Fracture toughness measurements of soft sediments based on gas injection tests

The gas in soft cohesive sediments tends to transport through fractures or cracks, and the study on fracture toughness of soft soil is an important component of the research on gas migration. A method for measuring fracture toughness of soft sediments is proposed in this paper. The gas injection tests on soft soil at constant flow rate were conducted, and the fracture toughness of soft soil could be calculated combined with the theory of linear elastic fracture mechanics based on the gas pressure and the orifice diameter. Through direct observation of the bubble growth in Laponite RD transparent soil, the law of gas pressure variation and the mechanism of bubble fracture growth in soft soil were further verified. The methods and instruments proposed in this paper are convenient and easy for operating, which are suitable for measuring fracture toughness of soft soil in laboratory. The fracture toughness of soft soil obtained by the method presented in this paper is consistent with the measurements of the in-situ soft clay proposed in the literature, which suggests that the fracture toughness measurement method of soft soil proposed in this paper is reasonable.