含软弱层反倾岩质边坡开挖卸荷失稳模式与预锚固机理

The failure mechanism caused by excavation unloading of toppling rock slope with weak layers is complex and it is also difficult to control, while its stability is the key to the success of the project. Taking the right bank rock slope in the dam of Baihetan Hydropower Station as an example, integrated with multidisciplinary of engineering geology, tectonic geomorphology, fracture mechanics and information analysis, combined with sophisticated engineering geological survey, a large physical model test and multi-sensor monitoring technology, the genetic relation of the ancient stress environment and valley evolution with dominant joint sets of the right bank slope in the dam of Baihetan Hydropower Station will be studied,and the geological evolution process of the right bank slope is rebuild. The physical model tests to simulate how toppling rock slope with weak layers deform, caused by excavation directly or excavation after pre-anchoring, will be carried out, and multi-physical monitoring database will be established. Then the response to excavation unloading of toppling rock slope with weak layers is studied, moreover unloading deformation and failure evolutionary stages of slope are divided, and the characteristic values in every evolution stage of each physical parameter are extracted, hence the temporal association rule model of slope deformation and damage evolution caused by excavation unloading is mined, finally the failure model by excavation unloading of toppling rock slope with weak layers is hopefully revealed. With that, the temporal-spatial evolution of axis forces and deformation of pre-anchoring body are studied, the pre-anchoring effect to rock slope is evaluated, and the pre-anchoring response mechanism of slope with excavation unloading is established, then the pre-anchoring mechanism of toppling rock slope with weak layers to excavation unloading is revealed. It is applied to study controlling the excavation deformation of the right bank abutment rock mass of Baihetan Hydropower Station.

含软弱层反倾岩质边坡开挖卸荷变形破坏机理复杂,治理难度大，是工程建设成败的关键。以白鹤滩水电站坝址区右岸边坡为研究对象，通过工程地质学、构造地貌学、断裂力学和信息分析学等多学科交叉融合，结合工程地质精细调查、大型物理模型试验和多传感器监测技术，研究白鹤滩水电站坝址区古应力环境、河谷演化与右岸边坡优势结构面的成生联系，重建右岸边坡演化地质过程；开展直接开挖和预锚固再开挖时含软弱层反倾岩质边坡卸荷变形物理模型试验，建立多物理量监测信息库，研究含软弱层反倾岩质边坡对开挖卸荷的响应规律，划分边坡卸荷变形破坏演化阶段，提取不同演化阶段各物理量特征值，挖掘边坡开挖卸荷变形破坏演化时序关联模型，揭示含软弱层反倾岩质边坡开挖卸荷失稳模式。研究预锚固体轴力和形变时空演化规律，评价预锚固效果，建立边坡开挖卸荷预锚固响应机制，揭示含软弱层反倾岩质边坡开挖卸荷预锚固机理，应用于白鹤滩右岸坝肩岩体开挖变形控制研究。

含软弱层反倾岩质边坡开挖卸荷变形破坏机理复杂，治理难度大，是工程建设成败的关键。以白鹤滩水电站坝址区右岸高陡边坡为原型，开展了直接开挖和预锚固含软弱层反倾岩质边坡卸荷过程离心模型试验，研究了含软弱层反倾岩质边坡对开挖卸荷的响应规律，直接开挖卸荷过程中模型边坡中应变发生了明显突变，表现为拉应变突增，压应变减小，而先预锚固再开挖时，边坡岩体卸荷应变受到明显限制，预锚固措施有效减小了卸荷位移的发展，同时也对边坡中裂隙的可能扩展起到了很好的抑制作用；开展了地震作用下反倾岩质边坡块状-弯曲倾倒物理模型试验，研究了反倾岩质边坡倾倒变形破坏全过程及空间演变特征，将块状倾倒破坏全过程概括为三个阶段，即折断倾倒变形累积阶段、破坏面局部贯通阶段和坡体倾倒溃滑阶段；开展了反倾软岩边坡弯曲倾倒破坏模式物理模型试验，揭示了弯曲倾倒破坏机制，并将弯曲倾倒破坏分为4个区，即后缘稳定区、牵引式拉裂区、推移式拉裂区和前缘剪切区，采用悬臂板理论和静力平衡理论，提出了弯曲倾倒破坏模式稳定性计算刚体极限平衡法。