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A laboratory evaluation of soil loss caused by rain in slopes with and without geomats

Water is the main triggering agent of erosive processes in slopes. Some types of geosynthetics can be used to protect slopes, minimizing soil transport along the slope face. The study of surface erosion triggered by rain precipitation along the face of a slope can be carried out in the laboratory using rain simulator equipment. For the purpose of evaluating the amount of soil loss in a slope subjected to rain precipitation, laboratory tests were carried out in such equipment with controlled intensity and uniformity of the rain. Also, a verification of the grain size variation of the soil eroded using a laser grain size analyzer was carried out during the tests. Four types of geosynthetics materials were used. Geomat 1 was manufactured with coconut fibers, a degradable polypropylene mesh and a reinforcing screen. Geomat 2 was also manufactured with coconut fibers and a degradable polypropylene mesh. Geomat 3 was composed by natural straws and Geomat 4 consisted of a flexible mat with a metallic reinforcement. The rainfall simulation tests were performed on a segment of a slope inclined 25° with the horizontal. The soil specimens dimensions were 1.0 m x 1.0 m x 0.15 m. Tests on protected and unprotected soil were conducted. Soil losses were measured during the test at 10 minutes intervals. The results obtained show the effectiveness of soil protection against surface erosion and identifies the main factors affecting the performance of the system.