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Nevy Sandra
Department of Civil Engineering, Faculty of Engineering, Universitas Negeri Padang, Indonesia
Mechanical Engineering

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Spatial modelling of shallow groundwater quality in coastal areas with Kriging interpolation Yaumal Arbi; Nurhasan Syah; Iswandi Umar; Indang Dewata; Mulya Gusman; Nevy Sandra
Teknomekanik Vol. 9 No. 1 (2026): Regular Issue
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/teknomekanik.v9i1.47272

Abstract

This study maps shallow coastal groundwater quality in Padang, Indonesia, using four operational parameters: potential of hydrogen (pH), electrical conductivity (EC), total dissolved solids (TDS), and salinity. We characterize spatial dependence using empirical variograms, evaluate directional anisotropy, and generate prediction surfaces with Ordinary Kriging. The variogram analysis indicates stronger spatial continuity along the coastline for EC and TDS, while salinity shows shorter continuity with a distinct directional structure, reflecting localized freshwater-seawater mixing processes. Groundwater pH remains neutral to slightly alkaline and exhibits lower spatial variability than EC, TDS, and salinity. Leave-one-out cross-validation supports the reliability of the kriging estimates at the study scale, indicating low prediction error and strong agreement between observed and predicted values. The resulting thematic maps enable a three-level quality zoning that differentiates a lower-risk northern segment, a transitional central belt, and a higher-risk southern segment consistent with seawater intrusion influence. These outputs provide a practical basis for prioritizing monitoring locations, protecting vulnerable wells, and strengthening evidence-based coastal groundwater management aligned with SDG 6 Clean Water and Sanitation and SDG 11 Sustainable Cities and Communities.
Application of ground penetrating radar for evaluating foundation structure condition after earthquake Risma Apdeni; Zel Citra; Fitra Rifwan; Prima Yane Putri; Nevy Sandra; Yosie Malinda; Paksi Dwiyanto Wibowo; Reza Ferial Ashadi; Annisa Prita Melinda
Teknomekanik Vol. 7 No. 1 (2024): Regular Issue
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/teknomekanik.v7i1.26772

Abstract

At the time of seismic activity, the failure of the foundation structure will lead to building damage. When the West Pasaman 2022 earthquake occurred, PT. XYZ is constructing a feed mill tower. Since strong earthquake shocks were felt at the project location, foundation structure evaluation is needed to ensure the safety of the building. Ground Penetrating Radar (GPR) is a tool that is widely used to detect subsurface conditions. This study used GPR as a non-destructive testing technique to evaluate the condition of the foundation structure. The building evaluated is a high-rise steel building, using spun pile foundation. GPR test was carried out in specified lanes, with measurement tracks set at 10 lanes. Any cracks or fractures on the foundation will be indicated by the interruption of waves at the point of the crack or fracture. The GPR test results from readings of electromagnetic wave propagation showed that waves can reach the end of each foundation tested, ranging from 17.10 m to 17.82 m deep. It means that there are no cracks or fractures found on the slab, pile cap, or foundation. Analysis results showed that all slabs and pile caps thicknesses and the detected foundation piles depths are in accordance with the foundation design, which means that the foundations are still in good condition.
Durability performances of ferronickel slag aggregate and seawater concrete Nevy Sandra; Muhammad Akbar Caronge; Jati Sunaryati; Keiyu Kawaai; Willick Nsama; Yaumal Arbi; Ari Syaiful Rahman Arifin
Teknomekanik Vol. 8 No. 1 (2025): Regular Issue
Publisher : Universitas Negeri Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24036/teknomekanik.v8i1.34572

Abstract

The rising demand for concrete in the building sector has resulted in the exhaustion of natural sand and freshwater supplies, leading to the pursuit of sustainable substitutes. Coastal areas have plentiful ferronickel slag (SL) and seawater (SW), which can be used to manufacture concrete. Nevertheless, the possibility of corrosion to steel reinforcement raises concerns that require further research. This investigation examines the mechanical and durability performance of concrete that incorporates SL as a partial replacement for fine aggregate and SW as a mixing component. The objective is to optimize SL content to improve compressive strength, resistance to chloride ions, and overall durability. Experimental results show that replacing 25% of the aggregate with SL yields the best combination of workability, strength, and durability, significantly enhancing compressive strength, decreasing porosity, and lessening chloride ion penetration, as evidenced by the Rapid Chloride Penetration Test (RCPT). Although seawater promotes early-age hydration and strength development, its extended use slightly diminishes compressive strength due to salt-induced micro-cracking. However, SL counters these effects, making SW–SL mixture a feasible and sustainable option for concrete production in coastal and resource-limited areas. A significant relationship between RCPT and compressive strength underscores the important role of SL in densifying the matrix and improving impermeability. The concrete mixture with 25% SL exhibits the lowest abrasion weight loss at 28 and 120 days, showing improved durability. This study highlights the potential of using SL and seawater to create eco-friendly and high-performance concrete for harsh environments.
Co-Authors Annisa Prita Melinda Ari Syaiful Rahman Arifin Fitra Rifwan Indang Dewata Iswandi Umar Jati Sunaryati Keiyu Kawaai Muhammad Akbar Caronge Mulya Gusman Nurhasan Syah Paksi Dwiyanto Wibowo Prima Yane Putri Reza Ferial Ashadi Risma Apdeni Willick Nsama Yaumal Arbi Yaumal Arbi Yosie Malinda Zel Citra