Application of the slump test method to measurement of the debris flow yield stress
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摘要: 屈服应力是泥石流的关键流变参数，但目前该参数的获取主要依赖常规的流变仪，无法对含有粗大颗粒的泥石流进行测试。针对此问题，引入塌落度-屈服应力理论，采用直径和高度均为10.8 cm的圆柱塌落度桶对“2010.8.18”怒江东月各泥石流堆积物原样中上限粒径为2 mm和2 cm的部分进行了塌落度-屈服应力测试研究，两种上限粒径重构泥石流屈服应力的测试结果分别采用桨叶法（桨式流变仪）和斜面法（斜面流变仪）进行校验。实验结果表明：对于上限粒径为2 mm的泥石流，塌落度法与桨叶法测试结果基本相同，相对误差为1.47%~17.5%，平均相对误差为7.37%；对于上限粒径为2 cm的泥石流，塌落度法测试结果平均略大于斜面法，相对误差为12.27%~19.07%，平均相对误差为16.89%；理论分析表明，该圆柱形塌落度法适用于碎屑上限粒径为42 mm、塌落度不小于10.8 mm的泥石流。塌落度法不仅可以大幅度提高测试对象的上限粒径，而且测试精度较高，尤其适合于泥石流屈服应力的现场测试。Abstract: Yield stress is the key parameter of debris flow. Currently it is mainly obtained from conventional rheological tests, which are not applicable to the debris flow containing coarse particles. In order to adress this problem, the slump-yield stress theory is introduced. In this paper, the deposits of the 2010 Dongyuege debris-flow event in Nujiang is taken as the research object and the slump-yield stress tests are carried out by using a cylindrical slump barrel with 10.8 cm in both diameter and height. The maximum grain size of the two kinds of tested debris-flow samples is 2 mm and 2 cm, respectively. The test results of yield stress were verified by vane-rheometer and the tilting plane rheometer, separately. The results show that for the debris-flow bodies with the maximum grain size of 2 mm, the yield stress values obtained from slump test method are generally consistent with that from the vane-rheometer, with deviation of 1.47 %-17.5 % and average deviation of 7.37 %. For the debris flow bodies with the maximum grain size of 2 cm, the yield stress values obtained from the inclined plane test method are slightly lower than that from the slump test method, with deviation of 12.27 %-19.07 % and average deviation of 16.89 %. Theoretically, the cylinder slump test is valid for the debris flow whose maximum grain size is 42 mm and the slump is larger than 10.8 mm. The slump test method can not only greatly enhance the maximum grain size of the test object, but also has a high test precision which is especially suitable for the debris-flow yield stress test in situ.
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Key words:
- debris flow /
- yield stress /
- slump test method /
- Nujiang debris flow /
- Dongyuege debris flow
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