深覆盖层上土石坝心墙与防渗墙连接型式研究

深厚覆盖层上建造的土石坝常采用封闭式防渗系统。当心墙坝防渗系统坝体采用沥青混凝土心墙、坝基采用封闭式防渗墙时,心墙混凝土基座、防渗墙与相邻土体之间将产生不均匀沉降,易引起基座混凝土断裂和坝壳及覆盖层土体剪切破坏。针对心墙坝坝体心墙与坝基防渗墙合理的连接型式问题,结合某水库工程,采用非线性有限元法,建立三维有限元模型,分析研究了心墙基座与防渗墙不同连接型式下坝体与坝基的变形和应力。通过坝体和坝基的变形协调分析以及心墙基座和防渗墙的应力分析,推荐了合理的连接型式,即深厚覆盖层上沥青混凝土心墙坝坝基采用封闭式防渗墙时,宜采用心墙基座与防渗墙间预留空隙的连接型式,其空隙大小与坝基覆盖层厚度及其力学特性以及防渗墙弹性模量有关,需经计算分析确定。

Reasonable connection type for cutoff wall and core wall of earth-rock dams on deep overburden layers

The earth-rock dams built on deep overburden layers often use a closed seepage control system which is composed of core wall of dam body and impervious wall of dam foundation. Uneven settlement will occur between concrete core wall base, impervious wall and the adjacent soil, which leads to the fracture of concrete base and the shear failure of dam body and its foundation when the asphalt concrete core wall is used in dam body and a closed impervious wall is used in dam foundation. Taking an earth-rock dam on a deep overburden layer as a study object, a three-dimensional finite element model is establised, and the deformations and stresses of the dam body and its foundation are analyzed by use of the nonlinear finite element method. By comparing the analyses of deformation compatibility of dam body and its foundation and the stresses of core wall with its base and impervious wall, a reasonable connection type is recommended for the core wall dams, which should reserve a gap between the base and the impervious wall for an earth-rock dam built on deep overburden layer which uses a closed seepage control system. The size of the reserved gap is related to the thickness of the overburden layer and its mechanical properties as well as the elastic modulus of the impervious wall, and it requires computational analysis for determination.