Civil Engineering and Architecture 10(1): 175-193, 2022 http://www.hrpub.org DOI: 10.13189/cea.2022.100116 Single Pile FEM Modeling: Ultimate Capacity Determination of Bored Piles Embedded in Silty-Sands Using Modified Drucker-Prager Cap Model Nathaniel E. Rivera * , Gilford B. Estores School of Civil, Environmental and Geological Engineering, Mapúa University, Manila, 1002, Philippines Received October 11, 2021; Revised December 15, 2021; Accepted December 26, 2021 Cite This Paper in the following Citation Styles (a): [1] Nathaniel E. Rivera, Gilford B. Estores , "Single Pile FEM Modeling: Ultimate Capacity Determination of Bored Piles Embedded in Silty-Sands using Modified Drucker-Prager Cap Model," Civil Engineering and Architecture, Vol. 10, No. 1, pp. 175 - 193, 2022. DOI: 10.13189/cea.2022.100116. (b): Nathaniel E. Rivera, Gilford B. Estores (2022). Single Pile FEM Modeling: Ultimate Capacity Determination of Bored Piles Embedded in Silty-Sands using Modified Drucker-Prager Cap Model. Civil Engineering and Architecture, 10(1), 175 - 193. DOI: 10.13189/cea.2022.100116. Copyright©2022 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Ultimate pile capacity determination is crucial before the structure construction. This essential pile resistance can be accurately predicted and studied using the finite element method. FEM is a numerical method that is anticipated to be indispensable in advances in pile analyses, aiming at pile effectiveness and material efficiency. Pile modeling is attainable using FEM for the stability investigation concerning the geotechnical findings. In addition, several constitutive mathematical models have been available for FEM applications to reasonably simulate soil behavior under pressure. This study conducts numerical modeling of eight bored piles of different diameters and lengths embedded in silty-sand soils. Using the FEM software ABAQUS, pile load-settlement curves are obtained to determine ultimate pile capacity, skin friction resistance, and pile base resistance. The modified Drucker Prager Cap model is used as a constitutive soil model for silty sand soils. In applying the MDPC model, the cap hardening behavior (hardening parameter) is obtained by having the site soils compression and swelling indices determined using the proposed regression equations in the literature. Piles were modeled successfully, and the results positively correlate with the results of the dynamic analysis test conducted in Davao del Norte, Philippines. Keywords Bored Piles, Finite Element Method, Modified Drucker-Prager Cap Model, Ultimate Pile Capacity, Pile Dynamic Analysis, Civil Engineering, Pile Foundations 1. Introduction The high demand for constructing essential structures in soft-soil conditions has resulted in efficient pile foundation construction. This pursuit causes the rise of analytical methods to predict ultimate pile capacity [1]. Ultimate pile capacity is the maximum compressive load that the pile can carry without exceeding its material strength or significant settlement. In a typical pile-load-settlement curve, the ultimate load of the pile occurs at settlement equals ten percent of its width or diameter. Another way of determining the ultimate load from the load settlement curve is by drawing two tangent lines and a vertical line intersecting the tangent lines' intersection. The magnitude of the load intersecting the vertical line is the ultimate capacity [2]. The most reliable procedure in determining pile integrity is by in-situ pile testing, either by Static Load Test or Pile Dynamic Analysis Test. The two tests can have different results for ultimate capacity [3]. However, these two methods can have more similarities when the PDA test results have been through Case Pile Wave Analysis Program (CAPWAP) software. This program analyzes PDA data to provide more accurate results for ultimate pile capacity [4]. Ultimate capacity can also be determined