Journal of Geoscience, Engineering, Environment, and Technology
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Groundwater Effect on Slope Stability in Open Pit Mining: a Case of West Kutai Regency, East Kalimantan, Indonesia
Full text linkThe stability of open pit slopes in Biangan district, West Kutai Regency, East Kalimantan Province, is greatly influenced by groundwater conditions. The existence of groundwater reduces the shear strength of the materials which causes a decrease in the stability value of pit slopes. The main objective of this study is to assess the impact of groundwater on the stability of the low wall and high wall pit mining. Groundwater modeling is used to determine the prediction of groundwater level on the pit slope which determines the value of the slope stability. Slope stability analysis in this study was performed using the Finite Element Method, producing output in the form of strain zones, deformation and displacement values. Therefore, the Strength Reduction Factor (SRF) approach was used, which is a gradual reduction of shear strength until the values of cohesion and friction angles reach minimums and the slopes are at a critical state. Groundwater modeling results indicate that groundwater flows to the Biangan river with hydraulic heads between 76 and 108 meters above sea level. Based on the analysis using the Finite Element Method, the stability values of the pit slopes, which are influenced by groundwater, are 0.65 on the low wall and 1.40 on the high wall. The total displacements are 0.019 meters on the low wall and 0.002 meters on the high wall. The impact of groundwater on the slope is an increase in the slope load. This increases the materials’ thrust and reduces the shear strength of the materials which reduces the rock mass that can function as a water seepage path. Thus, the recommendation for low wall pit construction is a safety factor of 7.79 with a total displacement of 0.020 meters
Resistivity Method for Characterising Subsurface Layers of Coastal Areas In South Sulawesi, Indonesia
Full text linkThe data presented in this paper are related to the characterization of a subsurface layer of coastal area in South Sulawesi. This research will fill the gap in the resistivity method study which is this method not yet use in the coastlines area, especially area influenced by seawater and coastal condition impact like South Sulawesi. The method used in this study is the method of resistivity Wenner configuration by taking the data 1-2 lines each region with lengths 45 m, 75 m, 105 m, and 120 m respectively. Data processing using non-linear least square optimization with that of the 2D inversion software Res2Dinv. The results show that the area is underlain by two layers of lithologic sections. In some sections interpreted by sandy layer, clay, sandstone, alluvium, sandy in seawater and metal minerals. From the analysis of the layers, all regions show the resistivity minimum is 0.00849 Ωm and 8.04 Ωm maximum resistivity. The result of this research can give n insight to study the large coastal area subsurface
Hydrogeochemical and Characteristics of Groundwater in Teluk Nilap Area, Rokan Hilir, Riau
Full text linkGroundwater plays important role as the main water resource for human needs. The vulnerability of groundwater to contaminants both naturally and by human activities can be not avoided as a trigger for groundwater quality degradation. Hydrogeochemical become important highlights in groundwater studies because groundwater conditions in quality and quantity influenced by the geological formation of rock minerals in aquifer. Naturally, the condition of the research area which consists of peat swamps can also affect the characteristics of groundwater. The aims of this research are to determine groundwater types and groundwater facies in study area with an analytical approach using stiff diagram and piper diagram. The method used was purposive sampling by collecting data from dug wells at the research site. 5 samples from dug wells were used as representatives in the groundwater facies analysis. The groundwater facies analysis was carried out by measuring the concentration of major ions such as Na, K, Ca, Mg, Cl, SO4, and HCO3. The highest groundwater level was in the northern part of study area (7,84 m) while the lowest groundwater level was in the southwest part of study area (2,05 m). The results showed three types of groundwater based on stiff diagram as sodium chloride (NaCl), sodium sulfate (NaSO4) and magnesium sulfate (MgSO4). The lithology conditions that composed the aquifer affected the facies or origin of groundwater. The alluvium layer in the research area which rich in sodium (Na+) minerals with chloride (Cl-) or sulfate (SO42-) anions forms chloride sulfate facies (Cl+SO4) which were located in the middle to the south of the study area and sodium (potassium) chloride (sulfate) facies (Na(K)Cl(SO4)) which were distributed in the northern part of study area
