Zoning of early warning for karst collapses in the Jingquan area of Shandong Province
As one of the most common geological disasters in the Jingquan area,covered karst collapses mostly occurred in the dry seasons from 2015 to 2017.With the frequent occurrence of karst collapses,the sustainable development of economy and the safety of people's lives and property are threatened.Therefore,it is urgent for us to find out the current situation of karst collapses,analyze their influencing factors and distribution rules,and carry out the research on the zoning of early warning for karst collapses under different environmental conditions,in order to provide a decision-making basis for carrying out targeted prevention and control.In view of the frequent occurrence of covered karst collapses in the Jingquan area,based on the exploration data of karst collapses in this area,this study analyzes and studies the background conditions and influencing factors of collapse formation with methods such as mathematical statistics,numerical simulation and comprehensive evaluation model.Through numerical simulation and fuzzy mathematical methods,the zoning of early warning for karst collapses under different environmental conditions(rainfall frequency of 20%,50%,80%and 95%,and the increase of mining volume of 30%,50%and 70%)is studied,and targeted prevention and control measures are put forward.The research conclusions mainly include the following four aspects:(1)The aquifer system in the Jingquan area can be generalized into three aquifer groups as a whole.The first layer—the shallow aquifer group—includes pore water in the Quaternary coverage area and shallow water in the exposed bedrock area.The second layer—the weakly permeable aquifer group—includes the Quaternary clay layer and the fractured deep aquifers of Cambrian and Ordovician in a certain depth range.The third layer—the deep aquifer group—includes Ordovician aquifers of carbonate fissure karst water and Cambrian aquifers of carbonate karst water.(2)In this study,the lower boundary of the water flow system has been set at the buried depth of 200 m in the Jingquan area.The atmospheric precipitation infiltration and the lateral runoff supply of groundwater are the main supply sources of groundwater in the study area.The main discharge of groundwater in the area is the exploitation of groundwater.The exploitation amount of the water source has been obtained through monitoring data,and the scattered exploitation amount has been obtained through investigation and statistics.(3)Given that other environmental conditions remain unchanged,the area of the red-early-warning area gradually increases with the continuous reduction of precipitation,and the degree of early warning gradually decreases from southwest to northeast.The denser the pumping wells are,the likelier karst collapses occur.The increase of karst water exploitation and the change of rainfall are the main causes of karst collapses.(4)In order to prevent karst collapses in this area,we should strengthen the management of water resources and make rational use of groundwater resources.We should also strengthen the monitoring of karst collapses in the red-warning area,and adopt a variety of engineering measures to change the geological background conditions of karst collapses to the greatest extent.