摘要
由于巴西圆盘抗拉强度公式是基于弹性力学平面问题的解析解,计算结果与直接拉伸试验得到的抗拉强度有较大的差异。基于此,对100余个不同厚径比的砂岩圆盘试样进行劈裂抗拉试验,试验结果表明,随着试样厚径比的减小,抗拉强度逐渐增大,当厚径比约小于0.3时,其抗拉强度逐渐增大并趋于一个相对稳定值,其变化曲线可用三次函数较好的拟合。为了更加完整地把握厚径比对抗拉强度的影响,特建立不同厚径比的三维有限元模型,对圆盘中心轴线上等效应力的分布规律进行详细的研究。研究结果表明,试样中轴线上的最大拉应力出现在试样端面的中心,而且试样的厚径比越大,圆盘的端面中点处拉应力相对越大,圆盘最先起裂的位置发生在端面中心点,而不是内部中心点,有限元计算的结果很好地解释了试验数据的分布规律;通过对有限元结果进行多元拟合,给出考虑厚径比的巴西圆盘抗拉强度修正公式,经验证修正公式具有较好的适用性。研究成果为岩石抗拉强度的正确测定提供有益的依据。
Because the Brazilian disc tensile strength formula is the analytic solution based on elastic mechanics plane problems, the results calculated by this formula are very different with the direct tension test results. Based on this, splitting tensile test on more than 100 sandstone disc specimens with different thickness-to-diameter ratios are conducted. The test results show that the tensile strength increases gradually with the decreasing thickness- to-diameter ratio; when the thickness-to-diameter ratio is less than 0.3, the tensile strength gradually increases and tends to a relatively stable value; and the change curve can be better simulated with cubic function. In order to fully grasp the effect of thickness-to-diameter ratio on tensile strength, 3D finite element models with different thickness-to-diameter ratios are established especially; and the distribution law of equivalent stress on disc central axis is studied in detail. The study results show that the maximum tensile stress on central axis appears in the center of the specimen end face; and the larger the specimen thickness-to-diameter ratio is, the greater the tensile stress in the center of disc end face is. The first fracture starting point is in the center of end face not in the internal center point; and the 3D finite element calculation results can provide a favorable evidence for the distribution law of tensile strength accurately. According to the multivariate linear regression of the 3D finite element calculation results, a modified formula of the Brazilian disc splitting strength considering the thickness-to- diameter ratio is given; and the modified formula has better applicability. The research results provide favorable evidence for testing tensile strength of rock accurately.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2012年第4期792-798,共7页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51109120)
宜昌市科学技术研究与开发项目(A2011–302–6)
三峡大学科学基金(KJ2011B008)
关键词
岩石力学
巴西劈裂法
抗拉强度
厚径比
rock mechanics
Brazilian splittingtest
tensile strength
thickness-to-diameter ratio
