Experimental Liquefaction Study of Southern Yogyakarta Using Shaking Table
DOI:
https://doi.org/10.5614/jts.2017.24.1.2Keywords:
Sandy soil, liquefaction, vibrational frequency, excess pore water pressure ratio, shaking table.Abstract
Abstract
An experimental study using shaking table was conducted to learn liquefaction. Samples used were sandy soils from South of Yogyakarta Special Region Province. Analysis of liquefaction potential was performed by considering several factors, i.e. peak ground acceleration (PGA) of 0.3 g to 0.4 g, vibrational frequency of 1.8 Hz, and vibration duration of 8, 16, and 32 seconds which reflect earthquake magnitudes of 5, 6, and 7. The pore water pressure was measured by using a pressure transducer. Liquefaction potential was determined by using the parameter of excess pore water pressure ratio (ru). Liquefaction potentially occurred when ru > 1, whereas ru < 1 indicated liquefaction didn't occur. The results of test showed that liquefaction potentially occur in each applied dynamic load, that maximum excess pore wate pressure (ru max) measured was equal to or larger than 1. The larger peak ground acceleration applied, the faster beginning time of liquefaction. The bigger peak ground acceleration applied, the slower dissipation time of pore water pressure. The duration of liquefaction become longer, along with the increase of applied peak ground acceleration. The bigger applied peak ground acceleration, the larger maximum excess pore water pressure.
Abstrak
Sebuah penelitian eksperimetal dengan menggunakan alat shaking table (meja getar) dilakukan untuk mempelajari likuifaksi. Bahan uji yang digunakan adalah tanah pasir yang diambil dari daerah selatan Provinsi Daerah Istimewa Yogyakarta. Analisis potensi likuifaksi dilakukan dengan mempertimbangkan beberapa parameter di antaranya percepatan maksimum gempa (PGA) sebesar 0,3 g sampai dengan 0,4 g, frekuensi getaran 1,8 Hz, dan waktu penggetaran selama 8, 16 dan 32 detik yang mewakili gempa dengan magnitudo 5, 6, dan 7. Alat pembacaan tekanan air pori yang digunakan adalah pressure tranducer. Likuifaksi ditentukan dengan menggunakan parameter rasio peningkatan tekanan air (ru). Likuifaksi berpotensi terjadi apabila nilai ru > 1, sedangkan nilai ru < 1 mengindikasikan bahwa likuifaksi tidak berpotensi terjadi. Hasil pengujian menunjukkan bahwa pasir dari selatan Provinsi Daerah Istimewa Yogyakarta berpotensi likuifaksi untuk setiap beban dinamik yang diberikan, dimana nilai rasio peningkatan tegangan air pori maksimum (ru max) yang diperoleh bernilai lebih besar atau sama dengan satu. Semakin besar percepatan maksimum yang diterapkan, maka waktu dimulainya likuifaksi semakin cepat. Semakin besar percepatan maksimum yang diberikan, maka waktu terdisipasinya tegangan air pori akan semakin lambat. Durasi terjadinya likuifaksi menjadi semakin lama, seiring dengan bertambahnya percepatan maksimum yang diterapkan. Semakin besar percepatan maksimum yang diterapkan, maka semakin besar pula tegangan air pori maksimum yang dihasilkan.
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