Large shear box apparatus

• Peak, critical and residual values of soil shear resistance at soil-soil or soil-geosynthetics contacts
• Coulomb strength parameters: angle of internal friction and cohesion
• Shear modulus at different strains
• Dilatancy angle

Large shear box apparatus consists of: load frame with electromechanical drive for vertical loading; shear device with electromechanical drive for horizontal load loading; interchangeable modules for direct shear and simple shear testing.

The structure includes:

1. Load frame
2. Shear device
3. Direct shear test kit
4. Simple shear test kit (option)
5. Measuring system with a set of sensors and electronic equipment
6. Software GeotekStudio
7. Control panel
8. Control cabinet

During shear testing on the consolidation phase, it is necessary to ensure that the vertical load is applied evenly. The load is applied in steps with vertical stress control. During the shear phase, the vertical load is controlled with stress and position control. The shear load is controlled in steps with stress control and kinematically with shear rate control.
Loading is carried out using electromechanical drives with axial force of up to 100 kN, providing static and kinematic load application with a feedback system.
A shear load is applied to the bottom of the specimen. The system includes a movable platform on low-friction guides, which exclude the possibility of platform rotation during shear. The lower part of the sample is attached to the platform with clamps. The upper part of the sample is attached to a traverse, which has the ability to move vertically to adjust the gap and freely dilate the sample during shear. 

The design of the large shear box apparatus provides for three types of shear tests:

• direct shear test; 
• simple shear test;
• geosynthetics shear test.

The system includes two interchangeable kits.
The direct shear test kit consists of an upper and lower race. The upper clip is attached to the vertically movable plate, the lower ring - to a horizontally movable platform.
The set includes a tray for soaking the sample directly in the system. The simple shear test kits consist of a bottom piston that attaches to a horizontally moving platform, an upper piston that attaches to a vertically moving traverse, and a set of low friction flat wheels. The kit includes a form for preparing and mounting the sample.

The measuring system measures vertical and shear loads, vertical and horizontal displacements. The vertical load is measured using a force measuring channel with a measuring range of 100 kN. Measurement of sample displacement is carried out using a measuring channel of linear displacements with a measurement range of 10 and 80 mm.

Electronic equipment as part of the large shear box apparatus is a complete and cost-effective solution specially designed to solve the problems of data collection and control of power devices with feedback.
Electronic blocks are used to perform static tests and are designed to perform the following tasks:

• control of axial loading actuators (drives), based on stepper and servo-stepper motors (up to 3 axes simultaneously);
• datalogging from force, pressure and displacement sensors (up to 8 sensors simultaneously);
• control of pressure control devices using pneumatic valves (up to 2 devices simultaneously).

Special software GeotekStudio is used to control the process of shear testing and provides the user with a set of preset algorithms for performing complex types of tests.
A complete picture of the testing process is implemented in graphs, sensor readings and calculated physical quantities and is shown using a set of graphical interfaces.
For special tests, the program provides the opportunity to develop your own sequence of commands to perform a unique type of test (write your own algorithm). Such algorithms are developed directly in the built-in environment for the development of algorithms in the GeotekStudio program in a block-graphical way.