ABSTRACT
A detailed discussion of laboratory test procedures to determine the undrained shear strength of clays and other fine-grained soils is beyond the scope of this manual; however, geotechnical engineers often use simple, inexpensive tests to make initial estimates of strength. These types of tests are often referred to as strength index tests because they can be quite crude and are not performed under carefully controlled laboratory conditions. Nonetheless, they actually can give a very good indication of the relative stiffness of different soils, and in some cases the results are quite useful. While these tests are primarily intended for use with undisturbed samples of predominantly fine-grained soils such as silts and clays, they may also be used on compacted fine-grained soils.
Four different laboratory Index Strength Tests are described in this chapter: 1) pocket penetrometer; 2) pocket vane (torvane); 3) laboratory miniature vane; and 4) Fall Cone. Even though the tests are normally intended for use in the laboratory, the pocket penetrometer and pocket vane may also be performed in the field during a site investigation by testing the ends of trimmed thin-walled samples.
