Advanced Materials Research Vols. 446-449

Abstract: Taking the deformation of row pile supporting structure of foundation pit in strata with rock-soil combination as the research target and taking an open cut metro deep foundation pit as an example, by in-site monitoring and numerical simulation, analyze the horizontal displacement of retaining piles and the change law of steel support axial force in the strata with rock-soil combination, and summarize the change law of row pile supporting structure in the process of excavation under the conditions of this strata, so that to provide experience and guidance for similar engineering design and construction. The results show that: the structure of foundation pit has obvious effects on deformation and internal force of supporting structure, the result obtained from numerical simulation fits well with the tendency of monitoring data changing. In which, the deformation of row pile supporting structure in the middle and upper part of soil strata is larger, the deformation of middle and lower part of soil strata is comparatively smaller, the lateral deformation of row piles to basement has a tendency of gradual decreasing by taking the interface of rock-soil as a boundary.

Abstract: In order to study how it influence the horizontal bearing capacity of the disk pile when there exists a vertical load, a group of model tests has been designed. Three double-disk piles were used in the test, and the distance of the two disks is 5 times as the disk diameter. First drew a vertical load V=200N/300N/400N on the top of pile1/2/3 respectively, then put on the horizontal load stage by stage. And by the test, we can study the differences of the pile bearing properties such as changes in the pile bending moment, the horizontal and vertical deformation on the top. Experiment showed that when the vertical load is quite small（V=200N、300N）, the existence of vertical load has little to do with horizontal bearing capacity. When a vertical load increases to a certain value（V=400N）, The maximum bending moment and horizontal displacement of the pile under the same horizontal load reduce, which indicates that the disks of the pile play a significant role in bearing combined loading.

Abstract: The deep excavation of the foundation pit adjacent to the metro tunnel will change the stress state of the neighboring soil. And the deformation of tunnel will be induced which will cause impair to daily operation and the safety of metro tunnel. According to the practice of deep excavation neighboring the metro tunnel in Guangzhou, the main influence factors of deformation and stress of tunnel will be analyzed based on exaction conditions and field data. The conclusions will be benefit to similar projects.

Abstract: Current practice of Dynamic compaction (D.C) depends mainly on field trials, past experience, and empirical equations based on reported records. In this paper, a numerical model is used to study the effectiveness of supplemental drains on densification of saturated dredger fill silty deposits during D.C. Typical numerical results are discussed using propose numerical model.

Abstract: The risk evaluation of deep excavation was investigated based on the monitor indexes of support structure. The potential accidents which may be caused by the abnormal of the monitor indexes were analyzed. The risk sources which might arouse the value variation of the monitor indexes were disclosed. The dynamic control measurements for the risk sources were suggested. The successful application of the dynamic method to the real project further verified its feasibility.

Abstract: As the cofferdam makes the water flow change, the river bed near the cofferdam has been washed; soil pressure on the cofferdam will be changed. In order to better grasp the force of the cofferdam, the earth pressure on the cofferdam need to be monitored. As it is difficult to monitor occasion, the computing earth pressure is necessary. In this paper, three-dimensional finite element model on the steel sheet pile, purlin, internal support and soil can be established. Through compassion computing value of model and monitoring value, conclusions are drawn.

Abstract: The heat and stress equilibrium equations of anisotropic media, coupled to the mass conservation equations of fluid, are studied here based on the standard space of physical presentation for consolidation of anisotropic saturated soils, in which a new compressible thermal constitutive model of soils is induced. The uncoupled diffusion equation of pore water pressure for anisotropic saturated soil affected by heat is deduced. The results show that the consolidation coefficient of saturated soils is affected by both anisotropic subspaces of soil and coupling coefficient between fluid and solid, and also thermal coefficient and thermo-coupling coefficient. Based on these laws, we discuss the consolidation behaviour for isotropic soils.

Abstract: Jiulian-mountain tunnel is an very important project for a section of Longyang Jiangxi in Da-guang highway. Because Jiulian-montain tunnel has a series of geological problems, like shallow-depth, bias-pressure, big-span,water-rich, rock burst and so on, which is a typical long - wide highway tunnel grew up under complex conditions, construction of the entrance segment is extremely difficult and slow in progress.In order to efficiently accomplish the construction of tunnel on time, it is necessory to elect rational construction scheme of the entrance segment. The numerical simulation for three construction methods,which are benching tunneling method、 method of core-keeping cut in stages and CD method , are carried out by means of Three-dimensional fast lagrangian analysis of continua method(FLAC3D) in this paper. Based on the result of the numerical simulation analysis and contrast, some conclusions and suggestions are proposed, some gist are offered in order to choose the construction method rationally ,and arrange the construction order scientifically, and control the construction pace optimally, and reduce the harm of the construction .

Abstract: This article analyze the slope stability by strength reduction method named Phi-c which supplied by FE software PLAXIS. The reduction factor is suggest to be the safety factor of the slope at the moment when the slope reaches instability, the numerical non-convergence occurs simultaneously. The position of sliding surface and dynamic simulation of instability can be obtain as well. This article has compared the results calculated by other methods Bishop and ABAQUS with difference between 2%-3% which attest to its accuracy and practicability in engineering.

Abstract: Centrifuge model tests were conducted to investigate the behavior of cohesive soil foundations during a construction of an embankment, considering different dry densities and moisture contents of the soil. During the construction, the deformation of soil foundation gradually increased and reached the peak value at the top of the foundation near the center of embankment. After the embankment was completed, the deformation of the foundation continued increasing. The dry density and moisture content of the soil significantly affected the deformation process of the foundation.