Experimental research on fracture toughness II of undisturbed frozen soil

Based on the study of fracture toughness II of frozen soil, the application of fracture toughness II is firstly used in undisturbed frozen soil in this paper. Because of undisturbed soil not vibrated and microstructures inside of the soil body not change, it is more realistic and more meaningful than remolded soil in laboratory. In the research, bend test stand was improved at first time, and drawing on prefabricated vertical cracks in rock fracture test to observe the cracks size by coloring. With the observations on layering frost heave of the local soil, the relations of frost heave, melt and time are obtained in different deep soil layers, so that the samples production and test temperature can be controlled strictly. The fracture toughness of four-point-bending vertical pre-cracked specimens of test II of undisturbed frozen soil is obtained. Experimental results indicate that the undisturbed frozen soil mechanics experiment is completely available, and it is feasible to measure the crack size with coloring technology, the fracture toughness II of undisturbed frozen soil is also obtained.