Utilizing Load Tests And Site Investigation Data To Predict Design Load Capacities For Drilled Shafts In Different Geologic Formations
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Utilizing Load Tests And Site Investigation Data To Predict Design Load Capacities For Drilled Shafts In Different Geologic Formations
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Author : Hosam Salman
language : en
Publisher:
Release Date : 2022
Utilizing Load Tests And Site Investigation Data To Predict Design Load Capacities For Drilled Shafts In Different Geologic Formations written by Hosam Salman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Engineering categories.
Precise predictions of the design capacities of drilled shafts on weak rock formations is vital for a better design of foundations. Irregularities in rock formations due to weathering cause discrepancies in actual bearing capacities and evaluating the bearing capacity typically requires frequent in-situ testing, using load test shafts at smaller intervals, which is time consuming and expensive. The typical design in Texas currently utilizes in-situ design charts that are developed based on Texas Cone Penetrometer (TCP) blow counts. This approach is found to have limitations related to maximum number of blows, rock characterization, and difficulty in incorporating influential parameters. Problematic soils in the North Central Texas region often lead practitioners to choose deep foundations, but the current design charts do not distinguish between the various types of rock or degradable materials such as intermediate geomaterials (IGM) or shale formations,and the software currently used for deep foundation capacity design does not incorporate all of the influential parameters.The purpose of this study is to better predict and assess the design parameters that are being used for deep foundation design and to improve the current drilled shaft design by either modifying the existing charts or developing new design charts for various types of rock formations such as limestone, sandstone, and intermediate geomaterials (IGM) such as shales. (IGMs are very soft to-medium hard rocks such as shale.) The principal goal and contribution of this research is to improve the methods for predicting drilled shaft design capacities by accounting for the geologic formations and learning from past projects. The following objectives were achieved to fulfill this goal: I. A database was compiled to employ statistical learning methods, as the applicability of a statistical learning outcome relies heavily on the type of database used and there were no databases that contained site investigation data in conjunction with load test data from drilled shaft projects. A database of site investigation data and load test data was compiled from projects undertaken in various geologic formations including shale,Woodbine shale, sandstone, and limestone. About 22 projects used for regression and validation, and approximately 38 load tests were performed for this research.II. Statistical correlations were developed between TCP, unconfined (uniaxial) compressive strength (Qun), dry unit weight, moisture content, recovery, rock quality designation, skin friction, and end bearing. About 96 predicted equations were developed to accommodate the various geologic formations. III. Design charts were developed to predict drilled shaft capacities, accounting for geologic formations and weathered conditions. This research discusses the advantages of the most recent load tests performed on drilled shafts in various design-build projects in the United States and on various types of geologic formations. Several loads tests, such as the Statnamic and bi-directional (O-cell) load cell tests (Osterberg) have been performed on various geologic formations distributed across the Dallas Fort Worth area. Various tables and plots were presented for each formation to show the Pearson correlations matrix and data distribution of each engineering parameter. The research demonstrated how the data were classified and sorted into 45 subsets per three classification systems per the FHWA guidelines to ensure the identification of the best fit regression and model of each geologic formation. It also discussed the challenges of the database such as missing data and outliers, provided methods to resolve these challenges, and showed the distribution of the engineering parameters. Over-designed (OD) or under-predicted (UP) and under designed (UD) or over-predicted (UP) foundation capacities are two common forms of negative variabilities that need to be avoided. Reducing the OD and UD requires the correct assessment of the rock quality and properties. It is always recommended to perform more field load testing to better optimize and predict the appropriate design charts.This research can be directly applied to many bridge design and foundation projects across the globe to ensure that the projects are designed to be safe, long lasting and provides cost savings to the agencies.
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 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 Shafts
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Author : National Highway Institute (U.S.)
language : en
Publisher:
Release Date : 1988
Drilled Shafts written by National Highway Institute (U.S.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with Earthwork categories.
This document was written as a resource for participants in a short course covering the topic of construction and design of drilled shaft foundations for bridges and other structures. It is the second edition of a Federal Highway Administration workbook on construction and design of drilled shafts. The first edition was written in 1988 (FHWA-SA-HI-88-042). While introductory material from the 1988 edition was retained, the emphasis in this document is on providing relatively comprehensive information for engineers who already have some experience with drilled shaft construction and/or design. The initial chapters cover an overview of the characteristics of drilled shafts, site investigations for drilled shafts (to collect information for both construction and design), and details of drilled shaft construction. These chapters are followed by several chapters on the design of drilled shafts in soil and rock for both axial and lateral loading, with examples. Both allowable stress design and load and resistance factor design principles are addressed. Details of design calculations procedures are provided in the appendices.
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.
Drilled Shaft Manual Construction Procedures And Design For Axial Loading
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Author : Lymon C. Reese
language : en
Publisher:
Release Date : 1977
Drilled Shaft 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 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.
Design Of Rock Socketed Drilled Shafts
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Author : Jamal Nusairat
language : en
Publisher:
Release Date : 2006
Design Of Rock Socketed Drilled Shafts written by Jamal Nusairat and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Bridges categories.
This project was aimed at evaluating and developing design methods for laterally loaded drilled shafts socketed in rock. Five lateral load tests on rock socketed drilled shafts with full range of instrumentation were conducted in Ohio. Detailed instrumentation included the use of vibrating wire strain gages, inclinometers, dial gages, and load cells. P-y curves representing site-specific lateral shaft-rock interaction were deduced from strain data. Field testing included the use of a borehole pressuremeter/dilatometer to obtain measurements that were correlated with rock mass strength and deformation parameters as well as with p-y curves. A comparison was made between the baseline p-y curves deduced from strain data of lateral load tests, the p-y curves predicted by using Reese's interim criterion, and the p-y curves from the pressuremeter tests in rock. A new hyperbolic p-y criterion for rock is proposed based on the field test data and extensive theoretical work. Validation of the proposed p-y criterion of rock was carried out by comparing the predictions of shaft deflections and bending moments using the hyperbolic p-y criterion against actual lateral load tests results. Based on the findings of this study, a complete solution for the design of drilled shafts socketed in rock or intermediate geomaterials under lateral loads is provided.
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.