It is widely accepted that soil investigation conducted in construction projects is limited . The budget allocated for soil investigation is often minimized in order to reduce preliminary cost of project, rather than being allocated to characterize properly soil properties. The budget allocated for soil investigation ranges from 0.1% to3% of the construction budget. These inadequate site investigations remain one of the main factors in the failure of structural foundations, and leading to unforeseen additional construction or repair costs. At the other extreme, inadequate site investigations can result in over-design of the foundation, increasing the cost unnecessarily. This study investigated the effect of limited soil investigation to estimate bearing stratum of pile foundation in the construction project. Case study was undertaken on the contruction project of Coal Unloading Jetty PT. Semen Tonasa in Pangkep, South Sulawesi, Indonesia. To characterize the soil properties of Coal Unloading Jetty with the area of 122??20 m2, soil investigations were conducted with limited amount, consisting of 1 SPTs. The limited site investigations was found to increase waste length of pile foundation, accounted for 9.19% of the total pile foundation length. If the waste is not recognized and paid by the owner of construction project, the waste cost to be a risk to the contractor. Therefore , Geostatistical methods including Kriging and Inverse Distance were employed to estimate bearing stratum of pile foundation with limited site investigation . The use of geostatistical methods found that the addition of 3 CPTs into the existing site investigation can reduce the waste length of pile foundation to be 5.38% and 5.39% for Kriging and Inverse Distance to a Power respectively. The results suggested that sufficient amount of site investigation with the use of Geostatistical method could enhance the design of pile foundation and reduce unpredicted cost of pile foundation during contruction.
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