含深卸荷岩体拱坝坝肩变形特性及稳定分析

Deformation Characteristics and Stability Analysis of Arch Dam Abutment with Deep Unloading Rock Mass

叶巴滩拱坝作为混凝土双曲拱坝,坝高达到217 m,坝址区断层、挤压破碎带密布交错,且两坝肩在各高程范围均有深卸荷岩体分布,特别是在2 750 m高程,左右坝肩均存在强烈松弛岩体,由于其自身强度较低,可压缩性较强,对工程的稳定安全存在较大影响。针对上述问题,本文以地质力学模型试验为研究方法,对含深卸荷岩体的坝肩稳定及变形特性开展研究。首先建立叶巴滩拱坝2 750 m高程平面地质力学模型,通过超载法试验获得坝体变位和应变、坝肩及抗力体变位分布规律以及模型破坏过程和失稳形态等,数据分析得到起裂超载安全系数K1为1.6～1.8、非线性变形超载安全系数K2为2.4～2.6、极限超载安全系数K3为3.8～4.2,揭示了深卸荷岩体变形特性及对拱坝工作性态的影响。对试验数据的综合分析得出,在叶巴滩拱坝2 750 m高程中,左岸松弛带Ⅳs类岩体距离拱端更近,变形较右岸更大,对变位、荷载的传递具有更加明显的衰减作用,对工程稳定安全的不利影响作用显著。

As a typical concrete double-curvature arch dam, Yebatan arch dam has a height of 217 m. The faults and crushing fracture zones are densely intertwined at the dam site area, and deep unloading rock masses are distributed throughout the elevation range on both abutments. Especially at the elevation of 2 750 m, there are strong relaxation unloading rock masses on the left and right abutments. Because of its low strength and strong compressibility, it has an important effect on the stability and safety of the structure. In view of the above questions, the geo-mechanical model test is used to investigate the stability and deformation characteristics of the abutments with deep unloading rock masses in Yebatan arch dam. Firstly, a 2 750 m elevation plane model of Yebatan arch dam was established. Through the overloading test method, the displacement and strain of dam body, the distribution characteristic of displacement of abutment and resistance body, and the failure process and failure modes are obtained. According to the data analysis, the breakaway overload safety factor K1 is 1.6~1.8, the nonlinear deformation overload safety factor K2 is 2.4~2.6, and the ultimate overload safety factor K3 is 3.8~4.2. According to the results of the model test, the deformation characteristics of deep unloading rock masses and the influence on the working behavior of arch dams are obtained. It also indicates that at the 2 750 m elevation of Yebatan arch dam, the relaxation unloading rock masses with type Ⅳs on the left bank is closer to the arch end,and has larger displacement than the right bank, which has more significant attenuation effect on transmission of the displacement and the load, which has a significant impact on the stability and safety of the structure.