IRISH COMPRESSIBLE SOILS: ORIGIN AND CHARACTERISTICS

Over one-seventh of the land area of Ireland is covered by bog. In addition, soft deposits occur near lakes, rivers and estuaries. Because many Irish cities and towns are situated near rivers, the problems, both technical and economic, presented by alluvial deposits are of considerable importance. This report describes the nature and mode of occurrence of these compressible soils, together with some of the morphological and environmental factors which determine their structural behaviour. Methods of identifying these soils are discussed and typical results given for the more common laboratory and in-situ tests. Special attention is given to the classical Terzaghi odometer test which is the most widely used basis for the preparation of forecasts of the behaviour under load of a deposit. The test is shown to be deficient, and a description is given of some of the better known attempts at improvement of its usefulness in the preparation of forecasts. Special mention is mmde of Biot's modifications of the Terzaghi equations of consolidation. Biot's equations, although derived in the early 1940's have not been wiiiely used, for reasons which are given subsequently. The method of the e sub g, e sub k parameters which has been developed in University College, Dublin, is briefly referred to. It is seen to be consistent with Biot's method, with the distinct advantage of being applicable to a real soil. The problems of total and partial stability are described and reference made to developments in methods of investigating this problem, such as classical plasticity, rheology, and numerical techniques. The recommendation is made that to avoid problems of instability during construction, the allowable applied load should never exceed twice the shear strength of the subsoil. This is a stricter criterion than that which is permissible in current European practice. (Author)

• Corporate Authors:

  An Foras Forbartha

  St Martin's House, Waterloo Road
  Dublin 4,   Ireland 
• Authors:
  • Hanrahan, E T
• Publication Date: 1979-9

Media Info

• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 111 p.

Subject/Index Terms

• TRT Terms: Bogs; Compressibility; Design standards; Forecasting; Highway design; Loads; Oedometers; Peat soils; Plasticity; Rheological properties; Shear strength; Soils; Structural analysis; Structural mechanics; Subsoil; Terzaghi's rule
• Uncontrolled Terms: Structural behavior
• Old TRIS Terms: Bog and marsh; Soil plasticity
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 00315378
• Record Type: Publication
• Files: TRIS
• Created Date: Dec 11 1980 12:00AM