Erosion of dune sands stabilised by grouting with lime–silica fume mix

Abstract

Dune sands are often an environmental hazard during strong winds and sand storms, particularly in the summer months. Wherever a granular soil surface is left unprotected, it can be subjected to wind erosion and dune formation. In this study, an attempt was made to stabilise sand dunes by grouting with a slurry of lime–silica fume (L–SF) material. Dune sand samples were collected from northern Iraq. In situ field density of the soil was determined by sand-cone tests for moisture content, classification, compaction, relative density, direct shear and chemical tests. Erosion tests were conducted using centrifugal fans, with wind applied to the soil at a speed of 90 km/h for 11 min. Silica fume (SF) and a L–SF mix were used for stabilisation and their effects on the dune sands were investigated. For grouting, a 1000 ml grout pump was used to stabilise a liquid tank of the L–SF mix; the maximum pumping pressure was about 25 kPa. It was found that when the dune sand was with a slurry of L–SF, there was a reduction in erosion by about 70% for a stabiliser grout of 33% (Lime to SF ratio, 3L : 4SF) with 67% water of the total mixture weight. The stabilisation effect increased with increases in the number and depth of grouting holes around the stabilised area. When wind was applied at a rate of about 90 km/h for 11 min, the eroded natural sand dune surface was about 66 mm, while for soil stabilised by grouting with L–SF, the erosion was 17–36 mm. An increase in the number of injection points and a reduction in the distances between them reduced the amount of soil erosion.