波浪作用下近海滑坡机制模型试验与数值模拟研究

Physical model tests and numerical simulations to determine mechanism of offshore submarine landslides under effect of sea waves

以舟山群岛朱家尖滑坡为工程依托,针对波浪对近海海底边坡失稳破坏的影响问题,研发了大型水槽类近海海底滑坡物理模型试验装置,搭建了以波分复用技术为基础的光纤监测系统,开展了波浪作用下近海海底滑坡模型试验,揭示了波浪引起边坡模型内部孔隙水压力、位移变化规律以及边坡模型表面流速变化规律,分析了波浪作用下近海海底滑坡触发机制以及灾变过程。同时基于SPH数值模拟,针对海底滑坡灾变演化过程,开展了波浪作用下海底边坡的滑动堆积特性研究。试验结果表明:海底边坡在波浪的持续作用下,边坡底部最先发生破坏,伴随着时间的推移,边坡发生失稳破坏,海底滑坡发生时,边坡中部及以下的位置位移发生突变,边坡顶部滑移距离相对较小;波浪对海底边坡的位移和孔隙水压力同时产生影响。边坡失稳破坏时,边坡位移与孔隙水压力均出现突变现象,但孔隙水压力突变时间略早于位移突变时间。同时基于朱家尖地质剖面I的滑坡模拟,初步得到了朱家尖近海海底滑坡的滑动堆积特征,形成了一套适用于波浪作用下近海海底滑坡的试验技术与方法,对近海海底滑坡现场研究有重要的指导意义及参考价值。

Based on the Zhujiajian landslide in Zhoushan Islands, this paper developed a large-scale water tank-like physical model test device for investigating the influence of waves on the instability and failure of offshore submarine slopes, and built a wave division multiplexing technology-based fiber inspection system. The model test of the offshore submarine landslide under the action of waves was carried out, the variation law of pore water pressure and displacement in the slope model caused by waves was revealed, and the variation law of the surface velocity of the slope model was analyzed. Based on the SPH numerical simulation, the research on the sliding accumulation characteristics of the submarine slope under the action of waves was carried out to understand the catastrophic evolution process of the submarine landslide. Results showed that under the continuous action of waves, the bottom of the submarine slope was the first to be damaged, and then the slope became unstable and was damaged with the time elapsed.When a submarine landslide occurred, the displacement in the middle location of the slope and below changed abruptly, while the slip distance at the top of the slope was relatively small;waves affected the displacement and pore water pressure of the submarine slope simultaneously. When the slope was destabilized and damaged, the slope displacement and the pore water pressure changed suddenly,but the time of the sudden change of pore water pressure was slightly earlier than that of the displacement. Meanwhile, based on the landslide simulation of Zhujiajian geological profile I, the sliding accumulation characteristics of Zhujiajian offshore submarine landslides were preliminarily obtained. A set of test techniques and methods suitable for offshore submarine landslides under the action of waves has been established, which provides important guiding significance and reference values for the field research of offshore submarine landslides.