狭窄河谷中的高面板堆石坝长期应力变形计算分析

Analysis on long term stress and deformation of high concrete face rockfill dam in narrow valley

根据已建面板堆石坝的竣工后沉降变形规律和室内大型三轴流变试验结果,提出了堆石体长期变形流变模型。对建设在狭窄河谷中的九甸峡混凝土面板堆石坝进行了三维应力变形分析,考察了三维效应、堆石体流变等因素对大坝长期应力变形特性的影响。结果表明,狭窄河谷岸坡对坝体存在拱效应,减小坝体应力,同时,由于右岸坡度缓于左岸,右岸侧坝体较左岸侧存在更大的朝向河谷中心的位移。拱效应也阻碍了面板的弯曲和沉降变形,使靠近岸坡的面板接缝拉开和错动,并可能导致河床段面板中上部发生挤压破坏。坝体流变变形增大了面板挤压破坏的可能性。库水推力导致面板在挠曲的同时发生顺岸坡向拉伸,坝体的后期流变变形则可减小或改变面板的拉伸状态。

A creep model describing the long term displacement of rockfill is proposed based on the analysis result of settlement records of several existing concrete face rockfill dams and large-scale triaxial creep test for rockfill of the Jiudianxia Dam. The model is applied to carry out the 3-D stress-deformation analysis for the 133m high Jiudianxia rockfill Dam, located at a narrow valley. The influences of 3-D effect and creep on long term stress-deformation characteristics of the dam are investigated. The result shows that the arch effect formed by the banks of narrow valley exists and reduces the settlement and stress of the dam. The dam body on the right side which has a less steep bank than the left side moves more significantly towards the center of the valley. The arch effect also reduces the bending and settlement of the concrete slabs resulted in the failure of the joints or slipping of slab. The slabs at upper part of the dam in valley canter region may be broken due to extrusion pressure. The creep effect increases the possibility of extrusion failure of the slabs along the direction of dam axis. The reservoir water pressure may cause the extension deformation when the deflection of slabs takes place, but the extensive stress may be reduced due to the deformation of post creep of the dam.