CAPACITY ANALYSIS OF SINGLE PILE BEARING CAPACITY BASED ON STATIC METHOD AND N-SPT TEST ON PILE DRIVING ANALYZER TEST (CASE STUDY OF PT. ASAHI FORGE INDONESIA PHASE II PROJECT)

Soil investigation has an important role before building a building. The carrying capacity of the soil obtained from the results of soil investigations is very influential on the shape and dimensions of the foundation itself. In the PT.Asahi Forge Indonesia Project, the SPT test data is out of sync with the actual piling results related to embedded pile penetration. The design plan for piles with a length of 7 m based on the N-SPT test turned out that in the field, the piles achieved a bearing capacity at a depth of 9 meters. The final project aims to analyze and compare the carrying capacity of a single pile based on static methods and N-SPT test on the Pile Driving Analyzer. The method used in this research is the study method of laboratory test results and N-SPT. Work steps include; preparation, literature study, data collection, carrying capacity analysis, and comparison of analysis results. The results of the analysis of the carrying capacity of the piles based on the static method by the  (Vijayvergiya & Focht, 1974) method amounted to 549,201 kN; The  (McClelland, 1974) Method of 426,292 kN; The U.S Army Corps Method is 459,545 kN and the Tomlinson (1977) Method is 474,191 kN. While the results of N-SPT were bearing piles bearing capacity with the Mayerhof (1956) method of 738,645 kN and the Schmertmann (1967) Method of 451,327 kN. Based on these results, the N-SPT test based on the Mayerhof (1956) Method of 738,645 kN was the closest to the PDA test results of 755,116 kN. The comparison of the results of the analysis between the static test, N-SPT and PDA test is 19: 24: 30. This means that the carrying capacity of the static pile and PDA test has a difference of 37% while between the N-SPT and PDA test has a difference of 20%.


INRODUCTION
The foundation is part of an engineering system that sustains the burden and passes on its own burden and weight to and into the soil and rocks located below (Bowles, 1997). One type of deep foundation is the pile foundation. Soil investigation has an important role before building a building. Soil investigation aims to obtain the necessary information about the soil and find out the technical properties of the soil such as the characteristics of strength, soil weight, carrying capacity, or seepage ability, as well as ground water level. Soil carrying capacity is very influential on the shape and dimensions of the foundation in order to obtain optimal planning. So that soil samples need laboratory testing. While testing in the field is obtained from the N-SPT Test Results. In the PT. Asahi Forge Indonesia Phase II Project. N-SPT test results in the field explained that the soil with a depth of 7 meters has reached a value of 50, meaning that the soil layer has reached the hard soil layer (boring log no. BH-28). So that the pile is designed in length (length) 7 m. However, during the erection, the pile reached hard soil at a depth of 9 meters. The lack of synchronization between design and implementation makes the need for deeper analysis. Based on the background of the problem above, identification of problems, namely: a. The design of the pile construction does not match the results of the pile in this case the length of the pile used. b. N-SPT test results in the PT. Asahi Forge Indonesia Phase II shows that soil with a depth of 7 meters has reached a value of 50 (hard soil layer). However, during the erection, the pile reached hard soil at a depth of 9 meters. The objectives of this research are : a. To get the carrying capacity analysis of piles based on static methods, N-SPT Test and pile driving analyzer test. b. To compare the carrying capacity of the pile between the static method, the N-SPT test and the pile driving analyzer test.

LITERATURE
Pile foundation is a foundation construction that is able to withstand orthogonal force to the pile axis by absorbing bending. The pile foundation is made into a monolithic unit by uniting the base of the drill pole under construction, with the foundation footing (Nakazawa, 2000). Pile foundations are used to support buildings when the soil layer is very deep. This type of foundation can also be used to support buildings that hold upward force, especially in high-rise buildings that are affected by wind-rolling forces. Poles are also used to support the pier building (Hardiyatmo, 2018 : 145).
According to Hardiyatmo, 2002, End Bearing Pile is a pole whose carrying capacity is determined by the end resistance of the pole. Generally the end bearing poles are in soft soil zones which are above hard soil. The poles are piled until they reach the bedrock or other hard layers that can support the burden that is not expected to cause excessive decline. Friction pile is a pole whose carrying capacity is more determined by the friction resistance between the pile wall and the surrounding soil ( Figure 2-4). The friction resistance and the effect of the consolidation of the underlying soil layers are taken into account in the calculation of pile capacity (Hardiyatmo, 2018 : 95).
Analysis of bearing capacity of piles based on static methods using the Terzaghi method (1943) for the carrying capacity of the tip (Qp). As for the frictional carrying capacity (Qs) using the λ (Vijayvergiya, 1974) method, the α (McClelland, 1974) method, the U.S Army Corps Method and the Tomlinson (1977) Method. In contrast, for the analysis of bearing capacity based on N-SPT results using the Mayerhof (1956) method and the Schmertmann (1967) Method for maximum carrying capacity (Qu).

RESEARCH METHODOLOGY
The research methodology used in this study is the document study method. The research instrument used in the form of document quality control record piling (piling) work and Quality pile driving record based on ISO 9001: 2008. While the research data source in the form of laboratory data for soil samples, N-SPT test data, PDA results data, plan drawings and pile foundation technical specifications. The sample to be analyzed consists of 3 samples, namely the point of bore hole 6 (BH-6), point of bore hole 8 (BH-8) and point of bore hole 9 (BH-9). From the study of documents, secondary data will be obtained which will be used to analyze the carrying capacity of the pile.
In this study begins with the literature study stage. Literature study aims to critically analyze parts of journal articles through the process of summarizing, classifying and comparing with previous research. The process begins with searching for journals of the last five years related to the carrying capacity of the pile. Then each journal is made a resume or summary to get information about the results of the research conducted. Then clarify whether the journal answers research issues that will be raised or not.  (1977). Carrying capacity of piles analyzed from N-SPT test results using the Mayerhof method, the Schmertmann method and the Brown method. Analysis Results in the form of carrying capacity of static stakes and N-SPT Test with several methods compared with the results of the pile driving analyzer test Comparison is done to find out which analysis method is the closest to the static method and N-SPT test on pile driving analyzer test.

Analysis of Carrying Pile Capacity The net ultimate resistance ( u Q ) static way
The results of the analysis of the net ultimate resistance ( u Q ) in the static way at the bore hole 9 can be seen in table 1 below.
. . 9 0,096 24 20,736    The results analysis of the permit support capacity ( a Q ) based N-SPT test in the bore hole-9 can be seen in

Comparison of Bearing Piles Carrying Capacity
From the results of the comparative analysis of the carrying capacity of the pile at bore hole-9 static way and the results of the N-SPT test, the two methods are compared with the results of the PDA (Pile Driving Analyzer) Test as described in table 7. below .