STUDY ON SAND GRADATION INFLUENCE AS EXPANSIVE SOIL STABILIZER

• Main Author: Tanadi, Billy
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84448
• Institution: Institut Teknologi Bandung

Expansive soil is soil that changes in volume if there is a change in water content. Volume change of expansive soil will exert pressure on structures at the ground surface, causing damage to these structures. As a tropical country dominated by clay soil, Indonesia has lots of regions with expansive soil. Therefore, there is a need for expansive soil improvement efforts in Indonesia. One method for improving expansive soil is the addition of certain materials to expansive soil, also known as the soil stabilization method. Sand has the potential as a stabilizing material for expansive soils, because it is non-plastic, non-expansive, and easy to compact. However, the influence of gradation and size of sand grains used to improve expansive soils has not been widely studied. In this research, the effect of sand gradation and sand grain size used to improve expansive soil was investigated. In this research, two expansive soils from the Cipamingkis River, Jonggol District, Bogor Regency and Kondangsari Village, Beber District, Cirebon Regency were used. Tests on original soil were carried out to determine particle size distribution, Atterberg limits, maximum density and optimum water content using Standard Proctor compaction, unconfined compressive strength, one-dimensional swelling, methylene blue value, mineralogy using X-Ray Diffraction (XRD) tests, and microstructure. using a Scanning Electron Microscope (SEM) test. Then, the two expansive soil samples were mixed with sand of various gradations and sizes. The sand used is quartz sand with four different grain sizes. To obtain variations in sand gradation, quartz sand is mixed with a certain composition to obtain artificial gradation. The effect of adding sand to expansive soil was analyzed on the Atterberg limit value, maximum dry density, optimum water content, unconfined compressive strength, swelling potential, swelling pressure, and methylene blue value. The effect of gradation and sand grain size used to improve expansive soil on the parameters of maximum dry density, optimum water content, unconfined compressive strength, swelling potential and swelling pressure was also analyzed. Then the most effective sand content and sand gradation to improve expansive soil for every parameters was determined. Based on the Atterberg limit, methylene blue value, mineral composition, and expansion potential, both expansive soils were identified as expansive soils with very high swelling potential. Then, from the results of sand addition with expansive soil, it was found that the addition of sand reduced the Atterberg limit, but not significant. The addition of sand to both soils increases the maximum dry density, reduces the optimum water content, and improves the shape of the irregular compaction curve. The addition of sand increases the unconfined compressive strength of Cirebon soil up to 10% sand and Cipamingkis soil up to 20% sand. At 20% sand content, Cirebon soil experiences a decrease in unconfined compressive strength. This difference in sand content is caused by the mineral composition of the Cirebon soil samples, which contain more expansive minerals than Cipamingkis soil, therefore more sensitive to additive materials. The addition of sand reduce the swelling potential value for both soils. The effect of sand addition on swelling pressure could not be investigated due to the incompatibility of the test method with the soil samples. The addition of sand can reduce the methylene blue value of both soils. By combining sand and lime, the methylene blue value decreases better than using sand alone. Uniform sand with a fine grain size (0.1-0.5 mm) is more effective for increasing the unconfined compressive strength of expansive soils. Well graded sand and medium and coarse uniform sand is more effective in increasing maximum dry density and reducing optimum water content, however the effect of sand gradation is inignificant on dry density increase. Medium sized uniform sand (0.5-1 mm and 1-2 mm) is more effective in reducing swelling potential and swelling pressure, but the effect of gradation and sand grain size is insignificant on reducing swelling potential and swelling pressure. Cirebon soil with a higher expansive mineral content is more sensitive to stabilizer additon than Cipamingkis soil, so it can only be repaired slightly with sand before the unconfined compressive strength parameter decreases. The most effective sand gradation for improving expansive soil is in the range of uniformly graded sand of medium fine size (0.5-1 mm) to improve density, unconfined compressive strength and swelling of expansive soil.