The rock mass characterization in the Rukoh Supplementation Tunnel was performed using the Multichannel Analysis Surface Waves (MASW) method. To correlate the MASW result, the Rock Mass Rating (RMR) method was measured by examining directly from the core drill. In this study, about 4 locations of core drill within the study area were selected to identify their rock masses in combination with the MASW method. Based on the MASW method, the velocity of S waves (Vs) can be obtained and the weathering grade of rock mass is classified. Results from MASW indicated that Location 1 near the inlet tunnel (BPR 1) consists of 3 weathering zones, which are very hard soil, hard soil, and highly weathered rock, with surface waves velocity (Vs) obtained from 238.476 – 434.363 m/s. Location 2 (BPR2) consists of 3 weathering zones, which are very hard soil, hard soil, and highly weathered rock, with Vs ranging from 216.936 – 489.722 m/s. Location 3 (BPR5) consists of 5 weathering zones, which are soft soil, very hard soil, hard soil, highly weathered rock, and slightly weathered rock, with Vs ranging from 129.808 – 633.510 m/s. Location 4 near outlet (BPR 7) consists of 3 weathering zones, which are very hard soil, hard soil, and highly weathered rock, with Vs obtained from 246.623 – 565.134 m/s. According to the Rock Mass Rating (RMR), the rock quality in TR 1 showed very poor to fair rocks, then TR 2 indicated very poor to fair rocks, while TR 3 classified very poor to fair rocks, and the rock quality of very poor to fair rocks were found in TR 4. Results implied that the MASW measurement gives a good correlation in terms of weathering zones with the interpretation of rock mass quality based on the RMR method.
Groundwater is a main resource for the majority of Indonesian people as a source of clean water to meet their daily needs. The increase in groundwater use is unavoidable due to increasing development in Indonesia, especially in Yogyakarta. Groundwater recharge is important in the hydrological cycle to meet groundwater needs. Therefore, this study aims to estimate groundwater recharge by the chloride mass balance (CMB) method on the southern slope of Merapi Volcano in Yogyakarta, Indonesia. This research was conducted in the rainy and dry seasons from August 2022 until January 2023. This research collects annual rainfall near the study area from the Meteorology, Climatology, and Geophysics Agency (BMKG) Yogyakarta station, monthly data collected from eighteen samples of groundwater station, and monthly data collected from fifteen samples of rainwater in the study area. The chemical content of groundwater and rainwater samples is analyzed using argentometry to obtain chloride concentration. The result of annual rainfall in the study area is 3,603.878 mm/year. The average chloride concentration in rainwater is 1.1 mg/L, while the average chloride concentration in groundwater is 8.015 mg/L. The CMB method calculation showed that the recharge in the study area ranges from 171.65 to 1,711.29 mm/year. The groundwater recharge has a positive correlation with elevation and rainfall. High groundwater recharge is also found in the northern area due to fractured lava aquifer.
Information on groundwater flow patterns is very important in groundwater conservation efforts. The patterns of groundwater flow will also affect the groundwater chemistry. However, information on this issue in some areas is often neglected or not yet available such as in Kendal district, Central Java Province, Indonesia. This paper presents the groundwater investigations in the Kendal groundwater basin area of Kendal district. The investigations cover geological survey, including 114 points of observation and measurements of shallow wells and deep wells. Groundwater sampling also carried out at 15 points that distributed evenly for groundwater chemical analysis. The results showed that the groundwater flow patterns in Kendal are generally flowed from south to north direction, for both the unconfined aquifer and confined aquifer. Based on the trilinear piper diagram, the groundwater facies for unconfined aquifer consists of magnesium bicarbonate, calcium chloride and mixed types. Whereas in the confined aquifer, the results obtained are of sodium chloride, calcium chloride and mixed types. Some similarities of groundwater facies found between the unconfined aquifer and confined aquifer, indicating an interaction of both aquifers. In addition, ion enrichment from the recharge area to the discharge area found due to the interaction of groundwater with aquifer material based on the stiff diagrams.
This study determined the excavation method and the support system in the diversion tunnel of Tiga Dihaji Dam, South Sumatera of Indonesia. Investigation performed in this study included surface geological mapping and evaluation of core drilling that are useful for determining rock mass quality. Geological conditions in the tunnel consist of tuffaceous sandstone lying unconformity over interbedded calcareous sandstone and calcareous siltstone. Based on the Geological Strength Index analysis, the excavation method for tuffaceous sandstone by hammer and blasting, and digging and ripping for the interbedded calcareous sandstone and calcareous siltstone. The support system is the installation of rock bolts of 3 m long with spaced 2.5 m on tuffaceous sandstone, 4 - 6 m long with spaced 1 - 1.5 m on interbedded calcareous sandstone and calcareous siltstone, and with shotcrete thickness of 50 -200 mm (Rock Mass Rating). While in the Q-system classification were 2.7 m long rock bolts with spaced 2.7 m on tuffaceous sandstone, 2.7 m long rock bolts with spaced 1 – 2.4 m, and a shotcrete thickness of 25 cm on interbedded calcareous sandstone and calcareous siltstone.
Groundwater is the primary clean water source for most Indonesian society. The increasing use of groundwater is inevitable due to the rapid development in Indonesia, particularly in Yogyakarta. Shallow aquifers are vulnerable to contamination due to anthropogenic influences. Therefore, this research aims to determine shallow groundwater's physicochemical and chemical characteristics on the southern slope of Mount Merapi, specifically focusing on nitrate and chloride concentrations in groundwater. This research collected monthly data from eighteen dug wells or springs and rainfall data in the study area during the rainy and dry seasons from August 2022 to January 2023. The analyzing sample used argentometry to determine chloride concentration and ultraviolet spectrophotometric to determine nitrate concentration in Yogyakarta Environmental Health and Disease Control Technical Center (BBTKLPP) laboratory. The physicochemical parameters were tested directly in the field using Hanna instruments. The results indicate that a significant portion of shallow groundwater has high nitrate concentrations, corresponding to the growing settlements in the research area. Furthermore, according to the comparison graph between nitrate and chloride, the nitrate source was indicated as anthropogenic. Fecal matter from sanitation practices using septic tanks will likely influence the nitrate increase.
Abstract Raimanuk and its surroundings are a potential agricultural area in Indonesia. Sufficient groundwater in this area was a significant factor for supporting agricultural activities and household needs. Therefore, identifying the aquifer connectivity is essential to determine the groundwater utilization pattern in this area. This research aims to determine the aquifer connectivity based on stable isotopes and hydrochemical from the groundwater and the meteoric water (rainwater). The groundwater samples were taken from ten deep wells, six dug wells, and four springs. While the meteoric water samples were taken from four rainfed locations, samples were analyzed using Los Gatos Research DLT-100, Ion Chromatography Metrohm 830IC, and acid-base titration. The result shows there are four groups of groundwater. Group I is the springs that come from local meteoric water. Group II consists of the dug wells that evaporated and showed a relationship to the meteoric water that falls in higher elevations. Group III was the drilled well groundwater from the local flow system. Furthermore, Group IV is the drilled well groundwater with a more enriched δ 18 O isotope ratio due to water-rock interaction. Even though they are in a different group, there is a hydraulic connection between Group III and IV.
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