干湿循环下花岗岩残积土裂隙演化及边坡稳定性

Crack development and slope stability of qranite residual soil under dry-wet cycles

为研究干湿循环作用下花岗岩残积土边坡的稳定性,开展两种干湿幅度5次循环次数的边坡模型试验.拍摄裂缝图像获得裂隙演化规律,得出裂隙面积与干湿循环次数近似成正比;结合坡内土体直剪试验结果,提出干湿循环下黏聚力和裂隙度的关系式,推导裂隙深度计算公式.以此数值建模分析裂隙影响下的残积土边坡稳定性,结果表明:随着干湿循环次数和幅度的增大,裂隙度增加,裂隙深度增大,渗透性增强,土体强度降低,导致坡体饱和区扩展;滑裂面上滑点位于张裂隙处;3次干湿循环后边坡安全系数降幅最大,之后趋于稳定.研究认为干湿循环作用下裂隙的扩展加快雨水浸润,缩短了边坡失稳时间,为残积土边坡的及时合理处治提供理论指导.

For the purpose of studying the stability of granite residual soil(GRS)slope subjected to dry-wet cycles(DWC),five cycle times are carried out on the slope model with two amplitudes.The development of cracks is recorded,and the relationship in which the crack area was proportional approximately to these DWC times is concluded.Furthermore,the relationship between the cohesion and crack ratio under DWC is proposed,and direct shear tests and calculation formula of the crack depth is deduced.Numerical simulations are carried out,so that the stability of residual soil slope in consideration of the influence of cracks can be analyzed.Results show that the width and the depth of cracks increase as times and amplitudes of DWC increase.Meanwhile,the soil permeability increases and the strength decreases,leading to(1)the acceleration of the saturated zone extension and(2)the fact that the slip point on the failure surface is located at the tension crack.After three dry-wet cycles,the slope-safety factor declines most steeply and then tends to become stable gradually.In conclusion,the propagation of cracks under DWC accelerates the infiltration of the rainwater into the slope and shortens the time of the slope failure,providing a theoretical instruction for timely and reasonable treatments of these GRS slopes.