坡积土边坡裂隙各向异性特征对雨水入渗过程的影响

采用有限元软件Geo-Slope中的SEEP/W模块分析了裂隙深度、渗透系数比、裂隙角度与裂隙数对雨水入渗过程的影响,结合非饱和渗流理论研究了裂隙渗流各向异性对边坡稳定性的影响。分析结果表明:降雨1、7 d时,1 m裂隙深度内最大孔隙水压力分别为9.69、9.70 kPa,雨水沿裂隙底部向下的入渗深度分别为0.5、1.5 m,裂隙内孔隙水压力随降雨的持续迅速增大,直至由负压力转变为正压力; 裂隙深度越大,裂隙内孔隙水压力越大,降雨停止时刻相应的入渗深度也越大,饱和区域的大小与裂隙深度正相关; 当渗透系数比为1时,裂隙范围内最大渗透系数为1.51×10-7 m?s-1,此时沿裂隙方向渗透系数小于降雨强度,降雨入渗过程受土体渗透系数控制,而当沿裂隙方向渗透系数大于降雨强度时,雨水入渗过程受降雨强度控制; 裂隙角度越小,在裂隙深度范围内的最大孔隙水压力越大,且出现正孔隙水压力的深度也越大,而边坡表层饱和区范围越小; 无裂隙存在时,降雨后边坡内部仍保持负压力状态,无饱和区存在,有裂隙存在时,雨水沿裂隙下渗并在边坡内部形成饱和正压力区,1～5条裂隙形成的饱和区面积分别为16.4、34.7、60.9、75.6、110.7 m2,饱和区面积与裂隙数呈乘幂关系,且随着裂隙数的增加,雨水对渗流场的影响范围与程度增大,长裂隙的集中分布是引起边坡内部大面积连通型饱和区出现与地下水位升高的直接原因。 

Effect of colluvial soil slope fracture’s anisotropy characteristics on rainwater infiltration process

The SEEP/W module of the finite element software Geo-Slope was used to analyze the effects of fracture depth, permeability coefficient ratio, fracture angle and fracture number on the rainwater infiltration process. The effect of fracture seepage anisotropy on slope stability was studied along with the unsaturated seepage theory. Analysis result shows that when the rainfall duration is 1 and 7 d, respectively, the maximum pore water pressure in a 1 m fissure is 9.69 and 9.70 kPa, respectively, and the rainwater infiltration depth along the bottom of the fracture is 0.5 and 1.5 m, respectively. The pore water pressure in a fracture increases rapidly with the rainfall until it changes from a negative pressure to a positive pressure. The greater the fracture depth, the greater the pore water pressure in the fracture, and the greater the infiltration depth is when rainfall stops. The size of the saturated area is positively correlated with the fracture depth. When the permeability coefficient ratio is 1, the maximum permeability coefficient in the fracture range is 1.51×10-7 m?s-1. At this moment, the permeability coefficient along the fracture direction is less than the rainfall intensity, and the infiltration process is controlled by the soil permeability coefficient. When the fracture permeability coefficient along the fracture direction is larger than the rainfall intensity, the infiltration process is controlled by the rainfall intensity. The smaller the fracture angle, the greater the maximum pore water pressure in the fracture depth range, the greater the depth of the positive pore water pressure, and the smaller the range of surface saturation zone is. When there is no fracture, the slope still maintains a negative pressure state after rainfall, and there is no saturation zone. When there is a fracture, the rainwater infiltrates along the fracture and forms a saturated positive pressure zone inside the slope. The areas of the saturated zones formed by 1-5 fractures are16.4, 34.7, 60.9, 75.6 and 110.7 m2, respectively. A power relation exists between the saturation area and fracture number. The influence range and degree of rainwater on the seepage field increase with the increase of fracture number. The concentration distribution of long fractures directly forms a large connected saturated zone and raises groundwater. 1 tab, 14 figs, 33 refs.