摘要:
降雨入渗过程中孔隙气压力变化是影响边坡稳定的重要因素,为了分析这种影响,提供一种考虑孔隙气压力影响的边坡稳定分析方法.首先基于水气两相流的理论与方法,计算降雨入渗下坡体的孔隙水压力、孔隙气压力和饱和度的分布,并获取降雨入渗过程中孔隙气压力引起的荷载变化量.而后,结合非饱和土抗剪强度理论及剩余推力法,将孔隙气压力引入到边坡稳定分析中,并以谭家河滑坡为例模拟分析考虑孔隙气压力对边坡稳定的影响.结果显示,降雨导致坡体表层趋于饱和,在坡表与滑带之间的孔隙气压变化较为敏感,而沿滑床向深层方向传递过程中孔隙气压发生衰减;坡体表层饱和区孔隙水压力通过孔隙气向坡脚传递,形成沿坡脚方向的孔隙气压力梯度,增大了滑体的下推力.结果表明,在相同的渗流条件下,考虑孔隙气压力的影响使同一滑动面上的安全系数降低,对边坡稳定分析不利.该方法在坡体濒临失稳时考虑孔隙气压力作用影响显著,对反映某些具体工程滑坡现象更加符合实际.%As the change of the pore air pressure during rainfall infiltration is an important factor to affect slope stability,a method for analyzing slope stability under the consideration of the effect from the pore air pressure is proposed herein for analyzing the effect concerned.In this method,the distributions of the pore water pressure and the pore air pressure as well as the saturation degree of slope are calculated at first based the relevant theory and method of water-air two phase flow,and then the load variation caused by pore air pressure during the rainfall infiltration is obtained.Moreover,combined with the theory of unsaturated soil shear strength and the residual thrust method,pore air pressure is introduced into the slope stability analysis.Thereafter,a simulative analysis on the slope stability is made under the consideration of the effect from the pore air pressure by taking Tanjiahe Landslide as the study case.The result shows that the surface layer of the slope tends to be saturated by rainfall and the change of the pore air pressure between the slope surface and the sliding zone is more sensitive,while the pore air pressure attenuates during its transmission along the sliding bed to the deep direction and the pore water pressure in the slope saturated zone is transmitted to the slope toe through the pore air,which forms a gradient of the pore air pressure along the direction of the slope toe and increases the downwards thrust of the sliding body.Under the same seepage condition,the consideration that the effect of the pore air pressure makes the safety coefficient on the same sliding plane decrease unfavorable for the analysis made on the slope stability.The effect of this method is significant for considering the pore air pressure effect when slope is critically instable and it is more practical for reflecting the landslide phenomena of some specific projects as well.