The Influence of External CFRP String Reinforcement on The Behavior of Flexural RC Elements
Full text linkExternal reinforcement is an excellent method for improving the load carrying capacity and ductility behaviour of reinforced concrete members in flexure. Enhancement becomes a necessity when current standards mandate a higher performance compared to older codes. External reinforcement is an environmentally friendly and sustainable solution, since demolition and re-building could be postponed, and the building can be used while work in conducted on the members. Carbon Fiber Reinforced Polymers (CFRP), having a low weight-to-volume ratio and an excellent resistance to corrosion, can be used as external reinforcement to effectively increase the flexural and shear strength of a member. To evaluate the effectiveness of CFRP strings, two types of reinforced concrete T-beams were tested. The specimens consist of a strengthened member in both shear and flexure using CFRP wraps and CFRP strings, and a conventional reinforced concrete beam. The specimens were subjected to a one-point-loading system to simulate high shear stresses in combination with a maximum bending moment at mid-point. The installation of CFRP strings was conducted using the Near Surface Mounted (NSM) method, while the sheets were Externally Bonded Reinforcement (EBR). The strings and sheets were impregnated and pultruded on side. The test results showed that the strings and wraps substantially increased the ultimate load carrying capacity and ductility of the member. The ultimate load enhancement was found to be 32% from 117kN to 154kN, and the vertical deformation improved 25% from 16 mm to 20 mm. The failure mode was characterized by initial debonding of the strings in the interface between the strings and the epoxy, followed by string-rupture. The two strings ruptured concurrently, due to stress re-distribution within the member
Biometric similarity Test of The Population of T. (Zaria) bantamensis tjicumpaensis with T. (Zaria) javana as a Form of Phylogeny And Evolutionary Proximity
Full text linkBiometric aspects in the Turritellidae family need to be studied as an important identification parameter. Zaria, which is one of the sub genera in the Turritellidae family, deserves to be tested in order to determine the feasibility of the biometric aspect as an identification parameter. This paper aims to provide an overview of the benefits of the biometric aspect as an identification parameter. The method used to re-identify the biometric and morphological aspects of the T. (Zaria) bantamensis tjicumpaensis population with T. (Zaria) javana. The results of the identification were carried out by a T-Test on the biometric aspect to see the similarity of the biometric aspects of the two populations. Based on the results of the T-Test on the parameters of the Wsut: Wang and Wsut: L ratio, it shows that the two Zaria species are the same. Meanwhile, from the morphological aspect, there is a slight difference in the early growth peripherals
Resistivity Data Modeling for Subsurface Volcanostratigraphy Construction of Cibadak Sub-Watershed, Bogor, West Java, Indonesia.
Full text linkIn Mt. Salak, there are six volcanic facies divided by eruption time seen from geomorphology data analysis and to identified the subsurface layer DC Resistivity method is applied. Beside resistivity, geostatistical parameters also influence the result model interpretation, so for obtain best model correlation parameters such as tilting, surfacing, variogram, grid method, and logarithmic distribution is applied. Using 18 points of acquisition data subsurface model is produce and then section model made to describe vertical resistivity distribution then correlated with facies lithology model. Based on that, produce three facies resistivity type namely: 0 – 100 Ohm.m (Low Resistivity Value) Interpreted as pyroclastic material composed as tuff and breccia that lies under lava. 100 – 300 Ohm.m (Medium Resistivity Value) Interpreted as breccia lithology type. Harder that pyroclastic material due to by this product is avalanches of lava. And >300 Ohm.m (High Resistivity Value) Interpreted as lava lithology that lies at high elevation and the hardest lithology in this area. From the model, pyroclastic layer that is modeled found at low elevation and based on the direction it described as oldest facies layer, but at the bottom of this layer lies high resistivity value that unknown product. It can be Mt. Pangrango product due to at low elevation predicted as combine area product from product of Mt. Salak and Pangrango. High resistivity value show lava lithology and lava facies located in high elevation and medium resistivity describe breccia lithology as avalanche product of lava (youngest pyroclastic facies) and found at 500 – 100 meters msl
Characteristics of Chromite Deposits at North Kabaena District, Bombana Regency, Southeast Sulawesi Province, Indonesia
