Advanced Materials Research Vols. 243-249

Abstract: Difficult in soil-water characteristic curve achieved, existence of non-uniqueness and indistinct in influence of unlinear deformation characteristics of soil about density and water content, deformation characteristics of unsaturated soil were studied difficultly with general triaxial test, thus direct application of unlinear Duncan-Chang model in unsaturated soil was restricted. General triaxial tests with combined dry density and water content are carried out, changing rules of parameters of Duncan-Chang model are summarized, mathematical functions between dry density, saturation and parameters of the model are established. Analysis shows that deformation characteristics of unsaturated clay are influenced obviously by saturation and dry density. Among them, the larger the saturation, the higher strain becomes under the condition of the same dry density and main stress difference, and the less the dry density, the higher strain becomes under the condition of the same saturation and main stress difference. Moreover, the main parameters of Duncan-Chang model keep close correction with dry density and saturation, and the both mutual effect can be expressed by multiplication. This shows that mechanical characteristics of unsaturated soil can be studied with general triaxial test, thus it will be used easily in project.

Abstract: Soft-soil has obvious rheology character, it will induce subsidence distortion, landslide etc serious geotechnical engineering and geologic disasters, and make severe threaten to stability and security of projects. The initializing shear stress and viscosity of sullage soft-soil are tested under static load, and the influencing characteristics are analyzed of which the percentage of clay and water affect the rheological parameters. The mechanism of which the percentage of clay and water affect the rheological parameters are opened out by using the theory analysis and technology of structure micrograph..The research results have have theoretic and practical significance for us to analyse changing disciplinarian of rheological parameters, reinforce soft-soil foundation, raise bearing capacity and whole strengthen of soft-soil.

Abstract: This article has used the ADINA numerical calculus software to simulate the deep foundation excavation and supports process, as well as analyzing the analogue result in the project of the Xia Gong in ShenYang City. The results illustrate that (1) it is essential to optimize the pile earth's horizontal displacement and the mechanical situation of anchor rod. (2) It makes soil’s horizontal displacement and the mechanical situation of anchor rod more reasonable by changing the anchor rod vertical spacing and length ，hence obtains that the anchor parameter change has the great influence on the distortion of the support structure.

Abstract: The side hill cut of certain road cutting has a gradual slope and low slope height. But due to the location in fault zone, serious slump damage occurs during construction, leaving large crack. Aiming at the deformation damage of the side slope of the road cutting, this essay provides analysis of the deformation behavior and mechanism causing the slump through the geographic environment and monitoring data, and through summing up the experience in design and construction management, provides engineering analogy case and experience reference for similar side slope management.

Abstract: To study the working behavior of a rigid pile composite foundation of high-rise buildings, an in-situ loading test and stress test on piles and soil were carried out. According to the test results, the stress distributions and variations, load transferring characteristics, and stress distributions of piles were analyzed. The results showed that the piles with the formation of non-soil compaction technology can consolidate soil among piles. When the load level was greater than 240 kPa, a better consolidation effect can be obtained. The development negative friction at the top of piles was relevant to the load level. The adjustment effect of cushion on the composite foundation was mainly embodied before the load level reached the characteristic bearing capacity of the composite foundation. Under vertical load, the stress distributions along the internal and external sides of pile shaft were different and the loading plate would bring influence to stress distributions of the pile shaft. The influence range was from the middle to the top of the pile. Based on the test results, it is recommended to reduce the evaluation standard of the bearing capacity determined in the pressing plate test. The results can provide a reference for similar engineering.

