基于三维弹塑性有限元的洞室稳定性参数敏感性灰关联分析

GREY RELATION ANALYSIS OF PARAMETER SENSITIVITY OF CAVERN STABILITY BASED ON 3D ELASTOPLASTIC FINITE ELEMENTS

综合考虑岩体物理参数的不确定性,针对常规敏感性分析方法所存在的不足,提出基于弹塑性有限元的洞室稳定性参数敏感性灰关联分析方法,并确定点安全系数为考核指标,确定岩体弹性模量、泊松比、黏聚力、内摩擦角等强度参数为敏感性影响参数。以金沙江两家人水电站地下厂房区洞室为例,对开挖后的地下洞室典型断面点安全系数的诸多影响参数进行敏感性分析,结果表明:不同的影响参数变化对洞室稳定的点安全系数影响有差异,因洞室开挖后,拱顶或边墙处于临空状态,而拐角点受洞壁约束更大,所以洞室拐角点安全系数比临近拱顶或边墙节点要大。点安全系数的敏感度是考虑综合影响参数的结果,采用灰关联分析方法分析表明,对地下厂房洞室典型断面点安全系数影响程度最大的为黏聚力和内摩擦角,其次为弹性模量和泊松比。从而克服了单因素常规参数敏感性分析的局限性,使得影响参数对点安全系数影响的灵敏程度排序得到统一,并与数力学分析结论一致,得到很好验证,为洞室稳定性支护材料的选取提供指导作用,对黏聚力和内摩擦角的要求应更加重视。

Based on the comprehensive consideration of rock mass physical parameters and defects of conventional sensitivity analysis,grey relation analysis of parameters sensitivity of cavern stability based on 3D elastoplastic finite elements is put forward.Point safety factor is specified as examination index;and cohesion,angle of internal friction,elastic modulus,and Poisson＇s ratio are confirmed as sensitivity influential parameters.Taking Liangjiaren hydropower station on Jinsha River in China for example,the sensitivity analyses of many influential factors for point safety factor of excavated underground cavern typical sections have been conducted.Through the analyses,the influential effects for point safety factor of cavern stability are different when the influential factor has been changed.After excavation,the vault or sidewall of cavern is free and the constraint of cavity wall for inflection point is much larger,therefore,the safety factor of the inflection point is larger than that of vault or sidewall of cavern.Grey relation analysis shows that the scheduling of the influential degree of excavated underground cavern typical section on point safety factor is cohesion,angle of internal friction,elastic modulus,Poisson＇s ratio,therefore,the limitation of the conventional sensitivity analysis is overcome,and the sensitivity sequencing of the influential factors on key point safety factor are also unified,which verifies the mathematical and mechanical analytical results.Accordingly,clear direction for choice of support material of underground cavern stability is shown,and the requirements for cohesion and angle of internal friction must be paid more attentions.