Orange California sits on a mix of old alluvial fans and sedimentary deposits from the Santa Ana River, with groundwater often encountered between 3 and 8 meters depth. For any foundation or slope design in Orange California, the direct shear test provides the drained shear strength parameters that settlement analyses and bearing capacity calculations depend on. We run this test on undisturbed specimens trimmed from thin-walled tube samples or block samples. The procedure follows ASTM D3080, with shearing rates set to ensure full drainage for the soil type. Before shearing, we consolidate each specimen under the expected effective stress, then apply the horizontal load at a constant rate of displacement. The result is a reliable Mohr-Coulomb failure envelope.
Peak friction angle in Orange California alluvial sands ranges from 32 to 38 degrees; residual values drop 4 to 7 degrees lower.
