Geotechnical Site Characterization of a Mud Eruption Disaster Area Using CPTu for Risk Assessment and Mitigation (IPL-195)

Abstract

A mud eruption in East Java that occured on May 29, 2006 is well known worldwide. The mechanisms of the causes of the eruptions are still in debate, whether it was triggered by gas well drilling or by pressurised fluid reactivated by the Jogjakarta earthquake of May 26, 2006. This debate is not the main issue in this report. Instead, this paper discusses mainly the results of CPTu tests recently conducted and mitigation and risk reduction. The volume of the mud discharge is estimated at 5000 m(3). Dykes were constructed to contain the mud, which covered areas reaching 650 ha (Sofyan 2015). The location of the disaster is in the middle of the town of Porong in the district of Sidoardjo, near Surabaya International airport, and mud has blocked the major arterial roads from north to south of East Java. The soil condition of the site is deep soft clays which causes instability of the dykes. Some dyke failures occurred, endangering residential areas due to the flow of the mud (Rahardjo 2015). This paper describes the characterics of the soil conditions from a number of drillings and CPTu tests conducted by the authors for designing the replacement of the arterial road and for dyke reinforcement, and also in the middle of the mud. The paper discuss the geotechnical problems of land subsidence over large areas and differential settlement that cause damage to infrastructure, including roads, gas pipes, railways, bridges and buildings, and is of particular importance to the safety of the dykes. The mud has been discharged through the Porong River, and sedimentation is part of the problem.