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

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.

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

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.

scholarly journals Field Tests on Bearing Characteristics of Large-Diameter Combined Tip-and-Side Post Grouted Drilled Shafts

2021 ◽  
Vol 11 (24) ◽  
pp. 11883
Author(s):  
Zhitong Zhang ◽  
Weiming Gong ◽  
Guoliang Dai ◽  
Xiaolin Cao ◽  
Yu Zhu ◽  
...  
Keyword(s):  
Large Diameter ◽  
Standard Penetration Test ◽  
Drilled Shafts ◽  
Load Test ◽  
Cohesionless Soil ◽  
Cement Slurry ◽  
Test Procedures ◽  
Loading Test ◽  
Static Test ◽  
Tip Resistance

This paper presents a field study on the axial behavior of four large-diameter drilled shafts embedded in coarse sand. The grouting and loading test procedures were reported. The bearing capacity of shafts (TS1 and TS2) and grouted drilled shafts (TS3 and TS4) were herein determined by the bi-directional static test and top-down load test, respectively. The enhancement mechanism of bearing characteristics of the grouted shafts was discussed in detail. The test results indicate that the bearing characteristics and load transfer mechanisms of the test shafts were significantly affected by the quantity of pressurized cement slurry and the mechanical properties of the soil surrounding the shafts. Furthermore, the tip resistance of shaft can be mobilized more rapidly and fully after grouting, the side and tip resistance are mobilized in a more synchronized and coordinated manner due to the pre-mobilization of the grouted cement. Additionally, the standard penetration test (SPT) prediction model was introduced to calculate and predict the SPT blow counts of soil after grouting. The results show that the post grouting has a more obvious improvement on the strength of cohesionless soil.

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