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A Study In The Characteristics And Prediction Of Land Subsidence For Beijing Daxing District Planning Area

Posted on:2012-03-18Degree:MasterType:Thesis
Country:ChinaCandidate:H X YueFull Text:PDF
GTID:2180330332488860Subject:Geological Engineering
Abstract/Summary:PDF Full Text Request
The land subsidence of Beijing occurred mainly in the plain areas. The current size of the settlement in Beijing reached 1800km2, the maximum total settlement more than 925mm, harming the economic construction and development directly or indirectly. Up to 2009, the total amount of land subsidence in Daxing new city was 40-560mm. Overall, from the northwest Langfa to the southern Panggezhuang, the settlement was from 40mm to 550mm. The rapid development of land subsidence in Daxing area was due to excessive exploitation of underground water which caused a significant drop in groundwater level. The soil structure in northern regions of Daxing mainly contained a single layer of sand and gravel, with the water table rise and fall, and its main features of elastic deformation. Despite the over-exploitation of groundwater in the region which caused a substantial decline in groundwater, sand and gravel layer compressed slightly with water releasing, so subsidence was not obvious. From central to southern regions of Daxing, the layer gradually became clay-based multi-layer soil structure, containing fine sand layer, sand and gravel layer and multi-layer thin clay. As clay content and thickness of soil layer increased, soil compression caused by groundwater exploitation gradually increased with water releasing. So the spatial distribution of land subsidence showed a trend that amount of the south was more than the north.At present, domestic and international land subsidence prediction model for studies focused on Terzaghi one-dimensional settlement consolidation based on the theory of quasi three-dimensional models (including the two-step model and part of the coupled model), the main shortcomings of these models contained: difficult to accurately describe land subsidence due to the release of water from the aquitard; the aquitard was treated as isotropic, which conflicted with the actual anisotropic of aquitard with alluvial origin in many parts of China. In this paper, MODFLOW and the IBS software package were used for numerical simulation of land subsidence in Daxing District.According to Daxing District planning area hydrogeologic data analysis on the current development of deep groundwater, the groundwater level dynamics and the distribution of cone of depression to study the expansion of deep groundwater depression cones law; establishing numerical model of groundwater system to predict the status of exploitation of groundwater dynamics changes and future trends cone of depression; analyzing the relationship between groundwater exploitation and land subsidence; Based on the extent of land subsidence in the area, hydrogeological and engineering geological conditions, zoning land subsidence. Using a combination of qualitative and quantitative analysis, establishing land settlement model; Applying coupling model of soil and water, giving the quantitative prediction of the development trend of land subsidence under mining after the completion of Daxing District; according to characteristics and development trend of land subsidence, proposing land subsidence control measures and proposing new town construction.
Keywords/Search Tags:Daxing District, geological environment, land subsidence, coupling water and soil, numerical simulation
PDF Full Text Request
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