摘要
岩溶塌陷是岩溶区主要的地质灾害类型,具有突发性和隐蔽性的特征,给当地人们的生命财产安全造成威胁。文章以曲靖市马龙区东侧岩溶塌陷为研究对象,以多元结构盖层的地面塌陷为例,在室内构建了与原型相符的地质物理模型,开展两种典型工况下的地下水位下降触发岩溶塌陷试验。基于试验数据分析,提出此类型盖层的致塌机理,并分析透-阻-透型塌陷变形演化特征。研究表明:(1)地下水位下降导致盖层和溶洞中均出现负压带,盖层内的孔隙水压力和溶洞中的真空压强会随着排水波动增长至峰值,地下水位降速越大,压强的增长速率和峰值就越大;(2)根据压强和盖层形变量随时间的演化特征,可将塌陷演化过程分为土洞发育阶段、土洞扩张阶段和盖层失稳塌陷3个阶段;(3)马龙区的水位降速达到0.1 cm·min^(-1)(1.44 m·d^(-1))时,所产生的真空压强能提供足够大的真空吸蚀力,联合渗透压力可导致覆盖层塌陷。研究结果可为马龙区岩溶塌陷灾害的防治减灾及其塌陷预警预报提供参考。
With continuous development of society and economy,acceleration of urbanization,increase of water consumption in industry and agriculture and improvement of people's life,the interference and destruction of environment caused by human activities and engineering construction are increasingly serious,and the number of karst collapses is rising day by day.As a major type of geological disaster in karst areas,karst collapses threaten local people's life and property because of their suddenness and covertness.Therefore,it is of great significance to study the induced factors and development mechanism of karst collapses.Since the construction of the diversion tunnel of Chemabi reservoir in 2017,a large number of ground collapses have occurred in Malong district of Qujing City.The field geological investigation found that there is a Quaternary overburden layer with sandy clay-clay-sand structure in the study area in which occur strong karst development and frequent groundwater activities.Karst collapses in the study area are mainly distributed near rivers.In this study,we took karst collapses in the east of Malong district,Qujing City as the research objects.On the basis of fully understanding the geological conditions,hydrodynamic conditions and geological prototypes of collapses in the study area,we took the collapses of multi-structure overburden as examples,among which we selected a typical karst collapse as the prototype.Then we scaled down the geological prototype in equal proportion under the principle of similarity.Meanwhile,we prepared the materials similar to the physical parameters of the soil samples from overburden layers of the geological prototype,and constructed a geophysical model consistent with the prototype in the laboratory.Subsequently,according to the water discharge of the construction near the subsidence area and the data of observation well,we estimated the rate of groundwater drawdown,and monitored the pore water pressure in the overburden layer,the vacuum pressure in the karst cave and the cumulative displacement of the overburden soil.Finally,we carried out the experiments of karst collapses triggered by the groundwater drawdown under two typical working conditions.According to the experiment data,we put forward the collapse mechanism of the overburden layer,and the evolution characteristics of karst collapses with permeable layer-aquiclude-permeable layer.The results show as follows:(1)Negative pressure zones in covered layers and karst caves may occur because of groundwater drawdown.Due to the air recharge caused by relatively closed aquitards and the water-holding effect of the soil in overburden layers,the pore water pressure in overburden layers and vacuum pressure in karst caves will increase to the maximum with the fluctuation of groundwater discharge.The faster the rate of groundwater drawdown becomes,the greater the growth rate and peak of pressure will be.(2)According to the evolution characteristics of pressure and the deformation quantity of overburden layer,the collapse evolution can be divided into 3 stages:the stage of development of soil caves with rapid pressure increase but small displacement of overburden surface,the stage of soil cave expansion with the reducing growth rate of pressure but a rapid increase of displacement of overburden surface and the stage of instability and collapse of overburden layers when both pressure and displacement of the overburden surface reach the maximum.At the first stage,upper aquitards and middle strong permeable layers,i.e.the soil above the water level,are subjected to the erosion of pore water and the vacuum suction effect of pore water pressure generated in the negative pressure zone within the overburden layer.At the second and third stages,the vacuum pressure in the karst cave plays a leading role in the vacuum suction erosion of the entire overburden soil.(3)The rapid decrease of groundwater level is the main factor leading to the collapses in the study area.When the rate of groundwater drawdown is relatively small,the overburden soil may undergo minor deformation but will not collapse.However,when the rate of groundwater drawdown in Malong district reaches 0.1 cm·min^(−1)(1.44 m·d^(−1)),the vacuum pressure can provide the force of vacuum suction erosion.Together with osmotic pressure,this force is large enough to generate collapses.The research can provide reference for the prevention and early warning of collapse disaster in Malong district.
作者
李京天
朱凯
肖先煊
尹艳
刘皓
许模
何志攀
LI Jingtian;ZHU Kai;XIAO Xianxuan;YIN Yan;LIU Hao;XU Mo;HE Zhipan(State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Qujing Chemabi Reservoir Engineering Construction Administration Bureau,Qujing,Yunnan 655099,China;PowerChina Kunming Engineering Corporation Limited,Kunming,Yunnan 650041,China)
出处
《中国岩溶》
CAS
CSCD
北大核心
2024年第2期406-420,共15页
Carsologica Sinica
基金
四川省科技计划项目-应用基础项目(2021YJ0320)。
关键词
岩溶塌陷
模型试验
多元结构
地下水位下降
致塌机理
karst collapse
physical model experiment
multi-structure
groundwater drawdown
collapse mechanism
