Standard Pneumatic Shear Apparatus: Direct Machine

Standard Pneumatic Shear Apparatus: Direct Machine

The Direct/Residual Shear, Standard Pneumatic includes a capacity load cell with digital readout to measure shear load and dial indicators for consolidation and shear displacement measurements. The apparatus has a capacity load cell that can measure up to 1,500lbf (6.67kN) so you can be sure of accurate load application and data collection during testing. The machine comes with all the necessary components to get you started with laboratory shear testing right away. Some items such as shearbox assemblies and related accessories are ordered separately.

Shear displacement tests determine direct and residual shear of consolidated drained and un-drained soils and gives engineers valuable information to evaluate soil strength and stability. The test is performed on various soil types with either undisturbed or remolded soil samples. The specimens are trimmed into a Direct Shear Box which is split horizontally to allow individual movement of the top and bottom halves. Shearbox assemblies are required for standardized shear testing and must be ordered separately. A vertical confining load is applied to the specimen and a horizontal shear force is applied to the bottom half of the box. The top half of the shear box remains stationary during testing. After shearing failure has occurred and force measurements have been taken, the direction of shear force can be reversed to determine residual shear values. Both a vertical strain transducer and a horizontal strain transducer are included to measure vertical and horizontal deformation during testing.

Tabletop units with pneumatic vertical loading use the patented CONBEL® loading system to apply confining pressures to the sample. Vertical loads are applied using two pneumatic pistons. A small, rolling diaphragm piston applies light loads of 4-100lbf (0.018-0.44kN) and the large diameter piston applies loads up to 1,500lbf (6.67kN). This design increases the sensitivity and accuracy of the light load system. Loading is controlled by setting the precision regulator to the desired pressure per the included calibration chart. The front panel has manual valve controls and a digital display so you can easily adjust loads and monitor data in real time. Manual valve controls are available for user friendly operation so you can get started right away. Load settings are displayed digitally and are accurate to ±0.25%. Both pneumatic shear machines are self-contained units and no loading weights are required.Stepper motor drive controls strain rates to ±1% from 0.0001-0.3in/min (0.0025-7.62mm/min) and is easily set with digital thumbwheels. Advanced test control and machine control is available to control tests via software or manual interface. Computer controlled is available to integrate with Next Software for automation, real-time monitoring and remote operation. Next Software provides advanced data acquisition, test control and report generation for geotechnical testing. Total shear capacity is 1,500lbf (6.67kN). 2.5in (63.5mm) diameter stainless steel shear ring, porous stones, drainage plates and a water chamber constructed of Teflon coated, anodized aluminum for corrosion resistance are included. Counter-balance devices and additional porous stones are available and may be ordered separately.

Electrical: 110V/60Hz

Meets Test Methods: AASHTO T236, ASTM D 3080. For information on the 24 x 5/8in Stainless Steel Tamping Rod, Mini Slump Cone, concrete slump testing and standards, see ASTM C143.

Introduction

Direct shear machines are the fundamental tool in geotechnical engineering to evaluate the shear strength of soils and other construction materials. By applying a controlled horizontal shear force to a prepared soil specimen, these machines allow engineers to measure the shear load and determine residual shear values which are critical to evaluate the long term stability and safety of structures. The ability to do direct shear tests and analyze residual values makes direct shear machines essential for projects involving foundations, slopes, embankments and retaining walls. Precise measurement of shear force and load allows engineers to make informed decisions about soil behavior under various loading conditions and ultimately lead to safer and more efficient designs.

Direct Shear Machines

Direct shear machines apply a vertical confining load to a soil sample and then a controlled horizontal force. This allows measurement of both load and the resulting horizontal and vertical displacement to get the material’s shear strength. These machines come in various configurations, pneumatic, semi-automated and fully automated models to suit different testing needs and laboratory environments. Direct shear machines are used in soil mechanics, geotechnical engineering and materials science to evaluate the performance of soils under stress. By measuring the effect of vertical load and horizontal force these machines help engineers to understand how soils will behave in real world applications and ensure the reliability and safety of construction projects.

Standard Pneumatic Direct Shear Machine Features

The standard pneumatic direct shear machine is designed for precision and ease of use. This tabletop unit uses a pneumatic system to apply a consistent vertical load to the soil specimen. The direct shear box holds the carefully trimmed sample and is engineered for optimal fit and minimal sample disturbance. A stepper motor drive controls the strain rate and is easily set with digital thumbwheels. The load cell measures the load and horizontal and vertical strain transducers measure displacement in real time. Total shear capacity is 1,500lbf (6.67kN). Robust construction includes a pneumatic direct loading system and corrosion resistant materials for long life and low maintenance.

Operation

Operating the direct shear machine is a simple but precise process. Trim the soil specimen to fit within the direct shear box, using a blade mixer in dispersion for soil for thorough mixing if required. Secure the sample and apply a vertical load using the pneumatic system. Load settings are adjusted with the precision regulator. Monitor the load and displacement on the numerical display and real-time graphical chart. Apply force to the specimen simulating field conditions. Adjust and monitor the machine to ensure each test is done under the same conditions. Observe the specimen, measure the shear strength and gather data for analysis all while using the machine’s intuitive interface and reliability.

Data

Today’s direct shear machines come with advanced data acquisition systems to simplify testing and analysis. Independent data acquisition channels capture all test data which can be accessed via a LAN-networked computer or used in stand-alone mode. The system’s graphing capabilities allow you to see test results in real time to help you interpret data and trends. Data can be stored indefinitely and exported in several formats including CSV files for seamless integration with other software. The machine has a user friendly interface to support live test monitoring to full unit customization reports. Additional features like a counter-balance device available as a retrofit kit and a water chamber made of Teflon-coated, anodized aluminum for corrosion resistance are available to make the machine more versatile and durable. This allows engineers to manage, analyze and report on their direct shear tests for high quality research and reliable engineering results..