Modification Model of Pile Foundation Due To Additional Ground Water Tank

The office buildings located in Palembang has a plan for 4 floors building. The building construction system changed due to the addition of the ground water tanks (GWT). The most influential changed in the structure is on pile foundation. To get the elevation depth of GWT, the ground should be dug to a depth that is expected. Pile foundation used to support the building when the hard layer is deep inside the ground. The foundation of this type can also be used to support the building resist upward lifting force, especially in buildings that are influenced overthrow level due to the wind load. Masts also are used on supporting the building dock. At this building, poles have been affected by the forces of the collision of ships and water waves (Hardiyatmo, 2002). The analysis is to determine the magnitude of the load on the structure for the plan under or foundation structure. The calculation of the foundation structure uses a combination of loading 1DL + 1 LL (factored load). Pile was initially driven at 13.5 meters at the qc = 120 kgf/m. Design changed and the addition of ground of water tank causes the piles just as deep as 5 meters so the friction of pile capacity was reduced. Carrying capacity of a small friction causes the carrying capacity of the foundation is not able to withstand the axial load of the upper structure. The addition of piles at the same depth (5 meters) analized only on the foundation of the group that does not meet the needs of its carrying capacity. The addition of a pile depth of 5 meters to 11 meters with N-SPT value of 43 (on a soil depth of 19 m), leading into a large pile bearing capacity. Pile with a depth of 11 meters with the appropriate amount of advance planning is able to withstand the axial bearing capacity of the structure above. The ratio of the concrete due to addition of the pile with a depth of 5 meters is 1.9%. The ratio of the depth of concrete due to the addition of piles 11 meters is 2.2%. Increasing the number of piles is more efficient than the addition of depth piles for 0.3%.