Research on shear characteristics and timeliness of soft rock slope of dump under freezing-thawing cycle

In order to solve problem of stability of waste dump under the freeze-thaw cycle,based on the influence of freeze-thaw cycle on the waste dump of open-pit mine in Inner Mongolia,the phenomenon of rock collapse at the top of the slope and single step landslide on the local steps of dump slope was studied.Grain grading and sample preparation tests were carried out for the materials. Freeze-thaw cycle and shear failure tests were carried out for the materials. The relationship between shear strength,cohesion and internal friction angle of the materials and freeze-thaw cycle times and moisture content was quantified. The exponential expression of the relationship between shear strength and freeze-thaw cycle times and moisture content and the aging stability of the frozen thaw cycle slope were put forward.The calculation formula reveals the regularity of time effect change of loose soft rock slope in dump under freeze-thaw cycle. The results show that under different normal stress,the shear strength of bulk soft rock material changes with the number of freeze-thaw cycles in a similar pattern,and the cohesion and internal friction angle decrease exponentially with the increase of the number of freeze-thaw cycles; the higher the moisture content,the greater the weakening range of cohesion and internal friction angle,and the weakening range ratio of cohesion When the internal friction angle is large,they tend to be stable after six freeze-thaw cycles; when the loose soft rock slope in the waste dump is affected by freeze-thaw,it is time-dependent; when the loose soft rock is accumulated,the new slope will be weakened rapidly after the initial freeze-thaw,resulting in a sharp decline in the stability coefficient after the accumulation. With the extension of the freeze-thaw cycles,the stability will be stable The decline rate of coefficient decreases gradually,and the slope tends to be stable after 6-7 years.