Slope structure and stress development rule under mining mode of land saving and ecological detraction

In order to realize the safety application of the land-reducing and ecological detraction mining technology in open pit mines,the slope structure,rock stress state and slope stability during the mining process are analyzed. The coupling law between the mining program,parameters,the stress distribution and stability of the slope is revealed. In this paper,two kinds of land-reducing and ecological detraction mining technology schemes suitable for expansion and new construction of open-pit mines are described by using the section method. The type of stress inside the slope is an- alyzed,the unbalanced stress differentiation model caused by deepening excavation or steep mining and the induced progressive failure model of the slope are established. Based on the development process of the open-pit mine end- slope in the eastern of Inner Mongolia,a three-dimensional model was established,and the simulation conditions were set as follows:the depth of the stope is from 0 m to 300 m,and the depth increases by 50 m each time;the end-slope angle was linear increased from 37° to 45°,and increases by 2° each time;the height of internal dumping is from 0 m to 300 m,and increases by 50 m each time. The variation law of the self-weight and horizontal stress during the deepe- ning excavation and steep mining process,and the variation law of the stability coefficient of end-slope during the deepening excavation and the internal dumping process are analyzed. According to the equipment production capacity of the mine and the amount of mining and stripping engineering,the engineering time required for deepening excava- tion and steep mining is calculated. The variation law of self-weight and horizontal stress with time length and the vari- ation law of time-dependent stability of end-slope are obtained through regression analysis. The results show that the self-weight and horizontal stress decrease by 1. 6 MPa and 5. 6 MPa respectively during the deepening excavation process,and the stability coefficient of the end-slope decreases from 2. 23 to 0. 83. During the steep mining process, the self-weight and horizontal stress are increased by 0. 5 MPa and 9. 4 MPa respectively. During the internal dumping process,the stability factor of end-slope increased from 0. 83 to 1. 87. Both the self-weight and the horizontal stress show a symmetrical structure with the centerline of the stope as the axis. In the stope range,the structure of self-weight stress is arched and the horizontal stress is “wedge-shaped”. With the increases of excavation depth or slope angle,the self-weight stress dome curvature and the horizontal stress wedge curvature decrease continuously. The peak value of self-weight and horizontal stress decreases with the increase of excavation depth as a quadratic function,and decreases linearly with the increase of excavation time length,which also increase with the increase of end-slope angle as quad- ratic function. The stability coefficient of the end-slope decreases with the increase of the excavation depth,and decrea- ses with the increase of time,while it increases exponentially with the change of the internal dump height and the time length.