库水位升降作用下土质岸坡变形特征实验研究

库水位升降作用下三峡库区土质岸坡坡体吸水、应力集中及滑移变形,形成不同时段和不同空间部位的裂缝体系。通过模型试验的方法,分析了土质岸坡在一个蓄水降水循环周期内裂缝体系的时空演化分期配套规律。试验结果表明:蓄水初期,裂缝主要出现在岸坡前缘水位线附近,且出现频率高、规模逐渐增大,岸坡出现局部坍塌破坏;蓄水中期,岸坡前后缘均有裂缝出现,但出现频率低、规模减小;蓄水后期,前缘裂缝发育基本消失,后缘裂缝继续发育,岸坡以沿滑动面整体蠕滑为主;水位上升过程中暂停蓄水时裂缝发展缓慢。降水阶段,拉张裂缝主要出现在岸坡坡体后缘,初期降水裂缝出现频率较低,发展缓慢;后期降水裂缝出现频率、规模变大,产生下座变形及下错台坎;水位下降阶段岸坡沿滑动面发生整体缓慢蠕滑。

Experimental Analysis of Deformation Characteristic for Soil Bank Slope Under Reservoir Water Level Fluctuation

Under reservoir water level fluctuation, soil bank slope water sucking, stress concentration and slip deformation in Three Gorges Reservoir area form slope cracks system at different periods and different spatial parts. In this study, laws of cracks spatial evolution in different deformation periods for soil bank slope were analyzed during a water cycle of impoundment and decline by model test. The test results indicated that, in the initial impoundment period, cracks appeared near the water line at the bank slope leading edge with high appearance frequency, and scale increased gradually and partial bank slope collapsed and damaged. In the middle impoundment period, cracks appeared in the front and trailing edges of bank slope, the frequency of occurrence and the scale of which decreased. And in the late impoundment period, the leading edge of the cracks development disappeared, the trailing edge of the cracks continued to develop and the bank slope crept along the sliding surface as a whole. Cracks expanded slowly in the pause impoundment as the water level raised. In the water level decline stage, tensile cracks mainly occurred in the back edges of bank slope. In the early water level decline, cracks appeared in low frequency and it grew slowly. In the late water level decline, cracks appeared in high frequency and large scale, and where the bank slope produced lower seat deformation and dislocated berm. Moreover, in water level decline stage, bank slope crept along the sliding surface as a whole.