FDTD simulation and GPR study in Rwanda tropical soil using permittivity variation

Abstract

It is very useful to know the soil capabilities on different external impacts acting on it, especially for electromagnetic waves from Ground Penetrating Radar. In the underground detection domain actually, dealing with soil permittivity is one of the challenging research problems nowadays. In this paper, we study tropical soil constitution, taking in account the tropical climate region and we took Rwanda as a case study. Rwanda's elevation ranges from 1,000m (south and east) to 4,500m above sea level. The “thousand hills” terrain is dominated from north to south by a watershed (2.500m high) that separates the basin of the Congo River from that of the Nile and by the Ibirunga volcano chain. In spite of its proximity (2 degrees south) to the equator, the country enjoys a fine spring climate (due to its altitude), with two rainy seasons and two dry seasons. In fact, when considering the tropical climate region with his considerable rainfall period, it is better to collect information regarding the zone in consideration. Using Finite Difference Time Domain(FDTD) simulation with GPRMax simulator, and varying the permittivity, the aim of this paper is to have a benchmark of dry and rainfall season; this will help when doing measurements with the GPR instruments and others non destructive tools. In this paper, we analysed the clay soil (one of the component of Rwandan pedology) and from the variation of dry clay to wet clay associated with different fixed frequencies (300MHz, 600MHz, 900MHz, 1200MHz and 1500MHz). For each fixed frequency, we vary the clay permittivity from dry to wet clay and analysed data after simulation. From this benchmark, and in the near future work, we will use the GPR instrument and the Time Division Reflectometry(TDR) to verify the simulation results.