The rheological direct shear apparatus is a professional instrument used to determine the shear strength and rheological properties of soil. It combines the functions of traditional direct shear apparatus with intelligent rheological analysis technology, and can conduct long-term mechanical behavior research such as creep and stress relaxation under stress control. The core principle is based on Coulomb's law, which measures the failure shear stress of soil samples by applying different normal and shear forces, and then calculates the internal friction angle and cohesion.
1、 Working principle
Shear mechanism: Place the soil sample between the upper and lower shear boxes, apply vertical pressure through a pressure plate, and apply horizontal thrust to the lower box, causing the sample to undergo shear displacement along the predetermined interface until failure.
Automated control: using servo motors or pneumatic drive systems, combined with high-precision sensors (such as grating displacement sensors, load sensors), to achieve closed-loop control.
Rheological experiment support: Real time monitoring of deformation characteristics of soil samples over time under constant shear force or strain conditions to obtain long-term strength parameters.
2、 Details of use
Sample preparation and installation
Sample specifications: The standard size is 100mm × 100mm × 100mm or 150mm × 150mm × 100mm, and it needs to be compacted in layers and controlled for moisture content.
Permeable stone placement: Place a permeable stone at the bottom of the shear box and cover it with filter paper to ensure smooth drainage.
Alignment and fixation: Adjust the pressure transmission plate screws to align the frame pressure transmission screws with the center of the steel ball, avoiding eccentric loading.
Equipment debugging and calibration
Airtightness test: After connecting the trachea, fill it to a pressure of 0.2MPa and hold it for 10 minutes without any leakage before use.
Leverage balance adjustment: Rotate the balance hammer to balance the weight of the lever, and remove the additional counterweight after tightening the nut.
Range calibration: Regularly verify the calibration value of the measuring force ring to ensure that the error is ≤ 1% FS.
Test Procedure
Vertical loading: Apply normal force according to engineering requirements and start shearing after settlement stabilizes.
Shear mode selection: The strain control type advances at a constant speed of 0.01~2.4mm/min and records the peak shear stress; Maintain a constant load through stress control and observe the development of deformation.
Data collection frequency: It is recommended to record data every 0.5mm displacement increment, and continue measuring until the residual strength stage after the peak value appears.
Special function extension
Unsaturated soil test: Replace the dedicated sealing chamber component and integrate a vacuum pumping device to control the matric suction.
Multi link parallel testing: Four link models can conduct comparative experiments simultaneously to improve efficiency.
The rheological direct shear apparatus has become a tool in modern geotechnical engineering research due to its precise control system and flexible expansion capability. In practical operation, it is necessary to strictly follow the standardized process and optimize the test plan based on specific soil conditions in order to fully utilize the instrument's efficiency.