Evaluasi Kapasitas Dukung Sistem Fondasi Tiang pada Tanah Pasir dengan Berbagai Metode Pemancangan pada Bangunan Monumental
I Made Dirgayusa, Dr. Eng. Sito Ismanti, S.T., M.Eng. ; Dr. Ir. Ahmad Rifa’i, M.T.2023 | Tesis | S2 Teknik Sipil
The foundation of a monument project changed the design of the pile cap which was originally under the embankment became one same level with the top surface of the embankment. There were several piles that have been driven to the initial elevation and several piles in a free standing position with the pile head at same level with the top surface of the embankment. The pile heads below the embankment were extended by curing concrete on top of the pile so that the new pile heads had the same elevation as the top of the embankment, then the installed piles were filled with sand. The purpose of this study is conducting an analysis of these special conditions to determine the safety of the foundation and propose a redesign if the foundation is unstable. Another objective of this study is to determine the frictional resistance that occurs in backfilled piles and compare it with normal conditions.
Comparison of frictional resistance of backfilled and driven piles will be favorable when referring to methods that are able to properly calculate the bearing capacity of the soil in the field. The method was selected by comparing soil bearing capacity analysis methods with field test results. The comparison and analysis will be used as the basis for analyzing the existing condition of the foundation to determine the safety of the foundation and the proposed redesign.
The results of the analysis and comparison of soil bearing capacity show that the U.S. Army method has the most similar to the results of testing in the field and the comparison of frictional resistance of backfilled piles with frictional resistance of driven piles has a lower value by 35%. The finite element method analysis of the existing foundation showed that the allowable soil bearing capacity was less than the applied axial force, and the Y-axis deflection exceeded the required allowable deflection. The unsafe design of the existing foundation requires redesign to produce a safe foundation. The redesign analysis resulted in recommendations for changes in pile dimensions from 40 x 40 cm square piles with lengths ranging from 11 m - 12.1 m to spun piles with a diameter of 80 cm and a length of 13 m, the number of piles from 48 piles to 32 piles. The redesigned design has an allowable soil bearing capacity that is greater than the axial force that occurs and a deflection that is smaller than the allowable deflection. These results show that the redesign recommendations are safe and meet the requirements of SNI 8460: 2017.
Kata Kunci : Kapasitas Dukung Tanah, Tiang Pancang, Tanah Timbunan, Redesain Fondasi, Metode Finite Element