Dielectric Characteristics of Unsaturated Loess and the Safety Detection of the Road Subgrade Based on GPR

Abstract

We present a moisture content and permittivity model to simultaneously detect and estimate defects in loess subgrade. Based on the ground-penetrating radar (GPR) method, the dielectric properties of loess in the northwest of China and the imaging feature of the moisture content of different strata were studied. The relative permittivity of loess with different moisture contents was experimented in the laboratory. It was found that the relative permittivity of unsaturated loess was positively related to moisture content. The relationship between relative permittivity and moisture content in different antenna frequencies of GPR was analyzed. Electromagnetic wave reflection rules in the loess interface were studied using the numerical method with different moisture contents. With the increase in moisture content, the amplitude of GPR was increased. When the above conclusions were applied in the engineering practices, there are good effects to detect the defects of the road subgrade. It is a significant guidance for determining the qualitative research of defects in the roadbed.

Inversion Model of GPR Imaging Characteristics of Point Objects and Fracture Detection of Heritage Building

“…The data of key points of hyperbolic curves are fitted by conjugate gradient method, and the hyperbolic formulas are obtained. The values of long and short axis are obtained by comparing hyperbolic formulas with (5). The detailed data are listed in Table 1.…”

“…The conjugate gradient method is also used to realize hyperbolic formula fitting. And the values of long and short axis hyperbolic formula are obtained by comparing hyperbolic formulas with (5). The detailed data are listed in Table 2.…”

“…Nowadays, nondestructive techniques which can detect the positions and sizes of point objects are rebound method, ultrasonic method, electrical method, and electromagnetic wave method [3]. Because of high resolution and high flexibility, ground-penetrating radar (GPR) is nowadays considered as one of the most effective and powerful NDT methods [4,5]. The information of hidden objects, such as the location and geometry, can be deduced by detecting imaging research of point object.…”

Study on the dielectric properties and dielectric constant model of laterite

“…In recent years, domestic and foreign scholars have deeply studied on the dielectric properties of soil with fruitful results. They found that the dielectric properties were not only affected by water content, but also affected by soil type, composition, texture, bulk density, temperature, dry density, porosity, saturation, humidity and test frequency (Chen et al, 2012;Liao et al, 2016;Christian et al, 2017;Lv et al, 2018;Dong et al, 2020;Xiao et al, 2020;Pan et al, 2021). However, the existing studies have built different dielectric constant models for the different soil types.…”