Preliminary Research On Micromechanism And Fluid-Solid Coupling Model Of Land Subsidence

As a kind of slowly developing geological disaster,land subsidence has become a serious environmental geological problem around the world due to its obvious engineering characteristics.Land subsidence usually have a wide impact range and always have a long duration time.Further more,it always need a long developing process.Its form mechanism is complex and hard to prevent and control.Based on the phenomenon of land subsidence induced by mining underground water,from the view of mesoscopic,this research takes Dezhou in shandong province as an example,using multidisciplinary and cross knowledge including hydrogeology,engineering geology,rock mechanics and groundwater dynamics to study the ground subsidence caused by underground water mining in the region of Dezhou.This research mainly focus on the mesoscopic mechanism and fluid-solid coupling model behind the phenomenon of land subsidence.We do some preliminary exploration in this field of knowledge and achieved some results.Through typical research methods including theoretical research;site survey;laboratory test and numerical analysis,this paper try to analyse the internal forming mechanism of land subsidence from the view of microscopic.This paper reveals the essential characteristics and microscopic mechanism of the process of consolidation and settlement induced of water loss.During this whole research process,the soil layers and soil types are different under the action of groundwater exploitation.The fluid-solid coupling analysis model of ground subsidence caused by groundwater exploitation is established.The following works were mainly carried out:(1)Through literature reading and theoretical analysis,this paper summarizes the current research and occurrence situation of land subsidence at home and abroad,and mainly focuses on the three aspects:the macro level causes of land subsidence;experiment of soil microstructure and the mesoscopic mechanism of soil consolidation and settlement.According to the data of field investigation,the hydrogeology and engineering geology situation along with the occurrence situation of land subsidence in Dezhou are summarized.(2)By drilling core near the land subsidence observation point in dezhou city,we have got real soil samples of deep soil layer,and then consolidation compression experiment and SEM scanning experiment were carried out.Based on the SEM scanning results,the microstructure parameters of different soil masses were quantitatively analyzed using the soil microstructure analysis and processing software PCAS,and the variation rules of microstructure parameters of soil masses at different depths in Dezhou under consolidation and compression conditions were summarized.(3)A generalized micro-numerical analysis system of ground subsidence induced by pumping water is established by means of particle flow numerical simulation method This method is based on a two-dimensional fluid-solid coupling fixed grid model and a pipe domain model,including the initial state model of soil consolidation and the hydraulic coupling dynamic effect model,the microscopic mechanism and settlement rule of soil consolidation induced by water loss were observed.(4)Based on the fluid-solid coupling theory of CFD-DEM,a three-dimensional geological model was established.The model is designed for the process of water-pumping consolidation of soil.The soil item is made by sand and clay layers,and the influence of different water seepage velocity in the aquifer on the settlement and movement of the soil was studied.This research try to track and record the migration law of some typical fixed particles near and far from the well wall of the sand-clay layer pumping well,at the same time,we analyze the migration path of different soil particles under the action of different seepage velocity of the aquifer and study the influence law of water flow velocity on the settlement displacement and settlement rate of soil particles.