Back Analysis Of Seepage Field Parameters And Research Of Stratum Creep Effect In Dezhou City

The groundwater level is lower than the normal level due to long-term excessive extraction to form the funnel of groundwater and cause the land subsidence,which has serious impact on the production and life of the people in the region and the healthy development of the society,economy and ecological environment.Since the first time in 20s in Shanghai,we found that there have been problems of land subsidence,up to now more than 50 cities have different degrees of land subsidence.The land subsidence area in the northwest plain of Shandong Province has exceeded 13 thousand and 200 square kilometers since the land subsidence was found in 80s of last century.The city of Dezhou is the most serious and the maximum settlement of ground subsidence center is about 1.2 meters,which associated with the ground subsidence in Cangzhou,Hebei,is one of the most serious part of the North China area ground subsidence.At present,the distribution of land subsidence in Shandong is relatively large,the development trend is strong,the groundwater overdraft is serious and the causes are complex and so on.Therefore,in this paper the land subsidence in Dezhou as the engineering background,and the geologic parameters of the flow field and the creep in different strata during the subsidence process are obtained by using various methods include theoretical analysis,indoor and outdoor test and numerical simulation to research.The research contents of this paper are as follows:(1)The engineering data of the study area were collected and sorted out.Based on the mechanism of ground subsidence,the distribution of mining wells in the study area and the data of groundwater level monitoring were analyzed.The soil samples obtained from the 800m drilling Test to obtain the relevant geological parameters affecting the ground subsidence.(2)By using the Calman filter program to filter the ground water head and to obtain more accurate values.Based on the relevant parameter values of the study area,the groundwater simulation software was used to invert the permeability coefficients of the current third to fifth main aquifers,and the mean values of the permeability coefficients are 1.44m/d and 0.976m/d,0.77 m/d.After obtaining the flow field parameters,the changes of the groundwater flow field in the study area are analyzed,and the draft of the groundwater drop funnel in the current study area is obtained.(3)Based on the groundwater flow field,the creep effect of the stratum in the study area is analyzed by using the theory of soil rheology.Combined with the subsidence and groundwater seepage model,the creep deformation of soil in the process of ground subsidence caused by groundwater extraction in the study area is calculated.Through the analysis,it is found that the creep effect is mainly occurred in impermeable layers and the maximum of the creep deformation is the third impermeable layer.