Study Of Side Shear Stress Development For Drilled Shafts In Very Weak Porous Limestone Using Axial Load Transfer Analyses

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Study Of Side Shear Stress Development For Drilled Shafts In Very Weak Porous Limestone Using Axial Load Transfer Analyses

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Author : Matias R. Frediani
language : en
Publisher:
Release Date : 2023

Study Of Side Shear Stress Development For Drilled Shafts In Very Weak Porous Limestone Using Axial Load Transfer Analyses written by Matias R. Frediani and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with Civil engineering categories.

This thesis presents a series of axial load transfer analyses performed to investigate the mobilization of side shear stresses of drilled shafts installed in a very weak, porous limestone formation in Puerto Rico (PR). The numerical analyses presented are predictions of two axial load tests carried out on instrumented drilled shafts installed in very weak, porous limestone at a test site located in northwest PR. The field test component was performed by a former MS student of the research group of Dr. Pando when employed by the University of Puerto Rico at MayaguÌ8ez. The test site involved an outcrop of a very weak, porous, and highly weathered limestone with a representative unconfined compressive strength (UCS) of 2.7 MPa, and an average rock quality designation (RQD) of 34%. Descriptions of the test site and the rock characterization are provided in this MS thesis. The main objective of this thesis was to investigate the mobilization of the side shear stresses of the two test drilled shafts installed in this unique very weak, porous limestone and assess whether load transfer analyses are suitable to predict the observed experimental behavior. The first focus of this study was to evaluate whether existing static methods could reasonably predict the measured ultimate side shear stresses, also referred to as unit shaft resistance. A total of 10 static methods were evaluate and the range of predictions of the unit shaft resistance was found to be very large, highlighting the need to improve our capability of predicting this important design parameter. Furthermore, the measured ultimate side shear stress values at the PR test site were found to be above the upper bound of the range of predicted values using the selected static methods. The higher measured unit shaft resistance values are attributed to limitation of the selected static methods that are solely based on only the intact rock UCS, and do not incorporate other important variables such as the surface roughness of the rock socket walls or stiffness ratio between drilled shaft and surrounding rock mass. The second focus of this MS thesis was to evaluate the ability to capture the axial load transfer mechanisms of the test drilled shafts and the experimental axial load versus settlement curves using load transfer analyses. The load transfer analyses behavior of the axial load tests was simulated using 1D finite element models of the deep foundation and springs using nonlinear T-Z curves to represent the development of the side shear stresses as a function of level of relative movement between the foundation and the rock. The literature review identified two T-Z curves formulations for very weak limestone. One formulation is from McVay and Niraula (2004) who proposed T-Z curves developed from centrifuge tests on simulated Florida limestone. The second formulation is a model developed by Asem and Gardoni (2019) based on a comprehensive database of drilled shaft load tests on very weak to weak rock. These two T-Z formulations were used to predict the experimental load-settlement curves. The predictions using the McVay and Niraula (2004) were much stiffer than the observed behavior. A modified T-Z formulation, based on the Asem and Gardoni (2019) was found to yield the best predictions and exhibit more flexibility because it depends not only on the unit shaft resistance but also on the stiffness or modulus of deformation of the rock mass. The modified load-transfer model was found to be reasonably adequate to predict the measured experimental behavior of the two test drilled shafts installed in the unique, very weak, porous limestone rock from the karst formation in northwest PR.

Drilled Shafts In Rock

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Author : Lianyang Zhang
language : en
Publisher: CRC Press
Release Date : 2004-05-15

Drilled Shafts In Rock written by Lianyang Zhang and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004-05-15 with Technology & Engineering categories.

Drilled shafts in rock are widely used as foundations of heavy structures such as highway bridges and tall buildings. Although much has been learned about the analysis and design of drilled shafts in rock, all the major findings are published in the form of reports and articles in technical journals and conference proceedings. This book i

Drilled Shaft Manual Structural Analysis And Design For Lateral Loading By

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Author : Lymon C. Reese
language : en
Publisher:
Release Date : 1977

Drilled Shaft Manual Structural Analysis And Design For Lateral Loading By written by Lymon C. Reese and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with Shafts (Excavations) categories.

Drilled shafts have been used on a limited scale for many years as an alternative to driven piles in a variety of foundation problems. However, uncertainty about the behavior of the drilled shaft has forestalled widespread adoption. The subject package, by Dr. Lymon C. Reese of the University of Texas, is intended for use by bridge engineers, geotechnical engineers, and builders of pile foundations. The manual contains rational procedures and practical guidelines for the design and construction of drilled shaft foundations. Volume I presents a rational design procedure for drilled shafts under axial loading and includes guidelines on construction methods, inspection, load testing, specifications, and cost estimates. Volume II presents alternative methods for computing the response of the shaft to lateral loading and presents the structural design of the shaft for axial and/or lateral loading.

Analysis Of Laterally Loaded Long Or Intermediate Drilled Shafts Of Small Or Large Diameter In Layered Soils I E Soil

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Author : Mohamed A. Ashour
language : en
Publisher:
Release Date : 2004

Analysis Of Laterally Loaded Long Or Intermediate Drilled Shafts Of Small Or Large Diameter In Layered Soils I E Soil written by Mohamed A. Ashour and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Lateral loads categories.

