Research Of Calculation Method Of Land Subsidence Induced By Building In The Yellow River Delta

Land subsidence is a geo-hazard of progressive loss of ground elevation which cannot be detected in a short time,so it is also called the “silent land crisis”.Land subsidence is irreversible,and once formed,it is difficult to be recovered.Land subsidence disasters will cause seawater intrusion,elevation point failure and road cracks subsidence,serious affecting ecological environment,and even threaten the survival of mankind.The factors that lead to land subsidence can be divided into natural factors and human factors.Natural factors mainly include crustal movement,sediment consolidation compaction,sea level rise,and so on.Under normal circumstances,land subsidence caused by natural factors(except the earthquake,abandoned channel sediment consolidation)showed characteristics of long cycle and small amplitude.Therefore,at an early stage,it hasn't attracted people's attention.But with the frequent exploitation of a larger area of underground fluid(such as groundwater,oil and gas),land subsidence has been increasing year by year.The earliest attention of land subsidence caused by engineering construction was drew in the Yangtze River Delta(Shanghai),and land subsidence exists in the Yellow River Delta as well.The phenomenon of land subsidence caused by engineering construction has been highlighted year by year.This paper aimed at 3 engineering examples in the Yellow River Delta(Comprehensive ward building of Shengli Oilfield Center Hospital,Xinbang Mingjun,Chang'an Tower),using layer-wise summation method,chord-modulus method,correctional chord-modulus method,undisturbed soil tangent modulus method and undisturbed soil secant modulus method,respectively,and calculating the land subsidence caused by the buildings.The results showed that the data calculated by the undisturbed soil tangent modulus method were the closest to the measured data(3.46 mm,4.50 mm and 10.85mm).Undisturbed soil tangent modulus method was then used to calculate the time series of settlement of Shengli Oilfield Central Hospital and Xinbang Mingjun respectively.The obtained curve is consistent with the measured curve.So it is proved that the undisturbed soil tangent modulus method is more suitable for the calculation of the settlement of the Yellow River Delta.In addition,we used the settlement monitoring results of other high-rise buildings in the Dongying district to evaluate the accuracy of our calculation and monitoring results.In order to validate that the undisturbed soil tangent modulus method is much more suitable in the calculation of land subsidence caused by buildings in the Yellow River Delta,the undisturbed soil tangent modulus method is used to calculate the land subsidence caused by the buildings in Dongying.We collected remote sensing images of the Yellow River Delta(Dongying)in 2007-2010,and then preprocessing those images.Through the combination of computer automatic classification and visual interpretation,building changes in the study area from 2007-2010 are interpreted.In the selected new built-up intensive area in 2010,through the image interpretation and data collection,we got new built-up area construction parameters such as built-up area,covered area and average layer number of buildings.Then we used the suitable method,undisturbed soil tangent modulus method,to calculate the settlement of the new builtup area,and analyzed the selection of the thickness of compressible stratum.The results showed that the stress control method is more appropriate to the thickness of compressed layer of buildings with a large area.The land subsidence is 7.52mm/a from 2007 to 2010 in Dongying district.The results are in accordance with the existing data.Less parameters are required in the calculation process,and the remote sensing images are also easy to be obtained,so manpower and material resources can be saved.This paper provides a method for calculating the settlement caused by regional building construction.