อิทธิพลของอัตราส่วนระยะยืนอิสระต่อความสามารถในการรับแรงในแนวดิ่งและแนวราบของฐานรากเสาเข็มเอียง

Abstract

Vertical piles and inclined piles are wildly used in constructions in Thailand (Department of Public Work and Town & Country Planning, Thailand, 2547). Frequently, they were installed in the sites where are vulnerable to scouring e.g., bridge foundation, retaining wall. However, there a few research on that area, Lin et al. (2010), Qi et al. (2016), Askarinejad et al. (2019) ,and He et al. (2019). Therefore, this thesis object is to investigate the influence and effect of free-standing ratio (Rf*) to inclined pile foundation based on numerical simulation via Finite Element Method (FEM). There are two types of model piles; single pile and symmetrical 2x1 pile group. In order to validate the numerical simulation in PLAXIS3D, the physical model tests of the previous research were included in the validation process. Each physical pile was made of stainless steel and 400 mm.-long in length. They were placed in dry sand (Relative Density = 70%) with 0, 10, 20 and 30 degrees of inclination with L/D = 19.68, 19.50, 18.93 ,and 17.85 ,or equivalent to Rf* = 0.375, 0.381, 0.399 ,and 0.433 ,respectively. In the investigation process, the soil level was varied relative to pile length: Rf* of 0.2 - 0.6 for single inclined pile and 0.1 – 0.6 for inclined pile group. The result of numerical simulation indicates that the increment of Rf* is directly related to the decrement of pile’s bearing capacity. However, the tendency of decrement also depends on variation of pile types, inclinations, and load directions. The bearing capacities of vertically loaded - single inclined piles with inclination more than 10 degrees at Rf* = 0.6 were decreased more than 65%, whereas those with inclination less than 10 degrees were decreased about 30%. For vertically loaded inclined pile groups, the bearing capacities were decreased 25% - 50%. For horizontally loaded inclined single piles and pile groups at Rf* = 0.6 in both positive and negative load directions, the bearing capacities were decreased 75% - 85%