反倾边坡倾倒变形演化过程的模型试验研究

MODEL TEST STUDY ON TOPPLING DEFORMATION EVOLUTION PROCESS OF COUNTER-TILT SLOPE

以西藏扎拉水电站坝址右岸反倾边坡为工程依托,基于地质认识及相似理论建立边坡物理模型,采用分级开挖的方式模拟河谷下切作用,研究反倾岩质边坡倾倒变形的演化过程。模型开挖后变形破裂发展的过程表明:该类反倾边坡倾倒变形模式为初期卸荷回弹变形、长期重力弯曲(破裂)变形及后期蠕滑变形。通过对位移、变形速率和变形加速度变化规律的分析发现:反倾边坡倾倒变形的过程可以根据变形加速度a划分为3个演化阶段即倾倒启动阶段、稳态变形阶段和快速失稳阶段,各阶段分别对应衰减蠕变、稳态蠕变和加速蠕变的变形特征。在此基础上采用变形加速度a作为倾倒边坡稳定性判别指标,并尝试将变形加速度突破稳态蠕变上限值(a≥a_2)作为边坡失稳预警判据。

Relying on the counter-tilt slope of the right bank of dam site of Zha La hydropower station in Tibet,a slope physical model is established based on geological knowledge and similarity theory. A method of staged excavation is adopted to simulate the incised action of a valley,and the evolution process of toppling deformation of a toppling rock slope is studied. The development process of deformation and fracture after excavation shows that：The toppling deformation modes of counter-tilt slope are initial unloading rebound deformation,long-term gravity bending（ fracture） deformation and creep deformation in the later stage. Through the analysis of the law of displacement,deformation rate and deformation acceleration： The toppling deformation process of counter-tilt slope can be divided into 3 evolution stages（ the stage of toppling initiation,the stage of steady deformation and the stage of rapid destabilization） according to the deformation acceleration a. Each stage corresponds to the deformation characteristics of attenuation creep,steady creep and accelerated creep respectively. On this basis,the deformation acceleration a is used as the criterion of slope stability,and try to use a（ deformation acceleration） ≥a2（ upper limitof steady-state creep） as a slope instability prediction criterion.