Calculation and application of three-dimensional foundation bearing capacity for large-scale open caissons
LI Jiahang1, 2, GUO Mingwei1, 2*, LU Zheng1, 2, DONG Xuechao1, 2, ZHENG Qinggang3, JIANG Fan4,PENG Wei3, YIN Dongya5
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China; 3. China Railway Major Bridge Reconnaissance and Design Institute Co., Ltd., Wuhan, Hubei 430050, China; 4. China Railway Bridge and Tunnel Technology Co., Ltd., Nanjing, Jiangsu 210061, China; 5. Jiangsu Provincial Transportation Engineering Construction Bureau, Nanjing, Jiangsu 210004, China)
Abstract：The calculation formulas for foundation bearing capacity recommended by the current standards are typically derived based on the plane strain conditions of strip footings or obtained from small-scale load tests. However, there are still certain limitations in the calculation of foundation bearing capacity for super-large open caissons. Based on the spatial elastic stress state of a semi-infinite soil mass under a vertical circular load, a simplified three-dimensional bearing capacity formula is derived. For non-circular foundations, conversion is performed based on the equivalent area of the foundation base. For rectangular foundation types with different aspect ratios (), the finite element analysis method is used to reveal the variation law of the three-dimensional bearing capacity of the foundation. The calculation errors of the bearing capacity of rectangular foundations with different aspect ratios were clarified. The results show that, for a constant base area, the calculation error of the bearing capacity of the simplified formula increases with the increase of the aspect ratio of the rectangular foundation. When , the calculation error is less than 5%. When , the error is less than 16%. When , the error approaches or even exceeds 20%. The calculation results of the large caisson foundation project of Changtai Yangtze River Bridge show that the allowable bearing capacity of the silty clay layer at the bottom of the open caisson obtained by the simplified formula is 2.93 MPa, which is about 23.1% higher than the value calculated by the railway code. Moreover, field settlement monitoring of the open caisson indicates that the foundation is generally in the elastic deformation stage, which to some extent verifies the rationality of the results. This study clarifies the calculation errors of the three-dimensional bearing capacity formula for rectangular foundations with various aspect ratios. The findings enrich the theoretical calculation of bearing capacity for large-sized deep foundations, and provide an important reference for the design of similar large rectangular, rounded rectangular and rounded-end open-caisson engineering.
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2026, Vol. 45 
