基于结构面粗糙度随机场表征的抗剪强度变异性

Shear Strength Variability Based on Random Field Representation of Rock Discontinuities Roughness

岩体结构面抗剪强度参数具有变异性是客观事实,而受限于室内外直剪试验成本而导致抗剪强度变异性指标获取困难是目前制约岩质边坡可靠度评价发展的主要原因之一。鉴于此,提出了一种利用少量实测结构面粗糙度曲线样本和岩块物理力学参数,结合JRC-JCS(joint roughness coefficient-joint compressive strength)剪切强度模型、随机场理论和非侵入式离散元数值试验,获取结构面抗剪强度参数变异性指标的方法。将此方法应用于某隧道进口段岩质边坡可靠度评价中,研究发现:(1)该岩质边坡主控结构面粗糙度纵坐标方差为0.012 5 cm2,相关距离为0.75 cm,生成的随机粗糙度曲线与实测样本相似;(2)结构面黏聚力和内摩擦角均值分别为0.427 MPa和54.9°,标准差分别为0.229 MPa和4.47°,变异系数分别为53.63%和8.14%;(3)此边坡稳定性系数服从正态分布,失稳概率为2.8%,可靠度为1.52。

The shear strength parameters of rock discontinuities have variability is a common sense and the shear strength variability is difficult to obtained due to the cost of direct shear tests.It is one of the main reasons restricting the development of rock slope reliability evaluation.In view of this,combined with a small number of measured rock discontinuities roughness curve samples,rock mechanical parameters,the JRC-JCS(joint roughness coefficient-joint compressive strength)shear strength model,random field theory and non-invasive discrete element numerical experiments,a method to obtain the variability index of rock discontinuities shear strength parameters was proposed.Applying this method to the reliability evaluation of a rock slope at the entrance section of a tunnel,The result show these as follows.The variance of the ordinate roughness of the main control rock discontinuities of the rock slope is 0.0125 cm 2,the correlation distance is 0.75 cm,and the generated random roughness curve is similar to the measured sample.The average cohesion and internal friction angle of the rock discontinuities are 0.427 MPa and 54.9°,the standard deviations are 0.229 MPa and 4.47°,and the coefficients of variation are 53.63%and 8.14%,respectively.The slope stability coefficient obeys the normal distribution,the instability probability is 2.8%,and the reliability is 1.52.