Numerical Analysis of Bearing Capacity and Settlement of Helical Piles under Tensile and Compressive Loading

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Numerical Analysis of Bearing Capacity and Settlement of Helical Piles under Tensile and Compressive Loading

ارائه دهنده: Provider: Sara Bandehkhoda

اساتید راهنما: Supervisors: Dr. Masoud Makarchian

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Abbas Qadimi and Dr. Mohammad Maleki

زمان و تاریخ ارائه: Time and date of presentation: 2022/10/12

مکان ارائه: Place of presentation: Faculty of Engineering

چکیده: Abstract: Nowadays, the use of helical piles is increasing due to their unique features. Today, these piles are used to withstand compressive, tensile, or lateral loads. In recent years, their use in engineering projects to support and rehabilitation structures under various loadings, or in static and dynamic conditions due to advantages such as: cost-effectiveness, easy installation method in all weather conditions, very low vibration during installation, The possibility of loading immediately after installation and the light weight of the installation equipment have been expanded. These piles are used in various projects around the world for the foundation of houses, commercial buildings, electric light poles, pedestrian bridges, as underpinning element for defective foundations and foundation upgrading to increase the load of the building, etc. In the present research, the bearing capacity and settlement of helical piles in sandy and clayey soil under compressive and tensile loading have been studied using the finite element method and numerical modeling in PLAXIS 3D, V.2020, Update 4 software. First, it was validated with the field test article under compressive and tensile loading, and the result was validated. Then, for sensitivity analysis, the effective factors in modeling such as: model geometry and depth, modeling dimensions and type of meshing were studied and suitable parameters were selected for modeling. The investigated variables of this research include the diameter of the helical plates, the length of the helical pile, the space of helical plates from each other, the space of helical piles from each other in the pile group, the type of local soil and the type of loading (tensile, compressive). The diameter of the central shaft is constant and equal to 324 millimeters. The ratio of the diameter of the helical plates to the diameter of the pile is 2, 2.5, 3, 3.5, and 4, the length of the helical pile is 7, 8, 9, 10, 11, and 13 meters, the space between helical plates is 2, 2.5, 3, 3.5, and 4 times the plate diameter and also the center-to-center space of helical piles in the group 1, 2, 3 and 4, times the plate diameter is considered. For each of the cases, according to the recommendation of the references and the FHWA standard for helical piles, a settlement of 5% of the diameter of the helical plate was applied to the pile and the bearing capacity of the modeled helical piles was calculated. Investigations showed that the bearing capacity of the helical pile increased a lot compared to the ordinary piles. As expected, it was observed that the bearing capacity of helical piles in sandy soil is higher than in clayey soil and under compressive loading than tensile loading. By increasing the length of the pile, the bearing capacity has increased in both types of soil and under compressive and tensile loading. The increase in the diameter of the helical plate in both types of soil and under compressive and tensile loads caused an increase in the bearing capacity and the increasing process was faster at the beginning and gradually became slower. Increasing the space of helical plates until the pile works in an integrated way and does not come out of the cylindrical shear mechanism, has increased the bearing capacity. For the space of helical plates, the transition boundary from the cylindrical shear behavior in sandy soil was at a space of about 3 times the diameter of the plate and in clayey soil at a space between 2 and 3 (about 2.5) times the diameter of the plate. Increasing the space of helical piles in the group, which reduces the overlapping of the stressed zones, increases the bearing capacity. In order to minimize the interaction of helical piles in the group, the space of piles in the group, has been appropriate at least 3 times the diameter of the helical plate in sandy soil and at least 2 times the diameter of the helical plate in clay soil. At the end of the research, the values and trends of changes for the results obtained from the numerical analysis were compared with the theoretical values, which were in good agreement

فایل: ّFile: Download فایل