Study On The Law Of Ground Collapse In Covered Karst Area

Karst areas are widely distributed in China.With the development of economy,urbanization and infrastructure construction have changed the original hydrogeological environment,resulting in frequent geological disasters of karst ground collapse,which seriously threatens the safety of human life and property.In the covered karst area,the underground karst channels are intricate and interconnected.In the construction of urban underground space,the deep foundation pit pumping groundwater from time to time causes the regional water level to drop,which gradually forms a groundwater depression funnel,improves the hydraulic gradient of groundwater and the frequency of groundwater level changing up and down,accelerates the potential erosion of groundwater on soil mass,and increases the risk of ground collapse.Based on the geological disaster control project of karst ground collapse in Guigang built-up area,this paper studies the disaster causing law of ground collapse in covered karst area.By means of laboratory simulation experiment and discrete element numerical simulation,the collapse rules under different control conditions such as rock,soil and water are studied.The evolution process and collapse form of ground collapse are analyzed.At the same time,the collapse cases are analyzed and relevant prevention and control suggestions are put forward.The specific research contents are as follows:(1)The laboratory simulation experiment is carried out,and the collapse process is analyzed through the simulation experiment.The relationship between the ground collapse mode and the size of karst cave opening,the change height of groundwater level and the thickness of overlying soil layer is studied.At the same time,according to the experiment results,the prone coefficient of karst ground collapse is defined(2)Through the laboratory simulation experiment,the law of collapse caused by the combination of two caves is studied.This paper studies the process and form of collapse caused by the combination of two karst caves,and analyzes the collapse law under the condition of different opening size and spacing of two adjacent karst caves.This paper analyzes the development and connection process of soil tunnel under different experiment conditions,and summarizes the expansion rule of soil tunnel and the form of soil collapse(3)Through the numerical simulation of PFC2D,the process and results of subsidence under different control conditions are obtained,and the change law of land subsidence displacement under different experiment conditions is analyzed.The simulation results are in good agreement with the laboratory experiments.The evolution law of physical field in the process of collapse is simulated.(4)This paper analyzes a case of karst ground collapse in Guigang City,studies the causes of the collapse,verifies the effectiveness of the collapse prone coefficient according to the actual situation of the collapse,and puts forward reasonable prevention and control measures according to the actual disaster situation.