Force transmitted below the soil surface by human gait

A force platform, which can provide three dimensional forces and moments on its top surface, was used to study force transmitted by human gait below the soil surface in order to understand detonation of antipersonnel landmines. Soils of varying depth were packed on the top surface of the platform to measure the forces transferred from the soil surface. Experimental variables included subjects (people), soil depth, soil type, moisture content, and compaction level. Soils used in this study were sand and sandy loam. There were medium and high two compaction levels for each soil. Sandy loam soil included two moisture contents; sand tested involved two moisture contents and dry sand. Soil depth varies from 0 (bare platform) to 200 mm. Five subjects with different weights were selected and used in this study. The subsoil force and its duration were measured for different subjects at a depth up to 200 mm. The impulse in subsoil was then calculated and used in evaluating the effect of different subjects on the force transfer in soil. The results indicated that loose soil can transfer larger force to subsoil than dense soil; test results showed that heavier subjects also created larger subsoil forces than lighter ones. Whether the effect of soil depth on subsoil impulse was significant was depended on the soil conditions. For the sand with 5.5% moisture content and bulk density of 1800 kg/m³, soil depth significantly affected subsoil impulses. For the sandy loam soil, the mass of subject increased from 50 to 100 kg resulted in 100% increase in subsoil impulses at all four depths; for the sand, the mass of subject increased from 55 to 100 kg approximately. This resulted in 80% increase in subsoil impulses under all four depths regardless of moisture content and bulk density. The results of this study will helpful for designing new equipment and evaluating existing machines for neutralizing landmines.