Standard Pneumatic Shear Apparatus: Direct Machine

Standard Pneumatic Shear Apparatus: Direct Machine

The Standard Pneumatic Direct Shear Apparatus is engineered for the precise determination of direct and residual shear strength of soils. This advanced system includes a high-capacity load cell with a digital readout to accurately measure shear loads up to 1,500 lbf (6.67 kN), along with dial indicators for both consolidation and shear displacement. It’s an ideal choice for laboratories performing standardized shear testing and in-depth geotechnical analysis.

During testing, soil specimens — whether undisturbed or remolded — are trimmed and placed in a direct shear box that splits horizontally, allowing independent movement of the upper and lower halves. A vertical confining load is applied, followed by a controlled horizontal shear force to evaluate soil strength and post-failure behavior.

This machine is part of Certified MTP’s geotechnical testing lineup and shares foundational applications with products like the Digital Pneumatic Direct Shear Machine, which offers enhanced digital controls and data acquisition tools for automated direct shear testing.

Pneumatic Loading & Control System

The tabletop unit utilizes a patented pneumatic loading system to apply accurate and repeatable vertical loads without traditional dead weights. Two pneumatic pistons deliver loads ranging from 4 to 1,500 lbf, improving sensitivity at low pressures while maintaining precision at higher loads.

Load adjustments are made through a precision regulator and monitored on a digital display with ±0.25% accuracy. The front panel’s manual valves and controls allow users to monitor and adjust test conditions in real time.

For laboratories that need only the core mechanical shear strength setup, accessories such as the 50mm Square Shear Box are available separately; these boxes fit within direct shear machines to hold soil specimens during testing. 

Shear Displacement Testing

Shear displacement tests determine the shear strength of consolidated drained and undrained soils, generating data essential for evaluating soil stability and structural performance. The apparatus includes:

• A high-capacity load cell for precise load measurement
• Dial indicators for tracking consolidation and shear displacement
• Pneumatic pistons for smooth vertical load application

Different shear box sizes, like the 100mm Diameter Shear Box, are compatible with direct shear units and allow testing of larger specimens for more detailed analysis. 

Data Acquisition & Software Integration

For enhanced automation and reporting, this apparatus can be paired with NEXT Software, enabling real-time monitoring, automated control, and professional report generation. Independent data channels capture vertical and horizontal deformation, and the results can be stored indefinitely or exported in CSV format for further analysis.

Engineers can operate the machine in stand-alone mode or connect it to a LAN, centralizing data management — an advantage for high-volume geotechnical labs.

Included Components & Standards Compliance

The system includes:

• Pneumatic pistons for vertical load application
• Digital load readout and regulators
• Strain measurement controls

The unit is built with corrosion-resistant materials, including a Teflon-coated aluminum water chamber and stainless steel shear ring, drainage plates, and porous stones. Optional accessories such as counters and additional porous stones are available separately as needed.

Specifications:

• Electrical: 110 V / 60 Hz
• Standards: Meets ASTM D3080 and AASHTO T236 testing protocols

For labs that require additional geotechnical assessment tools, products like the Soil Pocket Penetrometer provide quick field tests for soil strength that inform pre-testing decisions. 

The equipment is robust, versatile, and built to support repetitive direct shear testing with accuracy and efficiency in professional geotechnical environments.