Research on Strata Reinforcement and Resource Utilization Technology of Shield-Discarded Soil Based on New Cementitious Materials

Aiming at the problems of environmental pollution and land occupation caused by solid waste and according to the concept of transforming waste into treasure and green development, a new type of cementitious material suitable for consolidation of overflow tailings and soft soil was developed that has the advantages of being nontoxic and harmless and having fast hydration and consolidation speeds, high consolidation strength, and good stability. Based on the engineering application of new cementitious material (NCM) in the reinforcement of coastal soft soil strata and core drilling test results, it was found that high strength and low cost could be achieved when the NCM was used in the processes of a triaxial mixing pile. Under the optimal situation on site, the compressive strength and cost of the mixing pile with NCM are 1.5 times higher and 62.5 % lower than those of using ordinary portland cement (OPC), respectively. Furthermore, in terms of other reinforcement technologies, such as the metro jet system (MJS) and deep cement mixing method (DCM), the applicability and economy are significant, which is better than that of OPC. Equipment for simultaneous grout preparation was developed and optimized. The industrialization test of synchronous grouting with shield-discarded soil as aggregate was carried out, which realized the dual goals of economy and environmental protection by turning waste into treasure. The performance of synchronous grout prepared on a construction site is much higher than the technical indicators of the specification requirements. The monitoring results for the horizontal and vertical attitude of the segments meet the technical requirements. The control effect of the new synchronous grouting material on ground surface deformation and resistance to water leakage is obviously better than that of the conventional cement-based grout material.