Analisis Penurunan Muka Tanah (Subsidens) Menggunakan Metode Empirik Di Terowongan Penstock Sta 10+150 PLTA Kerinci Merangin, Kabupaten Kerinci, Provinsi Jambi.

Abstract

Subsidence analysis in this study was carried out in the Kerinci Merangin hydropower pentstock tunnel construction sta 10+150. The depth of the tunnel at the study site ranges from ± 35 m so that it is included in the shallow tunnel category with the rock at the face of tunnel, namely slate (foliated metamorphic rock) with rock mass conditions is jointed rock with an RMR value of around 23. Predicting subsidence in this study was conducted to assess and determine recommendation due to land subsidence risk based on SNI 8460:2017. Calculation of subsidence values uses the empirical Peck method (Peck, 1969) using primary data in the form of coordinates based on sta location, identification of rock masses and tunnel geometry while secondary data in the form of contour maps is intended to determine the depth of the tunnel. Calculation of subsidence using the peck method requires an inclination point (i) based on the recommendation of Mair (1993), and the land subsidence ratio VL is obtained from the table of the results of Goldsapand's research (1993). Based on the research results, it is known that the maximum subsidence value is 0.97 mm and is right at the center of the tunnel. Furthermore, the value of i or the inflection point is 17.5 m from the tunnel axis with a subsidence value of 0.11 mm and the maximum influence area is at a distance of 20.6 m from the tunnel axis. Based on the SNI 8460: 2017 table, the subsidence in the study area is included in category 1 with recommendations