Controlling Mass Concrete Effects in Large-Diameter Drilled Shafts Using Full-Length Central Void

2018 ◽  
Vol 115 (5) ◽  
Author(s):  
Gray Mullins ◽  
Kevin R. Johnson ◽  
Danny Winters
Keyword(s):  
Large Diameter ◽  
Drilled Shafts ◽  
Full Length ◽  
Mass Concrete ◽  
Central Void

Establishing and Satisfying Thermal Requirements for Drilled Shaft Concrete Based on Durability Considerations

2021 ◽  
pp. 036119812199635
Author(s):  
Andrew Z. Boeckmann ◽  
Zakaria El-tayash ◽  
J. Erik Loehr
Keyword(s):  
Mechanical Response ◽  
Large Diameter ◽  
Thermal Cracking ◽  
Drilled Shafts ◽  
Maximum Temperature ◽  
Design Parameters ◽  
Mass Concrete ◽  
Temperature Differential ◽  
Thermal Requirements ◽  
Ettringite Formation

Some U.S. transportation agencies have recently applied mass concrete provisions to drilled shafts, imposing limits on maximum temperatures and maximum temperature differentials. On one hand, temperatures commonly observed in large-diameter drilled shafts have been observed to cause delayed ettringite formation (DEF) and thermal cracking in above-ground concrete elements. On the other, the reinforcement and confinement unique to drilled shafts should provide resistance to thermal cracking, and the provisions that have been applied are based on dated practices for above-ground concrete. This paper establishes a rational procedure for design of drilled shafts for durability requirements in response to hydration temperatures, which addresses both DEF and thermal cracking. DEF is addressed through maximum temperature differential limitations that are based on concrete mix design parameters. Thermal cracking is addressed through calculations that explicitly consider the thermo-mechanical response of concrete for predicted temperatures. Results from application of the procedure indicate consideration of DEF and thermal cracking potential for drilled shafts is prudent, but provisions that have been applied to date are overly restrictive in many circumstances, particularly the commonly adopted 35°F maximum temperature differential provision.

Design of large-diameter drilled shafts for the Northumberland Strait bridge project

1997 ◽  
Vol 34 (4) ◽  
pp. 580-587 ◽  
Author(s):  
D J Walter ◽  
W J Burwash ◽  
R A Montgomery
Keyword(s):  
Large Diameter ◽  
Drilled Shafts

Large Diameter Double Underreamed Drilled Shafts

1983 ◽  
Vol 109 (8) ◽  
pp. 1082-1098 ◽  
Author(s):  
Ray E. Martin ◽  
Raymond A. DeStephen
Keyword(s):  
Large Diameter ◽  
Drilled Shafts

Special-Design Precast Concrete Beams for Sidney Lanier Bridge Replacement Project

2000 ◽  
Vol 1696 (1) ◽  
pp. 48-51
Author(s):  
Edwin Callicutt
Keyword(s):  
Concrete Beams ◽  
Precast Concrete ◽  
Drilled Shafts ◽  
Bridge Piers ◽  
Mass Concrete ◽  
Department Of Transportation ◽  
Special Design ◽  
Construction Methods ◽  
Bentonite Slurry ◽  
Type V

The Sidney Lanier Bridge Replacement Project is a $100 million undertaking in Brunswick, Georgia, that will lead to the replacement of an existing 40-year-old steel lift-span structure. The approach bridges that lead to the project’s main-span unit consist of 16 spans of 54.9-m (180-ft), special-design, precast concrete beams as well as 14 spans of 36.6-m (120-ft) Type V AASHTO girders. The special-design beams are 2.3 m (7.5 ft) deep, are erected as simply supported members and are then made into two-span continuous units by longitudinal posttensioning, and are rigidly connected transversely with cast-in-place diaphragms. The riding surface is a cast-in-place concrete deck constructed on stay-in-place metal forms. The 54.9-m (180-ft) beams, supported by hollow tapered concrete piers with hammerhead caps, are founded on 1.2-m (48-in.) drilled shafts. Wet-hole construction methods with bentonite slurry were required for the drilled shafts. The bridge piers are over land and water, and large cofferdams were required to facilitate construction. Additionally, the sizes of the cast-in-place footings and hammerhead pier caps required mass concrete thermal considerations. The approach bridges lead to the main-span portion of the project, which will be a 762-m (2,500-ft) concrete, cable-stayed unit with a 381-m (1,250-ft) center span. The design, casting, and erection of these beams, and construction of the substructure, posed many challenges to the Georgia Department of Transportation designers and contractors. These beams are among the longest erected in Georgia.

Field and theoretical analysis of response of axially loaded grouted drilled shafts in extra-thick fine sand

2020 ◽  
Vol 57 (3) ◽  
pp. 391-407
Author(s):  
Zhi-hui Wan ◽  
Guo-liang Dai ◽  
Wei-ming Gong
Keyword(s):  
Large Diameter ◽  
Fine Sand ◽  
Drilled Shafts ◽  
Rational Approach ◽  
Hyperbolic Model ◽  
Drilled Shaft ◽  
Base Resistance ◽  
Displacement Response ◽  
Head Displacement ◽  
And Performance

Research on post-grouted drilled shafts has focused primarily on post-grouted tips. Here, four full-scale shaft load tests were conducted to investigate the behaviors and performance of combined tip-and-side grouted superlong and large-diameter drilled shafts in extra-thick fine sand layers. The enhanced mechanism of the combined grouted drilled shafts is analyzed, and a rational approach for analyzing their load–displacement response is presented. The side and base resistance of the combined grouted drilled shafts exhibited significant strengthening, substantially increasing the bearing capacity and effectively controlling settlement. Under the ultimate load, >60% of the shaft head displacement was caused by shaft compression; a relatively small load proportion was carried by the shaft base. The superlong and large-diameter drilled shaft can be treated as a friction shaft, and the combined tip-and-side grouting cannot change the bearing characteristics. The hyperbolic model describes the relationship between the side resistance and relative shaft–soil displacement and captures the base resistance–displacement response. The proposed approach is verified with a case history, and the bearing behaviors of a large-diameter drilled shaft under an extra-thick fine sand layer are analyzed. These results clarify the bearing characteristics of combined grouted shafts and can help guide the design of post-grouted shafts.

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