Study of a dirt road condition, the Greater Caucasus, Russia

December 25, 2013

Field works

Field works

The study was held at the road construction site in the Greater Caucasus by "Stroygazservis" LLC with the usage of the GROT 12E type ground penetrating radar, manufactured by Timer CJSC.

The aim of the work was to determine the depth of the bedrock at the dirt road, situated between two slopes of sedimentary rocks.

The place of the works is a north-western part, surrounded with beech-fir forest, of the Greater Caucasus and is located in the southern part of Azish-Tau mountain range. Width of the territory under study - from 4 to 6.5 meters, length - 288 meters.

GPR research was carried out through creating a system of tracks: on the main track, located along the dirt road, and on additional tracks, located across the main one every 9 meters.

Fig. 1. Scheme of gpr tracks.

Fig. 1. Scheme of gpr tracks.

As the probing depth depends on the electromagnetic properties of rocks, the choice of the antenna unit was based on the results of preliminary experiments. The flexible version of the antennas with the length of 4 meters and central frequency of 37 MHz was chosen. The georadar with these antennas could locate the geological boundaries at the depths of up to 50 meters.

The radargram, containing the main track GPR survey results, was used to define the area of bedrock, located at the depths of 16-38 meters. At those and greater depths the signal inversion took place, and that indicates a change in lithology:

Fig. 2. GROT 12E s  ignal trace and the radargram; (a) with filtration applied, (b) a copy of the screen.

Fig. 2. GROT 12E signal trace and the radargram; (a) with filtration applied, (b) a copy of the screen.

Measurements, carried out on the additional tracks, located perpendicular to the main one, confirmed the depth of the bedrock.

At the depth of 15 meters 2 subvertical anomalies were localized at the distances of 58-88 meters and 130-160 meters from the main track beginning.

The research results were: "loose / bedrock" type extensive geological boundaries locations and the recommendations, given on the further soils physical and mechanical properties evaluation, required for the construction.

We thank "Stroygazservis" LLC for the provided materials!