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Investigation of the liquefaction of a soil profile using in situ tests

Jessett, C. A. (1992). Investigation of the liquefaction of a soil profile using in situ tests. (Unpublished Doctoral thesis, City, University of London)


Liquefaction is defined here as a sudden reduction in soil strength and stiffness resulting from a rapid increase in pore pressure. It is a behaviour typically associated with extensive deposits of fine granular soils. The mechanisms of liquefaction are identified as the generation and dissipation of excess pore pressures. Failure due to liquefaction can occur at the point of excess pore pressure generation (coincident liquefaction), or elsewhere in a soil profile or structure (noncoincident liquefaction). Existing methods available to the engineer for assessing the likelihood of liquefaction have been reviewed. None of these appear correctly to assess excess pore pressure generation and dissipation within real soil profiles. Therefore, these cannot always correctly predict liquefaction behaviour. A new approach based upon an in situ test is proposed.

New laboratory equipment was built which enabled the rapid preparation of uniform beds of soil and the monitoring of pore pressure generation and dissipation. It was used to study aspects of excess pore pressure generation due to rapid single increment loading and their subsequent dissipation. Two mechanisms of dissipation are identified; one dimensional consolidation and hindered settling. The latter would appear to be relevant in correctly understanding liquefaction failure.

The same equipment was used to assess which type of in situ instrument is able to determine in situ soil state. The research indicates that testing with a piezovane is potentially the best way of determining soil state and excess pore pressure dissipation characteristics throughout real soil profiles. It is proposed that the use of this approach in conjunction with correct numerical modelling of excess pore pressure dissipation should be developed as an appropriate engineering method of assessing the likelihood of liquefaction at a site.

Publication Type: Thesis (Doctoral)
Subjects: Q Science > QE Geology
T Technology > TA Engineering (General). Civil engineering (General)
Departments: School of Science & Technology > Engineering > Civil Engineering
School of Science & Technology > School of Science & Technology Doctoral Theses
Doctoral Theses
[thumbnail of Jessett thesis 1992 PDF-A.pdf]
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