Ultimate bearing capacity and failure mechanism on cyclic lateral loaded pile group

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10650482
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geotechnical engineering
• Research Institution: KYOTO UNIVERSITY
• Principal Investigator: ADACHI Toshihisa Kyoto University, Dept. of Civil Eng., Professor, 工学研究科, 教授 (20026173)
• Co-Investigator(Kenkyū-buntansha): KOBAYASHI Shunichi Kyoto University, Dept. of Civil Eng., Research Associate, 工学研究科, 助手 (10243065) ; KISHIDA Kiyoshi Kyoto University, Dept. of Civil Eng., Research Associate, 工学研究科, 助手 (20243066) ; OKA Fusao Kyoto University, Dept. of Civil Eng., Professor, 工学研究科, 教授 (10111923)
• Project Period (FY): 1998 – 1999
• Keywords: Pile foundation / Pile group / Bearing capacity / Cyclic load / Finite element method / Elasto-plastic / Cast-in-place pile

Research Abstract

(1) In order to investigate the failure mechanism of the axially loaded concrete piles under cyclic lateral loading, the model of group pile is tested under centrifugal condition (50G). Mortar piles reinforced with piano wires and circular brass rings which are analogous to real cast-in-place concrete is about 2 mm. It was already found in the former tests that the damage occurred at the pile head first and when the magnitude of cyclic displacement became larger, damage of pile also took place at the depth under ground surface. In this paper, the influence of axial load on the failure behavior of the pile ground are investigated. After the test, cracks of piles are also observed.
(2) Pile foundation in soft ground usually will be subjected to a lateral cyclic loading during an earthquake. In a major earthquake, it is reasonable to think that the mechanical behavior of a pile foundation and the surrounding ground is nonlinear. In recent year, the limit state design method became predominant in the design of foundations of toll bridges and other structures. The investigation on the mechanical behavior of the pile foundations subjected to lateral cyclic loadings up to an ultimate state, therefore, is very important to provide evidences for the designing method. In this paper, a real scale field test of 9-pile foundation, with a diameter of 1.2m, subjected to cyclic lateral loading up to an ultimate state, is simulated using a 3-dimensional elasto-plastic finite element analysis (DGPILE-3D). The nonlinear behavior of RC pile is simulated with an axial-force depend hysteretic model proposed in this paper. Meanwhile, the soil of the ground is simulated with Drucker-Prager model. The purpose of the paper is to provide an applicable numerical way of evaluating the mechanical behavior of a pile foundation subjected to cyclic lateral loading up to an ultimate state.