A Study on the Limitations of Geophysical Surveying Techniques to Survey Underground Cavities and Areas Affected by Loosened Grounds

Several geophysical surveying techniques are available as means of exploring underground cavities and areas affected by loosened grounds. However, such geophysical surveying techniques are affected by the properties of the underground media, and in actuality, the properties of the earth, or, soil, of the ground entail complex factors that affect the geophysical surveying process. It is, therefore, necessary to approach the process by analyzing the effects of such factors on geophysical surveying techniques upon understanding the engineering properties of the ground earth. For the purpose of considering the various and complex factors from actual complex grounds, a testbed was built and used to analyze survey limitations undertaken via Ground Penetrating Radar (GRP) surveying and electrical resistivity surveying. As a result of the surveying, this study found that a GPR survey at a frequency of 250 MHz in clay sand medium was capable of accurately identifying underground cavities 0.1 m in diameter at a depth of up to 3.7 m. In addition, while an electrical resistivity survey was found to present low resistivity in areas affected by loosened grounds, the survey technique was limited in its ability to pinpoint the location.