NUMERICAL PREDICTION OF THERMAL SIGNATURES OF BURIED HEAT CONDUCTING LANDMINES

Abstract

Landmine detection assumes significance in the current situation of increased terrorist activities and frequent wars in some part of the globe, where the bursting of landmines has caused physical injuries and loss of life. Metal detectors have been widely used for detecting the buried landmines. In order to avoid the detection of mines using metal detectors, now a day's landmines are being made using plastic and similar materials. This has made de-mining a challenging task. Hence there is a necessity for developing landmine detection techniques which can detect mines made of non metallic substances. Landmines made of non metallic materials can be detected using techniques such as infrared imaging, X-Ray backscattering, acoustic/seismic, ground penetrating radar etc. It is found from literature that infrared imaging technique seems to be a promising technique for landmine detection in large surface area. Basically this method works on the principle of determination of thermal signature obtained due to the variation of solar radiation in the day and night times in a given day. The presence of a landmine affects this sinusoidal temperature variation of the surface of the soil due to varying solar radiation in a diurnal cycle. The problem of determination of thermal signature is reduced to the study of heat and moisture transport in soil in the presence of a landmine with solar radiation heat flux as boundary condition. Simultaneous heat and moisture transport through porous materials is a coupled phenomenon. In the present work a theoretical model has been developed to predict the thermal signature of a soil surface using continuum based governing equations for heat and moisture transport through the soil in the presence of solar radiation. These governing equations have been solved using Galerkin's weighted residual finite element method for a two-dimensional computational domain for the prediction of thermal signatures. An iterative method has to be used to find the exact location of the landmine by comparing the thermal imaging obtained suing the infrared camera and the simulated results. Hence a parametric study has been carried out after validating the model. Results are obtained to study the effect of land mine size, location from the soil surface and initial soil moisture content. Thermal signatures are observed to be strong with increase in size of mine whereas weak thermal signatures are obtained with increase in depth of mine and increase in initial moisture content of the soil.