with different stress levels was studied. The results show that the inner fluctuation of AE sequence is a well-regulated multifractals, which is rather a long-range correlated process determined by intrinsic self-similar properties and not complete random on time scale. The trend of AE parameter H corresponds well with the process of coal-rock fracture development; the ‘maximum-decrescence’ model of which can be used as a precursory factor of coal-rock failure. The results provide a theoretical basis and method for monitoring and forecasting coal-rock stable condition based on acoustic emission in site.

Based on analyzing the essential characteristics of the stability situation of current Qinghai-Tibet railway slope embankment in permafrost regions, and combining the study status quo of calculation and analysis method for stabilities, a method is put forward practically, which analyzes and calculates the stability of slope embankment from both thermal and mechanical aspects respectively and gives a comprehensive evaluation about it. Through analyzing and calculating an on-site typical cross-section, it can be seen that: ①For the slope embankment of which thermodynamic properties show a dynamic variation, that analyzing its most unfavorable conditions could be in line with the actual results of its stability. ②When slope embankment is at the thermal steady state, its mechanical stability may be presented unstable situation. Therefore, to get a more comprehensive and in line with the actual conclusion, it is needed to analyze its stability from the two aspects of thermal and mechanics. This method is simple in principle, and the result is clear, and it also is of important guiding significance to analyze and evaluate the stability of slope embankment in permafrost regions during the operational phase.

Based on the structural plane group (a total of four, named J1－J4) in Qingfeng Ancient Quarry located in Shepan Island of Zhejiang Province of China, the values of long-term shear strength parameters, cohesion and internal frictional angle, of the corresponding structural planes of the tuff were carried out using back analysis method. The results show that the cohesion is 0.078 MPa and the internal frictional angle is 15.76°, which are lower considerably than that of the rock mass with cohesion of 16.55 MPa and the internal frictional angle is 48.2°. The steps of the back analysis method are as follows. Firstly, it is assumed that structural planes of J1-J4 are consistent with Mohr-Coulomb strength criterion; and the rock mass is homogeneous elastic and isotropic. Secondly, the equilibrium equations with the cohesion and internal frictional angle for the unknown parameters are given based on that the structural planes are under the state of the limit equilibrium. Thirdly, carry on the 3D numerical calculation using the software of FLAC3D, extract the data needed for solving the above equations from the calculation results, substituting the above extracting data into the corresponding equation, and then four linear equations of two unknowns will be attained. Fourthly, the values of the long-term shear strength parameters, cohesion and internal frictional angle, of the structural planes can be obtained by solving this contradictory equations.

Strength increment of soft soil of a real project in Shanghai is studied. Strength parameters of polygonal line equation which considering the effect of soil structure and linear equation which didn’t consider soil structure are obtained by direct shear test and triaxial test. Shear strength increment is calculated with these parameters by the two methods, and compared with the field results obtained by vane shear test. Because of soil structure, strength increment calculated by linear equation is greater than that by the polygonal line equation. When using polygonal line equation to predict soil strength, the result is more close to result of vane shear test. And it is suggested that the strength parameters should be obtained by triaxial test

With consideration of nonuniform skin effect factor, the mathematical model for 3D radial flow for anisotropic confined aquifer is presented. To attain solution for the corresponding problem, the skin effect factor is deemed as piecewise continuous functions, according to which the confined aquifer is divided into N layers. Then the method of finite difference is used to transfer the original problem into matrix differential equation with boundary conditions; and finally, by matrix theory, the solution is attained. With mathematical software, the solution is applied to numerical examples. Results show that: In the region close to vertical well, the variation of drawdown and flux component is inversely related to the skin effect factor; that is, larger skin effect factor leads to smaller drawdown and flux, vice versa, while in the region far from vertical well, the same tendency of variation keeps only for the situation that vertical permeability is far smaller than radial permeability. Therefore, the amplitude value of the curves s*- r* for different layers of confined aquifer depends on both the value of skin effect factor and the ratio of vertical permeability to radial permeability.

