Distribution Rules Of Sand-Gravel Layer And The Foundation Pit Supporting System Reserrch On Nanning Basin

Along with the advancement of China’s urbanization, industrialization process, nanning is facing the urban population, nervous land resources, traffic congestion, environmental pollution, energy shortages, and many other problems. In order to break the bottleneck which restrict the development of the city, relieve the contradictions of urban space, the exploitation of urban underground space has become a trend.In nanning basin of shallow development process, the accidents caused by unclear of sand-gravel layer distribution, the characteristic, and construction measures of underground engineering. In this paper, through a large number of information collection, with the help of a professional geological modeling software of GOCAD, nanning sand-gravel layer for the 3d simulation, to study the space distribution state. And with the combination of models and collect information analysis on the engineering properties of the sand-gravel layer in nanning, and in this special conditions, puts forward suggestions and solutions on the problem of foundation pit supporting system. The specific conclusions are as follows:(1) sand-gravel layer 3D geological model is established By GOCAD, from nanning basin horizontal longitudinal understand the spatial distribution of sand-gravel layer, make its geological structure and the distribution more clear; The establishment of the 3D model for nanning basin provides a good geological database, can use at any time and continue to add layers, and can be assisted at the early stage of the planning staff reasonable drilling layout. According to certain principles, zoning nanning, and has made the detailed analysis of the characteristics of each region.(2) From nanning sand-gravel layer, which is based on analyzing the situation of exploration of nanning basin sand-gravel layer effects on underground structures; And through the study of a large number of investigation report giveing a scientific and reasonable value size and methods of sand-gravel engineering characteristic parameters of nanning basin:shear strength parameters, the permeability coefficient and compression modulus;(3) Through the analysis of investigation data, and through the statistical analysis of 58 of supporting successful cases, rational selection of supporting structure for general judgment, to be used for guiding sand-gravel areas in the selection of foundation pit supporting structure design; And analyze the main supporting structure in the regional distribution of the sand-gravel layer of nanning basin, putting forward solutions and measures for concrete construction problem;(4) Considering the special geological conditions, to make the reasonable choice of precipitation method; Combining with the measured settlement of foundation pit and the analysis of investigation data, to explore the precipitation’s impact in nanning basin deep gravel area;(5) According to the project case of sand-gravel layer in nanning basin, to analysis the validity of sealing wall, and discussing the anti-floating problem of sandygravel layer, guarantee the foundation pit engineering achieve anti-floating requirements from two aspects of the design and construction.