ISSN 2096-4498
CN 44-1745/U
Tunnel Construction ›› 2021, Vol. 41 ›› Issue (1): 37-43.DOI: 10.3973/j.issn.2096-4498.2021.01.004
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XI Zhendong, HU Linhao*, ZHANG Shuxiang, ZHANG Bo
Online:
Published:
Abstract: During the construction of largediameter shield tunnels in waterrich sandy pebble strata, the following difficulties are often encountered: collapsing tunnel faces, water gushing, rock falls, and jamming of screw cutters. Meanwhile, due to the high shield torque, high muck temperatures, and large volumes of slag, soil conditioning becomes essential. Accordingly, many laboratory experiments are conducted to explore the optimal mixing proportion of bentonite and foaming agent, and according to analysis, proportion and evaluation indices for soil conditioning are proposed. The following conclusions are drawn: (1) The viscosity of bentonite increases with increasing sodium bentonite ratios. (2) The foaming multiples and halflife period of the foam solution increases with increasing foaming agent concentration. (3) The fluidity of the conditioned soil significantly increases with increasing proportions of bentonite and foaming agent; the permeability of the conditioned soil decreases with increasing proportions of bentonite and increases with increasing foaming agent proportion. Finally, it is recommended that the bentonite viscosity should not be less than 35 s, bentonite volume should be 10%~12% of the soil volume, foaming multiple of the foaming agent should be less than 15, and volume of foam should be limited to approximately 20% of the soil volume. The soil conditioning effect is verified by actual soil sampling and excavation parameter analysis.
Key words: largediameter earth pressure balance (EPB) shield, soil conditioning, waterrich sandy pebble strata, laboratory experiments, bentonite, foaming agent
CLC Number:
U 455
XI Zhendong, HU Linhao, ZHANG Shuxiang, ZHANG Bo. Soil Conditioning for Largediameter Shield Boring in Waterrich Sandy Pebble Strata: a Case Study on a ShieldBored Section of Chengdu Metro[J]. Tunnel Construction, 2021, 41(1): 37-43.
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URL: http://www.suidaojs.com/EN/10.3973/j.issn.2096-4498.2021.01.004
http://www.suidaojs.com/EN/Y2021/V41/I1/37
Research on Soil Conditioning of WaterRich Sandy Gravel Strata Based on Shield Tunneling Effect