Method for determining shear strength of calcareous sands under high stress

The invention discloses a method for determining the shear strength of calcareous sands under high stress. The method comprises the following steps: taking calcareous sands and quartz sands with the same grain composition, and preparing samples with different relative densities; respectively carrying out 1500KPa, 3000KPa and 000KPa constant-stress single shear tests by adopting layered filling; under the condition that the shearing force tends to a stable value, determining the soil sample to be sheared, otherwise, stopping the test when the shearing displacement reaches 20%; drawing a stress-strain relation curve, and calculating a maximum internal friction angle of the sandy soil through a coulomb formula; calculating a shear expansion angle to obtain maximum shear expansion angles of different sandy soil with different densities; calculating a critical internal friction angle; acquiring a breakage rate BrH or BrM of the sample by using a Hardin method or a Marsal method; fitting unbroken quartz sands to ob