Model Test And Numerical Simulation Of Overburden Karst Collapse

Engineering practice shows that the field covered karst caves are in complex geological conditions,karst channels vary widely and play an important role in groundwater migration,it is also difficult to determine the size of the cave opening.Due to field test constraints,direct tests to identify the characteristics of karst channels and the corresponding collapse insidious situation is difficult to achieve.Research cap-collapse cave system and simulation model test,summarize the formation mechanism of karst collapse area,use three-dimensional numerical simulation to Simulated the process of drawdown.This article,based on covered karst collapse along the Yangtze in Anhui,use model tests and numerical simulated methods to research karst collapse critical water level decline,in order to provide a theoretical basis for engineering practice.The conclusions are as follows:(1)Collapse caused by groundwater level fluctuation,especially the water level drop collapse is the mainly collapse mode in this area.The rapid decline of groundwater caused by human exploitation of groundwater and early mine drainage can easily lead to the occurrence of karst collapse.Suffosion with vacuum effect is the main collapse mechanism.(2)Propose critical water level decline formula,according to different cave opening,soil density and cover thickness,design four model collapse experiments.The critical level drop measured data shows the formula is feasible.(3)Critical level drop associate with rock and soil cover layer thickness,strength index,karst cave opening,pressure inside the cave,groundwater change level and flow rate.Cave opening size is a key factor in the collapse occurred.(4)On the basis of physical model experiments,numerical simulation methods were compared.numerical simulation results agree well with the actual.(5)Tongling Chaoshan karst collapse numerical simulation results show that in a certain cave opening size range,as the cave diameter increases,the critical water level fell rapidly reduced;after the cave beyond a certain diameter range,the fell slowly reduced.Cave opening size is no longer the key factor.