NEW DESIGN PROCEDURE FOR STABILITY OF SOFT CLAYS

Comments are made regarding SHANSEP, a new design method which uses CU tests that are Ko consolidated beyond the in situ maximum past pressure in order to minimize the effects of simple disturbance, as opposed to CIU or CKoU tests consolidated to the in situ vertical effective stress; the CKoU tests are performed at slow strain rates with different modes of failure to measure anisotropic behavior. CKoU tests are performed at different overconsolidation ratios, and the results expressed in terms of "unique" Normalized Soil Parameters (NSP) and design parameters are computed from a knowledge of the in situ stress history and the measured NSP, in contrast to the usual procedure of selecting these directly from the results of field or laboratory tests, or both. Fundamental criticisms of this method are considered. These relate to: SHANSEP's indirect utilization of strength data in contrast to present practice based on field vane and UU tests wherein the information is used directly in design; the validity of the NSP concept. and particularly the consolidation procedures used to obtain NSP; and the additional uncertainity introduced by the need to know the in situ stress history. The importance is stressed of the quality and accuracy of the strength values. The NSP concept does not apply to "quick" clays and naturally cemented deposits. It is recommended that tests be performed to determine if the soil in question shows normalized behavior. If it does, SHANSEP could be used to obtain initial in situ values of a s sub n and also changes in s sub n due to consolidation of the foundation soil. Comments are also made regarding the determination of OCR from consolidometer tests, and analysis of Bjerrum's field vane data and correction factor.

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  • Accession Number: 00131541
  • Record Type: Publication
  • Report/Paper Numbers: ASCE #11674 Proceeding
  • Files: TRIS
  • Created Date: May 14 1976 12:00AM