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Title:Axial behavior of drilled shafts socketed into weak Pennsylvanian shales
Author(s):Baghdady, Ahmed K.
Director of Research:Stark, Timothy D.
Doctoral Committee Chair(s):Stark, Timothy D.
Doctoral Committee Member(s):Mesri, Gholamreza; Long, James H.; Elbanna, Ahmed
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Drilled Shaft
Weak Shales
Abstract:Weak Shales of the Pennsylvanian period are frequently encountered at shallow depths in Illinois. Drilled shafts socketed in weak shales are increasingly used to support structural loads from bridges and other transportation structures because they are more economical compared to other deep foundation systems. The design of a drilled shaft requires the knowledge of both strength and compressibility parameters of the weak shales. However, in most cases, the weathered nature and fragility of the weak shales prohibit recovering undisturbed core samples for laboratory triaxial compression testing. As a result, in situ tests are required to quantify the compressive strength and compressibility of weak shales. In this study, the procedure for conducting the standard penetration test (SPT) was modified and calibrated to assess the in situ properties of weak shales for drilled shaft design. Correlations between the penetration rate in weak shales and the unconfined compressive strength and undrained modulus were then developed based on a subsurface investigation at twenty-one (21) weak shale sites throughout Illinois. Two (2) Osterberg load cell (O-cell) field tests on instrumented drilled shafts socketed into weak shales also were conducted during this study to investigate the load transfer mechanism in side and tip resistance and the magnitude of the mobilized resistances in weak shales. Modified standard penetration tests and shale coring were conducted at these two load test sites and other fourteen (14) full-scale load test sites in Missouri and Illinois to validate the penetration rate design correlations. In addition, two (2) databases of measured side and tip resistance of drilled shafts in weak shales, around the world, were collected from the literature and also utilized in this investigation. Finally, a numerical model was developed to investigate the factors influencing the axial behavior of drilled shafts in weak shales. The results of the numerical analysis, field load tests, and penetration rates in weak shales are used to develop a design procedure for axially loaded drilled shafts in weak shales.
Issue Date:2018-12-06
Rights Information:Copyright 2018 Ahmed Khaled Hassan Ahmed Baghdady
Date Available in IDEALS:2019-02-07
Date Deposited:2018-12

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