Study On The Influence Of Adjacent Funnels On Ground Settlement In Tianjin Area

As early as 1923,land subsidence appeared in Tianjin.With the rapid development of industry and agriculture,especially the exploitation of deep groundwater in urban and rural areas,the water level in the area has dropped sharply,which has caused ground subsidence problems to become increasingly prominent.Land subsidence in Tianjin has attracted the attention of the State Council,local governments and scholars from all walks of life,and has gradually carried out a large number of land subsidence investigation,monitoring and prevention work.After years of hard work,many achievements have been made in the investigation and monitoring of land subsidence,pointing out that the extraction of groundwater is the main cause of land subsidence in Tianjin.Research and analysis of the results already achieved can predict the amount of ground settlement in the future,which is of great significance for the prevention and control of land subsidence.The relationship between land subsidence and pumping flow is one of the core issues in the study of regional land subsidence caused by groundwater exploitation.In this paper,the semi-logarithmic linear relationship between settlement and distance is derived by the formula,s=c₁+c₂ lnr,and the coefficients c₁ and c₂ are linearly related to the pumping flow rate and a linear relationship is obtained,so that the relationship between land subsidence and total pumping volume is obtained.The theoretical derivation results have been well verified by the actual measurement data of two projects in Pinghu City and Dezhou City and the land subsidence models established by the groundwater flow simulation software Processing MODFLOW.The result is simple and practical.According to the regression of the historical monitoring data of the local pumping volume and settlement in the subsidence area,the coefficient of the settlement-distance formula can be obtained,which can provide reference and grounds for land subsidence prediction and groundwater mining planning.There are four settlement funnels in Tianjin:Hangu,Yangcun Town,Tianjin City and Tanggu.By fitting the settlement value of a single funnel and the measured settlement value at one point,this paper obtained the expression of land subsidence value in the area of four settlement funnels,S=0.671S_SQ+0.567S_TG+1.445S_HG+2.063S_YC-0.506.The applicability of this expression is well verified by 40 points in the area which is jointly affected by four funnels.This expression can be used to calculate the settlement value of unknown points in the area affected by four funnels.So the expression is of great significance for the construction of the project and the prevention of land subsidence.