Extensive Load Test Drilled Shaft Program with Integrity Assessments

Challenge:

A project in Ohio for a large plant was initiated in 2023. A substantial test program was established. The goal of the program was to confirm the shaft design in compression, tension, and lateral capacity, as well as establish proper shaft installation techniques for production shafts. Integrity testing was used to identify potential anomalies in the concrete shafts.

Method:

The job was divided into three test locations, which each utilized compressive static load testing, tension and lateral load testing, dynamic load testing, low strain integrity testing, and thermal integrity profiling all on 36-inch diameter drilled test shafts. These shafts were installed using 39-inch outer diameter temporary casings. The shafts were constructed using the free fall method of concrete placement in a dry shaft

Results:

Sample results from Test Site Location 3 will be used to show testing results. The compressive static load test utilized a maximum compression load of 1,05 kips in increments of 5% with each load being held for 10 minutes. The load was removed in 5 decrements, each held for 10 minutes. Measurements collected by displacement gages can be viewing in Figure 3-1. The tension load test was applied and held for 10 minutes per increment. Measurements from the tension load test can be reviewed in Figure 3-2. The lateral load test was specified to be 300 kips. Results can be viewed in Figure 3-3.

The dynamic load test utilized an APPLE 9 load test system with a 16-ton ram weight. The load was dropped from distances ranging from 6 inches to 5 feet. A top force transducer was utilized, as well as plywood for cushion. One of the impacts from the test was selected for CAPWAP analyses. Results from this analysis can be reviewed in Figure 3-4.

Thermal Integrity Profiling was utilized to assess the shaft shape, integrity, and concrete quality. TIP results are displayed in Figure 3-5. Low Strain Integrity Testing was also conducted, and results can be viewed in Figure 3-6.