深厚覆盖层上超深防渗墙细部设计问题探讨

Discussion on detail design of ultra-deep cut-off wall on deep overburden

超深防渗墙细部设计是深厚覆盖层上修建土石坝防渗处理的关键性问题。为此,在归纳总结国内外已建工程中超深覆盖层上防渗墙设计和建设经验的基础上,提出坝基防渗墙的设计中几点需要关注的问题,包括采用刚性墙还是塑性墙问题、防渗墙上下游侧的处理问题、封闭式防渗墙入岩深度问题、防渗墙顶部是否布设钢筋问题。针对这些问题在设计中需要注意以下几方面:(1)应根据数值计算的应力和变形指标确定钢塑性选择标准,加大研究塑性混凝土墙并推广应用;(2)结合有限元数值计算,分析防渗墙顶部一定范围内与两侧覆盖层之间的应力状况,评价防渗墙的上下游设置固结灌浆的必要性;(3)入岩深度的确定要结合岩石的坚硬完整性或岩石的破碎程度考虑;(4)防渗墙应力指标作为防渗墙顶部墙内特定范围内是否设置钢筋笼的标准。

The detail design of the ultra-deep cut-off wall is a key link for the anti-seepage treatment for the earth-rockfill dam built on deep overburden.Therefore,several problems those are necessary to be paid attention to during the design of the cut-off wall in dam foundation are put forward herein on the basis of summarizing the experiences from both the designs and the constructions of the cut-off walls on ultra-deep overburdens within the existing projects at home and abroad,including whether adopting rigid wall or plastic wall,the treatments of both the upstream side and the downstream side of cut-off wall,the penetrating depth of closed cut-off wall into rock and whether arranging reinforcing cage on the top of cut-off wall.Targeting at these problems,attentions must be paid to the flowing aspects:(1)the rigid-plasticity selection standard is necessary to be determined in accordance with the relevant numerically calculated stress and deformation indexes,and then the study on the plastic concrete cut-off wall is necessary to be strengthened along with the application and popularization of it;(2)the stress states within a certain range of the top of cut-off wall and between the overburdens on both the sides are necessary to be analyzed and the necessity of arrangement of consolidation grouting on both the upstream and downstream sides is necessary to be evaluated in combination with finite element numerical calculation;(3)the penetrating depth into rock is necessary to be determined under the consideration of rock hardness and integrity or the fragmentation of rock;(4)the stress index of cut-off wall is necessary to be taken as the standard for whether arranging reinforcing cage in cut-off wall within a specific range on the top of cut-off wall.