Large Direct Shear Machines test the shear resistance between a geosynthetic or geosynthetic clay liner (GCL) and the contact surface of a large soil sample according to test methods in ASTM D5321 and ASTM D6243. Using these pneumatic CONBELâ„¢ system, horizontal shear loads are applied to 12in (304.8mm) square samples by four pneumatic pistons: two smaller pistons apply lighter loads up to 1,000lbf (454kgf) and two larger pistons apply loads up to 10,000lbf (45kN) or 20,000lbf (90kN), depending on the model used.
Horizontal shear rate from 0.002â€”0.2in/min (0.0508â€”5.08mm/min) is easily set with digital thumbwheels on the control panel. Limit switches control the home position and limit total horizontal displacement to 4in (102mm). Vertical loads are controlled through a precision regulator, using the included calibration chart and are accurate to Â±0.25%. Loading and unloading of the specimen and shear box assembly is simplified using the compaction table. The convenient table rollers allow the loaded shear box assembly to slide easily into and out of the chamber. Sample compaction, geotextile placement, and specimen preparation are performed on the table.
The rugged design of the Large Direct Shear Machine stands up to the most stringent laboratory environments. All steel parts are powder coated and all aluminum parts are anodized to resist corrosion. Locking casters on the compaction table allow it to be easily relocated.