Full text linkThe study area is located in North Kabaena District, Bombana Regency, Southeast Sulawesi. This paper is aimed to describe characacristics of chromite deposits. This study is conducted in three stages, three stages including desk study, field work and laboratory analysis. Desk study mainly covers literature reviews. Field work includes mapping of surface geology and sampling of representative rocks types. Laboratory analysis includes the petrologic observation of handspecimen samples, petrographic analysis of the thin section and ore microscopy for polished section. The results of petrographic analysis show that olivine minerals are generally replaced by minerals orthopyroxene and has been alterated by lizardite type serpentine veins with a fractured structure. The mineral olivine is also replaced by the mineral chrysotile as a secondary mineral with a fibrous structure. Based on ore microscopy analysis show that chromite has generally experienced a lateritification process and has been replaced by magnetite, hematite and geotite minerals. Chromite has experience process of weathering and alteration from its source rock caused by tectonics that occurred in the study area. The results shows that the characteristics of chromite deposits in North Kabaena District Chromite deposits has generally encountered in peridotite rock which have a grain size of 0.3-20 cm. Furthermore, chromite deposits in the study area are also encountered in podiform deposits, distributed locally and shows podiform to tubular shape with the dimensions of 30-60cm
A Tracer Streamline Practice for Re-Evaluation Waterflood Pattern to Introduce a Cyclic Water Injection Scheme
Full text linkWaterflood introduces in the oil field a couple of years ago. Several waterflood schemes have been implemented in the fields to get the best incremental oil, such as peripheral injection, pattern waterflood, and etcetera. Many waterflood schemes are not working properly to boost the oil recovery due to unpredicted and unexpected water tide array. Then, the tracer practice started to be used for getting a better picture of the transmissibility reservoir as well as the direction of water pathway. This practice honors the parameters, such pressure, water cut, GOR, and rates. The streamline modeling is used to map the tracer, and it concludes that the selection of location of the injector should be based on the highest oil recovery achieved. Subsequently, the cyclic water injection method is one alternative. Apparently, this approach yields a quantify incremental recovery. This research utilizes the pressure different approach to figure out the route of water in the formation. The inter-well tracer technique in this modeling study is a tool to review communication between injectors and producers in the existing pattern. Many scenario should be tried to find the best options for the new pattern opportunities. In parallel, a innovative scheme of waterflood technique should be implemented too for escalating oil recovery. The stream pathway observes a new potential of the waterflood scheme. It is called "cyclic injection" scheme. The novelty of this approach is the ability to solve the poor sweep efficiency due to improper pathway of water influx in the oil bearing"
Feasibility Study on the Application of Dynamic Elastic Rock Properties from Well Log for Shale Hydrocarbon Development of Brownshale Formation in the Bengkalis Trough, Central Sumatra Basin, Indonesia.
Full text linkIn modeling the hydraulic fracking program for unconventional reservoir shales, information about elasticity rock properties is needed, namely Young's Modulus and Poisson's ratio as the basis for determining the formation depth interval with high brittleness. The elastic rock properties (Young's Modulus and Poisson's ratio) are a geomechanical parameters used to identify rock brittleness using core data (static data) and well log data (dynamic data). A common problem is that the core data is not available as the most reliable data, so well log data is used. The principle of measuring elastic rock properties in the rock mechanics lab is very different from measurements with well logs, where measurements in the lab are in high stresses / strains, low strain rates, and usually drained, while measurements in well logging use the principle of measured downhole by high frequency sonic. vibrations in conditions of very low stresses / strains, High strain rate, and Always undrained. For this reason, it is necessary to convert dynamic to static elastic rock properties (Poisson's ratio and Young's modulus) using empirical equations. The conversion of elastic rock properties (well logs) from dynamic to static using the empirical calculation method shows a significant shift in the value of Young's Modulus and Poisson's ratio, namely a shift from the ductile zone dominance to the dominant brittle zone. The conversion results were validated with the rock mechanical test results from the analog outcrop cores (static) showing that the results were sufficiently correlated based on the distribution range