Distribution of earth pressure of rigid retaining wall is closely related with mode of rotation and wall movement. Analytical method of earth pressure considering displacement can be used to calculate the distribution of active earth pressure only when the wall movement is known. The method of determining wall top displacement of active equilibrium condition and earth pressure distribution behind rigid retaining wall rotating about wall toe is put forward from the aspect of satisfying the requirement of overturning stability and eccentricity of wall base compressive stress. Influence of wall width and frictional coefficient behind retaining wall on earth pressure distribution is analyzed. Analytical results show that the earth pressure of active equilibrium condition is larger than Coulomb active earth pressure. The overturning moment rotating about wall toe induced by active earth pressure with working condition is also larger than it calculated by Coulomb active earth pressure. Active earth pressure distribution is more close to static earth pressure with increasing of wall width, and as the decrease of it the distribution of earth pressure will be transferred from static earth pressure to Coulomb active earth pressure. Frictional coefficient is closely related with overturning moment. The width of smooth wall back satisfying the requirement of overturning stability is increased distinctively compared with rough wall back.

On the assumption that the beams are rigid, and that the slope body is elastomeric, the anchoring concentrated force is translated into rectangular distributed force. And then, according the characters of soil-like slopes, the transferring equation of the prestressed force from slope surface into slope body in frame anchored soil-like slope is deduced. The transferring coefficients of the prestressed force are put forward according to the transferring formula. Some centrifugal model tests are carried out according to a granite soil-like slope locating at K617 of G232 national highway. In the centrifugal model tests, earth pressure cells are set at different points of the slope body to monitor the increased earth pressures caused by the prestressed force. And then the transferring discipline of the prestressed force from slope surface into slope body can be brought out. The results drawn out from centrifugal model tests agree with what from theoretical study mainly. The conclusions are drawn out from the calculations and model tests that the plastic deformation of the frame anchored slope body is distinctly small than single anchored slope body; and that the effect on distribution factor of prestressing force in frame anchored slope is smaller than what is in single anchored slope. The distribution factor of prestressing force is 0.4 in frame anchored slope, while it is 0.9 in single anchored slope, which indicates that about 56% of the prestressing force is well spread around. It is obvious that the compression strain in frame anchored slope is smaller than what is in single anchored slope, and that the decreasing of prestressing force can be smaller in frame anchored slope. The optimal space of anchors can enlarge to 4.2m for frame anchored slope from 3.2m in single anchored slope.

Slope stability is the multi-dimensional nonlinear problem which is influenced by complex factors. There is uncertainty in most of slope engineering. A large number of test and engineering practice have proved that the factors affecting slope state have significant randomness and parameters have variability. So we can use Kolmogorov-Smirnov test (K-S test) for the raw data to determine the distribution type of parametric variation from the perspective of probability and practical engineering. It will overcome artificial assumption. And sample the parameters to obtain state function and determine the safety factor and reliability index using Latin hypercube sampling (LHS) method and Monte Carlo method, respectively. Comparison of two sampling methods, the number of simulation based on LHS is less than the Monte Carlo method. Also the convergence of failure probability curve with LHS is better than the Monte Carlo method.

Following a tunnel excavation in low-permeability soil, it is commonly observed that the ground surface continues to settle with time, as the dissipation of the excess pore pressure leads to the consolidation settlements. For studying the consolidation settlement of soil caused by shield tunneling, an initial excess pore water pressure formula during the tunnel construction is presented based on Henkel pore water pressure theory; and it can be used to calculate the consolidation settlement by means of numerical analysis. This approach has been applied to the engineering case of the Shanghai metro tunnel-line 2; and the calculation results are obtained based on the soil geological condition. As shown in the analytical calculation, the maximum value of the initial excess pore water pressure is located at the spring-line of the tunnel. The calculation results of the consolidation settlements are in good agreement with the field data.

