Urban Construction Volume Rate Of Extraction And Its Relationship With The Land Subsidence Analysis

Land subsidence is a phenomenon of the slowly loss of regional ground elevation caused by the consolidation compression of underground loose strata which is induced by natural or man-made factors. More attention has been paid to the environmental and geological problem of land subsidence internal and external countries which has the characteristics of wide range affects, long duration and slow response. For its complicated causes and it is difficult to prevent and hardly to be recovered, land subsidence has become a serious geological problem. Furthermore, most of the disasters occurred in large and medium cities with potential harm which have great influence and restriction to the sustainable development of the local economy.Beijing land subsidence develops rapidly. Since the first discovery in1935, it has formed five major subsidence areas such as Shunyi, Changping etc. At present, the Beijing plain area has become one of the most serious domestic ground subsidence areas. And the subsidence poses a great threat to the municipal infrastructure, buildings and people’s lives and property which has aroused widespread concern. The formative factors of the disaster mainly includes the tectonic movements, secondary consolidation settlement of soft soil, groundwater table descent and construction projects.With the rapid development of urban construction in Beijing, the impact of multi-storey and high-rise building environmental effects to the land subsidence, except the groundwater factor, becomes remarkable. The loads of such construction projects increase the effective stress of the soil. And the land subsidence will be caused by the compressing of soil. According to the definition of building floor area ratio, it reflects the amount of the building load to a certain extent. The paper intends to study the influence law between the building floor area ratio and the land subsidence in Beijing typical area using GIS analysis methods.With the development of remote sensing technology, the method based on high resolution images has become one of the fastest and simplest ways to obtain the city building floor area ratio. Such methods using the three-dimensional information contained in remote sensing shadows to carry out the estimate of the floor area ratio, so the identification accurate of shadows is the foundation to improve the estimation accuracy of the floor area ratio. Firstly, according to the characteristics of QuickBird images, the paper proposes a method which uses the multi-band fusion technology and object-oriented classification to extract shadows from the images. Secondly, the height of every building can be calculated using GIS method based on the relationship between the building heights, shadow lengths, sun elevation angle and the satellite elevation angle. In the end, the paper establish the relationship between shadow area and floor area ratio and the relationship between building heights and floor area ratio of samples to calculate the floor area ratio of the whole study areas.After gaining the floor area ratio of typical regions in Beijing, the paper compares and analyzes the result with the subsidence data. Then the fishnet that covered the whole area is established to calculate the average value of the floor area ratio and land subsidence fall on each grid. The paper carries out the analysis the relationship between the Beijing building floor area ratio and land subsidence by the methods of scatter diagram and regression analysis. The result shows that the relationship between floor area ratio and land subsidence is more remarkable in smaller areas, and the coefficient of determination(R2) of them in several experimental zones are all greater than0.5, and the correlation coefficient (R) are greater than0.7. While the coefficient of determination (R2) is only0.0001in a large extent, the relationship between floor area ratio and land subsidence was not significant. The paper carries out the prediction analysis of Beijing ground subsidence with the mutual response relationship between Beijing building floor area ratio and land subsidence in an extent, and provides a reference for the prevention of ground subsidence.