Studi Karakteristik Aliran Tanah Terlikuefaksi Berdasarkan Uji Viskositas

Abstract

Abstrak Gempa bumi di Kota Palu sebesar 7,5 Mw pada tahun 2018 menyebabkan likuefaksi di Desa Lolu dengan pergerakan lateral tanah hingga 150 meter. Pergerakan ini terjadi akibat perilaku mencairnya tanah atau disebut likuefaksi. Beberapa peneliti telah membuktikan bahwa perilaku tanah terlikuefaksi dapat dianalisis dengan cara mensimulasikan tanah sebagai cairan yang memiliki kekentalan (viscous fluid). Perilaku pergerakan tanah pada saat likuefaksi terjadi dapat dipelajari melalui karakteristik aliran tanah. Karakteristik aliran tanah terlikuefaksi dianalisis dari nilai viskositas terhadap gaya yang diberikan. Dilakukan pengujian di laboratorium menggunakan alat rotational rheometer untuk mendapatkan nilai viskositas. Terdapat 6 (enam) sampel tanah uji yang digunakan pada penelitian ini, yaitu 3 (tiga) sampel dari area aliran dan 3 (tiga) sampel dari area terdampak. Tanah dari area aliran terdiri dari silty sand, coarse sand, dan fine sand. Sementara tanah dari area terdampak terdiri dari sand gravel, sand gravel boulder, dan silty sand. Seluruh sampel tanah uji menunjukkan karakteristik aliran tanah terlikuefaksi Non-Newtonian, yaitu shear thinning. Variasi kadar air dan suhu yang diterapkan pada seluruh sampel tanah uji menunjukkan bahwa semakin tinggi nilai kadar air dan suhu, maka semakin rendah nilai viskositas yang dihasilkan. Berdasarkan komposisi tanah, semakin besar persentase butir halus yang terkandung maka semakin besar nilai viskositas atau dapat dikatakan tanah mengalir dengan lebih lambat. Kata-kata Kunci: Likuefaksi, rotational rheometer , laju geser viskositas, kadar air suhu. Abstract An earthquake in Palu City of 7.5 Mw in 2018 caused liquefaction in Lolu Village with lateral ground movement up to 150 meters. This movement occurs due to the behavior of melting soil, called liquefaction. Several researchers have proven that the behavior of liquefied soil can be analyzed by simulating the soil as a viscous fluid. The behavior of soil movement when liquefaction occurs can be studied through the characteristics of soil flow. The characteristics of liquefied soil flow were analyzed, from the value of the viscosity due to the applied force. Laboratory tests were carried out using a rotational rheometer to obtain the viscosity value. There were 6 (six) soil samples used in this study, namely 3 (three) samples from the flow area and 3 (three) samples from the affected area. The soil of the flow area consists of silty sand, coarse sand, and fine sand. The soil from the affected area consists of sand gravel, sand gravel boulders, and silty sand. All of the tested soil samples showed non-Newtonian soil flow characteristics, namely shear thinning. Variations in water content and temperature applied to all tested soil samples indicate that the higher the water content and temperature values, the lower the resulting viscosity value. Based on the composition of the soil, the greater the percentage of fine grains contained, the greater the value of viscosity, or it can be said that the soil flows more slowly. Keywords: Liquefaction, rotational rheometer, viscosity shear rate, temperature water content