Calculation Method of Long-Term Settlement and Optimal Tunnel Depth of Shield Tunnel in Under-Consolidated Soft Soil Under Static and Dynamic Load

doi:10.3973/j.issn.2096-4498.2024.09.012

Tunnel Construction ›› 2024, Vol. 44 ›› Issue (9): 1829-1840.DOI: 10.3973/j.issn.2096-4498.2024.09.012

Calculation Method of Long-Term Settlement and Optimal Tunnel Depth of Shield Tunnel in Under-Consolidated Soft Soil Under Static and Dynamic Load

ZHANG Wengang^{1, 2, 3}, TANG Xuecheng¹, LIU Hanlong^{1, 2, 3}, YANG Wenyu^{1, *}, LIU Zhicheng⁴, WANG Luqi¹, LI Hongrui¹

（1. School of Civil Engineering, Chongqing University, Chongqing 400045, China; 2. Key Laboratory of New Technology for Construction of Cities in Mountain Area, Chongqing University, Chongqing 400045, China; 3. National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas, Chongqing University, Chongqing 400045, China; 4. Guangzhou Metro Group Co., Ltd., Guangzhou 510220, Guangdong, China)

Online:2024-09-20 Published:2024-10-12

Abstract

Abstract: In order to study the long-term settlement and its variation law for shield tunnel under combined action of surface load, train load, and consolidation settlement of under-consolidated soft soil, a finite element model is established by PLAXIS to calculate the long-term settlement of shield tunnel under external action based on the Nansha-Zhuhai (Zhongshan) intercity line in Guangzhou. The effect of each influencing factor on long-term settlement is analyzed by single factor sensitivity analysis and nonlinear fitting method, and five key influencing factors are identified. The calculation method of long-term settlement and optimal tunnel depth is proposed. The results show that: (1) The over-consolidation ratio and tunnel depth have the greatest influence on long-term settlement, followed by the load magnitude, load width, and train load, while the effects of load distance, train speed, and permeability coefficient on long-term settlement can be neglected. (2) In order to solve the long-term settlement of shield tunnel, a calculation method is proposed for shield tunnel in under-consolidated soft soil under static and dynamic load, and the calculation result is in good agreement with the simulation result. (3) By taking the control value of 20 mm for shield tunnel deformation specified in the national standard as the tunnel settlement control value, and substituting it into the equation for long-term settlement, the equation for optimal tunnel depth is obtained. The under-consolidation characteristics of soft soil have the greatest influence on the optimal tunnel depth. In order to effectively control the long-term settlement, it is suggested that the entire tunnel should be constructed in soil with better quality. If a tunnel has to be constructed in mud and mucky soil strata, foundation treatment should be carried out, and drainage consolidation should be performed to improve the consolidation degree of soil.

Key words: under-consolidated soft soil, shield tunnel, long-term settlement, nonlinear fitting, surface load, train load

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Calculation Method of Long-Term Settlement and Optimal Tunnel Depth of Shield Tunnel in Under-Consolidated Soft Soil Under Static and Dynamic Load

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