【scope of application】<\b>
The coarse-grained soil triaxial shear testing machine is designed and manufactured in accordance with the GB/T50123-2019 "Geotechnical Test Method Standard", with all performance parameters fully compliant with relevant specifications. This testing equipment is used to measure soil properties such as shear strength, deformation, and pore water pressure under isostatic loading conditions. The system supports various testing modes including unconsolidated undrained (UU), consolidated undrained (CU), and consolidated drained (CD) tests.
The instrument is composed of three parts: measurement and control system, loading system, and accessories (including φ300mm pressure chamber, double-jaw die, electric lifting mobile frame, etc.).
【Instrument Features】<\b>
1. The core control system of the instrument measurement and control system employs a high-speed 32-bit ARM microcontroller, with ultra-high-speed sampling and computational capabilities ensuring precise data acquisition and display during the experiment.

2. The test and control system's operation interface utilizes an industrial tablet computer with integrated touch functionality. The test and control software features comprehensive functions, including data display and automated testing as required by standards, along with robust record-keeping and report generation capabilities.

3. The axial loading system is driven by an AC servo oil source, ensuring a more stable shear rate, and is controlled by a constant-pressure proportional valve with a large-loop feedback system.

4. The system operates without external air compressors or other pressure sources, achieving self-contained hydraulic control and confining pressure generation and regulation. Its stable performance meets the requirements of various triaxial tests.

【Main Working Principle of the Testing Machine】<\b>
1. During the triaxial test, the prepared sample is wrapped with a rubber membrane and placed in the pressure chamber. Pressure is then applied through the confining pressure system and backpressure system according to test requirements. The loading system's worktable increases shear force at the specified rate until the soil sample fails. Throughout the test, relevant data is collected via pressure sensors and a 0-150mm displacement sensor for subsequent data processing.

2. The control method of confining pressure and back pressure is to use water as the medium, and the required pressure is obtained by compressing the water through the piston of the pressure regulating cylinder moving forward or backward.

3. The volume change of soil sample is measured by volume tube or water tube.

【Schematic Diagram of Structural Principles for Triaxial Compression Test of Coarse Grained Soil】<\b>
The saturated test of non-cohesive coarse-grained soil is carried out by the methods of air saturation, water head saturation and carbon dioxide saturation.

The saturated test of the clay coarse-grained soil sample is carried out by the method of pumping out air and the method of reverse pressure.













1. Axial load sensor; 2. Sample; 3. Axial displacement sensor; 4. Pressure chamber cover; 5. Top cap; 6. Upper water permeable plate; 7. Lower water permeable plate; 8. Rubber membrane; 9. Water measurement tube; 10. Volume change tube; 11. Measurement and control cabinet (pressure chamber); 12. Pressure gauge (confining pressure/counter-pressure); 13. Porous pressure valve; 14. Sample water inlet valve; 15. Drainage valve; 16. Water measurement tube valve; 17. Peripheral pressure valve; 18. Counter-pressure valve; 19. Ventilation valve; 20. Exhaust valve; 21. Exhaust/water valve