基于电测法的路基土物理性质室内测试方法研究

路基土在长期服役过程中性能会发生衰变,其中含水率及压实度是路基施工时的重要控制指标,因此,土体的含水率控制及压实质量是关系路基性能评价的关键因素。为了弥补现有检测方法的不足,基于四极电测量法研发了一种土体物理参数室内快速测试装置,通过改变含水率对不同压实度土样的电阻率、极化率变化进行了一系列室内试验,得到了其相关关系及变化趋势,分析了含水率、压实度对电参数的影响,提出了依据土含水率、压实度计算电阻率、极化率的计算公式,探讨了测试方法的可行性。结果表明:不同地区土的电阻率均随含水率、压实度增加而减小,极化率随含水率、压实度的增加而增大,不同压实度下,土的电阻率、极化率随含水率变化分别呈现相似指数、对数特征;对于天津王庆坨地区壤土,压实度在84. 47%~94. 41%范围内,含水率从15%变化至20%时,电阻率下降为原来的1/3~1/2倍,极化率增大为原来的1. 4~2. 3倍,得到了室内拟合公式;实际工程中,电阻率法更适用于土体含水率检测,极化率法更适用于土体压实度检测;综合应用电阻率、极化率指标对于路基工程具有较好的勘探前景。研究成果将为路基土的工程性质检测及评价提供理论基础。

ELECTRICAL MEASUREMENT BASED LABORATORY TESTING METHOD OF PHYSICAL PROPERTIES OF SUBGRADE SOIL

The performance of subgrade soil can decay during long-term service. The moisture content and compaction degree are important control indicators for subgrade construction. Therefore,soil moisture content control and compaction quality are the key factors in the performance evaluation of subgrade. The research results can provide a theoretical basis for the detection and evaluation of the engineering properties of subgrade soil. In order to make up for the deficiencies of the existing detection methods,we developed a rapid indoor test device for soil physical parameters based on the quadrupole electric measurement method,while we changed the water content between the different compactions. We carried out a series of laboratory tests on the resistivity and polarizability of soil samples and obtained the correlation and change trend. We analyzed the influence of water content and compaction on electrical parameters and proposed the soil moisture content and compaction degree. We calculated the calculation formula of resistivity and polarizability and discussed the feasibility of the test method. The results show that the resistivity of soil in different regions decreases with the increase of water content and compaction. The polarizability of soil increases with the increase of water content and compaction. Under different compaction degrees,the resistivity and polarity of soil shows a similar index and logarithmic characteristics with the change of water content. For the loam of Wangqingtuo area in Tianjin,when the compaction degree ranged from 84.47% to 94.41% and the water content changed from 15% to 20%,the resistivity falls to original 1/3~1/2 times and the polarizability falls to 1.4~2.3 times. And we obtain the indoor fitting formula. In practical engineering,the resistivity method is more suitable for soil moisture detection,and the polarizability method is more suitable for soil compaction detection. The comprehensive resistivity and polarizability index have good prospects for roadbed engineering. The research results can provide a theoretical basis for the detection and evaluation of the engineering properties of subgrade soil.