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All Journal Sinergi Indonesian Geotechnical Journal
Gumay, Herdian
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Civil Engineering, Building, Construction & Architecture Control & Systems Engineering Earth & Planetary Sciences Electrical & Electronics Engineering Engineering Industrial & Manufacturing Engineering

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Effect of near-surface heterogeneities on the pore-water pressure distribution and slope stability Gofar, Nurly; Pangestika, Ega Nanda; Harianto, Yudi; Gumay, Herdian; Satyanaga, Alfrendo
SINERGI Vol 28, No 2 (2024)
Publisher : Universitas Mercu Buana

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22441/sinergi.2024.2.012

Abstract

Seepage and slope stability are important problems analyzed in geotechnical engineering. Conventionally, the analysis is performed in conditions where the soil is intact. However, near-surface soil is subjected to various conditions that lead to heterogeneity, for example, the presence of cracks in clay, relics in weathered rock, and plant roots. The presence of cracks and other forms of heterogeneity on the near-surface layer increases the rainfall infiltration into the slope and changes the pore water pressure distribution accordingly. Water infiltration increases the pore water pressure, raises groundwater level, and decreases the matrix suction of unsaturated soils - which is a critical factor for the stability of slopes. This study aims to evaluate the effect of varying permeability of near-surface soil on the rainwater infiltration to slope and, subsequently, the safety factor. In this case, the near-surface soil is modeled as a layer with higher permeability. Numerical analysis performed in this study using SEEP/W and SLOPE/W indicated that considering this condition results in a higher safety factor of the slope because the higher permeability resulting from heterogeneity helps dissipate pore water pressure, which is critical in maintaining the slope stability during heavy rainfall.
Water Retention Curve of Soil at Simpang Meo Region South Sumatra Purnamawati; Gumay, Herdian; Gofar, Nurly
Indonesian Geotechnical Journal Vol. 4 No. 2 (2025): Vol. 4, No. 2, August 2025
Publisher : Himpunan Ahli Teknik Tanah Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.56144/igj.v4i2.122

Abstract

Steep slopes are typically formed on residual soil with deep groundwater levels; hence, the slopes are in the unsaturated zone. Therefore, in analyzing the stability of steep slopes, it is necessary to consider the properties of unsaturated soil. The main property of unsaturated soil is the Water Retention Curve (SWCC), which describes the relationship between matric suction and soil moisture content. Many methods are available to determine the SWCC of a soil, such as laboratory and field tests, as well as empirical equations. Laboratory testing is considered the best method for determining the SWCC. However, the laboratory work involved in the determination of SWCC is tedious; thus, several models have been developed by researchers to obtain SWCC. This study compares SWCC obtained based on the results of laboratory testing using an Osmotic Tensiometer assisted by soil shrinkage measurements using a 3-D scanner, and the SWCC obtained using the empirical equation proposed by Zapata for plastic soil based on the percentage of particles passing the No. 200 sieve and the soil plasticity index.   The soil samples were retrieved from a location in the Simpang Meo region in South Sumatra. Air entry value for the SWCC was obtained both graphically and deterministically. Both methods resulted in a lower air entry value (AEV) for the Zapata equation as compared to the osmotic tensiometer test. A lower AEV indicates that lower suction is required for water to enter the soil pores.  Therefore, analysis of rainfall infiltration and slope stability using SWCC curves estimated from the Zapata equation could result in later saturation of soil, hence a slightly higher factor of safety
Co-Authors Alfrendo Satyanaga Harianto, Yudi Nurly Gofar, Nurly Pangestika, Ega Nanda Purnamawati