Abstract
Great practical significance and engineering application value can be achieved when the large amount of discharged soil produced by EPB shield tunnels is recycled and comprehensively utilized. As one of the key processes of shield construction, synchronous grouting needs a large amount of bentonite, cement, fly ash, sand, and other materials. The research on the reuse of shield muck as synchronous grouting material is carried out based on Zhengzhou subway project. The physical properties and phase of the discharged soil from EPB shield tunnels are studied by using laboratory tests and XRD. The statistics show that the shield muck meets the performance requirements of bentonite and fine sand in synchronous grouting materials. The optimal grout ratio of the reused muck is obtained based on the optimization idea of multiobjective programming by MATLAB. Considering the combined effect of seepage field, stress field, and the timeliness of the grout, the influences of grouting pressure and the filling rate of synchronous grouting on surface settlement, plastic zone of strata, and segment deformation are analyzed by using finite difference method. The results prove that the surface settlement and segment deformation can be better controlled when the grouting pressure is at 0.18 MPa and the grouting rate is at 120%–150%.
Highlights
EPB shield method has become the most widely used construction method in urban subway construction in China
A large amount of muck is generated during shield construction. e shield muck occupies a large amount of land, reduces soil quality, and affects air and water quality and has certain security risks
Zha et al [1] studied a formula for converting wastewater-based drilling fluid into environmentally friendly soil. e treatment process can achieve harmless treatment and effective utilization of drilling waste. rough data analysis of the unconfined compressive strength, triaxial compressive strength, indirect tensile strength, humidity sensitivity, and seismic modulus, Shon et al [2] conclude that it is feasible to use modified drilling waste as a basic material for road construction
Summary
Zhong et al [7] studied the reuse of excavated silty fine sand in shield synchronous grouting. He. Advances in Civil Engineering et al [8] used shield muck sand (modulus at 1.88) from Shuangdun Station to Wangjiadun Center Station of Wuhan Metro Line 3 as fine aggregate to prepare environmentally friendly single-liquid synchronous grouting material with high performance through optimizing experimental mix proportion. In view of this, based on the construction example of a section crossing silty clay stratum and clayey silt stratum with sandy silt in Zhengzhou Metro, this paper discusses the feasibility about the reuse of shield muck, and the best synchronous grouting proportion with the reused shield muck is obtained. Reinforced concrete segments are used as tunnel lining. e segment has an outer diameter of 6.2 m, a thickness of 0.35 m, and a width of 1.5 m. e theoretical muck output per ring is 49.4 m . e theoretical grouting volume per ring is 4.1 m , and the filling factor is 1.5–2.0
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