Artificial Ground Freezing Impact on Shear Strength and Microstructure of Granite Residual Soil Under an Extremely Low Temperature

The Artificial Ground Freezing (AGF) method, which is widely used in tunnel excavations, significantly affects the properties of geotechnical materials frozen walls under extremely low temperatures. In order to simulate AGF process, freezing treatment with a temperature −30°C and thawing 25°C were performed on natural specimens granite residual soil (GRS). Subsequently, triaxial (TRX) tests conducted evaluate mechanical Nuclear Magnetic Resonance Image (NMRI) applied detect pore distributions GRS. To clarify variations microstructure after freezing-thawing, relaxation time (T 2 ) distribution curves T -weighted images from NMRI results thoroughly analyzed perspective quantization visualization. Results show that shear strength as well cohesion GRS are reduced sharply by while internal friction angle decreases gently. size (PSD) converted curve constituted two different peaks, corresponding micro-pores diameters 0.1 10 µm macro-pores 1,000 µm. Under impact, expansion shrinkage simultaneously exist specimen, was verified visualized images. frost heaving damage attributed microstructural disturbance caused presence large-scale pores uneven deformations GRS, subjected impact an temperature.