Study of the characteristics and application of new filling material for buried Karst caves

Abstract

Abstract During the construction of the subway, the treatment of the abandoned soil would bring a series of problems, including higher transportation costs, environmental pollution, material waste, and so on. Therefore, a new type of fill material for buried Karst caves was collocated using the abandoned soil in this paper. Firstly, in-situ soil, volcanic ash silicate cement (P·P 42.5), nanoscale silica, sodium silicate, polycarboxylate superplasticizer, and water was the raw materials and systematic orthogonal experiments with three influencing factors at four levels designed. Concurrently, the compressive strength of samples sourced using unconfined compressive strength tests, and the experimental data (curing time is 28 days) met the demand for actual engineering reinforcement. Subsequently, the analysis of range of experimental data was conducted, and the optimal mixing proportion ( In-situ soil：volcanic ash silicate cement (P·P 42.5)：Nanoscale silica：Sodium silicate：polycarboxylate superplasticizer：water) is equal to 2000:500:12.5:30:7.5:444. Finally, the SEM (scanning electron microscope) analysis of in-situ samples shows the microstructure of the new kind of fill material was the filamentous and sheet-like connection, and the application of buried Karst cave filling in Shenzhen Metro Line 3 Project proved the validity of the new kind of fill material. All the above conclusions provided significant support and data reference for the grouting treatment of buried Karst caves.