Austin Independent School District
Austin, Texas

Project Description

The 32-acre site consists of utilities; a retention pond; a 157,833 square foot school building; access roads; a parking lot; a football field with all-weather track; an outdoor concrete play-slab; a soccer field and two softball fields. The staggered "step-down" elevation of the site made the placement of the ball fields unique, with each ball field situated on a different "step". Construction began in May 2006 and the school is scheduled to be open in the fall 2007.

Kleinfelder provided construction materials testing. Services included: proof-rolling observation; soil compaction and moisture tests; pier observation; concrete testing; reinforcing steel observation; tilt-wall observation and structural steel inspection and testing.

Client Issues

• One challenge for Kleinfelder was to ensure that the drilled pier operation was being done correctly. The piers are designed to be 20 feet deep with a bell shape at the bottom so that the settlement is minimized and there is a safety factor of three against shear failure. Bell piers are more difficult than normal piers to inspect for compliance. Kleinfelder recommended that the driller use a chain on the belled drill bit, which allowed the inspector to verify that the chain remained taut while the drill was spinning. A floodlight and mirror were used to check this action while the bell was being drilled 20 feet below the surface.
• Another challenge for the driller was to keep the bell shape intact without sloughing into the pier hole. To address this issue, numerous depth measurements were taken to ensure the bottom depth was not rising due to soil sloughing off of the bell.
• The project site also required extensive clearing of existing trees and debris.

Kleinfelder's Role
Kleinfelder provided construction materials testing services.

Client Benefits
Kleinfelder has provided the client with two full-time, on-site technicians to provide continuous pier observation and soils testing services. The client is updated on project progress with field observation and testing reports—any problems are communicated directly to the project superintendent if/when they arise.

By providing geotechnical services to the client prior to construction, Kleinfelder has been able to serve as a trusted advisor concerning earthwork activities at the site. Kleinfelder’s staff of engineers and technicians has provided valuable input concerning the initial phases of the project, and the on-site testing ensures the design recommendations are being implemented during construction.