ACIP Pile Performance at IAH Airport in Houston TX-PPT Presentation

PPT Presentation

Pdf Summary

The presentation reviews auger-cast-in-place (ACIP) pile performance for foundation work at George Bush Intercontinental Airport in Houston, Texas. The project was initially designed with 24-, 36-, and 48-inch drilled shafts to depths of about 95 feet. The bid scope introduced 18-inch ACIP piles, and some 24-inch drilled shafts were later changed to ACIP piles; the larger shafts remained drilled.<br /><br />The site has a high water table and layers of clay, sandy clay, and sand- or silt-bearing strata. These conditions, along with active airport operations and limited access, shaped construction and testing.<br /><br />Load tests substantially exceeded design demands. One test reached 750 tons, with estimated ultimate capacity of 975 tons—about 3.5 times the stated design capacity. Another reached 485 tons, with estimated capacity of 650 tons, or about 3.2 times the design load. A low-headroom ACIP pile carried 300 tons in testing; its estimated capacity was 380 tons, with a separate estimate derived from measured values of 420 tons.<br /><br />The presentation notes that ACIP capacity can be underpredicted in overconsolidated or desiccated clays and similar materials. Possible causes include outdated databases, tests that stop short of failure, treating maximum test load as ultimate capacity, unmodified use of the Davisson offset method, and differences in installation efficiency. It also raises questions about how undrained shear strength is measured and whether the conventional α·Su approach appropriately estimates shaft resistance for grouted piles.

Keywords

auger-cast-in-place

ACIP piles

drilled shafts

foundation engineering

load testing

pile capacity

George Bush Intercontinental Airport

Houston Texas

overconsolidated clay

undrained shear strength