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The Main Spillway and Diversion Tunnel construction at the Manikin Dam, Nusa Tenggara Timur, is constructed in a claystone Bobonaro Formation. Alongside the construction process, this paper aims to evaluate the engineering geological condition and tunnel excavation method that is expected to provide technical consideration in the process of selecting the fieldwork method. Field investigations were carried out in evaluation of rock mass quality for tunnel boring log. The Rock Mass Rating (RMR) method determines rock mass quality. Subsurface samples were laboratory tested for soil/rock parameters in numerical modeling using the finite element method with numerical evaluation by Phase2 (Rocscience) software. The results of tunnel modeling are in the form of displacement with additional effect earthquake analysis and without earthquake analysis (static load). As a result of subsurface geological mapping, the dominant lithology which passes through the tunnel is scaly clay with the category of rock mass quality as Poor Rock and Fair Rock. Based on the Bieaniawski (1989), the excavation method can be multi drift, benching, or full face. The multi drift excavation method is estimated to earn a lower displacement value than other methods. It produces an estimated roof strength factor value of >1.25, which indicates the tunnel construction is in stable condition. [ABSTRACT FROM AUTHOR]

The Sigli-Banda Aceh Toll Road is part of the Trans Sumatra Aceh-Lampung Toll Road, located in Padang Tiji District, Pidie Regency, Aceh Province. In the implementation of tunnel construction, proper tunnel excavation methods are needed. One of them is knowing the stand-up time, the stand-up time is a curve that can determine when the right supports are installed, the distance between the supports and the length of rock that survives. The longevity of these rocks is in a matter of days, weeks, months, or years. Stand up time is determined from the chart described by Bieniawski [1], by knowing the roof span of the tunnel and the value of Rock Mass Rating (RMR89). Tunnel 2 of the Sigli-Banda Aceh Toll Road was designed by PT. Hutama Karya [2], with a width of 12 meters and a height of 10 meters. The RMR89 value was obtained from 7 core drill points at the tunnel elevation, which was calculated considering 6 parameters, namely Uniaxial Compressive Strength (UCS) of intact rock material, Rock Quality Designation (RQD), spacing of discontinuities, condition of discontinuities, conditions of groundwater and the discontinuity orientation. The average RMR89 value at the tunnel construction elevation of the drill point T-1A obtained 60.3 (fair calcareous sandstone), T-2A obtained 66.5 (good calcareous sandstone), T-3A obtained 65.5 (good calcareous sandstone), T-4A obtained 68.9 (good calcareous sandstone), T-5A got 53.6 (fair calcareous sandstone), T-6A got 41.5 (fair calcareous sandstone) and T-7A got 63.8 (good calcareous sandstone). From the stand up time curve, it can be concluded that for a roof span of 12 meters, calcareous sandstone at drill point T-1A can last for approximately 2 weeks, calcareous sandstone at drill point T-2A, T-3 and T-4 can last for no more than 3 months, calcareous sandstone at drill point T-5A can last for 6 days, calcareous sandstone at drill point T-6A can last for 10 hours and calcareous sandstone at drill point T-7A can last for 3 months. To follow up the results of this study, it is necessary to analyze the determination of the excavation method, tunnel support system and tunnel stability analysis based on the results of the RMR89 value and stand-up time that have been carried out. [ABSTRACT FROM AUTHOR]

The Tunnel 2 Project for the Sigli-Banda Aceh Toll Road Section I, located in Padang Tiji District, Pidie Regency, Aceh Province, is one of the toll road projects built on sedimentary rocks of the Kotabakti Formation of Padang Tiji Members. Rock mass quality classifications of Rock Mass Rating (RMR89) and Japan Society of Civil Engineers (JSCE) were used to determine the empirical design of the excavation method and tunnel support system of 2 Sigli-Aceh Toll Road. Tunnel 2 was designed to have a horseshoe shape with 830 m length, 12 m width, and 10 m height. The data used in this study were obtained from engineering geological mapping, seismic refraction surveys, and drills core evaluations. Analysis of rock mass quality at the study site used subsurface data from the results of 7 boreholes at the position of tunnel depth, namely T-1A, T-2A, T-3A, T-4A, T-5A, T-6A and T-7A. The results show that based on the RMR89 rock mass classification, the tunnel path is in calcareous sandstone with rock mass class's fair to good. T-1A, T-5A, and T-6A are classified in fair rock at the boreholes. At the boreholes, T-2A, T-3A, T-4A, and T-7A are classified as good rock. Based on RMR89, the recommended excavation method for tunnel sections with fair to good rock mass is the full-face, top heading, and bench method. The recommended support system is a rock bolt with a length of 3-4 m, spacing of 1.5-2.5 m, and shotcrete thickness of 5-10 cm. Meanwhile, based on JSCE, the quality of rock mass at boreholes of T-1A and T-5A are in the DI rock category. At boreholes, T-2A, T-3A, T-4A, and T-7A are in the CII rock category, and the borehole of T-6A is in the DII rock category. The recommended excavation method based on the JSCE classification with DI, DII, and CII rock categories are the bench cut method and the full-face method with the auxiliary bench cut method. The recommended support system is a rock bolt with a length of 4.0 m, 1.0 m to 1.2 m spacing, 15 cm to 20 cm thick shotcrete, H-150 and H-200 steel ribs, 1.0 m to 1.2 m steel support spacing, and 40 cm lining on the walls and the arch, and 40 cm to 50 cm lining on the floor. [ABSTRACT FROM AUTHOR]

Underwater wet welding is one option that can be applied in overcoming underwater emergencies, especially in the case of saving the ship damage. Although the results of the weld with SMAW method are between fair and good, but it is still feasible to be used. It is due to the fact that this method is the most popular, economical and efficient for wet underwater welding. In this study, KI-A36 steel plate material was used and implemented for underwater wet welding using E7016 and E7018 electrodes. Both types of electrodes are low hydrogen electrode group that can be found easily in the market. This study investigated the mechanical properties of the underwater welding of marine steel plate by using E7016 and E7018 low hydrogen electrodes. The welding method type with heat inputs of 0.8kJ/mm, 1.5kJ/mm and 2.5kJ/mm were performed at depths of 5m and 10m. The results of radiography test showed that specimen welded at depth of 5m and 10m indicated the occurrence of incomplete penetration defects. It might be due to the influence of considerable pressure and the higher cooling rate that the molten weld could not penetrate completely to the parent material. Nevertheless, this study revealed the absence of porosity in underwater wet welding by applying both E7016 and E7018 electrodes. Tensile test results also showed insignificant decline in the strength of underwater welding results and a considerable elongation. The hardness of welded samples showed insignificant difference between base metal, HAZ and weld metal. The use of E7016 electrodes with the heat input of 1.5kJ/mm provided the optimum mechanical properties of underwater wet welds. [ABSTRACT FROM AUTHOR]