复杂岩基上高拱坝坝基坝肩浅层卸荷影响与稳定性研究

采用3维地质力学模型综合法试验以及非线性有限元计算,对考虑浅层卸荷影响的小湾拱坝与地基整体稳定问题进行研究。试验中,用不同尺寸、不同力学参数的微小菱形块体对开挖出现的浅层松弛卸荷岩体进行重点模拟,同时还模拟了坝基坝肩主要的地质构造和加固方案,对主要的断层采用变温相似材料模拟,以便进行降强试验;有限元计算采用与模型试验一致的力学参数以及降强、超载步骤,对坝基浅层卸荷带用加密单元进行模拟。通过模型试验及计算分析得出,受坝基浅层卸荷的影响,在超载过程中坝踵和坝趾附近岩体首先出现开裂（对应模型试验）或产生塑性区（对应计算）,最终上游坝踵附近裂缝或塑性区贯通,说明坝基浅层卸荷对坝与地基稳定性有一定影响,为保证运行后工程安全,建议对中下部高程坝基采取固结灌浆等加固措施。

Study on Influence of Dam Foundation Shallow Unloading and Stability of High Arch Dam with Complicated Rock Foundation

Combining with Xiaowan Project, and considering the influences of shallow unloading and relaxation rocks, a 3D geo-mechanical model test and 3D nonlinear FEM calculation are carried out to study the global stability of high arch dam and foundation. In the test, the shallow unloading and relaxation rocks caused by excavation are the focuses to be simulated using different sizes and different mechanical parameters of rhombus small blocks. At the same time, the main geological structures and the reinforcing schemes at the dam abutment and dam foundation are simulated, using temperature analogous material to simulate the major weak structural planes in order to carry out strength-decreasing test. Finite element calculation uses the same mechanical parameters and the same steps of strength-decreasing and overloading. The shallow unloading zone of dam foundation is simulated using dense element. Through the model test and calculation analysis obtains, the rocks nearby the dam heel and dam toe crack firstly (corresponding to model test) or appear plastic zone firstly (corresponding to calculation) affected by the shallow unloading rocks in the process of overloading test, finally the crack or the plastic zone transfixion nearby the upstream dam heel, that is shows the shallow unloading rocks have a certain influence on the stability of dam and foundation. To ensure the safety of engineering after the operation, suggestion adopt such as consolidation grouting reinforcement measures at the mid-lower elevation of dam foundation.