UNE-EN ISO 17892-6:2019

This International Standard specifies a method of estimating the undrained shear strength of both undisturbed and remoulded specimens of fine grained soils by the fall cone method. This International Standard is applicable to the laboratory estimation of undrained shear strength of a soil test specimen within the scope of geotechnical investigations.In the fall cone test, a cone is allowed to fall with its tip towards a soil specimen, and the resulting penetration of the cone into the soil is measured. The penetration values are used to estimate the undrained shear strength. The fall cone test produces a complex shear in the test specimen, and does not simulate either a vertical compression or a horizontal shear test. For undisturbed soil test specimens, the results of the test are dependent on the quality of the specimen. Also the degree of saturation of the test specimen may not be the same as the in situ soil, resulting in a different result. As the test is performed on a small laboratory specimen, the result may not agree with laboratory tests on larger specimens. In addition, the test specimen may not be fully representative of the soil in its natural state in the field, for example the test specimen may not have fissures present in situ at a larger spacing than the specimen size. Therefore, for the above reasons, the test should be regarded as an estimation of un-drained shear strength, rather than a true measurement of it. The ratio of the remoulded shear strength to the undisturbed shear strength may be used to estimate the sensitivity of a soil specimen. Time dependent measurement of the shear strength may be used to assess the thixotropic regain of strength of a remoulded soil specimen. NOTEThis document fulfils the requirements of the strength index testing of soils for geotechnical investigation and testing in accordance with EN 1997-1 and EN 1997-2.