Abstract: According to the space position between the strata in the gob caving and filling slurry, super-high water material god filling cementing body is divided into four basic forms, namely pure super-high water material cementation body(class 1), super-high water materials and waste rock mixed materials in lower half and pure super-high water material in upper half (class 2), super-high water materials and waste rock mixed materials in upper half and pure super-high water materials in lower half (class 3), and the super-high water materials and waste rock overall mixed materials (class 4). The uniaxial compressive strength, tensile strength and shear strength mechanics parameters have been tested, and a mechanical model of “filling body-main roof” for backfilling mining has been established. Due to the mechanical model, the influence of the material parameters on limit span of the main roof has been analyzed. Study results show that, during the process of pressing, the features of stress-strain of the four types materials are nearly the same, and the class 4 material has the largest compressive strength, higher than class 1 by about 20%. The tensile strength and the shear strength of class 2, 3, 4 are commonly higher than class 1, and the maximum value can be increased by 40% and 50%. The analysis results of the influence of the material parameters on limit span of the main roof show that, the broken immediate roof mixed into the pure super-high water material and formed the materials of class 2, class 3 and class 4 can increase strength of the filling body, which are of benefit to the stability of the main roof for backfill mining.

Key words: super-high water filling material, backfill mining, engineering characteristics, experimental study, filling process