ANALYSIS THE EFFECTIVENESS OF STONE COLUMN IN SOIL IMPROVEMENT AT LIQUEFACTION POTENTIAL AREA
Soil is an element that has a very important role in geotechnical work because almost all fields of civil engineering are related to soil. However, geotechnical work in a project frequently experiencing problems, one of them is to build a construction on a low relative density granular soil with a h...
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| Format: | Theses |
| Language: | Indonesia |
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| Online Access: | https://digilib.itb.ac.id/gdl/view/47356 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Soil is an element that has a very important role in geotechnical work because almost all fields of civil engineering are related to soil. However, geotechnical work in a project frequently experiencing problems, one of them is to build a construction on a low relative density granular soil with a high water level, as in the case of the construction of runway embankments in Yogyakarta Regency. Besides being very prone to earthquakes due to plate collision activities in the Indonesian Ocean, this area is also very prone to earthquakes due to active cesarean activity on land. The impact by the dynamic load on granular soils which have a low relative density with a high water level is liquefaction.
This study analyzes the impact of potential liquefaction on increased pore water pressure ratio (ru) on soil. ru parameter is defined as the increase in pore water pressure on effective vertical stress in the soil. As long as dynamic loads occur, pore water pressure and also soil shear strain starts to rise gradually, and ru parameter value is close to 1. In this condition, 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 liquefaction potential is done by simplification method and with finite difference method using FLAC 2D. The earthquake period used is located in Yogyakarta Regency. Because of limited data, in this analysis, the EZ-FRISK 7.52 software was used to obtain ground motion synthetics in Yogyakarta Regency and DEEPSOIL software to analyze earthquake wave propagation from bedrock to surface. Mitigation of liquefaction is done by using stone column, and the modelling of stone column is done by using FLAC 2D. The stone column configuration used is a triangle pattern with a diameter of 0.5 m, 0.8 m and each space of 1.5 m, 1.8 m, and 2.1 m.
Based on the results of the analysis, stone column installation affects the surrounding soil parameters, such as increasing bearing capacity, accelerating the process of pore water dissipation, increasing soil stiffness, and minimizing seismic shear strains caused by earthquakes which have an impact on the smaller pore pressure values resulting in a safe layer of potential liquefaction. The stone column installation pattern also greatly affects the results of liquefaction mitigation. The larger the dimensions and the more tightly spaced, the better the role of the stone column in mitigating liquefaction. The effective dimension is one of the outputs of the results of this analysis. |
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