Load And Resistance Factor Design Of Drilled Shafts In Shale Using Standard Penetration Test And Texas Cone Penetration Test Measurements
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Load And Resistance Factor Design Of Drilled Shafts In Shale Using Standard Penetration Test And Texas Cone Penetration Test Measurements
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Author : Mark Daniel Pierce
language : en
Publisher:
Release Date : 2013
Load And Resistance Factor Design Of Drilled Shafts In Shale Using Standard Penetration Test And Texas Cone Penetration Test Measurements written by Mark Daniel Pierce and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Electronic dissertations categories.
Missouri Department of Transportation (MoDOT) designers currently follow American Association of State Highway and Transportation Officials (AASHTO) design methods for design of drilled shafts in shale and other weak rock. These methods are generally based on Load and Resistance Factor Design (LRFD) methods that relate uniaxial compressive strength measurements of rock cores to the side and tip resistance for drilled shafts. However, shale and other weak rock can be notoriously difficult to effectively sample and test, which poses practical problems for those tasked with designing drilled shafts in such materials. The difficulty in sampling shale has lead geotechnical engineers to consider in-situ tests, such as the Standard Penetration Test (SPT) and the Texas Cone Penetration test (TCP), as surrogates for conventional coring and laboratory testing. In order to utilize results of in-situ tests for design of drilled shafts using Load and Resistance Factor Design (LRFD), it is necessary to correlate in-situ test measurements with side and tip resistance and to establish calibrated resistance factors that account for the reliability of the correlations and the in-situ test measurements. This thesis describes efforts undertaken to develop improved correlations among in-situ test measurements and drilled shaft capacity and to develop resistance factors that produce established target reliabilities for different classes of roadways.
Load And Resistance Factor Design Of Drilled Shafts In Shale For Lateral Loading
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Author : Andrew Boeckmann
language : en
Publisher:
Release Date : 2014
Load And Resistance Factor Design Of Drilled Shafts In Shale For Lateral Loading written by Andrew Boeckmann and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Bridges categories.
A research project involving 32 drilled shaft load tests was undertaken to establish LRFD procedures for design of drilled shafts subjected to lateral loads. Tests were performed at two Missouri Department of Transportation (MoDOT) geotechnical research sites. All shafts were founded in shale. Shafts were instrumented to measure the displacement of the shaft head, and the structural response of each shaft was interpreted from strain gage data as well as from ShapeAccelArray (SAA) data. The load tests achieved significant displacement of the top of the shaft, and successfully transferred load into the rock layers.
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.
Load And Resistance Factor Design Of Drilled Shafts At The Service Limit State
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Author : Thanh Thuy Vu (Engineer)
language : en
Publisher:
Release Date : 2013
Load And Resistance Factor Design Of Drilled Shafts At The Service Limit State written by Thanh Thuy Vu (Engineer) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Electronic dissertations categories.
A practical and efficient procedure for evaluation of drilled shafts at the service limit state is proposed. The procedure uses Load and Resistance Factor Design (LRFD) concepts to achieve target probabilities of failure without requiring case-specific probabilistic analyses. Proposed resistance factors are primarily dependent on four parameters: the normalized load, the coefficient of variation of the geomaterial strength, the target probability of failure, and the shaft length-to-diameter ratio. The proposed procedure can be implemented using several charts or analytical equations provided.
Calibration Of Resistance Factors For Drilled Shafts For The New Fhwa Design Method
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Author : Murad Yusuf Abu-Farsakh
language : en
Publisher:
Release Date : 2013
Calibration Of Resistance Factors For Drilled Shafts For The New Fhwa Design Method written by Murad Yusuf Abu-Farsakh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Load factor design categories.
As a continuing effort to implement the Load and Resistance Factor Design (LRFD) design methodology for deep foundations in Louisiana, this report will present the reliability-based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts using Brown et al. method (2010 FHWA design method). Twenty-six drilled shaft tests collected from previous research (LTRC Final Report 449) and eight new drilled shaft tests were selected for statistical reliability analysis; the predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using both 1999 FHWA design method (Brown et al. method) and 2010 FHWA design method (O'Neill and Reese method). The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test. For the 30 drilled shafts that were tested using O-cells, the tip and side resistances were deduced separately from test results. Statistical analyses were performed to compare the predicted total , tip, and side drilled shaft nominal axial resistance with the corresponding measured nominal resistance.
