临空条件对边坡稳定性的影响

Influence of Free Face Condition on Slope Stability

公路作为一种纵向延伸的线性工程,穿越不同的地形、地貌单元,所涉及的边坡具有种类广、数量多的特征。在充分调研的基础上,建立了各种常见的公路边坡形式的数值模型,对其稳定性和可能的破坏模式进行研究。研究发现:(1)坡脚处剪应变随坡高增加而增加,边坡稳定系数随坡高增加呈幂函数减小,坡高小于20 m时稳定系数减小明显,大于20 m后其变化趋势变缓;(2)随着坡度的增加,坡脚剪应变增加更为明显,边坡的稳定系数随坡度增大同样呈幂函数减小,坡度小于40°时变化较大,大于40°后变化趋缓。另外对比来看,稳定性系数对边坡坡度的变化要更加敏感一些;(3)若坡体内部存在外倾的结构面,边坡破坏时将在覆盖层内拉张产生圆弧形滑面,并沿接触面产生复合式滑动,此时边坡的稳定性将主要受接触面的性质所控制,如结构面倾角、强度参数等。(4)阶梯形边坡比一坡到顶的直线形边坡稳定性好,但大平台阶梯形边坡各级边坡自身的稳定性不容忽视。微凹形、直线形、微凸形3种坡面形态下边坡稳定性依次变差,工程中建议合理利用凹形边坡,而对于凸形边坡应该慎重利用。

As a lengthwise extended linear construction passing different terrains and landforms,highway involves several types of slopes. Based on sufficient investigation,the numerical models of common highway slopes are established to analyze the stability and possible failure modes of the slopes. The result shows that（1） With the increasing of the slope height,shear stain in the slope foot increased and the Fsdecreased in a power function,it decreased significantly when H 20 m and it changed gradually when H 20 m.（2） With the increase of the slope angle,the shear stain in the slope foot increased more obvious and the Fsalso decreased in a power function,it decreased significantly when β 40°and it changed gradually when β 40°.By contrast,Fsis more sensitive to the change of β.（3） If there is an extroverted structural plane inside the slope,the most likely failure mode is stretching out in the covering layer to produce a circular arc slip surface and then occurring composite sliding along the contact surface,the stability of the slope will be controlled mainly by the property of the contact surface,such as dip angle,strength parameters,etc.（4） The stepshaped slope has a better stability than a linear slope,while the stability of slopes at all levels should not be neglected. The stability of concave shaped slope is better than that of linear slope relatively,and the stability of convex shaped slope is the worst,rational use of concave shaped slope and carefully use of convex slope is suggested.