Doctoral Dissertations

Abstract

"A systematic experimental investigation has been made to ascertain the liquefaction (cyclic strength) behavior of loessial (silty) soils. No information on the mechanism governing the behavior of these soils under cyclic loads was previously available. This study is important in view of the seismicity of the mid-western region and loessial deposits in the area, especially those near the urban centers.

The test program for this purpose consisted of cyclic triaxial tests on both undisturbed and reconstituted samples. The soil samples used in this investigation were obtained from Shelby County, Memphis, Tennessee. The influence of parameters such as cyclic stress ratio, effective confining pressure, sample remoulding, natural water content, overconsolidation ratio and plasticity index on the liquefaction susceptibility of a loessial soil has been investigated. Strain controlled cyclic triaxial tests were also performed to determine the shear modulus and damping values for this soil. The influence of significant parameters, namely effective confining pressure and shear strain amplitude, on the modulus and damping values has been studied.

The test results indicate that the application of cyclic loads to saturated samples of loess results in a build up of pore water pressure equal to initial effective confining pressure. The samples also underwent failure defined in terms of 5, 10 or 20 percent double amplitude strain. Test samples at natural water content (degree of saturation < 100%) also suffered failure due to large cyclic strains. It was observed that the effect of increased plasticity reduced the build up of pore water pressures. A comparison was also made of the behavior of saturated loessial soil with that of a saturated sand and the difference in behavior of the two have been examined.

It was observed that the dynamic shear modulus for this loessial soil decreased with increasing shear strains increased with increase in effective confining pressure, and was sensitive to secondary time effects. The damping was found to be strain dependent, increasing with an increase in shear strain amplitude. Within the range of confining pressures used in the tests, no well marked effect of confinement on damping was noted"--Abstract, pages ii-iii.

Advisor(s)

Prakash, Shamsher

Committee Member(s)

Stephenson, Richard Wesley
Schmidt, Norbert O., 1925-2009
Senne, Joseph H.
Hansen, Peter G., 1927-2010

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

Ph. D. in Civil Engineering

Publisher

University of Missouri--Rolla

Publication Date

Summer 1984

Pagination

xxii, 295 pages

Note about bibliography

Includes bibliographical references (pages 277-294).

Rights

© 1984 Vijay K. Puri, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Subject Headings

Soil liquefactionLoam soils -- Plastic propertiesShear strength of soilsLoess

Thesis Number

T 5070

Print OCLC #

11701772

Electronic OCLC #

942596622

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