Abstract
This paper presents the investigation of surface geology and subsurface engineering geology to analyze the excavation method and stand-up time of the DK99-DK100 Jakarta-Bandung high-speed railway Tunnel, Indonesia. Rock mass quality, tunnel excavation method, and stand-up time determined using Geological Strength Index (GSI), Basic Quality (BQ) systems, converted to Rock Mass Rating (RMR) and The Japan Society of Civil Engineering (JSCE) for comparison. The result shows that the study area consists of slightly to completely weathered andesite breccia and slightly weathered andesite lava. The rock masses at the tunnel elevation had very poor to poor quality and were associated with high weathering degrees. The recommended rock excavation method based on the GSI is digging. The recommended tunnel excavation method based on RMR is multiple drifts, top heading, and bench, while based on JSCE is bench cut method. The tunnel stand-up time is 30 minutes - 2 hours based on the RMR, while it is predicted to be unstable without support based on the BQ. The recommended design is expected to be applied effectively according to the geological conditions. It is expected to understand better the tunnel excavation method in poor rock masses, especially in Indonesia.
Highlights
The construction of the Jakarta-Bandung fast train is one of the national strategic projects to reduce congestion problems, air pollution, and travel time
The 1:4000 scale geological mapping showed the area formed by the andesite lava and andesite breccia rock unit
The tunnel elevation is located in two engineering geological rock units: completely weathered andesite breccia and highly weathered andesite breccia rock unit
Summary
The construction of the Jakarta-Bandung fast train is one of the national strategic projects to reduce congestion problems, air pollution, and travel time. Design of the tunnel cut through mountainous areas consisting of various types of rocks layers and the influence of geological structure conditions. The condition of rock quality in each rock layer will affect what kind of tunnel excavation method is effectively applied. It is necessary to conduct engineering geological investigations to obtain information on soil and rock mass characteristics, geological structures, and groundwater that may affect the construction site. The authors choose The GSI classification because it is easy to use in field observations and poor rock conditions due to prominent tectonic influences and high weathering rates suitable for use in research locations dominated by volcanic rock affected by tectonic processes. The expected results of the excavation method and stand-up time in the DK 99 – DK 100 tunnel design are appropriate according to the geological conditions found in the field.
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