水-岩作用下蠕滑岸坡变形规律及演变机制研究

Reservoir landslide is a severe geological hazard which is caused by the hydrodynamic change due to rainfall and fluctuation of reservoir level， and the instability of reservoir slide is a major geological problem that is more common and has greater hazard. Therefore, carrying out comprehensive research on deformation regularity and evolution mechanism of reservoir slide under water-rock interaction has important theoretical value and engineering significance. The JinLongShan slide is a typical reservoir bank slope, locates at the left bank of Ertan Hydropower Station which is situated the downstream of the YaLongJiang river. Monitoring data has been obtained since 1985, covering the periods before, during and after the impoundment of the reservoir. In this study, the JinLongShan slide will be taken as the research object to investigate the deformation regularity and evolution mechanism of full life cycle reservoir slide. First, based on detailed geological investigate，through 28 years’ monitoring and analyzing,deformation characteristics and regularity in periods of prior, during and after reservoir impoundment will be analyzed in detail, and we will focus on rainfall parameters and reservoir level changes to investigate their influence on in depth displacements of a borehole inclinometers and on precise measurements at the surface of reference points, deformation responding of slide under the condition of rainfall and rising of reservoir water will be carried out. Then, in order to investigate the deteriorated shear strength under 'saturation-air drying' in water-rock interaction concern the effects of reservoir water level on the weakening of strength parameters of slide interface, experiments will be performed to simulate the process of water-rock interaction on bank slopes during fluctuation of water level with basalt rock as a representative of rock mass. At last, finite element model for saturated-unsaturated seepage computing will be established and permeability coefficient of landslide will be carried out. Meanwhile, the limit equilibrium method and finite element method of landslide stability under seepage will be discussed, and the hydrodynamic evolvement and deformation mechanism of landslide under fluctuation of reservoir level will be analyzed. Through research, revealing deformation evolution mechanism of reservoir slide under water-rock interaction in the whole life cycle and, establish deformation and multivariate mathematical model, proposed quantitative indicators stability evaluation. This research project is of great theoretical significance and practical value.

位于二滩电站的金龙山谷坡为一典型的蠕滑岸坡，至今已连续获取了近30年的监测资料，成果较好地体现了坡体在不同时期的变形特征及总体发展规律，这对研究该类岸坡变形规律及演变机制具有重要意义。本项研究以其为研究对象，基于监测成果分析不同情况下坡体的变形规律及各因素的影响效应；结合蓄水过程和水库运行情况设计试验方案，从岩体蠕变特性、力学性质弱化的角度研究蓄水后水-岩作用效应；建立考虑渗透力作用的岸坡的极限平衡及有限元计算模型，探讨降雨和水位变化对坡体变形、稳定的影响。研究内容重点包括：（1）不同时段的变形特征及演变规律（2）水位变动下的水岩作用及其时间效应。通过研究，揭示水-岩作用下蠕滑岸坡的变形规律及演化机制，提出该类岸坡变形及稳定的预测评价方法，建立变形与多因素的数学模型，提出稳定性评价的定量指标。研究成果拟为水库蓄水安全及长期稳定性评价提供参考，同时为水-岩作用机理研究作出一定贡献。

本项目基于原位监测、室内试验和数值模拟多种研究方法，针对蠕滑岸坡的变形演变机制及长期稳定性评价问题展开研究。借助原位监测分析了岸坡总体变形特征及发展演变规律，研究了不同时期变形影响因素及其作用效果，总结降雨作用下水-岩耦合作用效果及降雨与库水位联合作用下的水-岩耦合作用效果；通过含水率试验及饱水试验，研究了水-岩相互作用下岩土体物理力学性能的变化；数值模拟了降雨、水位骤升以及周期性变动对坡体渗流场、位移场的影响，综合分析水-岩耦合作用下坡体变形演变机制。.研究结果表明：坡体变形总体经历了蠕变-突变-再次蠕变的过程。蓄水前降雨对坡体变形起控制作用，雨季变形速率为旱季的两倍，降雨对变形的影响存在1-2个月的滞后。蓄水初期总体的坡体变形速率相当于蓄水前的8-20倍。最初阶段坡体变形对库水位上升的响应存在近2周的滞后，随后变形以10mm/月的速度快速上升，水位上升至一定高程后，坡体的变形速率又出现下降趋势。库水对坡体稳定影响复杂，稳定性分析结果表明最初阶段受库水位上升影响，坡体稳定性降低，当水位上升至某一临界值后，库水引起的横向约束发挥作用，短期内有利于坡体的稳定。.库水位周期性升降循环阶段，对于坡体上部未淹没区域，降雨是变形的主要影响因素；水位变幅带，坡体变形主要受库水位变动影响，变形与库水位升降负相关，即：库水位上升，坡体变形减小；库水位下降，坡体变形增大。坡体变形总体呈现缓慢增大趋势，变形速率随时间逐渐降低，与淹没区受库水影响逐渐减弱、变形趋于稳定有关。试验结果表明，水对岩体物理力学性能的影响，最初影响显著，饱水一定时间后，各参数随时间无明显变化， 这一趋势与坡体变形规律相吻合。推测库水对滑面的软化效应，在蓄水4年后达到极限。.研究成果对整体认识库岸斜坡在全生命周期内变形发展规律及水-岩耦合作用下变形演变机制具有重要意义，可为岸坡不同时期的稳定性评价及预测提供定量参考依据。