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| Soil stress path in the whole process of excavation and hoisting of working shaft in silty clay |
| Wang Dong1, Zhang Zhongkun2*, Liu Yan3, Zhang Shuming3, Hu Weidong4, Xu Jing1, Li Junyao5, Lü Changhuai6, Yang Fan7
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1. Jinan City Construction Group Co., Ltd., Jinan 250014, Shandong, China;
2. Jinan Construction Group Co., Ltd., Jinan 250014, Shandong, China;
3. School of Civil Engineering and Architecture, University of Jinan, Jinan 250022, Shandong, China;
4. China Railway Siyuan Survey and Design Group Co., Ltd., Wuhan 430063, Hubei, China;
5. Fourth Geological Group of Shandong Provincial Bureau of Geological Mineral Exploration and Development, Weifang 261021, Shandong, China;
6. China Electric Power Engineering Consulting Group Jiangxi Electric Power Design Institute Co., Ltd., Nanchang 330096, Jiangxi, China;
7. Jinan Dinghui Civil Engineering Technology Co., Ltd., Jinan 250002, Shandong, China |
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Abstract A study was conducted to reveal the stress evolution law of soil during foundation pit excavation and hoisting construction of a shield launching shaft and clarify the influence of principal stress axis rotation on soil mechanical properties, with the shield launching shaft of Jinan Yellow River Tunnel taken as the engineering background. By adopting the method combining theoretical analysis and stress path triaxial tests, the stress path boundary conditions of soil in different regions were determined, and the principal stress evolution and axis rotation characteristics of soil inside and outside the foundation pit were analyzed. The results showed that, compared with the traditional two-dimensional description only considering the mean compressive stress p and generalized shear stress q, the real stress state of soil under complex construction conditions could be more comprehensively reflected by the three-dimensional p-q-α stress path incorporating the major principal stress deflection angle α. During foundation pit excavation, the soil inside the foundation pit was dominated by vertical unloading, with decreased mean compressive stress and increased generalized shear stress. The major principal stress axis was rotated clockwise by nearly 90° in a stepwise pattern, and the rotation amplitude was attenuated with increasing distance from the foundation pit center; a significant spatial effect was observed. The soil outside the foundation pit was dominated by lateral unloading, with relatively stable generalized shear stress and a small rotation amplitude of the principal stress axis. The strength and stiffness deterioration effects induced by principal stress axis rotation inside the foundation pit should be emphatically considered in the analysis of foundation pit deformation and stability, while those outside the foundation pit could be largely ignored. Theoretical support for the design and safety management of deep foundation pit engineering was provided by the research results.
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Published: 12 October 2026
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