Abstract: Disaster caused by exploiting underground coal is due to original mechanical equilibrium of underground rock has been destroyed when underground coal is exploited. And Stress redistribution and stress concentration of wall rock in the goaf happened too. As many complex factors exist such as complex structures of ground, multivariate stope boundary conditions, many stochastic mining factors and so on, it is difficult to evaluate the damage of the geological environment caused the excavation by surrounding underground coal accurately. Besides that, the coexistence of continuous and discontinuous of deformation and failure of wall rock make a strong impact on the ground, and the co-exist of tension, compression and shear failure also pay a great deal contribution to the destroy. Due to the mechanical property and deformation mechanism of goaf are complex , changeable, nonlinear and probabilistic, which changes with in space and time dynamically, it can not be studied analytically by the classical mathematical model and the theory of mechanics computation. Through finite element analysis software ABAQUS, a numerical simulation of the process of underground coal mining have been made. After make a research of the simulation process, it shows the change process of stress environment of wall rock and deformation and failure process of rock mass during the process of coal mining. The numerical simulation of the process can provide theoretical basis and technical support to the protection and reinforcement of laneway the process of coal excavation. Besides that, it also provides a scientific basis and has a great significance to reasonable Excavation and control of mind-out area.

Abstract: A series of model tests were carried out to investigate the soil resistance when the buried pipe segment moved in the sand. In the tests, the pipe segments were pulled out in vertical, lateral and axial directions and the pipe segments movement and soil resistance were recorded. Observed data show that the soil resistance depends on the pipe diameters and the depth of cover. According to the uplift test results, the force-displacement relationships with smaller depth of cover are greatly different from those with larger depth of cover. The results of the lateral sliding and axial pull out tests show that the soil resistance initially increases before a peak value is reached and then keeps the same level. For the same covered depth, the lateral soil resistance is more than twice that for uplift. According to the uplift test results, the soil failure modes with smaller depth of cover are greatly different from those with larger covered depth.

Abstract: Based on the theory of particle flow code, the micro-numerical analysis model is established to study the anchorage performance of geotechnical prestressed anchorage structures. According to the numerical model tests, the development regularity of stress and displacement of surrounding soil around bar body under the effect of uplift loading is analyzed, and the interaction characters between anchor bolt and surrounding soil are also deeply studied. Conclusions can be drawn as follows: with the function of tensile load, two area of stress concentration form within the interior bond section of prestressed anchorage structure, and the soil porosity also changes accordingly. The interface shear stress peak point shift inward gradually with the increase of time-stepping, furthmore, the peak stress also enlarges gradually. According to the deformation mode, the surrounding soil can be divided into three zones. The radial displacement of soil between anchors is weakened because of the effects of group anchors, but the axial displacement is strengthened, which nominally is similar to the “single anchor character”. The research findings have a certain reference value for the study of anchorage mechanism.

Abstract: Pressured multi-branch bored pile is a new pile on the basis of squeezed branch reaming pile improved, it is a new pile technology focus on many advantages of the static pile, driven cast-in-place pile, belled pile and multi-branch bored pile. Pressured multi-branch bored pile has high bearing capacity, small settlement, cost-effective advantages of better. Numerical simulation of pressured double-branch pile on the vertical compression with ANSYS finite element analysis software obtained the alternate variation of the lateral friction and tip resistance of pile under the vertical load. Many branch of pile constitute multi-pivot friction and end-bearing pile, the bearing branch bear mainly bear vertical load, above branch force greater than the following branch. It is proposed recommended value about the vertical critical spacing of branch and the level spacing of pressured branch pile.

Abstract: Taking the unsaturated loess obtained from YanLiang district Shaanxi province as the research samples. CT images on structural damage evolution of unsaturated loess were obtained according to the results of the CT scanning and the triaxial shear test of the unsaturated loess. The obtained CT images were divided into five groups based on gray levels and treated through supervised classification method. The evolution of void in three layer sections can be clearly observed from the data of supervised classification. It can be seen that due to the existing of many structural defects such as void, microcracks and ginger like rocks in cross-section of the loess sample, the initial damage is large before shearing. With loess sample shear going on, large void is gradually closed and loess sample is compacted without failure surface, only making some adjustments in the internal structure of soil. The possible reason is that the sample has large moisture content, and soil skeleton is easy to creep and hard to form cracks. The general tendency of structure evolution on loess sample under shear process is as follows: the voids closed, the particle condensates dispersed and the particles realigned, the soil consolidated or worked hardening. This work provides a new experimental method for exploring the structural features of the loess under the triaxial shear conditions from the micro-scale.