Soil Conditioning Classification Mechanism for Earth
Pressure Balance&nbsp;


	Shield Tunneling in SandyCobble
Strata

ZHONG Xiaochun; LIU Jianmei; ZHENG Xiang; ZHU Nengwen; CHEN Ran

doi:10.3973/j.issn.2096-4498.2022.02.008

Tunnel Construction >

2022 , Vol. 42 >Issue 2: 237 - 243

DOI: https://doi.org/10.3973/j.issn.2096-4498.2022.02.008

Soil Conditioning Classification Mechanism for Earth Pressure Balance

Shield Tunneling in SandyCobble Strata

ZHONG Xiaochun ,
LIU Jianmei ,
ZHENG Xiang ,
ZHU Nengwen ,
CHEN Ran

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(1. College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, Jiangsu, China; 2. Guangzhou Metro Design & Research Institute Co., Ltd., Guangzhou 510010, Guangdong, China)

Online published: 2022-03-03

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Abstract

The earth pressure balance shield encounters many problems, such as multiple machine malfunction and difficult soil conditioning, due to high pebble content, large particle size, and high strength in sandycobble strata. To address these problems, the sandy cobbles are first divided into fine and coarse particles with a grain size of less than 2 mm and greater than 2 mm, respectively. A twophase physical model is established with porosities formed by coarse gravel residue filling and wrapping by fine particles, and the critical fine particle content is deduced. The sandy cobbles are divided into three types, i.e., very difficult to condition, difficult to condition, and easy to condition, according to the critical content ratio and sandycobble strata conditioning laboratory testing. Furthermore, the corresponding conditioning measures are given as follows: single mixing mode of stable foam agent, compound blending mixing mode of foam+bentonite slurry, and compound blending mixing mode of foam+bentonite slurry+polymer. Finally, the recommended measures are applied in a shielded section of the Chengdu metro line 17. Moreover, the soil states and shield tunneling parameters before and after soil conditioning indicate the rationality of the sandycobble strata conditioning and the established classification mechanism.

Key words： earth pressure balance shield; sandy-cobble strata; workability; critical content of fine particle; soil conditioning

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ZHONG Xiaochun , LIU Jianmei , ZHENG Xiang , ZHU Nengwen , CHEN Ran .

Soil Conditioning Classification Mechanism for Earth Pressure Balance

Shield Tunneling in SandyCobble Strata

[J]. Tunnel Construction, 2022 , 42(2) : 237 -243 . DOI: 10.3973/j.issn.2096-4498.2022.02.008

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