Detection of Subsurface Cavities by Surface Remote Sensing Techniques.

摘要

The research is part of a program underway to evaluate remote sensing instrumentation and methods for locating subsurface cavities that can cause serious highway construction and maintenance problems. Three methods of subsurface cavity detection based on different geophysical techniques were experimentally evaluated,including ground-penetrating radar,gravity profiling,and earth resistivity profiling. Tests were conducted at three sites having different geological environments. Verification tests showed all methods to be capable of locating air-filled cavities. Gravity measurements located large cavernous areas but could not detect mud-filled cavities. Radar detected several air-filled cavities at maximum depths of about 15feet (4.6 m). Radar only penetrated 10feet (3 m) with inconclusive results at one site and could not resolve 2-foot (0.6-m) diameter vertical cylindrical cavities at another. Earth resistivity measurements using a pole-dipole electrode arrangement located cavities at all sites,indicating targets at depths of 80feet (24.4 m). Both air-and mud-filled cavities including vertical cylinders were detected using the resistivity technique,giving accurate depth and size resolution.