Floor heave mechanism and stiff control technology by I-beam for deep mine roadway

Floor heave of upstand pulling type in deep roadway is one of the main geological disasters affecting the safe and efficient production in Jinchuan mine of China. To study the mechanism of non-uniform floor heave occurred in complex jointed rock mass (CJRM), the 610 m main ramp of Jinchuan No.2 mine is considered as the engineering background. Based on the limit equilibrium method and slip line field theory, the floor heave model of the roadway is constructed. It is found that the floor heave in the roadway consists of extrusion movement and shear misalignment. The section size, surrounding rock lithology and burial depth are the main factors affecting the depth of floor heave in the roadway. Distribution of joints and fissures in surrounding rock of a bare-rock roadway is investigated using a Leica P30 three-dimensional (3D) laser scanner. Numerical modelling of roadways in CJRM based on Monte-Carlo stochastic simulation in 3DEC software. Under the existing support condition, the floor and two sides in the roadway shows obvious non-uniform floor heave. The floor heave is divided into no floor heave, local small and local obvious floor heave based on its displacement amount. The control strategy to use discarded I-beams is proposed. The support effect is evaluated by considering the plastic zone of the surrounding rock and the arch formation coefficient K. The pressure relief zone and plasticity zone as well as the two sides of roadway can be effectively reduced by the original support. The range of pressure arch structure of the floor is increased and the self-stability of the surrounding rock is improved using the new support. The results of the study provide engineering guidance for the control of the floor heave in the deep roadway of Jinchuan mine, and provide a useful reference for the design of roadway support under similar conditions.