（中国铁建投资公司， 北京 100855)

［摘要］在泥水平衡盾构施工过程中，如何确保施工安全并减少对周边环境的影响受到国内外学者的广泛关注，地层土体稳定性问题显得尤为重要，但对于砂质地层开挖面稳定性的失稳机理及其稳定性分析尚处于经验阶段。利用大尺寸模型试验，研究了不同水头高度（无水、0.9m和1.1m）下两种地层中开挖面的主动破坏的发展模式和受力情况，并通过FLAC 3D数值模拟对试验结果进行了验证。结果表明：在砂质地层泥水平衡盾构开挖面稳定性的问题中水头高度扮演了十分重要的角色，根据水头高度不同，可将开挖面主动破坏发展模式划分为无水模式、低水头模式和高水头模式；开挖面失稳时存在土拱效应，地表对开挖面主动破坏的响应存在滞后效应，在干砂地层中土拱效应甚至于会消除对地表的影响；同时在确定支护力时，应在静止土压力和静水压力的基础上考虑超孔隙水压力的影响。

［关键词］泥水平衡盾构； 砂质地层； 主动破坏； 失稳发展模式； 土拱效应

中图分类号： U45.6 文献标识码： A文章编号： 1002-848X(2015)S2-0075-06

作者简介：蒋向阳，高级工程师，Email：zhnyang110@163.com。

Analysis of effect of waterhead on stability of excavation face of slurry balanced shield

Jiang Xiangyang

(China Railway Construction Investment Group Co., Ltd., Beijing 100855, China)

Abstract: In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the influence on the environment have arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter modeling tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield was investigated, and the stability mechanics was proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated.

Keywords: slurry balanced shield； sand body； active failure； failure develop model； soil arching