Numerical studies of floor heave mechanism and the effectiveness of grouting reinforcement of roadway in soft rock containing the mine water

Abstract

A floor heave is a serious failure phenomenon in mining roadways, especially in soft rock containing the mine water. Considering the influences of moisture content on rock properties, a case study of the floor heave mechanism and grouting control technology was performed in this paper. The results of laboratory tests showed that with the increase of moisture content, the compressive strength and friction angle of mudstone linearly decreased, while the deformation modulus and cohesion tended to a negative exponential decrease approximately. A numerical simulation was used to study the stress and strain distributions of the surrounding rock. It was found that significant floor heave was caused plastic deformation of mudstone under high moisture content. In the case of large floor heave a “core” of vertical expansion is formed in the floor strata. This area of the surrounding rocks is mainly involved in the development of floor heave. Grouting reinforcement was proposed to control the floor heave. Five grouting schemes with different depth of reinforcement were studied. The numerical simulation demonstrated that after grouting reinforcement, plastic strain in the floor strata was reduced effectively. The minimum required grouting depth is determined by the allowable floor heave and moisture content. Ideally, the floor heaves could be reduced when the grouting depth is greater than the area where the “core” of vertical expansion appears.