在河漫滩相下硬上软二元结构地层中施工地下连续墙时，阳角地层受到两次扰动，阳角单元槽段稳定性是需首先解决的问题。该文依托濒临长江的超深基坑群工程，通过Abaqus数值模拟软件建立了阳角槽段的三维有限元模型，利用有限元强度折减法计算了阳角槽壁的安全系数。结果表明:阳角槽壁的安全系数比一字型槽壁的安全系数低;在阳角成槽时，卸荷引发的槽壁坍塌易发生于砂层，尤其是厚砂层底部;深部砂层发生坍塌时，首选提高泥浆重度;浅部砂层发生坍塌时，首选提高泥浆液面。分析结果对于开发河漫滩相下硬上软二元结构地层中的地下空间有一定的参考意义。

During diaphragm-wall construction in soft-over-hard and binary-structured floodplain strata,the external corner area undergoes two disturbances and the stability of the external corner trench units must be addressed first. Leveraging the project of ultra-deep foundation pit groups on the Changjiang River,a 3D finite-element model of the external corner trench units is developed through Abaqus. The safety factor of the external corner wall is then calculated using the finite-element strength-reduction method.Results show that the safety factor of the external corner wall is lower than that of the straight-wall configuration. During trenching at the convex corner,unloading-induced collapses of the trench wall tend to occur within the sand layers,particularly at the base of thick sand strata. To mitigate collapses in deep sand layers,the mud weight should be increased as the primary measure. For collapses in shallow sand layers,raising the mud-liquid interface level is recommended. These findings provide valuable guidance for the design and construction of underground spaces within soft-over-hard and binary-structured floodplain strata.