Choi Chanyong, Song Minwoo, Kim Daehyeon, Yu Xiong
High Speed Railway Research Division, Korea Railroad Research Institute, 176, Cheoldobangmulgwan-ro, Uiwang-si, Gyeonggi-do 437-757, Korea.
Department of Civil Engineering, College of Engineering, Chosun University, 375 Seosuk-dong, Dong-gu, Gwangju 501-759, Korea.
Materials (Basel). 2016 Jun 2;9(6):439. doi: 10.3390/ma9060439.
Dry density and water content are two important factors affecting the degree of soil compaction. Conventional methods such as the sand cone test and the plate load test are used to measure such properties for evaluating the degree of compaction and the stiffness of soil in the field. However, these tests are generally very time-consuming and are inherent with some errors depending on the operator (in particular for the sand cone test). Elastic modulus is an indicator to describe the stress-strain behavior of soil and in some cases is used as a design input parameter. Although a rod type TDR (Time Domain Reflectometry) system has been recently proposed to overcome some shortcomings of the conventional methods (particularly the sand cone test), it requires driving the probes into the ground, thus implying that it is still a time-consuming and destructive testing method. This study aims to develop a new non-destructive TDR system that can rapidly measure the dry density, water content, and elastic modulus of soil on the surface of compacted soil, without disturbing the ground. In this study, the Piezoelectric Stack, which is an instrument for measuring the elastic modulus of soil, has been added to the TDR system with a flat type probe, leading to a non-destructive TDR system that is capable of measuring the dry density, water content, and elastic modulus of soil. The new TDR system developed is light enough for an engineer to carry. Results of the standard compaction and TDR tests on sand showed that the dry densities and the moisture contents measured with the new TDR system were in good agreement with those measured with the standard compaction test, respectively. Consequently, it appears that the new TDR system developed will be very useful to advance the current practice of compaction quality control.
干密度和含水量是影响土壤压实程度的两个重要因素。传统方法如砂锥试验和平板载荷试验用于测量这些特性，以评估现场土壤的压实程度和刚度。然而，这些试验通常非常耗时，并且取决于操作人员会存在一些误差（特别是砂锥试验）。弹性模量是描述土壤应力 - 应变行为的指标，在某些情况下用作设计输入参数。尽管最近有人提出了一种杆式时域反射仪（TDR）系统来克服传统方法（特别是砂锥试验）的一些缺点，但它需要将探头打入地下，这意味着它仍然是一种耗时且具有破坏性的测试方法。本研究旨在开发一种新的无损TDR系统，该系统可以快速测量压实土壤表面的土壤干密度、含水量和弹性模量，而不会扰动地面。在本研究中，将用于测量土壤弹性模量的压电堆添加到带有平板型探头的TDR系统中，从而形成一种能够测量土壤干密度、含水量和弹性模量的无损TDR系统。所开发的新型TDR系统足够轻便，便于工程师携带。对沙子进行的标准压实试验和TDR试验结果表明，用新型TDR系统测量的干密度和含水量分别与用标准压实试验测量的结果吻合良好。因此，所开发的新型TDR系统似乎对推进当前压实质量控制实践非常有用。
