Rock and Soil Mechanics ›› 2020, Vol. 41 ›› Issue (7): 2283-2292.doi: 10.16285/j.rsm.2019.6620

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A theoretical study of porosity characteristics on the excavation face of slurry shield in sand stratum

MAO Jia-hua1, YUAN Da-jun1, YANG Jiang-xiao2, ZHANG Bing3   

  1. 1. Key Laboratory of Urban Underground Engineering of the Education Ministry, Beijing Jiaotong University, Beijing, 100044, China 2. Shantou Suai Channel Construction Investment Development Co. Ltd., Shantou, Guangdong 515071, China 3. Shield Machine and Boring Technology, China Railway Tunnel Group Co., Ltd., Zhengzhou, Henan 450001, China
  • Online:2020-07-10 Published:2020-12-22
  • About author:MAO Jia-hua, male, born in 1990, PhD candidate, mainly engaged in research on the safety of shield tunneling.
  • Supported by:
    the Fundamental Research Funds for the Central Universities (2018YJS105), the Joint Funds of the National Natural Science Foundation of China (C19A1500010) and the National Natural Science Foundation of China (51678037).

Abstract: To maintain the stability of excavation face in slurry shield, a filter cake must be timely formed during the excavation work. With the filter cake, the slurry pressure can counteract the earth pressure and water pressure in the excavation stratum. In this study, a mathematical model of slurry penetration under constant pressure in sand stratum is established by considering the filtration effect. By means of this model, the influence of penetration time, slurry concentration, slurry pressure and initial stratum porosity on soil porosity and filter cake formation is analyzed. Combining the periodic disturbance of cutting-tools, the variation of soil porosity on the excavation face caused by multiple slurry penetration is summarized. Finally, the supporting mechanism of the excavation face is discussed during the shield tunneling based on the design of cutting wheel and tunneling parameters. The study results show that the slurry penetration behaviour is mainly affected by the characteristics of slurry stratum without disturbance of cutting-tools. In contrast, with the periodic disturbance of cutting-tools, the decreasing cycle of cutting will increase the difficulty of filter cake formation under the same cutting depth. In addition, the filter cake formation and the stability of excavation face can be significantly improved if the number of cutting-tools on same cutting track is reduced and the advance speed of shield and rotate speed of cutting wheel are decreased appropriately.

Key words: slurry shield, porosity characteristics, theoretical analysis, excavation face, filter cake, sand stratum