Seiya HORIKOSHI Investigation into The Fracture Properties of Compacted Soils with Cracks Using Multiple Test Methods Yutaka FUKUMOTO The existence of cracks in soil structures during embankment failures, which have recently become a problem, has an engineering impact on soil structures and can cause major problems not only from a geotechnical engineering point of view, but also from a geotechnical and environmental point of view. However, few experimental results and experimental methods have been studied as references for numerical modelling of compacted soils. The aim of this study was therefore to develop test methods and obtain data on actual fracture behaviour and fracture characteristics for fracture with cracking, which can be used to improve the analytical model. The test results were examined with a focus on three fracture properties: crack propagation behaviour, tensile strength and fracture toughness. The crack propagation behaviour was examined by crack tension tests, the tensile strength by crack tension tests and direct tension tests, and the fracture toughness by crack tension tests and three-point bending tests. The test methods used in each test were also examined to determine whether they were appropriate for obtaining fracture properties.The test results showed that the crack propagation behaviour differed depending on the initial crack angle, with some cases showing a strong open fracture mode, others showing a mixed mode of fracture with in-plane shear, and still others showing strong in-plane shear. In terms of tensile strength, there was a decrease in tensile strength due to the presence of initial cracks, with the greatest decrease in tensile strength at initial crack angles of 15 and 30, and a smaller decrease in tensile strength as the crack angle approached 90.@In the future, there is room for further clarification of the test method and for further testing to see whether results can be obtained from tests on materials other than blue clay. In addition to this, it is thought that the uniformity of crack shape by improving the method of setting cracks in the specimen will contribute to obtaining fracture characteristics unique to compacted soil that are different from those of other materials in the future.