When using the finite-element method to calculate the seepage fields with drainage wells, we adjusted the well boundary to reduce the total unit number and improve the element adjacency. Two methods were examined in this paper, one is to transform the circular well into an equivalent regular polygon, another is to transform one well into equivalent multiple n well elements possessing different permeability coefficients but same effects. The second method was first raised by Li Zu-yi (1984). For the well’s elements with tetrahedral shape, according to theoretical analysis，the reduced coefficient of areas from which flow quantity is calculated, is raised from 1/4 suggested by Li Zu-yi to 1/3 in this paper. The numerical solutions of all examples calculated by different well’s treating methods are compared with the theoretical results. By doing this the data may be chosen with better performance and less bias

The extended finite element method (XFEM) is a numerical method for modeling discontinuities within the classical finite element framework developed in recent years. In XFEM, jump functions and asymptotic crack-tip fields were added to enrich the finite element displacement using the framework of partition of unity to model the discontinuities of cracks. A key advantage of XFEM is that in fracture problems the finite element mesh does not need to be updated and remeshed. Based on the algorithm of XFEM, the J integral methods which calculate the stress intensity factor(SIF) are introduced. A numerical case with model I fracture is analyzed by XFEM. The results illustrate that the FEM mesh is independent of the crack interface. The major factors which influence the accuracy of SIF are discussed, such as integral domain and mesh density. Proper parameters to calculate the SIF are given; and the feasibility and accuracy of XFEM are validated.

Generally, the influence of the stress state on the seepage field was not considered in the seepage analysis for the embankment dams. However, the stresses in the embankment dams are very complex and have large variation during water filling. Furthermore, the stress state has evident impact on the seepage field. So some errors will be induced into the seepage analysis results if the influence of the stress is ignored. The seepage fields of the core wall rockfill dams on the conditions of considering or not considering the influence of the stress are analyzed and compared using the finite element method. The results show that induced by the stresses on the dams, local compressive deformation of the dams occurred, the seepage velocity of the dams decreases and the maximum hydraulic gradients at the seepage exit is much larger than those in the non-coupling analyses; it is shown that the seepage analysis without considering the effects of stress on the dam seepage is not conducive to dam safety.

Due to the carrying capacity of horizontal load, battered piles were generally used in the foundations of bridge, wharf and transmission power line. The horizontal and vertical load sharing of piles is not only force decomposition, which is related with the axial and lateral stiffness of inclined and vertical piles. The influence of axial and lateral stiffnesses coupling should be considered in the analysis of inclined group piles foundation. According to the studies of the axial and lateral stiffness of inclined and vertical piles and the analysis of load sharing of group piles, the force characteristics of battered pile foundation were gained. First, the lateral stiffness of positive inclined pile is biggest; and the lateral stiffness of vertical pile is bigger than that of negative inclined pile. Second, the influence of pile length on the axial stiffness is very significant. When the pile was lengthened, the axial stiffness was increased; and the differences between axial stiffness and lateral stiffness were expanded. Last, most of the vertical load was borne by the axial force of piles. When the ratio of axial stiffness and lateral stiffness is small, most of the horizontal load was borne by the lateral force of piles. When the ratio of axial stiffness and lateral stiffness is large, most of the horizontal load was borne by the axial force of piles. At the same time, due to the inclined angle of pile is small, the large axial force is created to resist horizontal load

The u-p (representing displacement of soil skeleton u and pore water pressure p) format 2.5D finite element equation of the saturated soil in the frequency domain is used to analyze the effectiveness of different vibration isolation countermeasures in isolating ground vibrations induced by trains moving at sub-and high-speeds. The vibration-isolation countermeasures considered herein include the installation of open trench, in-filled trench (concrete wall), and concrete slab (wave impeding block, WIB). The track and the attached sleepers are simplified as Euler beams resting on a saturated ground; the wave-number transform in the load moving direction is applied to reduce the three-dimensional (3D) dynamic problem to a two-dimensional (2D) problem. The 3D dynamic responses of the track and the ground are obtained from the inverse Fourier transform. For isolating the vibrations induced by trains moving at sub speeds, the isolation effectiveness of open trench and in-fill trench at elastic soil and saturated soil are almost the same; while quite different for WIB. In a word, open trench is not effective, in-filled trench is effective within a certain range; WIB is the best choice. For isolating the vibrations induced by trains moving at high-speeds, open trench can get certain effective at bigger width and depth, in-filled trench and WIB can achieve the desired vibration isolation effects at a smaller size.

