Studi Pengaruh Ukuran Butir Terhadap Porositas dan Konduktivitas Hidrolik Batupasir dan Batulempung (Study of The Effect of Grain Size on Porosity and Hydraulic Conductivity of Sandstone and Claystone)
DOI:
https://doi.org/10.30872/jtm.v10i2.9021Abstract
Abstrak
Porositas dan konduktivitas hidrolik berhubungan langsung dengan aktivitas penambangan, di antaranya pembuatan jalan tambang (ramp) pada front area penambangan. Proses penambangan yang menyebabkan pori-pori tanah semakin kecil (ruang pori berkurang) sehingga porositas mengecil disebabkan pengaruh ukuran butir. Untuk mengetahui pengaruh ukuran butir terhadap porositas batupasir dan batulempung serta pengaruhnya juga klasifikasi nilai porositas dan konduktivitas hidrolik batupasir dan batulempung ini, metode yang digunakan ialah analisis ukuran butir untuk mengetahui besarnya ukuran butir dan jenis batuan menggunakan skala Wentworth (1992) kemudian pada analisis porositas menggunakan pengujian sifat fisik, dilakukan untuk mencari nilai yang berpengaruh terhadap kekuatan batuan seperti natural density, dry density, saturated density, apperent specific gravity, true specific gravity, specific gravity, natural water content, saturated water content, derajat kejenuhan, porositas dan void ratio (Arif, 2016). Pada ada analisis konduktivitas hidrolik digunakan alat permeameter untuk mengetahui kecepatan air dalam satuan (meter/detik) dari sampel batupasir dan batulempung dengan jumlah 10 sampel berbentuk coring.
Hasil penelitian menunjukkan bahwa nilai ukuran butir batupasir adalah 1/8 atau 0,125 mm sedangkan batulempung adalah 1/256 atau 0,003 mm. Analisis porositas yang dilakukan pada sampel daerah penelitian menunjukkan persentase rata-rata 87,44 % untuk sampel batupasir dan 77,95 % untuk batulempung. Sedangkan dari hasil uji konduktivitas hidrolik batupasir didapatkan hasil 5,71 × 10-9 meter/detik dan 5,74 × 10-9 meter/detik.
Kata Kunci: Ukuran Butir, Porositas, Konduktivitas Hidrolik, Batupasir, Batulempung
Abstract
Porosity and hydraulic conductivity are directly related to mining activities, including the construction of a minerampon the front of the mining area. The mining process causes the soil pores to get smaller (reduced pore space) so that the porosity decreases due to the influence of grain size. To determine the effect of grain size on the porosity of sandstones and claystones as well as its influence on the classification of porosity and hydraulic conductivity values of sandstones and claystones, the method used is grain size analysis to determine the size of grains and rock types using the Wentworth scale (1992) then porosity analysis using the Wentworth (1992) scale. Physical property testing is carried out to find values that affect rock strength such as natural density, dry density, saturated density, apperent specific gravity, true specific gravity, specific gravity, natural water content, saturated water content, degree of saturation, porosity and void ratio ( Arif, 2016). In the hydraulic conductivity analysis, a permeameter was used to determine the water velocity in units (meters/second) of sandstone and claystone samples with a total of 10 coring.
The results showed that the value of the grain size of the sandstone was 1/8 or 0.125 mm while the claystone was 1/256 or 0.003 mm. Porosity analysis performed on the sample of the study area showed an average percentage of 87.44% for the sandstone sample and 77.95% for the claystone. Meanwhile, from the results of the hydraulic conductivity of sandstone, the results were 5.71 × 10-9 meters/second and 5.74 × 10-9 meters/second.
Keywords: Grain Size, Porosity, Hydraulic Conductivity, Sandstone, Claystone
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