Calculation methods of water-soil pressure for silty clay in Tianjin area

This research takes the Tianjin area as an example to analyze the development, distribution, and engineering characteristics of silty clay in the region. A correlation study of the shear indices within the five silty clay layers affected by the foundation pit was conducted. The univariate linear regression equations and statistical results of shear indices for each standard layer of silty clay were provided. In conjunction with multiple typical engineering cases in the Tianjin area, the safety and economic analyses of silty clay water-soil separate accounting and combined accounting methods were carried out. Additionally, through comparative analysis of measured deformations of foundation pits, the applicability of direct quick water-soil combined accounting and fixed quick water-soil separate accounting methods for silty clay in the Tianjin area was discussed. The research findings are as follows: (1) In the Tianjin area, the relationships between the shear indices c_q and c_cq, as well as φ_q and φ_cq of the silty clay layer are not significant, with the coefficient of determination R² ranging between 0.2 and 0.3. (2) Compared to the direct quick water-soil combined accounting method, the safety of the fixed quick water-soil separate accounting method for silty clay in the Tianjin area is relatively poor. (3) Regardless of whether it is a cantilever structure or a supported retaining structure, the calculated bending moments and shear forces of the retaining structures using the direct quick water-soil combined accounting method are generally smaller than those using the water-soil separate accounting method, resulting in better economic efficiency. (4) Analysis of measured deformations indicates that the on-site measured values of deep horizontal displacement and surrounding surface settlement of the retaining structures for various projects are more closely aligned with the results calculated using the direct quick combined accounting method than with the fixed quick water-soil separate accounting method.