Field Measurements and Numerical Simulations of Temperature and Moisture in Highway Engineering Using a Frequency Domain Reflectometry Sensor.

Yong Li,Yong-Sheng Yao,Zeng-Shun Chen,Jian-Long Zheng,Jun-Hui Zhang

doi:10.3390/s16060857

Abstract

This paper presents a systematic pioneering study on the use of agricultural-purpose frequency domain reflectometry (FDR) sensors to monitor temperature and moisture of a subgrade in highway extension and reconstruction engineering. The principle of agricultural-purpose FDR sensors and the process for embedding this kind of sensors for subgrade engineering purposes are introduced. Based on field measured weather data, a numerical analysis model for temperature and moisture content in the subgrade’s soil is built. Comparisons of the temperature and moisture data obtained from numerical simulation and FDR-based measurements are conducted. The results show that: (1) the embedding method and process, data acquisition, and remote transmission presented are reasonable; (2) the temperature and moisture changes are coordinated with the atmospheric environment and they are also in close agreement with numerical calculations; (3) the change laws of both are consistent at positions where the subgrade is compacted uniformly. These results suggest that the data measured by the agricultural-purpose FDR sensors are reliable. The findings of this paper enable a new and effective real-time monitoring method for a subgrade’s temperature and moisture changes, and thus broaden the application of agricultural-purpose FDR sensors.

Highlights

Moisture content is an important physical parameter when we study soil properties, which will change with the variation of moisture content
As subgrade soil is unsaturated soil, there exists a certain correlation among its moisture, temperature and modulus: the moisture and temperature have a substantial effect on the modulus, especially the change of moisture content significantly affect the modulus, sometimes even plays a decisive role [2,3,4,5,6]; the moisture and temperature are main factors influencing the settlement deformation of the subgrade [7,8]
Based on the field monitoring and numerical simulation, the following conclusions can be drawn: (1) frequency domain reflectometry (FDR) sensors were applied to the subgrade in a highway reconstruction project for the first time, and the embedding method and process of the sensors are illustrated

Summary

Introduction

Moisture content is an important physical parameter when we study soil properties, which will change with the variation of moisture content. The soil-filled structure for the highway subgrade is compacted in layers according to specific technical standards, and the moisture content and temperature changes in the soil have important influences on subgrade performance (modulus and settlement) [1]. As subgrade soil is unsaturated soil, there exists a certain correlation among its moisture, temperature and modulus: the moisture and temperature have a substantial effect on the modulus, especially the change of moisture content significantly affect the modulus, sometimes even plays a decisive role [2,3,4,5,6]; the moisture and temperature are main factors influencing the settlement deformation of the subgrade [7,8]. Previous researchers have done extensive laboratory tests

Methods

Results

Conclusion