Volume Calculation of Sidoarjo Mud Using TLS Data and Numerical Methods

Abstract

Sidoarjo Mud is one of the phenomena of mud volcanoes located in the northern part of Java Island. A mud volcano is a phenomenon where mud material is released from the earth due to pressure (eruption). The mud continuously flows and accumulates around the central embankments. This phenomenon has caused the embankments to break several times due to the uncontainable mud volume. Observing the volume of Sidoarjo Mud is expected to help mitigate this problem. The Sidoarjo Mud volume was calculated using point cloud data obtained from Terrestrial Laser Scanner (TLS). Numerical methods such as the Trapezoidal and Simpson rules were employed to determine the mud volume. These numerical methods involve approximating the volume of irregularly shaped earthwork surfaces using mathematical techniques. The numerical method approximates the area under a trapezoid or curve representing the cross-section of the earthwork. In this study, kriging interpolation was conducted with a grid size of five meters. The relative difference between the numerical methods was found to be within acceptable limits, not exceeding 2.78% based on the American Society for Testing and Materials (ASTM) 2002 and not exceeding 2% based on ASTM 1998 as an industry acceptance error. Considering the relative difference results and the institutional report, the Trapezoidal method with a 5-meter grid size was considered the accurate volume calculation method. Based on the processed data, the total volume of Sidoarjo Mud within the embankment was 32,793,917.171 m3 in February 2022, 32,889,012.793 m3 in April 2022, and 33,390,051.407 m3 in June 2022. The volume calculation results show a difference of 95,095.622 m3 between February-April and a difference of 501,038.613 m3 between April-June. The mud flow rate for the February-April period was calculated as 1,872.114 m3/day, while for the April-June period was determined as 9,278.492 m3/day.