STUDI METODE PERKUATAN LERENG MENGGUNAKAN GEOMAT, SHOTCRETE, DAN SOIL NAILING (Studi Kasus: Lereng Spillway Bendungan Sadarwana Paket II Subang)

Abstract

The landslide of the upper slope in the excavation work of the spillway Sadawarna
Dam Package II Subang occurred after rain, precisely at the STA location from
0+500 to 0+520. The purpose of the study was to compare soil reinforcement on the
previous spillway slope using geomat and shotcrete with soil reinforcement using
soil nailing. Based on soil data the spillway slope consists of two types of slopes, the
upper slope consists of CL (BS:03) while the lower consists of ML (BS:04). The
shear strength parameters C and Phi of both slope soils are quite high. Using Plaxis
V.21, Slope/W and Seep/W, with C and Phi the slopes were found to be stable.
However, in reality there was a landslide on the upper slope. Therefore, back
analysis was performed by lowering the strength parameters of the top soil adjacent
to the slope until the landslide was realized. The reinforcement used on the two
slopes was different, the upper slope used geomat while the lower slope used
shotcrete, then the geomat was changed to soil nailing. Two seasonal models were
applied to all reinforcements. The results showed that the factor of safety values
from the back analysis modeling in the wet season using geomat and shotcrete were
less than 1 (Unstable). However, reinforcement using soil nailing has a Safety
Factor higher than 1.5. Based on these results, soil nailing can be a solution to
minimize landslides on the spillway slope.