Mechanical Characteristics of Superhigh-Water Content Material Concretion and Its Application in Longwall Backfilling

Superhigh-water content material (SCM) has been widely utilized for goaf backfilling, grouting, and fire prevention and extinguishing. In this paper, the engineering mechanical characteristics of superhigh-water content material concretion (SCMC) were studied for two types of backfilling technologies in longwall miningopen-type and pocket-type backfilling. The mechanical properties and responses of the SCMC were assessed under different cementation states, varying loading conditions and at different scales. The results indicate that: (1) the compressive and tensile strengths of SCMC specimens in different cementation states increase as the curing time increasesthe SCMC formed by a mixture of SCM and gangues has higher strength than that of pure SCM; (2) the SCMC is under different loading and confinement conditions when different backfilling technologies is applied; however the strength of SCMC increases with curing time and decreases with water volume percentage; and (3) large-size specimens of pure SCMC enter into an accelerated creep state at a leveled load of 1.4 MPa. The effects of SCM backfilling on subsidence control has been verified by field applications. The results presented in this paper can provide data support for the optimization of backfill mining technology using SCM, as well as for the design of hydraulic supports parameters at longwall faces.