Repeat on fresh specimens at two or more further normal stresses.<\/li>\n<\/ol>\nCalculation & Reporting<\/h2>\n
Shear stress = shear force \/ corrected area. Report peak and residual stress for each normal stress, the fitted c′ and φ′, consolidation data and shearing rate.<\/p>\n
Acceptance Criteria<\/h2>\n
Typical drained friction angles: loose sand 28–32°, dense sand 35–45°, silts 26–32°, normally consolidated clays 20–28° with c′ near zero. Results outside expected ranges usually indicate too-fast shearing or disturbed specimens.<\/p>\n
Frequently Asked Questions<\/h2>\nDirect shear or triaxial \u2014 which test should I specify?<\/h3>\n
Direct shear is faster and simpler for sands and interface strength, but forces the failure plane and gives no pore-pressure data. Specify triaxial testing where undrained strength, stress paths or accurate clay parameters are needed.<\/p>\n
Why must shearing be slow for clays?<\/h3>\n
The test assumes drained conditions. Shearing faster than pore water can escape generates excess pressures, understating the true effective-stress parameters.<\/p>\n
Recommended Apparatus<\/h2>\n
NL Scientific manufactures the Digital Controller Direct Residual Shear Box<\/a> for this method. Browse the full Soil Testing Equipment<\/a> range or request a quotation<\/a> from our engineers.<\/p>\n
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