PRELIMINARY REPORT ON EXPANSIVE CLAYS AS AN ENGINEERING PROBLEM IN THE BOISE FOOTHILLS, BOISE, IDAHO

Residential construction in Boise, Idaho is currently expanding into the foothills. To date, the geology of the foothills has not been well established; however, some features such as creep, landslides and faulting have been addressed. This report will assess potential engineering problems caused by clay layers and clay-rich soils associated with Tertiary volcanics in the foothills. Much of this clay is expansive, particularly near construction sites located in the foothills. Preliminary field mapping of the area has revealed the presence of numerous sedimentary clay accumulations associated with Late Tertiary volcanics. X-ray diffraction analysis of these clays reveal a high content of montmorillonite. Montmorillonite, a smectite clay, has been shown to undergo as much as a three-fold expansion between the silicate layers with the addition of water. With increasing water saturation, shear strength of these clay accumulations is considerably reduced. In the foothills area, over-steepening of slopes containing these clay accumulations can lead to slope failure. It is hoped that this report will bring to the attention of the construction industry the presence of expansive clays in the Boise foothills, and their potential as a soils engineering problem. (Author)

  • Supplemental Notes:
    • Proceedings of the Eighteenth Annual Engineering Geology and Soils Engineering Symposium, held at the Red Lion Inn, Boise, Idaho.
  • Corporate Authors:

    Idaho Transportation Department

    3311 W State Street, P. O. Box 7129
    Boise, ID  United States  83707-1129

    University of Idaho, Moscow

    Department of Geology and Geological Engineering
    Moscow, ID  United States  83844-3025

    Boise State University

    Department of Geology and Geophysics
    Boise, ID  United States 

    Idaho State University, Pocatello

    Department of Geology
    Pocatello, ID  United States  83201

    Idaho State University, Pocatello

    Department of Geology
    Pocatello, ID  United States  83201
  • Authors:
    • Bagan, W M
    • Davis, L E
  • Conference:
  • Publication Date: 1980-4

Media Info

  • Features: Figures; References;
  • Pagination: p. 255-267

Subject/Index Terms

Filing Info

  • Accession Number: 00334071
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Sep 16 1981 12:00AM