震后坡面松散堆积体失稳水力学机理研究

为研究震后强降雨条件下沟道泥石流产生的力学机制及水力学机理,以都江堰市龙池镇银洞子泥石流沟为研究对象,构建坡面松散堆积体地下水位变化水力模型,按照水力学渗流理论,分析了震后泥石流形成区坡面松散堆积体内潜水位变化的特征和规律,定量研究了动静水压力对坡体的作用特点。根据理论分析、实例验证与物理模拟试验的研究结果,获得了对坡面松散物源启动力学机理、启动临界条件及启动模式的深刻认识: ①在强降雨激发作用下,随着坡体内潜水位不断升高,水力条件不断恶化,最终导致坡面松散堆积体发生失稳破坏; ②堆积体内潜水位高度是坡面面积(S)、稳态降雨强度(I),坡体几何参数、导水系数(TD)等参数的综合函数,S、I越大,则潜水层厚度( H)越大,反之,当坡面集雨面积和稳态激发降雨强度一定时,导水系数、坡体宽度和潜水面倾角越大,则坡体内产生潜水层垂直厚度越低; ③随着坡体内静水压力(P)增加,堆积体基底抗滑力将会降低; 随着坡体内动水压力(Gd)增加,坡体下滑力将会增加; ④根据剩余下滑力的存在形式,震后坡面松散堆积体的启动模式可分为2种,即坡体整体启动的推移式失稳和分段解体启动的牵引式失稳。研究成果可为沟道泥石流的超前预警提供理论及技术支持。

Study on hydraulic mechanism of loose accumulation in post-earthquake slope

In order to analyze the mechanical principle and hydraulic mechanism of channel debris flow under strong rainfall after earthquake, the authors take debris flow gully in Yindongzi of Longchi Town in Dujiangyan as a case study to establish the hydraulic models of underground water level change in loose accumulations. The characteristics and laws of ground water level change of loose accumulation in post-earthquake debris flow slope are analyzed according to the percolation theory in hydraulics, and the effects of hydrodynamic pressure and hydrostatic pressure on slope body are quantitatively studied. Through the combination of theoretical analysis, example verification and physical simulation test, a deep understanding of mechanical mechanism, critical condition and mode of start-up of loose source on slope was achieved. The results show that: ①Under the excitation of heavy rainfall, the hydraulic condition deteriorates continuously with the increasing diving level in the slope, which eventually leads to the stability failure of the loose accumulation body on the slope. ②The phreatic level generated by the accumulation body is a comprehensive function of slope area S, steady-state rainfall intensity I, slope geometric parameters (θ、W、H、Z) water conductivity coefficient T and other parameters. Tthe larger and I are, the higher the height of phreatic level H will be; Conversely, under the premise that the rainfall collecting area and steady-state rainfall intensity are determined, the larger T, W and θ are, the lower the phreatic level generated in the slope body will be. ③With the increasing hydrostatic pressure P in slope body, the sliding resistance of accumulation body base will be decreased; As the hydrodynamic pressure G_d inside the slope increase, the sliding force of the slope will increase. ④According to the existence form of residual sliding force, the starting mode of the loose accumulation body on the slope after earthquake can be divided into two types: the sliding mode of the whole slope starting and the traction mode of the disintegration in segments starting. The research results can provide theoretical and technical support for the advance warning of gully debris flow.In For the study of earthquake under the condition of strong rainfall channel debris flow mechanics and hydraulics mechanism, combining with the town of Dujiangyan order of the silver named debris flow gully is analyzed, the construction of slope are underground water level change under the premise of hydraulic model, with the aid of seepage theory of hydraulics, area after the earthquake were analyzed by slope loose accumulation is the characteristics and regularities of the variation of the groundwater level in the body, The effects of hydrodynamic pressure and hydrostatic pressure on slope body are quantitatively studied. Through the combination of theoretical analysis, example verification and physical simulation test,