ANALISIS KUAT TEKAN UNIAKSIAL PADA BATU TUFA MENGGUNAKAN POINT LOAD INDEX UNTUK MENENTUKAN ROCK MASS RATING DAN SLOPE MASS RATING

Abstract

Sibolangit Village and its surroundings are hilly areas so they are prone to landslides, especially on the slopes of Jalan Jamin Ginting km 37-39 which leads to Brastagi city. This research uses a point load test or Point Load Index as a laboratory test to determine rock mechanics. This research aims to determine the compressive strength values, slope geometry, Rock Mass Rating classification, and Slope Mass Rating. This research method is Rock Mass Rating, a rock mass classification to determine the quality of the rock mass with 5 parameters, namely, rock compressive strength, Rock Quality Designation (RQD), joint spacing, joint condition, ground water condition. This RMR value is a classification of the Slope Mass Rating, the dip direction of the slope surface (αs), the dip direction of the discontinuity plane (αj), the slope angle of the slope (βs), and the slope angle of the discontinuity plane (βj). The results of Point Load Index testing on slope 1 have 8 rock samples with an average PLI (Is) of 0.486 Mpa and uniaxial compressive strength (σc) of 11.17 Mpa. On slope 2 there are 5 samples, the average value of PLI (Is) is 2 MPa, and the uniaxial compressive strength (σc) is 49 MPa. The geometry results for slope 1 obtained a height of 6.1 meters and slope 2 obtained a height of 7.045 meters. Rock Mass Rating results for slope 1 with a score of 32 and rock mass class IV with a poor description, and for slope 2 with a score of 62 and rock mass class II with a good description. Slope Mass Rating results for slope 1 in segment 1 where the potential for rolling landslides is 87.50%, in segment 2 the potential for rolling landslides is 71.43%, and in segment 3 the potential for wedge landslides is 80.00%. The results of the Slope Mass Rating for slope 2 will have a potential for rolling avalanches of 42.86%.