EVALUATION OF LIQUEFACTION POTENTIAL IN LOOSE SAND LAYER 15 METERS UNDER RECLAMATION LAYER ON CILEGON, BANTEN

• Main Author: Faizal, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71211
• Institution: Institut Teknologi Bandung

In coastal areas in Indonesia, loose sand layers are most commonly found on the soil surface/seabed. Infrastructure development in coastal areas requires land expansion by means of reclamation, but due to the acceleration of time, work to repair the original loose sand layer is not carried out before the reclamation process. In the reclamation process using material from hill blasting without sorting. So that the current reclamation area has dense soil strata on it but has a layer of loose sand and medium clay in between. Soil improvement is carried out around the reclamation area This study analyzes the potential impact of liquefaction in the reclamation area on soil pore water pressure (ru). The value of ru is defined as the increase in pore water pressure over the effective vertical stress in the soil. When dynamic loads occur, the pore water pressure begins to increase gradually, when r reaches a value of 1 the pore water pressure is equal to the effective vertical stress of the soil so that the soil loses its strength and liquefaction occurs. Analysis of the liquefaction potential was carried out using the simplification method and using finite difference software. The earthquake period used is 2500 years with 3 input motions of 0.2 seconds, 1 second and peak ground acceleration (PGA) obtained from site specific response analysis (SSRA) and probabilistic seismic hazard analysis (PSHA) reports that have been carried out in the study area. There are several mitigation options for liquefaction but seeing from the condition of the study area where there is a reclamation layer containing boulders, liquefaction mitigation is carried out using jet grouting. The jet grouting model used is a rectangular pattern with a diameter of 1.2 and 1.8 meters and a spacing of 1.5 meters and 3 meters respectively. Based on the results of the analysis, the application of jet grouting affects the value of the soil parameters around the structure, which means it increases soil stiffness and minimizes deformation caused by earthquakes which has an impact on the ru value or ratio of soil pore water pressures to become smaller so that the soil layer is safe from potential liquefaction. The pattern of application of jet grouting also affects the results of liquefaction mitigation where the larger and denser the spacing, the better the role of jet grouting in mitigating liquefaction. Dimensions and effective distances are one of the outputs from the results of this analysis. To obtain better results, it is recommended to carry out additional laboratory tests to minimize correlation with soil parameters so that the analysis results become more accurate. It is also necessary to carry out several variations of the jet grouting specifications and dimensions such as diameter, spacing, pattern, and depth in order to know the characteristics of the jet grouting so that a more effective configuration is obtained. .