Pengaruh Jarak Antar Drain Hole Terhadap Penurunan Muka Air Tanah pada Lereng Tambang Terbuka Batubara

The presence of groundwater on the slopes of the mine, which means that the slopes are saturated with water, will cause a decrease in slope stability. Drain hole is a method that can be applied to decrease groundwater level on a mine slope. This research was conducted to determine the effect of horizontal distance between drain holes on the mine slope on the decrease in groundwater level (groundwater drawdown). Groundwater flow simulation on the slopes of an open pit coal mine with 3 scenarios, without drain holes, 100 m horizontal space between drain holes, and 50 m horizontal space between drain holes, was carried out to answer the goal of this research. The results obtained from the simulation, the third scenario with a distance between drain holes of 50 m has the maximum result compared to the other two scenarios, which are the percentage of groundwater drawdown of 54.1% and groundwater discharge of 167.3 L/s. So it can be concluded that the denser the horizontal distance between the drain holes on the mine slope, the higher the groundwater drawdown on the slope

Physical Model of Vertical Water Movement Inside a Soil-Column Apparatus for Infiltration Study with A Two-Way Orientation Approach

To improve the theory of Richard's equation, studying infiltration under free-draining conditions at the ground surface is necessary. Verification is required to clarify the physical model of water movement. The aim of this study was to describe multistage measurements of both the wetting and the drying front scheme of one-dimensional infiltration at laboratory scale. A soil-column infiltration apparatus was built consisting of a double acrylic wall, a sensor set and a light bulb. Acrylic was chosen as the material for the wall to minimize possible heat conduction on the wall side, which was wrapped in double insulation to achieve adiabatic condition. The following three main sensors were used and controlled by a microcontroller: water-content, pressure and temperature sensors. Meanwhile, the light bulb at the top of the apparatus was set to non-isothermal condition. The instrument was successfully built to describe vertical water movement. Slight modifications were carried out to ensure more precise observation. This resulted in the initiating of new shape interpretation based on the water-ponding measurement to refine the simplified pattern that was introduced by the conventional Green-Ampt theory

Physical Soil Parameter and Resistivity Profile in the Vadose Zone: Preliminary Result of Groundwater Recharge Study

In tropical-volcanic-dominated areas, such as Java Island in Indonesia, aquifer recharge is highly impacted by rainfall intensity and soil characteristics. The first stage of recharge begins with the soil surface's response to rainwater until it percolates to the deep layer. The primary objective of this research was to study groundwater recharge processes from the soil surface to deep percolation in the volcanic deposit at the northwest flank of Mount Pangrango, West Java, Indonesia. The present study also includes the 2D geoelectrical survey results combined with the soil core drilling. A vertical undisturbed soil profile 4 to 4.5 meters deep was drilled to determine parameters such as soil water content, total porosity, permeability, organic content, and soil texture. Results from core drilling activities confirmed that resistivity values are in the range of 80 to 360 ohm.m, which is related to wet soil layers at 1 to 4 meters below the surface. It is found that the most significant difference between organic and mineral soils in terms of resistivity value is that of organic content. Depth and radius of Pinus merkusii and Melia azedarach tree according to resistivity and soil drilling result confirmed at 2.5; 4.5 meter and 0.9; 2.2 meters respectively. By profiling these factors, the behavior of water movement may be better described, allowing the net recharge rate from rainwater to the water table in the unsaturated zone to be estimated

Simulation of Agricultural Wetland Area of Typology C through The Van Genuchten Model Approach

Abstract. The use of groundwater flow equations in porous media is often applied optionally, i.e. under saturated soil or only for unsaturated conditions. Tidal agricultural zone of typology C, is an example of how these two assumptions can occur simultaneously. The parameters of the hydraulic conductivity values in this zone can be illustrated by Van Genuhten model approach so that the distribution of water content in spatiotemporal can be described precisely. The numerical model used in land wetting simulation is a finite different method of up to 1D horizontally with an explicit scheme. In the context of the managerial aspects of water management, the scheduling system of tidal-lowland for agricultural purposes, will also be explained from the simulation results

Konduktivitas Hidrolik Material Setara Lanau Pada Tanah Tak Jenuh Air

Nilai konduktivitas hidrolik memiliki nilai ketidakpastian yang beragam. Pada tanah tak jenuh air, nilai konduktivitas hidrolik bervariasi terhadap distribusi kadar air. Variasi nilai konduktivitas hidrolik tersebut dapat diaplikasikan, salah satunya pada proses konsolidasi tanah tak jenuh air, dimana umumnya proses konsolidasi ditinjau pada tanah jenuh air. Penelitian ini mencoba mengambil studi kasus konduktivitas hidrolik material setara lanau dengan menggunakan pendekatan logaritma potensial kapiler (pF), persamaan rumus van Genuchten, dan spreadsheet Microsoft Excel. Hasil penelitian ini berupa nilai konduktivitas hidrolik material tanah setara lanau yang bervariasi terhadap distribusi kadar air pada tanah tak jenuh air, sehingga penelitian ini nantinya diharapkan dapat memberikan kontribusi positif pada perkembangan keilmuan hidrogeologi bidang geoteknik terutama yang berkaitan dengan konsolidasi pada tanah tak jenuh air

Karakterisasi Derajat Kejenuhan Tanah Berdasarkan Pendekatan Logaritma Potensial Kapiler (pF)

