ONR 24423

This ONR specifies the laboratory determination of undrained shear strength of undisturbed and remoulded specimen of fine grained soils by use of a fall-cone. This ONR specifies the fall-cone test, in which a cone is allowed to fall with its tip towards a soil specimen, whereupon the penetration of the cone into the soil is measured. Tests performed according to this test yield penetration values which can be used to estimate the undrained shear strength. The test is applicable to both undisturbed and remoulded soil test specimen. For undisturbed soil test specimen, the results of the test are dependent on the quality of the specimen. Because of possible effects of anisotropy, it can also differ depending on what undrained shear strength the relation refers to. The evaluated value of the undrained shear strength of the "undisturbed" soil refers to its state during the test in the laboratory. This value is not necessarily indicative of the undrained shear strength of the soil in its natural state in the field. Therefore, the test should be regarded as an index test. NOTE 1 For non-homogeneous soil samples, this method yields values of the undrained shear strength which are less representative for the bulk shear strength of the sample than other tests involving a larger volume of soil. NOTE 2 For disturbed soil samples and fissured soil samples this method normally yields higher strength values than tests involving a larger volume of soil.