南京长江第四大桥南锚碇基础为支护开挖深埋扩大基础，采用井筒式地下连续墙支护体系，平面形状为“∞”形，长82 m，宽59 m，由两个外径59 m的非完整圆和一道隔墙组成，壁厚为1.5 m。隔墙为前后两个非完整圆的支撑结构，抬高隔墙底标高，使得基础底板为一整体结构；填心混凝土施工完成后凿除部分墙体，既解决了开挖状态下的支护问题，又使基础顶板有效连为整体。采用“∞”形比圆形或矩形结构形式布置平面面积小，截面惯性矩大，且半径较小，墙体环向应力小，安全性及可实施性高，有效降低了工程投入，提高了结构的安全性。

This paper introduces the design of deep buried spread foundation with braced excavation system for the South Anchorage of the Fourth Nanjing Yangtze River Bridge. The braced excavation system applied can be described as shaft diaphragm wall foundation with the plane section of "∞" shape including two 1.5 m-thick 59 m-diameter semi-circle and one 1.5 thick separation wall, and total length of 82 m and width of 59 m. However the separation wall provides the support for two semi-circles, it will not separate the bottom plate of foundation as the bottom elevation of wall is constructed in a higher level; and the separation wall is to be removed slightly in order to construct the top plate as a whole. The form of "∞" shape is superior than that of circle and rectangular by smaller plane area, larger cross sectional moment of inertia, smaller radius, smaller circumferential stress of diaphragm wall and better safety and feasibility, which great reduces the total costs and improved the construction safety.

崔冰（1966—），男，河北枣强市人，教授级高级工程师，研究方向为桥梁设计