Publication: Properties of physically stabilized granitic laterite soil
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Date
2020-05-01
Authors
Rosli, Ros Nadiah
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Abstract
Laterite soils are abundantly available in the hilly areas of Peninsular Malaysia and their usefulness in the construction industry necessitates further investigation on their engineering properties. In the study of this thesis, the general aims were to provide the geotechnical properties of a range of laterite soils sourced from Bandar Baharu District, Kedah while the properties pursued had also involved the extended ones beyond the normally considered. Soil samples were subjected to compaction efforts with energies spent including to more than the modified Proctor with the specific aims of exploring the maximum strength and minimum permeability constant achievable by such effort. Three qualifying criteria were specifically considered namely the California Bearing Ratios (CBR) of 20 and 80% respectively for the subgrade and subbase strengths in road construction, and the permeability constant (k) of 10-9m/s for the final cover in landfill closure. Three laterite soil samples were sourced from Bandar Baharu District and were denoted as LS1, LS2, and LS3, each representing a different fines content with LS1 having least and LS3 having most. The soil classifications by the Unified Soil Classification System (USCS) were respectively SM, SC, and MH for the three given soils. Each soil was treated by various compaction energies ranging between 596 and 3576kJ/m3 to meet the CBR requirements and bentonite contents ranging between 1 and 5% to meet the k requirement. It was found that Maximum Dry Density (MDD) increased and Optimum Moisture Content (OMC) decreased with increasing energy spent in the compaction. With increasing bentonite content, MDD decreased and OMC increased. With increasing energy
spent in the compaction, k value reduced but the 10-9m/s figure for landfill cover requirement was not achievable even with the maximum energy of 3576kJ/m3 spent for the compaction. With bentonite added, it became possible to reduce k value to the required 10-9m/s range for each soil however with varying amount of bentonite used and energy spent in the compaction. With the modified Proctor compaction applied, it was possible to have k reduced to within the 10-9m/s range with minimum bentonite use of 1% for LS3, 3% for LS2, and 5% for LS1. The Unconfined Compressive Strength (UCS) for each soil increased with increasing compaction energy applied. However, UCS reduced with increasing bentonite added to the soils. For the three soils, the soaked and unsoaked CBR increased with compaction energy spent increased from 596 to 3576 kJ/m3, however only for LS1 that CBR went beyond the 20% mark. After adding 5% bentonite to the soils, none of the resulting CBR values achieved the 20% mark; in this case the modified 2682kJ/m3 compaction energy for CBR was used in all tests. The morphology analysis indicated that with decreasing MDD and increasing OMC due to bentonite addition, the pore sizes shrank for all soils as the structure became more flocculated. Finally, the correlations between properties were analyzed, and the one with highest correlation coefficient was that which relates MDD to OMC.
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