Full Scale Load Testing Of 75 90 M Long Post Grouted Drilled Shafts In Suzhou Stiff Clay
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Author : Ye Lu
language : en
Publisher:
Release Date : 2018
Full Scale Load Testing Of 75 90 M Long Post Grouted Drilled Shafts In Suzhou Stiff Clay written by Ye Lu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Foundations categories.
This article evaluates the effects of post-grouting on axial behavior of long drilled shafts in stiff clay. Static axial compression and tension load tests were conducted on four ungrouted and six post-grouted shafts to investigate the effects of post-grouting on axial capacity and load-transfer mechanism. After post-grouting, axial capacity increased more than 100 %. Prior to failure, the relationship between the normalized axial load Q/Qmax and shaft head displacement ?/D was nonlinear for ungrouted shafts. Compared with cases presented in the literature, much greater shaft displacements were required to mobilize shaft tip resistance and skin resistance, indicating a softer load-displacement response. The contribution of tip resistance to the overall load capacity was small for both ungrouted and post-grouted shafts because of their length. Shaft load capacity was significantly underestimated by the standard penetration test (SPT)-based method and ?-method and was more reasonably estimated by the ?-method. The cone penetration test (CPT) direct method yielded generally reliable predictions of skin resistance mobilized in the upper stiff clay soils; however, this method significantly underestimated skin resistance in the underlying very stiff to hard clay layers. Considering uncertainties in current design methods, results of this study suggest that field load tests are needed prior to construction to obtain site-specific design parameters.
Development Of Recommended Resistance Factors For Drilled Shafts In Weak Rocks Based On O Cell Tests
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Author : Xiaoming Yang (Writer on geotechnical engineering)
language : en
Publisher:
Release Date : 2010
Development Of Recommended Resistance Factors For Drilled Shafts In Weak Rocks Based On O Cell Tests written by Xiaoming Yang (Writer on geotechnical engineering) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Load factor design categories.
From October 1, 2007, the new bridges on federal-aid funded projects are mandated to be designed to meet American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications. LRFD is a simplified form of reliability-based design. By multiplying calibrated factors to load and resistance components, the designed structure will maintain a specific level of reliability (or probability of failure). By concept, the load and resistance factors should be calibrated by large number of test data; however, they are often unavailable in geotechnical engineering. Significant efforts are needed to calibrate load and resistance factors based on test data of good quality. In this study, 26 O-Cell test data were collected from Kansas, Colorado, Missouri, Ohio, and Illinois. Seven methods available in the literature were selected to estimate the load capacities of 25 out of 26 drilled shafts. The "FHWA 0.05D" method was found to yield the closest and conservative predictions of the nominal resistances to the representative values; therefore, it was adopted in this study when calibrating the resistance factors for Strength Limit State design. These test data were analyzed and used to calibrate side and base resistance factors for drilled shafts in weak rock. Resistance factors were calibrated at two different target reliability indices: 2.3 (i.e., failure probability, Pf ~ 1/100) for shafts with greater redundancy and 3.0 (Pf ~ 1/1000) for shafts with less redundancy. Side resistance factors were calibrated from two different datasets of measured resistance: total side resistance and layered unit side resistance. The resistance factors calibrated from layered unit side resistance are considered more reliable, therefore, they are recommended for design. The recommended resistance factors from this study are compared with those in AASHTO specifications. Some of those calibrated resistance factors from this study are considerably lower than those in AASHTO specifications. The main reasons for such lower resistance factors are mainly attributed to the low efficiency of the FHWA design method and the limited quality and number of O-Cell test data. These resistance factors may be improved by increasing the size and the quality of the test data in the future. At present, field load tests on drilled shafts are recommended as an alternative to using lower resistance factors, which will also accumulate more test data for future improvement.
Drilled Shafts
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Author : Michael W. O'Neill
language : en
Publisher:
Release Date : 1999
Drilled Shafts written by Michael W. O'Neill and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Foundations categories.
Modified Standard Penetration Test Based Drilled Shaft Design Method For Weak Rocks
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Author : Timothy D. Stark
language : en
Publisher:
Release Date : 2017
Modified Standard Penetration Test Based Drilled Shaft Design Method For Weak Rocks written by Timothy D. Stark and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Boring categories.
Load And Resistance Factor Design Lrfd Resistance Factors For Tip Grouted Drilled Shafts
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Author :
language : en
Publisher:
Release Date : 2019
Load And Resistance Factor Design Lrfd Resistance Factors For Tip Grouted Drilled Shafts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Bearing capacity categories.
University of South Florida researchers established Load and Resistance Factor Design (LRFD) resistance factors for postgrouted end bearing drilled shaft piles.