Numerical and Experimental Investigation of Thermal Signatures of Buried Landmines in Dry Soil

Abstract

This paper reports a numerical and experimental investigation conducted to study the thermal signature of buried landmines on soil surface. A finite-volume-based numerical model was developed to solve the unsteady three-dimensional heat transport equation in dry homogeneous soil with a buried mine. Numerical predictions of soil thermal response were validated by comparison with published analytical and numerical values in addition to data obtained experimentally. Experiments were performed inside an environmental chamber and soil temperatures were measured during cooling, using two measurement techniques, after exposing the soil surface to a radiant heat flux for a specified period. In the first technique, the temporal variation of the surface and internal soil temperatures were recorded using thermocouples. In the second technique, the soil surface temperature was measured using an infrared camera that revealed the thermal signature of the mine. The transient temperature profiles generated numerically agreed with measurements, and the difference between predicted and measured values was less than 0.3°C at both the soil surface and in depth. The accurate matching of numerical and IR images at the surfaces was found to strongly depend on the use of a smaller soil thermal conductivity at the surface than at greater depths. The numerical model was used to predict the dependence of the peak thermal contrast on time, depth, and heating period. The thermographic analysis, when combined with numerical predictions, holds promise as a method for detecting shallowly buried land mines.

Spatial and temporal variance of soil and meteorological properties affecting sensor performance—Phase 2

“…Sensors used in our investigation, a FLIR Systems Inc. camera (model A300 with a Scout III 240 lens and model A310F), operate at 7.5-13 μm, well within the thermal-imaging band. The use of thermal IR as a detection mechanism is based on the concept that objects buried at shallow depths (Moukalled et al 2006) or disturbance of the soil may alter the thermal signature of soil. Materials differ in thermal capacities, resulting in different heating and cooling rates and associated IR radiation emissions (Simard 1996).…”

Evaporation from soils under thermal boundary conditions: Experimental and modeling investigation to compare equilibrium‐ and nonequilibrium‐based approaches

“…When the soil is bare, large diurnal temperature variations in the upper 15–20 cm of soil greatly influence vapor flow within the near surface layer, especially at moderate water contents [ Papendick et al , 1973; Pikul and Allmaras , 1984]. Water movement in unsaturated soil under nonisothermal conditions has been studied by many researchers in the context of understanding flow processes associated with evaporation from bare soil [ Philip , 1957; Cary , 1966; Jackson et al , 1974; Scanlon et al , 2003; Bittelli et al , 2008], efficient water management for agricultural applications [ Brutsaert and Chen , 1995; Ventura et al , 2001], land‐atmospheric interactions [ Judge et al , 2003; Brutsaert , 2005], the accurate detection of buried objects such as landmines [ Šimůnek et al , 2001; Das et al , 2001; Moukalled et al , 2006], and water and heat movement though landfill covers [ Khire et al , 1997; Scanlon et al , 2005].…”

Modeling of a multi-month thermal IR study

“…Interest in IR thermography as a sensor modality has increased in the past decade. Thermal IR is based on the concept that the thermal signature of soil is altered by objects buried at shallow depths, regardless of material type [4]. The technique measures surface-emitted electromagnetic energy in the IR radiation band, also known as thermal radiation.…”