Soil Composition Influence On Ground Penetrating Radar in a Mine Detection Task.

Ground penetrating radar (GPR) can assist soldiers in locating buried landmines by aiding them to distinguish between metallic clutter and actual landmines. Previous research using a variety of GPR systems has shown that soil properties, specifically sand and clay in the presence or absence of moisture, can influence the reliability of the ground penetrating radar system. We conducted a study using 10 imported soils placed in 150 gallon plastic stock water tanks in a replicated design to determine how soil properties and moisture interacted to influence the GPR system associated with the Army's current mine detector, the AN/PSS-14. Our objective was to determine if we could relate soil factors that degraded the capability of the GPR to specific classes of soil classified by the Unified Soil Classification System. We found that antitank mine simulants were generally unaffected in terms of soil influence on the GPR reliability regardless of soil composition or moisture; however, the smaller anti-personnel landmine (APLM) simulants were affected by the fine content of the soil. When we related fines content to the soils engineering index known as the Plasticity Index (PI) we began to see some trends that indicated to us that as PI increased in CL soils GPR reliability decreased. We had one CH soil in the study which had a PI greater than any of the CL soils, but which did not have any GPR influence. PI has potential to be used as an indicator of possible degraded GPR reliability under certain moisture conditions. We suspect that CH soils having higher PI values than the soil used in this study may also result in degraded GPR reliability under high moisture conditions. In a related study performed on an SM soil using real mines, we found variation in soil environmental influence on GPR reliability between APLM types based on soil moisture. For one APLM we saw the greatest influence on GPR during the month of June when soil moisture was high, and for another APLM we saw the greatest influence on GPR during the month of July when soil moisture was lower. Further, we observed variation in the GPR response of individual mine targets of both APLMs within the research plots; some mines produced a degraded GPR response at higher frequencies than other mines of the same type located elsewhere within the research plot.