A three-story medical office on the east side of Tucson sat on a patch of reddish-brown clay with visible caliche nodules. The developer needed bearing capacity numbers fast, and SPT blow counts alone weren't going to cut it for a deep foundation analysis. We mobilized the Shelby tubes, extruded undisturbed samples in the lab, and ran a consolidated-undrained triaxial test to nail down the effective stress parameters. That data fed directly into the footings design, saving the structural team from overconservative assumptions that would have added weeks to the piling schedule. In Tucson's basin-fill geology, where cohesive layers alternate with cemented gravels, the triaxial test remains the most reliable way to separate apparent cohesion from true drained strength.
Effective cohesion in Tucson caliche can drop by 40% once the sample is fully saturated and sheared slowly enough to dissipate pore pressure.
Quick answers
How much does a triaxial test cost in Tucson?
A standard three-specimen CU triaxial program runs between US$2,020 and US$2,480 depending on whether we handle the Shelby tube sampling or you deliver extruded specimens. The price includes saturation, consolidation, shear, and a full report with Mohr circles, stress paths, and interpreted c' and φ' values.
What's the turnaround time for triaxial testing?
UU tests typically report in 5 business days. CU and CD programs take 10 to 14 business days because the consolidation and shear phases are rate-controlled. Silt layers common in Tucson basin soils drain slowly, so we won't rush the strain rate and compromise the pore pressure data.
Do we need triaxial testing or are SPT correlations enough?
SPT correlations work for preliminary design but Tucson's cemented soils and caliche layers skew blow counts upward. If your project involves a deep excavation, a structure sensitive to settlement, or a slope near the Santa Catalina foothills, the triaxial test gives you site-specific strength parameters that a correlation can't match.
What soil types can you test?
We test cohesive soils, silts, and fine sands from undisturbed Shelby tube samples across the Tucson basin. Clean gravels and rock require different methods. If your boring log shows gravel with cobbles, we'll recommend a CPT test or large-scale direct shear instead.
