某水电站混合坝接头坝顶开裂成因分析

针对混合坝接头处存在软硬材料的接触界面并易产生坝顶裂缝的问题,以某水电站混合坝工程为例,针对其在初次蓄水后心墙堆石坝接头部位坝顶出现多处裂缝的现象,通过考虑坝料的湿化与流变特性,采用有限元耦合变形倾度法对右岸心墙堆石坝及接头坝段开展了三维数值仿真分析。结果表明:(1)蓄水引起的上游堆石湿化变形是导致接头坝顶开裂的主要原因;(2)接头部位的坝料受下部混凝土接头斜坡的支撑约束,沉降位移明显小于上游堆石,导致变形不协调,引起土体开裂;(3)坝顶沉降梯度较大是坝顶出现裂缝的主要原因,其中沿坝体顺河向的坝顶沉降梯度引起的裂缝与坝轴线平行,沿坝顶顺河沉降梯度引起的裂缝与坝轴线垂直。对比实际坝顶开裂部位,初步判断当坝顶不均匀沉降梯度0.6%时,产生开裂的概率较高。研究所得成果可为混合坝的设计施工提供参考。

Analysis on causation of cracking at crest of joint of composite dam for a hydropower station

Aiming at the problem of that an interface is there between soft and hard materials at the joint of composite dam， where cracks are prone to occur and taking the composite dam for a hydropower station as the study case， a 3-D numerical simulative analysis is made on the rockfill dam with core-wall on the right bank and its joint dam section with the FEM coupling deformation gradient method under the consideration of the characteristics of humidified deformation and rheological deformation of the dam construction materials in accordance with the phenomenon of that several cracks occur at the crest of the joint section of the rockfill dam with core-wall after its initial impoundment. The result shows that: （1） the humidified deformation of the upstream rackfill body caused by the impoundment is the main causation of the cracking at the crest of the joint dam section； （2） under the restriction from the underneath sloping support of the concrete joint， the settlement of the dam construction materials at the location of the joint is obviously less than that of the upstream rockfill body， and then leads to an uncoordinated deformation， thus causes the cracking of the earth mass therein； （3） the larger gradient of settlement is the main causation of the cracking at the dam crest， in which the crack caused by the settlement gradient along the river is parallel to the dam axis， while the crack caused by the axial settlement gradient is vertical to the dam axis. Compared with the actual cracking location on the dam crest， it is initially estimated that the cracking probability is higher， when the gradient of uneven settlement of the dam crest is more than 0.6%. The study result can provide a reference for the design and construction of composite dam.