Field Vane Shear Test (VST) Services in Austin

The field vane shear test (VST) is performed in situ, so the soil is tested at its natural stress state and moisture content. A lab vane test uses a remolded or undisturbed sample taken to the laboratory, which can suffer from stress relief and sample disturbance. The VST typically yields more reliable results for soft clays because it avoids these artifacts.

A standard VST profile in Austin typically ranges from US$650 to US$1,330, depending on the number of test depths, site access conditions, and whether sampling is included. The price reflects the specialized equipment and the time required to advance a borehole and perform the vane tests at multiple depths.

No. The field vane shear test is designed for soft to medium stiff clays with undrained shear strength below 200 kPa. In stiff clays or sandy soils, the vane may not penetrate without pre-drilling, and the torque required exceeds the tool capacity. For those soils, we recommend a [triaxial compression test](/) or a CPT instead.

Sensitivity is the ratio of peak undrained shear strength to remolded strength. A ratio above 8 indicates a sensitive clay that can lose most of its strength if disturbed. In Austin, some Taylor Group clays have sensitivity values between 4 and 10. Knowing this helps engineers design excavation slopes and select construction methods that avoid triggering a strength loss.