Study of Shear Strength Parameter of Lime Trass Stabilization on Clay: Ways to Improve Soil Strength
Listyawan, Anto Budi
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Clay soil is usually weak and has low shear strength because it contains many minerals that tend to be very high expansive. Expansive soils owe their characteristics to the presence of swelling clay minerals. As they get wet, the clay minerals absorb water molecules and expand; conversely, as they dry they shrink, leaving large voids in the soil. The problems arise when subgrade of highway pavement is made of expansive soil as it can be seen on Tanon, Sragen. The pavement damage is signed by cracking, settlement, and rutting. Tanon clay is classified as high plasticity inorganic clay (Wiqoyah, 2003). The Liquid Limit and Plasticity Index are 88.03% and 49.44% respectively. The cohesion and friction angle are 19.97 kg/cm2 and 2.140. The soil contains smectite clay minerals, such as montmorillonite, which exhibits the most profound swelling properties. Based on the last research on Tanon clay, the treatment should be carried out to improve the shear strength of the soil and to reduce all problems on the pavement. This research focuses to study the physical and mechanical characteristic of the Tanon clay mixed by lime and trass. The Tanon clay is mixed by lime and trass in the percentage of: 0%, 2.5%, 5%, 7.5% and 0%, 2.5%, 5%, 7.5%, 10% respectively. The mixed soil samples are tested in atterberg limit, gradation, specific gravity, and Unconsolidated-Undrained Triaxiall apparatus. The samples are in 3 days curing and 4 days soaking. The result shows that the lime and trass stabilization increases specific gravity, Plastic Limit and Shrinkage Limit. On the other hand, it reduces Liquid Limit and Plasticity Index. As the percentage of lime and trass increase, the friction angle tends to improve. The maximum friction angle occurs on the adding of both lime and trass of 7.5%. For 3 days of curing, the friction angle is 19.01o and for 4 days of soaking, it exhibits friction angle of 17.67o. The cohesion of Tanon clay stabilized by lime and trass also increases. The maximum cohesion of sample with 3 days curing occurs in the percentage of lime and trass of 7.5% and 2.5% respectively. On the other hand, the maximum cohesion of sample with 4 days soaking happens in the percentage pf lime and trass of 10% and 7.5% respectively. The simultaneous increasing of friction angle and cohesion show that the lime and trass stabilization on clay is effectively improving the soil strength.