The study of fracture phenomena and translational tipping deformation in RM hard rock slopes

Wei Sun Yiwei Gao Chengao Lu Xuhua Ren ^*

• Hohai University, Nanjing, China

Tipping is characterized by the continuous rotation of blocks. To date, research has primarily focused on the discontinuous mechanical behaviors such as boundary dislocation during the rotation process of blocks. Based on the load balance conditions under the self-weight of the blocks, criteria for the occurrence of tipping have been established. These studies are mainly suitable for the macroscopic assessment of the tipping potential in steeply inclined layered structural slopes with reverse slopes.The tipping deformations of high and steep hard rock slopes and steeply inclined layered slopes reveal that, under high in-situ stress conditions, the formation process of high and steep slopes involves a strong release of horizontal stress. Depending on the specific geological conditions of the slope, additional loads may be provided to the block rotation deformation through traction or push mechanisms, causing slopes that do not originally meet the tipping conditions to exhibit tipping deformations. For hard rock tipping, the load level must be sufficient to cause the rock blocks to fracture and overcome the constraints of their own strength on rotational deformation, allowing the blocks to continue rotating. Thus, hard rock tipping involves two types of mechanical behaviors: macroscopic discontinuous deformation of the block boundaries and the continuous-discontinuous mesoscopic fracturing of the blocks themselves. The RM section of the Lancang River, located in the southeast of the Qinghai-Tibet Plateau, is subjected to intense compression from neotectonic movements. The deep incision of water flow forms high and steep bank slopes, accompanied by significant stress redistribution. The middle steep slopes and large structural planes undergo notable shear deformation, pushing the lower pinch-out end rock masses and causing rock block fractures.When secondary reverse steeply inclined joints develop at the pinch-out end, a push-type tipping deformation occurs. This is the result of the combined effects of stress redistribution and rock mass structure under high in-situ stress conditions in hard rock high and steep slopes.