The concept of Borehole Shear presents a unique alternative in shear strength testing of soil and rock in that tests may be conducted rapidly on the sides of the hole on relatively undisturbed material; therefore the inherent problems associated with obtaining equivalent information from laboratory tests are eliminated. In contrast to other methods of measuring in situ shear strength (that is, vane shear, cone penetrometer and pressuremeter) the Borehole Shear Test (BST) and Rock Borehold Shear Test (RBST) give discrete values of friction angle and cohesion; therefore more complete analyses may be made for such fundamental problems as bearing capacity and slope stability. In the past the BST has been considered a drained test and the effective parameters φ' and c' have been reported. This may not always be the case.
The general use, operation, assumptions, and problems of the test are examined and examples of the interpretation of results are given. Because of the time, economics, and accuracy of this method, the technique of Borehole Shear should see increased use in future in situ geotechnical testing.
This paper describes a test procedure for determining the total surface area of fine-grained soils using the Ethylene Glycol Monoethyl Ether (EGME). The test involves saturating a soil sample with EGME and then removing the excess EGME in a vacuum desiccator, until the EGME forms a monomolecular layer on the soil surface. The results of the test are expressed as Specific Surface Area (SSA), which describes the surface area/unit mass of dry soil with units of m2/g. Test results are presented demonstrating the effect of various test parameters on the results. Results for a number of different fine-grained soils are presented. A detailed recommended test procedure is given. The proposed method uses simple and inexpensive laboratory equipment, is relatively simple to perform, and allows for rapid determination of SSA.
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