This study has extended the capability of the SW model in order to predict the response of laterally loaded large diameter shafts considering 1) the influence of shaft type on the lateral shaft response; 2) the nonlinear behavior of shaft material and its effect on the soil-shaft interaction; 3) developing liquefaction in the surrounding soil profile based on far and near-field induced water pressure; and 4) vertical side shear resistance along the shaft wall that has a significant contribution to the lateral shaft response

Resistance Analysis Of Axially Loaded Drilled Shafts Socketed In Shale

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Author : Terry Bryce Burkett
language : en
Publisher:
Release Date : 2013

Resistance Analysis Of Axially Loaded Drilled Shafts Socketed In Shale written by Terry Bryce Burkett and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.

An investigation into the load-settlement behavior of two drilled shafts, founded in shale, is presented. The motivation for this research is to advance the understanding on how drilled shafts react under loading in stiff clays and shales. The objectives of the study are to measure the strengths within the subsurface material at the test site, estimate the unit side shear and unit end bearing of the shale-shaft interaction by running two axial load tests, and compare the results to the current design methods that are used to predict the axial capacity of drilled shafts. A comprehensive field investigation, performed by Fugro Consultants, provided strength profiles of the subsurface material at the test site. Through the cooperation of the Texas Department of Transportation (TxDOT), the Association of Drilled Shaft Contractors, and McKinney Drilling Company, two drilled shafts were installed at a highway construction site in Austin, Texas. The load tests were performed by Loadtest, Inc.; using the patented Osterberg-CellTM loading technique to axially displace the shafts. Ensoft, Inc. installed strain gauges at multiple levels within the shafts, making it possible to analyze the shaft mobilization during loading. Ultimate end bearing values of about 100- and 120-ksf were measured for Test Shafts #1 and #2, respectively. The current methods for estimating unit end bearing, developed by TxDOT and the Federal Highway Administration, provide fairly accurate predictions when compared to the measured information. The ultimate side resistance obtained near the O-CellTM in each test was about 20-ksf, however, the measured ultimate side resistance steadily decreased nearing the tip of the shaft. For the zones where the side resistance was believed to be fully mobilized, the TxDOT design method accurately predicts the side resistance. A limited amount of information is currently available for load tests performed in soils with TCP values harder than 2-in per 100 blows. Additional load test information should allow for a stronger correlation between TCP tests and unit resistances for very hard clay-shales, as well as, allowing for further evaluation of the shale-shaft interaction near the shaft tip. The results presented herein demonstrate the effectiveness of the current design methods for drilled shafts and the non-uniformity of side resistance within one- to two-diameters of the shaft tip.

Drilled Shaft Design And Construction Guidelines Manual Construction Procedures And Design For Axial Loading

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Author : Lymon C. Reese
language : en
Publisher:
Release Date : 1977

Drilled Shaft Design And Construction Guidelines Manual Construction Procedures And Design For Axial Loading written by Lymon C. Reese and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with Boring categories.

Drilled Shaft Design And Construction Guidelines Manual Reese L C And Allen J D Structural Analysis And Design For Lateral Loading

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Author : Lymon C. Reese
language : en
Publisher:
Release Date : 1977

Drilled Shaft Design And Construction Guidelines Manual Reese L C And Allen J D Structural Analysis And Design For Lateral Loading written by Lymon C. Reese and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with Bridges categories.

Drilled Shaft Design And Construction Guidelines Manual

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Author : Lymon C. Reese
language : en
Publisher:
Release Date : 1977

Drilled Shaft Design And Construction Guidelines Manual written by Lymon C. Reese and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with categories.

Analysis Of Laterally Loaded Drilled Shafts In Rock

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Author : Ke Yang
language : en
Publisher:
Release Date : 2006

Analysis Of Laterally Loaded Drilled Shafts In Rock written by Ke Yang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Lateral loads categories.

Drilled shafts socketed into rock are widely used as foundations for bridges and other important structures. Rock-socketed drilled shafts are also used to stabilize a landslide. The main loads applied on the drilled shafts are axial compressive or uplift loads as well as lateral loads with accompanying moments. Although there exist several analysis and design methods especially for rock-socketed drilled shafts under lateral loading, these methods were developed with assumptions without actual validations with field load test results. Some of the methods have been found to provide unsafe designs when compared to recently available field test data. Therefore, there is a need to develop a more rational design approach for laterally loaded drilled shafts socketed in rock. A hyperbolic non-linear p-y criterion for rock is developed in this study that can be used in conjunction with existing computer programs, such as COM624P, LPILE, and FBPIER, to predict the deflection, moment, and shear responses of a shaft under the applied lateral loads. Considerations for the effects of joints and discontinuities on the rock mass modulus and strength are included in the p-y criterion. Evaluations based on comparisons between the predicted and measured responses of full-scale lateral load tests on fully instrumented drilled shafts have shown the applicability of the proposed p-y criterion and the associated methods for determining the required input of rock parameters. In addition to the development of a hyperbolic p-y criterion for rock, a method for predicting lateral capacities of drilled shafts in rock and/or soils is developed for assessing the safety margin of the designed shafts against the design loads. A computer program LCPILE is developed using VC++ to facilitate computations. An elastic solution based on a variational approach is also developed for determining drilled shaft elastic deflection due to applied lateral loads in a two-layer soil layer system. The computational algorithm was coded in a Mathematical file for easy application. Finally, Briaud's method for deriving p-y curves of rock from pressuremeter or dilatometer test results is evaluated using available field test data. A modification to the Briaud's method is recommended for applications in rocks.

Case History Evaluation Of The Behavior Of Drilled Shafts Under Axial And Laterial Loading

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Author : Yit-Jin Chen
language : en
Publisher:
Release Date : 1993

Case History Evaluation Of The Behavior Of Drilled Shafts Under Axial And Laterial Loading written by Yit-Jin Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.