复合土工膜与防渗墙联合作为围堰防渗体系，其联接部位处容易产生破裂而存在安全隐患，接头部位是该防渗体系的薄弱环节。因而，需开展土工膜与防渗墙联接型式的研究，避免复合土工膜因防渗墙与堰体的变形差异而产生破坏，确保围堰整个防渗体系的安全。以西部某水电站高土石围堰为例，采用有限元分析方法，重点研究了防渗墙与堰体联接部位土工膜的受力及变形规律，以及深厚覆盖层上高土石围堰的整体应力变形规律。结果表明：当土工膜与防渗墙之间采用不同联接型式时，对堰体和防渗墙的应力变形影响较小，但对防渗墙与堰体间位移差异和土工膜应变有显著影响。如土工膜采用平直铺设，则沉降错动会使得接头部分土工膜产生较大的拉应变。随着土工膜平铺段位置的抬高，接头处的土工膜应变大幅减小，受力较为有利。由此可知，将土工膜竖直抬高一定距离后再进行平直铺设是合理的，最终应结合室内拉拔试验成果，确定上覆土层的临界厚度。%The impervious system of cofferdam,which is composed of composite geomembrane and impervious wall, is easily damaged at the joint parts.In view of this,the pattern of joint between composite geomembrane and imper-vious wall needs to be studied in order to insure the safety of the whole cofferdam and to avoid the damage of geomembrane caused by the deformation difference between cofferdam body and impervious wall.A case study on the high earth-rockfill cofferdam of a hydropower station in west China was carried out by means of nonlinear finite element method.The research focused on the stress and deformation behaviors of the geomembrane and the high cof-ferdam built on deep overburden.Results show that the joint pattern had little influence on the stress and deforma-tion of dam body and impervious wall,but had significant influence on the geomembrane strain and the deformation difference between dam body and impervious wall.If the geomembrane is laid horizontally on the top of impervious wall,the settlement difference could induce large tensile strain of geomembrane at joint parts.With the rising of the location of geomembrane,the tensile strain decreased remarkably,which is beneficial for its safety.In conclusion, it is reasonable to lay the geomembrane above the impervious wall for a distance.The critical thickness of overlaying soil should be determined by indoor pull-out tests.
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