USING MICRO PILES FOR LIQUEFACTION MITIGATION IN LOW COMPACTED SANDY SOILS FOR ONSHORE STRUCTURES , CASE STUDY: KOOHESTAK FISHERY HARBOR
Abstract: Micro-piles are principally used as elements for foundation support to resist static and dynamic loading conditions, less frequently as in-situ reinforcements for slope and excavation stability and construction of onshore coastal structures in low consolidated sandy beds. The study was performed on Koohestak fishery harbor (Fisheries Organization, IFO), Hormozgan Province, IRAN. In this paper, using perforated micro-piles instead of steel piles was studied. The case study is located 200 km east of Bandar Abbas and 45 km south coast of Minab on the northern shore of the Persian Gulf with geographical coordinates equal to 260 8` N -570 1`E. According to the geotechnical tests and analysis, the basement has a significant liquefaction potential which could cause serious settlements in the foundation of the wharf. The design of the micro piles has been done in three steps. First, structural design, and the bearing capacity of the elements were determined. For the next step, geotechnical design, the bond strength of the micropile was calculated. Finally, the punching shear control was performed. Furthermore, based on the field and laboratory tests, especially the SPT test, the rectangular and triangular shapes were considered for the micropiles arrangement under the basement. As a result of the design procedure, 180 micro-piles with 12-meter initial lengths were designed to be installed in the basement of this project instead of using steel piles. Using this method has several advantages. As construction advantages, the installation procedure causes minimal vibration and noise. Also, the construction time will decrease. From a geotechnical point of view, using micro-piles in this project will lead to about a 30% decrease in liquefaction in comparison with steel bars that have no effect on the soil properties. In addition, from the economic point of view, about 15% will be saved by using micro piles instead of steel bars in this project.
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