Characterizing soil piping networks in loess‐derived soils using ground‐penetrating radar

Abstract

Soil piping remains a relatively unexplored phenomenon despite its substantial impacts on water and sediment transfer at the watershed scale at numerous locations around the world. One of the main limitations regarding the study of this singular process is the characterization of the pipe networks (in terms of number, position, dimensions, and connectivity of pipes). In this context, noninvasive subsurface imaging using ground-penetrating radar (GPR) has proven to be a promising technique. This study used two three-dimensional (3D), high-resolution GPR surveys performed in loess-derived soils to characterize small pipe networks with little prior information about their location. The adopted methodology relies on high spatial resolution scanning, 3D subsurface imaging, and automated detection of reflection hyperbolas using a 200-MHz center-frequency antenna. Two small watersheds affected by piping were investigated at Sippenaeken and Kluisbergen (Belgium). Over the two scanned zones, results revealed significant subsurface continuous patterns. Even though the most obvious patterns corresponded to recent or past anthropic activities (e.g., artificial drainage pipes), validation tests confirmed that the chosen methodology can be used for pipe network characterization because some important continuity patterns were related to soil piping: for instance, a fairly small pipe (approximately 10-15 cm in diameter) was detected and validated for more than 100 m. Nevertheless, the high variability in size, depth, and orientation of the pipes imply that GPR may only be truly efficient when using very high spatial resolution scanning, which limits its application to specific conditions not always met in piped areas.

Detection of Soil Pipes Using Ground Penetrating Radar

“…This study in a complex way has confirmed that GPR can be used to detect soil pipes: this is in accordance with previous reports [7,[18][19][20][21]. The reflections on radargrams that indicate soil pipes are well visible because there are significant differences in radar-wave response given by pipes filled with air and with water at the bottom (Figures 4e, 7d and 10c), and with the surrounding soil.…”

“…Among these methods, GPR has received the most attention, even though it seems that the potential of this method has not yet been fully exploited. Most reports have presented the preliminary results of GPR application in the detection of soil pipes [7,8,20], including only short conference abstracts [18,19]. On one occasion GPR was used to establish hydrological connectivity between pipes through the use of a tracer solution [21] and to estimate the pipe length [8].…”

“…On one occasion GPR was used to establish hydrological connectivity between pipes through the use of a tracer solution [21] and to estimate the pipe length [8]. Antennas of different frequencies were used, e.g., in the northern Pennine Hills (UK)-100 and 200 MHz [7,21], in the Bieszczady Mountains (Poland)-500 MHz, and in the loess belt in Belgium (Sippenaeken and Kluisbergen)-200 and 400 MHz [18,19].…”

“…Moreover, this study has emphasized the critical key in GPR surveys of soil piping, i.e., the selection of antennas with appropriate frequency which allowing the identification of pipes of different sizes and depths of Geophysical methods seem to be a promising tool to provide new, more detailed information on subsurface pipes. In natural environments, the following methods have already been tested in soil piping research: electrical resistivity tomography (ERT) [8,[13][14][15], seismic refraction tomography (SRT) [16], self-potential (SP) [17], and ground penetrating radar (GPR) [7,8,[18][19][20][21][22]. Under laboratory conditions, active and passive acoustic techniques have been tested to study pipe flow and internal erosion [23].…”

Improving GPR Imaging of the Buried Water Utility Infrastructure by Integrating the Multidimensional Nonlinear Data Decomposition Technique into the Edge Detection

“…It is common knowledge that detecting accuracy is vital to the investigation of a buried water infrastructure. A variety of data processing techniques have been proposed to improve the accuracy of GPR imaging [2][3][4][5][6]. Edge detection is a technique formerly used by computer engineers in the analysis of images to outline the essential information of the data [7][8][9].…”