考虑侧壁阻力的顺层边坡失稳机制及稳定性评价∗

侧壁阻力作用下，顺层边坡主滑方向将偏离岩层倾向，其变形及失稳机制具有典型特征。以四川盆地马边河流域某顺层边坡为例，基于其工程地质条件，总结顺层边坡不同变形区域的特征，结合失稳边界条件研究了考虑侧壁阻力的顺层边坡失稳演化机制；最后，对比主滑方向偏离岩层倾向与否的受力差异，分析考虑侧壁阻力的顺层边坡三维稳定性，并研究了各影响因素的作用效应。结果表明：（1）考虑侧壁阻力的顺层边坡变形可划为失稳滑走区、滑坡区和稳定区，滑坡区包含滑动区和蠕滑变形区，滑动区岩体滑动后解体风化为碎、块石土，蠕滑变形区受侧壁阻力影响岩体仅变形拉裂；（2）顺层边坡经岩体劣化和前缘临空后，总体呈下部滑动、中部蠕滑拉裂的顺层临空-后退式破坏；滑动区边界受前缘及侧壁临空控制，长度与侧壁冲沟下切段长度相近；蠕滑变形区部分侧壁由节理面转化为挤压带，侧壁阻力增大，稳定性高于临界失稳状态；受侧壁阻力及滑体厚度控制，蠕滑变形区与稳定区界限处因滑体厚度削薄而拉裂；（3）建立了考虑侧壁阻力的顺层边坡稳定性系数计算式，以及岩层倾角δ、滑面倾角α、主滑方向偏离岩层倾向夹角β 三角度间的换算关系式，侧壁摩擦系数和β 越大，侧壁阻力越利于顺层边坡稳定。

Failure Mechanism and Stability Evaluation of Bedding Slopes Considering Lateral Wall Resistance

Under the influence of lateral wall resistance, the main sliding direction of a bedding slopedeviates from the direction of rock layer orientation, exhibiting typical features in its deformation andfailure mechanisms. Taking a bedding slope in the Mabian River of Sichuan basin as a case study, wesummarized the slope deformation characteristics of different areas based on its engineering geologicalconditions. Then, we analyzed the evolution mechanism of bedding slope failure considering lateralwall resistance and the failure boundary conditions. Finally, the three-dimensional stability of beddingslope under the effect of lateral wall resistance was analyzed, and the effects of various influencing factors were studied by comparing the stress differences experienced when the main sliding direction devi-ated from or aligned with the rock layer orientation. The results showed that: (1) Considering lateralwall resistance, the deformation of a bedding slope could be categorized into an unstable sliding zone,landslide zone, and stable zone. The landslide zone included a sliding zone and a creep-slippage zone.After sliding, the rock mass in the sliding zone disintegrated and weathered into broken and block soil,and the creep-slippage zone experienced only deformation and cracking under the effect of lateral wallresistance. (2) After rock mass deterioration and the appearance of free surface at its forefront, the bed-ding slope presented a bedding-plane free-fall-backward failure with sliding in the lower part and creepcrackingin the middle part. The boundary of the sliding zone was controlled by the leading edge andthe free face of the lateral wall, with its sliding distance being similar to that of the undercut segmentof gully sidewall. The lateral wall was transformed from a joint face into a compression zone in parts ofthe creep-slippage zone, increasing the lateral wall resistance and resulting in a higher stability than thecritical instability state. The boundary between the creep-slippage zone and the stable zone wascracked due to the thinning of the sliding mass thickness and the lateral wall resistance. (3) A formulafor the stability coefficient of the bedding slope considering side-wall resistance was developed, aswell as a conversion equation between the rock layer dip angle, slip surface dip angle α, and the angle β between the main slip direction and the rock layer orientation. The results showed that the larger the β and the friction coefficient of lateral wall, the greater the contribution of the resistance to the stabilityof bedding slopes.