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Direct Shear Machines

Gilson Pneumatic Direct/Residual Shear Machines by Karol Warner use pneumatic pressure for accurate application of sensitive confining loads.  A precision stepper motor controls shear loads.

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ASTM D3080 and AASHTO T 236 Direct Shear Tests determine resistance to lateral shear forces applied to a soil specimen. The specimen is trimmed with special Cutters to exactly fit in a Shear Ring or Shear Box with two horizontal halves, and loaded with a vertical confining pressure. The upper half of the ring is displaced laterally until the specimen fails, or a predetermined level of strain is reached. The strain is recorded to produce a stress-strain curve. Results determine cohesion and angle of internal friction for the specimens. Residual shear strength is measured when the specimen ring is pushed back in the opposite direction.

The Standard model measures shear loads with a digital readout, while consolidation and displacement measurements are taken from analog dial indicators. The Digital model measures all parameters with load cells and digital transducers, and  can output data to a PC. Both require a source of clean, dry compressed air.

The Dead-Weight Direct/Residual Shear Machines use a 10:1 mechanical beam device and manual weights to apply confining loads. The same precision stepper motor is used for shear displacement, and shear force is measured by a load cell with digital readout. Analog dial gauges are standard for displacement measurements, with optional Horizontal Displacement Transducers available.

The unique Gilson High Capacity Direct Shear Machine, also by Karol-Warner, is made especially for large, 12in (305mm) square soil samples with or without geosynthetic fabric. Two pneumatic pistons provide shear loads. Consolidation and displacement are measured by linear displacement transducers. Shear load is measured by a load cell, and all parameters are routed through a four-channel readout to the user’s PC.