考虑地震力方向的倾倒式危岩可靠度分析

Reliability Analysis of Perilous Toppling Rock Considering Seismic Force Directions

侧向卸荷作用导致高陡边坡发育大量危岩体,危岩体在降雨、地震作用下易发生失稳破坏,判断其失稳的概率对危岩防治具有重要意义.该文以倾倒式危岩体为例,建立了考虑地震力作用方向下最危险方向的物理力学模型,利用函数极值理论建立了最危险地震力作用方向的表达式,结合可靠度理论建立了倾倒式危岩体可靠度指标、失稳概率表达式及判断标准.通过对重庆南川金佛山危岩体案例的分析表明:工况1的最危险地震力作用方向与水平方向的偏转角θ在5°范围内,工况2的最危险地震力作用方向与水平方向的偏转角θ在10°左右;危岩体最危险作用方向不是一个固定角,其值与危岩体形态、裂隙水作用力大小、岩腔深度等有关.当主控结构面裂隙长度较小时,最危险地震力作用方向与水平夹角很小,随主控结构面裂隙长度增大,最危险地震力作用方向与水平夹角显著增大;危岩体失稳概率随主控结构面裂隙长度增加而增大,工况2较工况1增大幅度更明显.该研究成果对危岩的防灾减灾具有重要意义.

Lateral unloading leads to development of many perilous rock masses on high and steep slopes.It is significant to judge the probability of instability under the action of rainfall and earthquake.For the perilous toppling rock,the physical and mechanical model with the most dangerous seismic force directions was established.Based on the extreme value theory for functions,the expression of the most dangerous seismic force direction was given.Combined with the reliability theory,the reliability index,the expression of the probability of instability and the judgment criterion for the perilous toppling rock were built.The proposed method was applied to analyze the stability of perilous toppling rock masses in the Jinfoshan district in Chongqing.The calculation results show that,the most dangerous seismic force direction in case 1 is within 5°,and in case 2 is about 10°;the most dangerous direction angle is not a fixed value,but related to the shape,the fracture water pressure and the depth of rock cavity,etc.When the control crack length is small,the most dangerous direction angle is small under other conditions but will increase significantly with the crack length.The probability of instability increases with the control crack length in case 2 more than in case 1.The research work is applicable to disaster prevention and mitigation of perilous rocks.