KARAKTERISTIK KUAT GESER SISA PASIR TERLIKUEFAKSI DI BALAROA

On September 28, 2018, a 7.5 Mw earthquake hit Central Sulawesi, triggered by the movement of the Palu Koro Fault. This earthquake led to liquefaction in Balaroa, a phenomenon where seismic forces elevate pore water pressure in sandy soils, reducing effective stress and causing a loss of shear strength. This research focuses on evaluating the residual shear strength characteristics of liquefied sand in Balaroa, examining how relative density affects this residual shear strength, and analyzing soil gradation at three liquefaction sites. The study employed direct shear testing on liquefied sandy soil samples from Balaroa, which passed through a No. 8 sieve and were retained on a No. 200 sieve. The samples were prepared with relative densities of 20%, 35%, and 50%, totaling 81 samples in total, with 27 samples from each site representing Upper Balaroa, Central Balaroa, and Lower Balaroa. The findings reveal that an increase in relative density significantly increases the cohesion and internal friction angle, both in terms of peak and residual shear strength.