Tanah merupakan hasil pelapukan batuan baik secara fisika, kimia, dan organik. Dari sisi keilmuan rekayasa air tanah, tanah memegang peranan yang sangat penting dalam menyimpan air. Kemampuan tanah dalam menyimpan air sesuai dengan ukuran butirannya. Klasifikasi ukuran butiran tanah dapat dibedakan berdasarkan klasifikasi tekstur, dan struktur, yang secara umum dibedakan atas kerikil, pasir, lanau, dan lempung. Setiap klasifikasi tersebut memiliki derajat kejenuhan yang bervariasi. Penelitian ini menggunakan pendekatan logaritma potensial kapiler (pF) untuk menyatakan energi penahan air di dalam tanah. Kapasitas tanah tidak hanya menahan air namun juga menahan udara sehingga dalam menentukan kelembapan tanah terdapat fraksi cair berupa air dan fraksi gas berupa udara. Tingkat kejenuhan air dan udara di dalam tanah dapat menentukan klasifikasi jenis tanah. Hasil dari riset ini berupa energi penahan air di dalam tanah yang dikorelasikan dengan parameter tanah lainnya berupa porositas, kadar air, dan derajat kejenuhan dalam bentuk grafik saturasi. Dari hasil pengolahan data, dilakukan interpretasi korelasi derajat kejenuhan air dan udara terhadap jenis tanah. Hasil yang diharapkan terkait dengan hasil penelitian ini adalah deskripsi distribusi kadar air pada zona tanah tak jenuh air dengan pendekatan logaritma potensial kapiler serta pola perbandingan derajat kejenuhan tanah berdasarkan parameter air dan udara

Estimasi Konduktivitas Hidraulik Rekahan Batuan Menggunakan ANFIS : Perbandingan dengan HC-System

Intensitas rekahan batuan yang tinggi pada proyek geoteknik seperti terowongan, lereng, dan pembangunan bendungan sangat dipengaruhi oleh kehadiran airtanah. Aliran airtanah media rekahan lebih sulit diprediksi daripada aliran media berpori. Konduktivitas pada media rekahan lebih umum diukur dengan packer test. Karena adanya batasan finansial dan waktu, pengukuran dapat digantikan menggunakan korelasi dengan parameter atau indeks yang lebih mudah didapatkan untuk mengestimasi dan memodelkan nilai konduktivitas yang sebenarnya. Salah satu sistem korelasi indeks yang umum yang digunakan yaitu HC-system. Sistem tersebut terdiri dari 4 indeks yaitu RQD, kedalaman, isian, dan permeabilitas pori batuan. Nilai HC-system berkorelasi sebesar R2 = 0,85 dengan hasil packer test dari metode regresi. Prediksi konduktivitas hidraulik dapat ditingkatkan dengan metode ANFIS (Adaptive Neuro-Fuzzy Inference System). Metode alternatif ini dapat menghasilkan korelasi keempat indeks dengan hasil packer test sebesar R2 = 0.9

Fuzzy-Based Prediction of Spatio-Temporal Distribution of Wet Muck in Block Cave Mine of PT Freeport Indonesia

Mud rushes, or wet muck spills, are hydro-geotechnical challenges in block cave mines where wet muck spills out of drawpoints formed by the accumulation of fine materials and water in drawbells. The purpose of this paper is to share the results of the developement of an improved predictive tool that can be used to manage wet muck spills. The tool was developed based on the hybrid modeling of wet muck distribution using fuzzy logic and fuzzy number operations. The fuzzy logic operations were applied to model the spatial distribution of wet muck classes, providing the spatial model of drawpoint status based on five contributing factors, i.e. the height of draw, the water content, the grain size of the fine material, rainfall, and no-mucking days. The fuzzy number operations were used in accordance with the mass balance principle to estimate the temporal distribution of wet muck that forms a mud deposit consisting of fine materials and water in a drawbell. The mass balance principle was expressed using the fuzzy ordinary differential equation, including the uncertainty of joining variables. A wet muck spill event at the Deep Ore Zone (DOZ) block cave mine of PT Freeport Indonesia was utilized as a case study as well as to validate the proposed method. The fuzzy-based approach shows promising results in predicting wet muck spill events

Modeling Spatial Distribution of 3D Isotropic Hydraulic Conductivity Based on HC-System for Fractured Groundwater Flow Media using Neural Network Case Study Grasberg Open Pit of PTFI

Hydraulic conductivity property is very important for groundwater flow modeling. It can be gathered through packer test and slug test. The high cost of the operational implementation of these tests lead to the limited availability of observational-based distribution of hydraulic conductivity data. Highly fractured rocks in Grasberg open pit mining and surrounding of PT Freeport Indonesia (PTFI) result in fractured-groundwater-flow media. It is related to the complex geological structure and lithological condition. Groundwater modeling needs 3D distribution data such hydraulic conductivity (K). On previous research, hydraulic conductivity is distributed homogenyneously at each layer model. In this paper, under limited observational hydraulic conductivity, isotropic hydraulic conductivity will be modeled based on the HC-System approach and will be three-dimensionally distributed using Artificial Neural Network (ANN). HC-System approach will be developed according to the packer test and slug test measurement using geotechnical data from drilling such as Rock Quality Designation (RQD), Lithology Permeability Index (LPI), Depth Index (DI), and Gouge Content Index. HC-System approach will be resulted in isotropic distribution of hydraulic conductivity. It is then checked at some points by the packer tests and slug tests observational data. It is further very beneficial for modeling of groundwater distribution flow with the heterogeny hydraulic conductivity