吸湿对土粒比重测定的影响研究  

Influence of hygroscopicity on the determination of soil specific gravity

作　　者：曾兴[1,2] 李裕恒 黄宽心 林志 苏佳 高桐 ZENG Xing;LI Yuheng;HUANG Kuanxin;LIN Zhi;SU Jia;GAO Tong(Hunan Province Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring,Hunan University of Science and Technology,411201 Xiangtan,China;MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering,Zhejiang University,310058 Hangzhou,China;Team 414 Hunan Bureau of Geology and Mineral Exploration and Development,413000Yiyang,China)

机构地区：[1]湖南科技大学岩土工程稳定控制与健康监测省重点实验室,湘潭411201 [2]浙江大学软弱土与环境土工教育部重点实验室,杭州310058 [3]湖南省地质矿产勘查开发局四一四队,益阳413000

出　　处：《应用力学学报》2022年第6期1125-1134,共10页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金资助项目(No.41702329);湖南省教育厅科学研究资助项目(No.17B097);湖南省自然资源厅资助项目(No.2020-15);湖南省自然科学基金资助项目(No.2022JJ40148)。

摘　　要：土粒比重通常采用比重瓶法进行测定,通过分析发现现行规范中的比重瓶法试验过程中会因为烘干土样存在吸湿行为导致测定结果偏小。通过7种土样的吸湿试验,发现黏粒含量最高的膨润土吸湿量最大,黏粒含量最低的砂土吸湿量最小。本研究基于规范中比重计算公式,推导了考虑土样吸湿影响下的真实比重计算公式,并探讨了烘干土样吸湿性对土粒的比重测定结果的影响,发现随着土样吸湿率的增大,比重值的误差随之增大。提出了一种改良的比重瓶法,该方法直接采用自然风干土样进行试验,避免了烘干土样吸湿对比重测试的影响。对7种土样分别进行了改良比重瓶法和传统比重法试验,对比发现:土类吸湿能力越强,则两种方法测得的比重值的差异越大。该改良方法的误差主要来自自然含水率测定误差,试验误差分析表明自然含水率值变化±0.5(含水率变化率4.162%~41.051%)对比重测试结果的影响不超过0.9%,说明该测试方法较现行规范中的比重瓶法结果稳定、重复性好。The specific gravity of the soil particles is usually measured by the pycnometer method.The author found that the moisture absorption behavior of the dried soil during the process of pycnometer method test in the current specification could result in a small measurement result.Through the moisture absorption test of seven kinds of soil,it was found that the bentonite with the highest clay content had the highest moisture absorption,and the sand with the lowest clay content had the smallest moisture absorption.The real specific gravity calculation formula considering the influence of soil’s moisture absorption was derived based on the specific gravity calculation formula in the specification,and discussed the influence of the moisture absorption of dried soil on the determination result of specific gravity of soil particles.It is found that the error of specific gravity value increased with the increase of moisture absorption of soil samples.A modified pycnometer method is proposed,which directly uses natural air-dried soil for testing,avoiding the influence of the moisture absorption of the dried soil to the specific gravity test.The modified pycnometer method and the traditional pycnometer method were carried out on seven soils and it was found that the stronger the moisture absorption capacity of the soil,the greater the difference between the specific gravity values measured by the two methods.The error of the improved method mainly comes from the error of the natural moisture content determination,and the test error analysis shows that the influence of the change of natural moisture content value±0.5(the moisture content change rate is 4.162%-41.051%)on the the specific gravity test results does not exceed 0.9%,which indicates the test method is more sTab.and reproducible than the pycnometer method in the current specification.

关 键 词：比重测定 比重瓶法 吸湿性 含水率 

分 类 号：TU41[建筑科学—岩土工程]