The stability of jointed rock slope is mainly controlled by the shear strength and distribution of joints. The failure of jointed rock slopes usually has large deformation and discontinuous features; therefore, discrete element method becomes an efficient way for stability analysis of jointed rock slopes. A general study of the intact rock properties and mechanical characteristics of joints are carried out using the particle flow code in two dimensions (PFC2D); and a heavily jointed rock slope is modeled using PFC2D to study the slope stability. The results reveal that the failure of jointed rock slopes is a gradual process; the joint connectivity has large effect on the stability of rock slopes with heavily joints; when the joint connectivity is more higher, the slope is more unstable; with the decrease of joint connectivity, the slope failure modes will change from the large scale slide into a partially collapsed form

The prediction of three-dimensional hydraulic fracturing morphology and extension is the main factor to evaluate the effects of hydraulic fracturing; adopting the method that combining damage mechanics and fracture mechanics to describe the mechanical behavior of cracks in the surface rock, and then the damage criterion and damage evolution equation in the crack surface are established. The equation is solved by using the method combining Newton-Raphson and the linear search; and then the dynamic crack extension process and the final morphology of hydraulic fracturing three-dimensional are obtained; and the mechanical essence is revealed. The correctness of the theory and calculation is verified through numerical examples; based on which, the main factor of crack extension is analyzed. The results provide more reliable and accurate prediction methods for hydraulic fracturing design, so as to improve reservoir hydraulic fracturing success rate.

In the course of implementing elastoplastic model in the FEM, it is necessary to carry out the process of stress return mapping algorithm. It may be not converging at singular points in three-dimensional space. The transforming method in principal stress space is put forward to overcoming this shortcoming. Also, the process of determining the region of return mapping is analyzed. At last, the consistent stiffness matrix is deduced. Based on the implicit algorithm in principal stress space, the UMAT subroutine of the Hoek-Brown model is developed in ABAQUS with the Fortran programming language. Through the example of triaxial compression test, it is easy to verify the feasibility and accuracy of this method by comparing the result with Mohr-Coulomb criterion in ABAQUS.

It is very difficult to measure the lateral load on the micropile in-situ, so the load transfer behavior and the stress characteristics are incomplete; so that numerical simulation of the flexible micropile (l/d more then 50 in general) with finite element software ABAQUS is made. The numerical analysis results are consistent with field measured results, so as to prove that the simulation parameters are effective and correct. They can reflect the field actual situation perfectly. Using finite element numerical simulation, the mechanical behavior of micropiles subjected to horizontal load, and parameters influencing on the lateral bearing capacity of micropile are discussed. Finally, some reasonable values of the pile length, pile diameter, elastic modulus and so on, are given. It is shown that the more larger diameter and the larger friction angle of soil, the more larger lateral bearing capacity of micropiles.

Liquefaction, seismic subsidence and lateral spreading should be considered when a sandy foundation in the seabed or maritime province sustains meizoseismic load. Zhaohui Yang’s nested constitutive mode is incorporated into OpenSees to evaluate its capacity of simulating soil liquefaction; and a simple method to get parameters is introduced. An interface between OpenSees and ANSYS is constructed; and then a dam on loose sandy foundation which is in the strong earthquake area is analyzed by the nonlinear finite element method. The results give out the liquefaction condition of the foundation and predict the seismic subsidence and lateral spreading, it would help us to do the foundation reinforcement treatment with such cases