Detection Method of Buried Depth of Single Crack in Rock Mass Based on Thermal Infrared Response

Abstract

Detecting the buried depth of cracks is an important link to reveal the internal structural state of rock mass. Based on the one-dimensional heat conduction theory, a detection method to obtain the buried depth of cracks through the surface temperature difference of rock mass was proposed, and the influences of heat flux density, diameter and buried depth of crack on the heat transfer characteristics and buried depth detection of rock mass with single crack were analyzed by laboratory tests and numerical simulation. The results show that the cracks hinder the heat flow transfer in rock mass, and the internal cracks with large diameter and shallow buried depth can be effectively identified by infrared thermal imaging technology; the surface temperature difference between the projection area of crack and intact rock is affected by heat flux density, buried depth and diameter of crack; the heat flux density is large, and the identification effect is good; the maximum temperature difference in the heating process is linear with the heat flux density and diameter of crack, and logarithmic normal distribution with buried depth of crack; the calculation error of buried depth of crack is mainly affected by heating time, when the heating time is the moment corresponding to the minimum value of the calculation depth change rate, the error is smaller, and the minimum error in the simulation test is only 0.6%; the cracks within the buried depth of 6 cm can be detected by heating for 20 min with the heat flux density of 2 000 W·m-2, and the detection for buried depth of crack can be improved by extending heating time and increasing heating power. Therefore, it is feasible to detect the buried depth of shallow cracks by infrared thermal imaging technology, which will have important application for rock mass engineering with strong structural sensitivity and special use requirements.