Session Start Date

5-6-1984

Abstract

Previously reported settlements of structures founded on loess soils in the United States have been limited to cases of rapid deformation: the result of wetting and structural collapse. While the possibility of subsidence is usually a consideration in design, when the potential for wetting does not exist, economics generally govern the use of a shallow foundation system; in which case an accurate prediction of settlement is required. Since most loess deposits occur as unsaturated sediments, the use of one-dimensional consolidation theory is not applicable to the problem of settlement prediction. In 1977, a circular mat foundation was constructed on typical subsident loess to support a water tank for a small town in eastern Iowa. Between 1977 and 1983, settlement observations were made to monitor the magnitude of deformation. Laboratory one-dimensional compression tests and triaxial stress path tests were conducted to provide a means to predict settlements. Unlike many structures which are monitored for settlement, a water tank allows an accurate measure of load, thus eliminating an important unknown. This paper compares the results of settlement measurements with a number of techniques to predict settlement. The results indicate a time-dependent behavior of deformation which must be considered creep in light of the current understanding of loess behavior.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

First Conference

Publisher

University of Missouri--Rolla

Publication Date

5-6-1984

Document Version

Final Version

Rights

© 1984 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 6th, 12:00 AM

Settlement Performance of a Mat Foundation on Unsaturated Loess

Previously reported settlements of structures founded on loess soils in the United States have been limited to cases of rapid deformation: the result of wetting and structural collapse. While the possibility of subsidence is usually a consideration in design, when the potential for wetting does not exist, economics generally govern the use of a shallow foundation system; in which case an accurate prediction of settlement is required. Since most loess deposits occur as unsaturated sediments, the use of one-dimensional consolidation theory is not applicable to the problem of settlement prediction. In 1977, a circular mat foundation was constructed on typical subsident loess to support a water tank for a small town in eastern Iowa. Between 1977 and 1983, settlement observations were made to monitor the magnitude of deformation. Laboratory one-dimensional compression tests and triaxial stress path tests were conducted to provide a means to predict settlements. Unlike many structures which are monitored for settlement, a water tank allows an accurate measure of load, thus eliminating an important unknown. This paper compares the results of settlement measurements with a number of techniques to predict settlement. The results indicate a time-dependent behavior of deformation which must be considered creep in light of the current understanding of loess behavior.