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300 m级高拱坝建基面开挖造成的岩体卸荷松弛对高拱坝的整体稳定性影响巨大。白鹤滩拱坝左岸建基面开挖至628 m高程时也出现了卸荷松弛、结构面错动等现象。基于变形加固理论,提出了使用不平衡力作为坝基岩体松弛卸荷的定量判据,阐释了不平衡力分析岩体开裂与坝基卸荷时效松弛的理论基础,通过试验和数值模拟的对比说明了不平衡力应用于卸荷松弛判据的准确性。使用三维非线性有限元程序TFINE,对白鹤滩拱坝原始地形和开挖过程进行精细模拟,分析了开挖过程中建基面基础(尤其是结构面)的卸荷松弛演变过程。分别对无基础处理、预留保护层和施加锚索情况下的开挖卸荷松弛进行了研究分析。模拟结果表明,在开挖到630 m高程时,在结构面交汇处和坡面出露段附近结构面的不平衡力与屈服区出现集中情况,这与观测到的建基面卸荷松弛以及结构面出现错动裂缝等现象符合;继续开挖过程中,LS331、LS3318不平衡力较大,相对比较危险。另外,坝体底部的陡坎开挖成型时,陡坎底部的不平衡力增加较明显,需减缓陡坎坡度。预留保护层和建基面锚固对控制松弛卸荷作用较小。
The unloading relaxation of rock mass caused by excavation of the 300 m-high arch dam has a huge impact on the overall stability of the high arch dam. When the left bank of Baihetan arch dam was excavated to the elevation of 628 m, unloading and relaxation occurred and the structure surface was in error. Based on the theory of deformation and reinforcement, the unbalanced forces are proposed as the quantitative criteria for relaxation and unloading of rock mass. The theoretical basis for analyzing the cracking of rock mass and the relaxation time-dependent relaxation of dam foundation by unbalance force is explained. The contrast between the experiment and numerical simulation The accuracy of unbalanced force applied to unloading relaxation criterion. The three-dimensional non-linear finite element program TFINE is used to simulate the original topography and excavation process of Baihetan arch dam. The unloading relaxation process of the foundation surface (especially the structural plane) during excavation is analyzed. The unloading, relaxation and relaxation under the condition of no foundation treatment, reserved protective layer and the application of anchor cable were studied respectively. The simulation results show that the imbalance force and the yield zone of the structural plane near the confluence of the structural plane and the exposed section of the slope are concentrated when the height of 630 m is excavated. This is consistent with the observed relaxation of the unloading on the foundation surface and In the process of excavation, the unbalanced forces of LS331 and LS3318 are relatively large and relatively dangerous. In addition, when the steep ridge at the bottom of the dam is excavated and shaped, the imbalance force at the bottom of the scarp increases more obviously, and the steep slope slope needs to be slowed down. Preserving the protective layer and the foundation anchorage have less effect on controlling relaxation and unloading.