为指导钻孔剪切试验在黄土地区的应用,利用改进的Iowa钻孔剪切仪研究了典型西安Q3黄土的钻孔剪切特性,探讨法向应力范围、加载剪切方式、剪切速率等因素对试验结果的影响规律。试验结果显示:当法向应力控制在初始应力和临塑应力范围内,抗剪强度与法向应力之间能较好地符合摩尔-库伦破坏准则;当法向应力小于初始应力时,试验求得的黏聚力偏小甚至为负值,内摩擦角偏大;当法向应力超过临塑应力后,试验得到的黏聚力偏大,内摩擦角偏小;分别加载剪切法与分级加载剪切法测得的抗剪强度参数相差不大;当首级法向应力固结10 min、分级法向应力固结5 min时,法向位移速率均＜0.005 mm/min,该值可作为固结变形稳定的判定依据;当剪切速率为1.7～2.3 r/s时,抗剪强度指标的测试结果相差较小。上述钻孔剪切特性影响因素的试验结果可作为试验操控和数据处理的参考依据。
Abstract
The borehole shear characteristics of typical Xi'an Q3 loess were studied using an improved Iowa borehole shear apparatus to guide the application of borehole shear tests in loess areas. The study present the influence of normal stress range, loading shear mode, shear rate, and other factors on test results. The test results showed that when normal stress is controlled within the range of initial stress and critical plastic stress, shear strength and normal stress can be in good agreement with the Mohr-Coulomb failure criterion. When normal stress is less than the initial stress, cohesion is smaller or even negative, and internal friction angle is larger. When normal stress exceeds critical plastic stress, cohesion is larger and internal friction angle is smaller. There is no significant difference in shear strength parameters between single-stage testing and multi-stage testing. When the loess is consolidated at first-stage normal stress for 10 minutes and graded stages for 5 minutes, the normal displacement rate is less than 0.005 mm/min, which can be used as a basis for determining the stability of consolidation deformation. When shear rate is in the range of 1.7-2.3 r/s, the difference between test results of shear strength index is small. The test results of factors affecting shear characteristics of boreholes can be used as a reference for test manipulation and data processing.
关键词
黄土 /
钻孔剪切试验 /
剪切特性 /
抗剪强度参数 /
法向应力
Key words
loess /
borehole shear test /
shear characteristics /
shear strength parameters /
normal stress
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基金
陕西省秦创原“科学家+工程师”队伍建设项目(2022KXJ-086);陕西省重点研发计划项目(2023-YBSF-499);国机集团重点研发项目(SINOMACH 2017-科-249);陕西省青年科技新星计划项目(2018KJXX-001)
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