The High Capacity Direct Shear Machine is specifically designed to measure the total resistance to shear of large, 12in (305mm) square soil samples or within a soil/geosynthetic specimen. These devices feature the exclusive Karol-Warner CONBEL® system for loading the large, soil or soil/geosynthetic samples. The specimens are mounted in a two-piece shear ring assembly, divided in half horizontally. The bottom half is held securely in place and a vertical confining force is applied. Horizontal force is then directed against the upper half of the ring to shear the specimen.
Shear loads are applied using two pneumatic pistons. Initial loads are applied using a small-diameter rolling diaphragm piston, for greater accuracy and sensitivity of lighter loads, up to 454kgf (1,000lbf) of force. The larger piston generates loads up to 45kN (10,000lbf), or 90kN (20,000lbf) depending on unit selected. Horizontal shear rate from 0.0508—5.08mm (0.002—0.2in) per minute is easily set with digital thumbwheels on the control panel. Limit switches control the home position and limit total horizontal displacement to 102mm (4in). Vertical loading is controlled through a precision regulator, using the included calibration chart to set the required pressure. Loads are displayed to two decimal places on the digital readout, and are accurate to ±0.25%. Consolidation and shear displacement are measured by Linear Displacement Transducers. Shear load is measured from a load cell attached to the water chamber. The four-channel readout displays all these values while directing data in ASCII format through the RS 232 serial port to the user’s PC. The included software imports data onto spreadsheets such as Excel® for analysis and reporting. Displayed values on the readout can be viewed at anytime.
Loading and unloading the specimen and shear ring assembly to and from the water chamber is simplified using the Compaction Table. Pulling the loaded shear rings onto the convenient table rollers allows the entire assembly to slide easily into and out of the chamber. Sample compaction, geotextile placement, and specimen preparation can be performed on the table, before placing the assembly directly into the water chamber with little effort.
HM-384 and HM-385 High Capacity Direct Shear Machines are capable of applying maximum piston loads of 45kN (10,000lbf), and 90kN (20,000lbf) respectively. Both are ruggedly designed for harsh lab environments. All steel parts are powdercoated, and hard-coat anodized aluminum components resist corrosion. Casters on the machine and Compaction Table make for easy portability in the lab. Compaction Table and Top and bottom Shear Rings are included. Top ring is 12x12x4in (305x305x102mm), and bottom ring is 12x16x4in (305x406x102mm). Software and data cable is also included. A 120psi (827kPa) source of clean, dry, compressed air is required for operation.