Penelitian ini bertujuan untuk menentukan parameter tanah tak jenuh melalui pengujian kadar air dan matric suction di laboratorium menggunakan alat High-Suction Polymer Sensor (HSPS). Tanah tak jenuh, yang berada di atas muka air tanah, memiliki karakteristik yang dipengaruhi oleh tekanan air pori negatif dan kadar air. Pengujian dilakukan pada sampel tanah lempung yang diambil dari lapisan atas Fakultas Teknik Universitas Indonesia. Metode penelitian meliputi pengujian indeks properti tanah seperti kadar air alami, analisis saringan, batas Atterberg, berat jenis, pemadatan, dan permeabilitas. Selain itu, dilakukan pengujian matric suction dan water content menggunakan HSPS untuk memperoleh Soil-Water Characteristic Curve (SWCC). Hasil penelitian menunjukkan bahwa hubungan antara matric suction dan kadar air dapat dijelaskan melalui kurva SWCC, yang diregresi menggunakan persamaan Fredlund dan Xing (1994) dan persamaan Satyanaga (2017). Pengujian ini juga mengidentifikasi faktor-faktor yang memengaruhi akurasi pengukuran, seperti kondisi lingkungan dan teknik pengujian. Penelitian ini memberikan kontribusi dalam memahami perilaku tanah tak jenuh dan meningkatkan akurasi pengukuran parameter tanah untuk aplikasi geoteknik.

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This research aims to determine the parameters of unsaturated soils through laboratory testing of moisture content and matric suction using the High-Suction Polymer Sensor (HSPS). Unsaturated soils, which are above the water table, have characteristics that are influenced by negative pore water pressure and moisture content. Tests were conducted on clay soil samples taken from the top layer of the Faculty of Engineering, University of Indonesia. The research methods included testing soil property indices such as natural moisture content, sieve analysis, Atterberg limits, specific gravity, compaction, and permeability. In addition, matric suction and water content were tested using HSPS to obtain Soil-Water Characteristic Curve (SWCC). The results showed that the relationship between matric suction and water content can be explained through the SWCC curve, which was regressed using the Fredlund and Xing (1994) equation and the Satyanaga (2017) equation. It also identified factors that affect measurement accuracy, such as environmental conditions and testing techniques. This research contributes to understanding the behavior of unsaturated soils and improving the accuracy of soil parameter measurements for geotechnical applications.