库水位和地下水位作用下岩溶地区水库防渗复合土工膜的应力变形分析

Stress and Deformation Analysis of Composite Geomembrane for Seepage Prevention of Reservoir in Karst Area Under the Action of Reservoir Water Level and Groundwater Level

采用复合土工膜对岩溶地区水库进行防渗处理具有一定优越性,但由于运行期库水位和地下水位的共同作用,可能会对土工膜产生不利影响。鉴于此,为研究复合土工膜在岩溶地区水库防渗应用适宜性,采用大型有限元软件MIDAS GTS NX,以重庆市黔江区李家坪水库为例开展了有限元分析。结果表明:在库水位和地下水位组合作用下,库盆沉降变形和水平变形分布规律差异不大,但地下水位下降会导致覆盖层地基有效应力增大,进而使得变形量增大。在当库水位达到校核水位且地下水位下降至基岩面时,库盆沉降、土工膜拉应力和拉应变达到最大值。通过计算,土工膜拉力安全系数和拉应变安全系数均大于规范要求的允许安全系数5.0,说明该水库防渗复合土工膜具有较高的安全裕度。

The composite geomembrane has some advantages for seepage prevention treatment of reservoirs in karst area,but it may have adverse effect on the geomembrane due to the joint action of reservoir water level and groundwater level during operation period.In view of this,in order to study the suitability of composite geomembrane for seepage prevention of reservoir in karst area,by taking Lijiaping Reservoir in Qianjiang District,Chongqing City as an example,this paper carries out the finite element analysis through the large finite element software MIDAS GTS NX.The results show that:Under the combined action of reservoir water level and groundwater level,the distribution law of settlement deformation and horizontal deformation of reservoir basin does not differ much,but the decrease of groundwater level will lead to the increase of effective stress of overburden foundation,and then the increase of deformation.When the reservoir water level reaches the check water level and the groundwater level drops to the bedrock surface,the settlement of the reservoir basin,the tensile stress and tensile strain of the geomembrane reach the maximum value.Through calculation,the safety factors of tensile stress and tensile strain are both greater than the permissible safety factor 5.0 required by the code,which indicates that the composite geomembrane has a higher safety margin for seepage prevention.