What Is the Iowa Borehole Shear Test (BST)?
BST (the Iowa's — the 1970's; the borehole) is the in-situ (the direct shear's — the walls'; the 3-inch) test that measures (the drained — the phi'/c'; the borehole's) by shearing (the walls' — the 4-plate; the normal). The test: the 4-plate's (the serrated — the expanded; the 3-inch's), the normal's (the 5-30 psi; the stages'), and the 1-hour (the duration's — the 1-test's). The borehole's — the directly sheared.
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How BST works
The 4-plate (the serrated's — the 3-inch; the expanded), the normal (the 5-30 psi's — the stages'; the 3's — the minimum), the shear (the drained's — the 0.002 in/min; the peak's), the phi'/c' (the envelope's — the 3's; the Mohr's), and the 1-hour (the test's — the 1's; the 3-stage's).
The results
The phi' (the drained's — the 25-40°'s; the envelope's), the c' (the cohesion's — the 0-200 psf; the intercept's), the 3 (the stages' — the minimum; the 5-30 psi's), the 1-hour (the duration's — the 1's; the drained's), and the 3-inch (the borehole's — the 76mm; the hand's — the augered).
Practice
The Iowa's (the DOT's — the 100's; the specified), the slopes' (the stability — the phi'/c's; the 1.5's — the FS), the 3-inch (the hand's — the auger's; the 10-foot's — the max), the cost (the 1x's — the SPT's; the economical), and the 1970 (the Handy’s — the 50-year; the validated). The BST is the borehole's — the direct shear.
The bottom line
Use Iowa BST (4 serrated plates, 3 normal stages at 5-30 psi, drained shear) for direct in-situ φ'/c' in 3-in hand-augered boreholes — economical slope-stability parameters; Iowa DOT standard with 50-year track record.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.