降雨作用对欢喜坡冰水堆积体斜坡稳定性的影响研究

EFFECT OF RAINFALL TO THE STABILITY OF ICE WATER ACCUMULATION OF THE HUANXIPO

为研究降雨对岷江上游冰水堆积体斜坡稳定性的影响,本文以欢喜坡为例,基于现场降雨模拟试验,完成渗透、含水量及抗剪强度等一系列试验,运用SEEP/W模块和SLOPE/W模块进行耦合,以分析降雨强度和降雨历时对该类型冰水堆积体斜坡稳定性的影响,研究结果显示:(1)欢喜坡冰水堆积体黏土矿物含量高达50%以上,饱和后含量可达85%以上;角砾土具有孔隙发育、级配不良的特点,双环渗透试验与降雨试验结果具有较好的一致性,综合确定角砾土渗透系数为1.315×10^(-3)cm·s^(-1),属中-弱透水介质。(2)角砾土天然状态下抗剪强度较高,含水率对其抗剪强度影响明显,从天然到饱和状态,黏聚力c衰减率明显高于内摩擦角φ,黏聚力c衰减可达64.4%,而内摩擦角φ仅降低22.5%;(3)在一定降雨强度条件下,斜坡体稳定性系数随降雨持时的增加不断降低;降雨持时相同时,降雨强度越大,坡体稳定性降低幅度越大,但稳定性出现陡降的时间拐点提前。

This paper studies the influence of rainfall on the slope stability of the ice accumulation in the upper reaches of Minjiang River. It takes the Huanxipo as an example. Based on the field rainfall simulation tests,a series of tests including permeability,water content and shear strength are carried out. The coupling of SEEP/W module and SLOPE/W module are used to analyze the influence of rainfall intensity and rainfall duration on the slope stability of this type of ice water accumulation. Research results show the follows.（ 1） The content of clay minerals in the ice accumulation body is up to 50%,and the content can reach more than 85% after saturation. The breccia soil has the characteristics of porosity development and poor gradation. The double loop permeability test is in goodagreement with the experimental results. The permeability coefficient of the breccia is determined comprehensively as 1. 315×10^-3 cm·s^-1,belongs to medium to weak permeable matrix.（ 2） In the natural state,the shear strength of the breccia soil is higher. Water content has obvious effect on shear strength. From natural to saturation,the decay rate of cohesion c is obviously higher than that of internal friction angle φ. The cohesion c can be reduced 64. 4%,while the internal friction angle is only decreased by 22. 5%.（ 3） Under certain rainfall intensity,the slope stability coefficient decreases with the increase of rainfall duration. When the duration of rainfall is the same,the greater the rainfall intensity,the greater the slope stability decreases,but the stability of the steep declines in the timing of the inflection point in advance.