沟谷型沙漠泥流堆积体起动过程中的孔压变化特性

Pore water pressure variation characteristics during the initiation processes of the accumulation body of the gully desert mud flows

以黄河上游宁蒙段典型风水复合侵蚀流域为研究区域,重点针对堆积体堵塞沟道极端条件下的沟谷型沙漠泥流,从堆积体起动成灾的环节入手,开展直槽概化模型试验,并采用基于有效应力原理的流固耦合模型,概化模拟上游暴雨洪水入渗条件下堆积体内孔隙水压力变化特性及其起动过程,从微观角度揭示其成灾机理。结果表明:堆积体起动过程中孔隙水压力与时间呈指数为0.5的幂函数关系;流固耦合作用下堆积体内经历了应力场→体积应变→孔隙率→孔隙水压力→渗流场→塑性应变→屈服破坏的复杂非线性变化过程。

Taking one of the typical aeolian-fluvial interaction dominated watersheds in the Ningxia-Inner Mongolia reach of the Upper Yellow River as the study area,while focusing on the gully desert mud flows characterized as a extreme pattern that the accumulation body blocks the channel,straight channel generalized model tests were carried out on the pore water pressure variation characteristics and the initiation processes of the accumulation body under the upstream runoff infiltration condition. Meanwhile,the fluid-solid coupling model based on the effective stress principle was adopted to simulate the catastrophic micro-mechanism from the perspective of the primary initiation stage of the mud flow disasters. The results indicated that the relationship between pore water pressure and time is a power function with an exponent of 0.5. Under the effects of fluid-solid coupling,the accumulation body experienced a complex nonlinear process of stress field → volume strain → porosity → pore water pressure → seepage field → plastic strain → yield failure. Our results can also provide a new method and approach for early warning and prevention of the gully desert mud flow disasters in terms of pore water pressure monitoring.