Abstract
In the process of open-pit excavation and stacking of dump along the side wall, the rock mass inside the composite slope undergoes complicated loading and unloading effect, which are manifested as triaxial stress → horizontal unloading → axial loading. In this study, a corresponding mechanical model of crack propagation in composite slope under loading and unloading effects was established. The stress-strain curves and deformation characteristics of rock under different stress paths were studied. A series of different tests under unloading pressure condition were carried out to study the behavior of the rock fracture under different confining pressure paths. The results showed that under the same initial stress conditions, the deviator stress required for rock unloading failure was less than that of the conventional triaxial compression. The axial deformation of rock samples was gradually increased with the increase of unloading, and the unloading easily led to rock failure. By analyzing the crack propagation mechanism under loading and unloading stress field, the analytic relation of the limit height of the composite slope with the crack morphology as the variation was determined when crack propagation occurred near the slope surface. This study provides a technical note on local damage and cracks propagation of a fractured rock mass under the loading-unloading effects in high composite slope.
Highlights
Rock mass fracture damage caused by unloading excavation has always been a topic of high consideration in the rock mechanics [1, 2]. e rock in the crust is compressed under the action of gravity and tectonic force of the overlying rock mass
As open pit gets increasingly deeper, it becomes more critical to understand in detail the stress distribution of high-steep composite slopes. e factors affecting the deformation and stability of the composite slope are the stress concentration caused by the unloading effect of the slope excavation and the loading effect on the slope by the external dump
E analytic relation of limit height H + ΔH of a composite slope with other known parameters is built up. It shows that if these parameters are given, the corresponding limit height H + ΔH of composite slope can be obtained when the crack propagation occurs near the slope surface under the unloading stress field
Summary
Rock mass fracture damage caused by unloading excavation has always been a topic of high consideration in the rock mechanics [1, 2]. e rock in the crust is compressed under the action of gravity and tectonic force of the overlying rock mass. E factors affecting the deformation and stability of the composite slope are the stress concentration caused by the unloading effect of the slope excavation and the loading effect on the slope by the external dump. Herrero [26] evaluated the impact of premining stress and excavation depth on the stability of jointed rock mass and pointed out the high-stress amplitude and stress redistribution caused by excavation sequence can promote rock damage and fracture propagation, leading to slope instability. E main objectives to achieve this goal include numerical simulation of stress distribution inside composite slopes, triaxial compression test of rock under different stress paths, fracture mechanism of crack under loadingunloading conditions, and establishment of a discriminant of the ultimate height for the composite slope E main purpose of this research is to quantify the effect of composite slope height and stress distribution on slope stability. is is done by studying the expansion process of the internal cracks in slopes, which can gradually reduce the strength of brittle rock masses and contribute to slope failure. e main objectives to achieve this goal include numerical simulation of stress distribution inside composite slopes, triaxial compression test of rock under different stress paths, fracture mechanism of crack under loadingunloading conditions, and establishment of a discriminant of the ultimate height for the composite slope
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