不同粗糙度结构面时效强度特征

Time-dependent strength of rock mass discontinuity with different values of JRC

为研究不同粗糙度结构面在长期荷载下的强度变化规律,选取Barton标准剖面为人工模拟结构面的表面形态,并用水泥砂浆浇筑,试样成型后,对其进行直接剪切试验以及剪切蠕变试验,基于试验结果,建立瞬时剪切强度公式,并对不同粗糙度结构面的剪切蠕变特征进行分析,提出确定长期强度的方法,并以此求解长期强度,进而分析粗糙度对结构面剪切时效特征的影响,研究成果表明:随着粗糙度的增大,蠕变整体位移减小,蠕变破坏曲线越来越陡,其蠕变速率以及剪切刚度在大于某个应力值时,相对于前一级均会发生显著变化;瞬时强度与长期强度均与粗糙度呈线性关系,随着粗糙度的增大,长期强度与瞬时强度的比值减小,这是连续完整岩石与不连续贯通的结构面具有不同的时效特征以及不同法向应力和粗糙度下剪切面积比的变化共同造成的,另外等速率曲线拐点法得到的长期强度符合蠕变特征变化得到的长期强度范围,其合理性和可靠性得到了验证。

To study the time-dependent behavior of rock mass discontinuity, the samples with artificial joint surfaces based on Barton＇s ten standard lines were poured using cement mortar. Direct shear test and shear creep test were conducted and the relationship between shear strength and JRC（joint roughness coefficient） was established, the characteristics of creep curves were described and the long-term strength of discontinuities with different values of JRC and normal stress were solved using new method for determining the long-term strength that proposed based on the isocreep-rate curve. The results demonstrate that the creep displacement decreased and the creep failure curves were steeper and steeper with the increasing of JRC. The creep displacement, creep rate and shear stiffness in loading section of muti-stage creep curves increased greatly when the shear stress was higher than stress thresholds. Instantaneous strength and long-term strength have linear relationship with JRC, and the ratio of long-term strength and instantaneous strength decreased with the increasing of JRC, which due to the difference between continuous rock and rock mass discontinuity in time-dependent behavior and the variation of shear area ratio. In addition, the long-term strength determined by inflection point of isocreep-rate curve method meet the range determined by the creep characteristics which can verify the reliability and rationality of the new method.