中文摘要：

三峡水库蓄水运行之后,库水位每年都在145 m的防洪水位和175 m的蓄水发电水位之间或缓慢或快速地升降变化,岸坡消落带区域岩土体长期处于干湿循环状态,其力学参数的劣化规律将直接影响岸坡的变形稳定。基于此,设计并进行了典型岸坡消落带土体的干湿循环作用试验。结果表明：（1）在干湿循环作用过程中,土体抗剪强度参数劣化幅度非常明显,其中,前4次干湿循环作用导致的抗剪强度参数劣化幅度占总劣化度的75%左右,4次干湿循环作用之后,劣化趋势逐渐趋于平缓;（2）在干湿循环作用下,土样内部的微观裂纹、裂隙反复张开闭合,逐渐发育、汇集,土样由密实状态逐渐变为内部裂纹发育的松散状态,土样内部的损伤是导致其抗剪强度参数逐渐劣化的根本原因;（3）考虑干湿循环作用下消落带土体参数劣化时,岸坡消落带区域局部安全系数劣化趋势明显,总体趋势与消落带土体抗剪强度参数劣化规律一致,而且岸坡消落带区域附近的局部滑动迹象明显,这与现场踏勘所见到的该区域明显发育的裂缝、下挫现象是一致的。研究成果对库水作用下岸坡的长期变形稳定评价具有较大的参考意义,相关分析方法也可以为类似试验提供参考。

英文摘要：

After the impoundment and operation of reservoirs,the water level changes slowly or rapidly between the flood control water level of 145 m and the impoundment water level of 175 m every year.Rock and earth mass in the hydro-fluctuation belt is under cycle of drying-wetting conditions for a long time.The degradation of mechanical properties direct impacts on deformation stability of the bank slope.In this study,the experiments of testing under drying-wetting conditions are designed and conducted on the soils from the typical hydro-fluctuation belt.The results indicate that：1） Shear strength of soil degrades under drying-wetting conditions.Specifically,shear strength deteriorates 75% by the first 4 cycles of the drying-wetting,and gradually becomes stable afterwards.2） During the drying-wetting cycle,the internal microscopic cracks of the soil samples open and close repetitively,and then gradually grow and assemble;dense soil samples gradually loosen with increasing internal cracks.3） Considering the degradation of soil properties during the drying-wetting cycles in hydro-fluctuation belt,the local safety factor of slope will degrade accordingly.The local slide and the developed cracks can be easily observed near the hydro-fluctuation belt in field investigation.The findings in this article can provide good reference for long-term deformation and stability evaluation on slopes in hydro-fluctuation belt.