湘中娄底市岩溶塌陷特征及影响因素研究

Genetic models and influence factors of karst collapses in Loudi City of central Hunan,China

湘中娄底市记录有281起岩溶塌陷事件以及上万个塌陷坑,是我国岩溶塌陷非常严重的城市之一。所有岩溶塌陷中,矿区岩溶塌陷有222起,占总数的79%,此外,还有地基工程造成的岩溶塌陷和降雨渗透潜蚀造成的岩溶塌陷。由此总结出娄底市具有真空吸蚀、浮托软化、荷载振动、渗透潜蚀4种岩溶塌陷发生模式,各模式均有4个致塌过程。其中,真空吸蚀塌陷和浮托软化塌陷主要为矿山活动所致,分别因矿区抽排水和矿区闭坑后回水所诱发;荷载振动塌陷主要为桩基施工等荷载外动力作用诱发,渗透潜蚀塌陷多为强降雨诱发的自然塌陷。岩溶塌陷的影响因素包括基础因素和诱发因素两个方面,基础因素有地层岩性、岩溶地貌、岩溶水富水性、与矿区相关性等,构成岩溶塌陷易发区的关键影响因素;诱发因素主要有矿区抽排水、闭坑矿区回水、工程振动、降雨过程等,其强度影响岩溶塌陷发生的时间、区域范围和规模。娄底市岩溶塌陷频发、突发,建议构建岩溶塌陷监测预警系统,科学编制岩溶塌陷防治规划和灾害应急预案,强化岩溶塌陷风险管理,保持岩-土-洞-水-气间的动态平衡。

Loudi City in central Hunan has recorded 281 karst collapse incidents and tens of thousands of collapse pits,which made it one of the cities in China experiencing the most serious karst collapses.Among all these karst collapses,222 karst collapses occurred in mining areas,accounting for 79%of the total.In addition,some karst collapses were caused by foundation engineering or by rainfall infiltration and erosion.By sorting out the temporal and spatial relationship between karst collapse events,karst collapses and collapse pits,it is concluded that karst collapses in Loudi City can fall into four occurrence modes,namely,vacuum erosion,floating–softening,load vibration and seepage erosion,and each mode has four collapse processes.Among them,vacuum erosion collapses and floating–softening collapses are mainly caused by mining activities,which are induced by drainage from the mining area and backwater after the mine has been closed;load vibration collapses are mainly induced by external dynamic loads such as pile foundation construction;seepage erosion collapses are natural collapses mostly induced by heavy rainfall.The influencing factors of karst collapses include basic factors and inducing factors.The basic factors include stratum lithology,karst landform,karst water abundance,correlation with mining areas,etc.,which constitute the key influencing factors in karst collapse-prone areas;the inducing factors mainly include drainage in mining areas,backwatering in closed mines,engineering vibration,rainfall,etc.,and the intensities of these factors can affect the time,scope and scale of karst collapses.In order to strengthen the risk management of karst collapses,it is recommended to establish a monitoring and early warning system for karst collapses,and scientifically develop risk assessment,prevention and control plans and disaster emergency response plans for karst collapses.Besides,controlling the area,method and intensity of engineering construction,prohibiting or limiting the mining of coal,gypsum,groundwater,etc.in karst areas,and maintaining the dynamic balance between rock,soil,cave,water and air are effective measures to prevent and control karst collapses.In this paper,the distinction between the basic factors and inducing factors of karst collapses can provide a scientific basis for their effective prevention and control in karst areas,and can provide a reference for the construction of harmonious and beautiful villages.