Strength characteristics of dune sand stabilized with lime-silica fume mix

Abstract

While more than half the land surface of Iraq consists of deserts covered mainly with sand dunes, little research has taken place to study the characteristics and the behaviour of sand dunes. The growth of economy, demography and building activities in Iraq necessitates carrying out geotechnical investigations for the dune sand. The purpose of the present work is to assess the suitability of sand dunes as subgrade layer for carrying roads and rail foundations. An extensive laboratory testing programme was carried out to study the geotechnical properties and the behaviour of sand dunes. Sand dune samples were collected from a region in Baiji area in Salah-Aldeen governorate, North of Iraq, in situ field density of the soil was measured by sand-cone test. The tests include moisture content, classification tests, compaction tests, relative density and direct shear test. Chemical tests and X-ray diffraction analyses were also carried out. Silica fume (SF) and lime-silica fume (L-SF) mix have been used for stabilising and their effects on the sand dunes were investigated. A grey-coloured densified SF is used. Four percentages are used for lime 0, 3, 6 and 9% and four percentages are used for SF 3, 6, 9 and 12% and the optimum percentage of SF is mixed with the percentages of lime. Several tests are made to investigate the soil behaviour after adding the lime, and SF. It was found that L-SF caused an increase in the angle of friction ϕ and cohesion c. Higher cohesion was reached; 10 kPa with higher percentage of 6% L + 12% SF. In addition, the angle of internal friction increases with increasing the maximum dry density, where the values of the angle of internal friction ranged between 35° and 41°.

Keywords:

• Dune sand
• lime
• silica fume
• stabilisation