Optimum Design Of Prestressed Anchor Cable For Toppling Rock Slope

The slope of the right bank of the Lancang River Huangdeng Hydropower Station is located in the Lanping Bai and Pumi Autonomous County,Nujiang Dai Autonomous Prefecture,Yunnan Province.The deformation and failure form of the rock slope is toppling creep damage.In this paper,the physical model test,numerical simulation,orthogonal test,and other methods are used to analyze the deformation and stress characteristics of the toppling rock slope.The design parameters of prestressed anchor cable support were optimized and the optimal combination of parameters was obtained.The main results are as follows:Taking the typical toppling creep rock slope of the right bank cable machine of Huangdeng Hydropower Station as an example,combining the regional geological background,the exploration data,and analyzing the engineering geological conditions of the dam area,the physical and mechanical parameters of the rock mass were comprehensively determined.The analysis showed that the instability mode of the shallow slope is toppling and collapsing,and that of the deep slope is dumping-braking-slipping.Based on the cross-section 0 + 030 of the right bank cable machine slope dam,a generalized engineering geological model was obtained.Based on similar principle indoor graded loading physical model tests were carried out to obtain the distribution of the displacement field and the stress field in the slope under different loading conditions,that is,the displacement was positively related to the loading weight,the displacement along the slope from top to bottom gradually increase,with a maximum displacement of 12.170 mm.The horizontal compressive stress in the toppling creep rock mass decreased first and then increased along the fractured surface from top to bottom.The vertical compressive stress in the slope gradually increased from top to bottom,at the same height,first increased and then decreased in the horizontal direction.The two-dimensional finite element method was used to compare and analyze the test results of the physical model with the results of the numerical simulation without anchoring.The results showed that the two-dimensional slope model established is reasonable.A comparative analysis of the slope deformation and stress characteristics before and after anchoring showed that Mises stress of the slope body after anchoring reduced,the range of the plastic zone increased thereby reduced PEEQ,the maximumhorizontal displacement of the slope after anchoring reduced from 12.7mm to 5.3mm,and the phenomenon of tensile stress concentration on the slope is significantly reduced after anchoring.It is proved it is remarkable to use a prestressed anchor cable structure to support the toppling rock slopes.Using the horizontal displacement at the slope step as an evaluation index,the orthogonal design was used to optimize the design parameters of the anchor cable support structure.According to the range analysis,the influence order is the inclination of the anchor cable,the length of the anchor cable,and the magnitude of the prestress.The analysis of variance shows that the influence of the length of the anchor cable and the inclination of the anchor cable on the horizontal displacement of the toppling rock slope is extremely significant,while the effect of the anchor cable prestress is not significant.The results show that the optimal parameter combination can effectively reduce the horizontal displacement at the first to seventh steps,and the number of yield points at the fracture surface,and the range of the plastic zone of the trailing edge of the slope,which indicates that the optimization effect is significant.There are 98 figures,19 tables and 155 reference in this paper.