Sandy cobble soil has characteristics including a large internal friction angle, high permeability coefficient, and poor fluidity, which can result in serious tool wear, groundwater spilling, and transportation difficulties during shield construction. A subway in Luoyang is presented as an example case of shield construction. The optimal soil-water ratio of the bentonite slurry is 1:10 based on a sand and cobble stratum in the shield construction, and the optimal expansion duration is 18 h. Large-scale shear, slump degree, and permeability tests were conducted on a sodium-based bentonite slurry mixed with the sandy cobble soil. It was found that, with increasing slurry injection rate, the viscosity of the sandy cobble soil increased; the sand and stone separation phenomenon gradually vanished; the shear strength, internal friction angle, and permeability coefficient non-linearly decreased; and the slump degree non-linearly increased. The slurry injection rate necessary to meet the friction requirement of sandy cobble soil in the shield construction was 17%; the slurry injection rate necessary to meet the permeability requirement was 14%; and the slurry injection rate necessary to meet the fluidity requirement was 13% – 17%. The total thrust and cutter torque of the shield were found to be reduced by approximately 1/3, and the earth pressure balance maintained relatively well after the sandy cobble soil was mixed with the bentonite slurry, these points being remarkably significant to the high-speed advance of shield construction. This study is important with respect to solving issues concerning sandy cobble layers in subway shields.


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    Title :

    Sodium-based Bentonite Slurry Improvement to Sandy Cobble Soil During Shield Excavation


    Additional title:

    KSCE J Civ Eng


    Contributors:
    Dong, Wenping (author) / Wang, Chuang (author) / Dong, Jinyu (author) / Shi, Shang (author)

    Published in:

    Publication date :

    2024-11-01


    Size :

    8 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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