基于国标试验的黏土真实缩限值确定  

Identifying true shrinkage limit of clay by updating experiments in Chinese standard GB/T 50123—2019

作　　者：周葆春[1] 单丽霞 郎梦婷 李颖 ZHOU Bao-chun;SHAN Li-xia;LANG Meng-ting;LI Ying(Henan Unsaturated Soil and Special Soil Engineering Technology Research Center,College of Architecture and Civil Engineering,Xinyang Normal University,Xinyang 464000,China)

机构地区：[1]信阳师范学院河南省非饱和土与特殊土工程技术研究中心/建筑与土木工程学院,河南信阳464000

出　　处：《岩土工程学报》2022年第8期1535-1540,共6页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金面上项目(11772290);信阳师范学院“南湖学者奖励计划”青年项目。

摘　　要：提出了一种黏土真实缩限值的确定方法,修正了《土工试验方法标准:GB/T50123—2019》“缩限试验”与“收缩试验”方法测试步骤和数据处理。采用6种黏土开展泥浆样“缩限试验”与泥浆固结样“收缩试验”,将GB/T50123—2019方法与所提方法获得的缩限结果进行了系统性的比较,结果表明:(1)由基于“缩限试验”的泥浆样与“收缩试验”的泥浆固结样获得的真实缩限值几乎相同,表明缩限取值与所采用的试验方法无关而具有唯一性。(2)GB/T50123—2019中“缩限试验”“收缩试验”方法确定出的缩限值约为真实缩限值的2.7倍。(3)真实缩限状态下,土是非饱和的,其饱和度介于22%~57%。GB/T 50123—2019高估缩限的原因是:“缩限试验”方法假定收缩至体积不变时土是饱和的;“收缩试验”方法用收缩曲线初始线性段与最终水平段的交点而非收缩至体积不变点确定缩限。The methods to determine the true shrinkage limit of clay are proposed by updating both the testing procedure and the data processing of the shrinkage limit and shrinkage test methods in the Chinese standard for geotechnical testing method(GB/T 50123—2019). The shrinkage limit tests on slurry specimens and the shrinkage tests on reconstituted specimens of six types of clay are carried out. A systemic comparison is carried out between the specified shrinkage limits in GB/T 50123—2019and the true shrinkage ones yielded by the proposed methods. The conclusions are drawn as follows:(1) The true shrinkage limits obtained from the slurry specimens(shrinkage limit tests) almost coincide with those obtained from the reconstituted specimens(shrinkage tests). This agreement indicates the true shrinkage limit is independent of testing methods, which is an inherent property denoting the consistency limit of clay.(2) The shrinkage limits given by the original methods in GB/T 50123—2019 are about 2.7 times larger than the true ones.(3) Upon the true shrinking limit, the clays are all unsaturated with the saturation between 22 % and 57 %. The reasons of the overestimation of the original standard-specified methods are speculated as: The method for the shrinkage limit tests assumes that the soil is saturated at the end of shrinking, while that for the shrinkage tests uses the intersection of the initial best-fitting inclined straight line and the final horizontal straight line of the shrinkage curve as the shrinkage limit.

关 键 词：黏土 缩限 稠度界限 缩限试验 收缩试验 泥浆样 泥浆固结样 

分 类 号：TU411[建筑科学—岩土工程]