ICE - Institution of Civil Engineers - Virtual Library

In this essay the author argues that education in the basic theory of structures, hydraulics and geotechnics is being neglected in favour of training in the practical aspects of geotechnical engineering and an over-reliance on design codes and standards.

Gassy soils are soils that contain gases under positive pressure. They can have a significant impact on the stability of excavations. This briefing note summarises two cases in southern Ontario, Canada, that highlight the importance of continued research into the behaviour of gassy soils.

Although long retaining walls are usually analysed in the permanent condition by means of a plane strain analysis, three-dimensional effects may be significant in limiting ground movements at certain stages during construction. This is particularly true for embedded diaphragm-type retaining walls propped at formation level. In this paper, a three-dimensional finite element analysis representing a typical construction sequence for such a wall is compared with a corresponding plane strain analysis and field data from the A4/A46 Batheaston–Swainswick bypass. The results are used to assess the significance of three-dimensional effects during construction, and suggest how these can be utilised to minimise ground movements.

A road tunnel 13·5 m in diameter and 800 m long has recently been constructed, through chalk, as part of the Ramsgate Harbour Approach Road Scheme. For the first time in the United Kingdom tunnelling has involved primary support being provided by a system of prevaults followed by the installation of an unreinforced concrete lining. This paper describes how an iterative grouting solution was evolved in response to unstable ground conditions during the early phases of tunnelling. As the tunnel drive progressed, and greater knowledge of the engineering behaviour of the chalk was gained, decisions were made to carry out trial injections using the tube-àmanchette and lance methods. These were installed from the surface in areas where it was perceived that future problems might occur. A comparison is drawn between the efficiency and relevance of the two systems in the ground conditions encountered on site.

Parts 1, 2 and 3 of this series of publications gave details of the development and application of a pilot in situ auger mixing treatment on a contaminated site in West Drayton, Middlesex. The treatment method employed was in situ stabilisation/solidification using cement-based grouts and applied using a soil-mixing auger. In these publications, details were given of the initial laboratory treatability study, the site trial and subsequent laboratory assessment of the treated contaminated made ground using samples cored at 55 days and tested at 0·2, 1·2 and 2·4 years after treatment. Recently, further coring of the treated ground took place at 4·5 years of in situ curing and the samples were tested at around 5 years after treatment. Hence this paper presents the longer-term behaviour of the in situ cured stabilised/solidified contaminated ground in terms of physical and chemical properties such as strength, leachability, leachate pH, permeability, freeze–thaw and wet–dry durability and microstructural analyses. The performance is presented of both soil types present, made ground and sand and gravel, from both single and overlap column mixes. The paper provides an insight into the effectiveness of the treatment at 5 years, a correlation between the performance of the different soils and mix conditions, and an assessment of the applicability of the available test methods and test criteria imposed.

Published bi-monthly by the National Research Council of Cananda, Ottawa; circa 275 pages per issue. Current overseas, personal subscription: $246US, including airmail delivery. ISSN 0 008 367 4.

The Canadian Geotechinical Journal generally has a pleasing mixture of practical and theoretical papers covering soil and rock mechanics and engineering. The reader will not be surprised to find the occasional paper in French; the generous number of papers published in each issue will amply compensate the non-Francophone. Papers on soil behaviour tend to form the majority, while, as for many international Journals, there is a stated desire to publish case histories of practical application that is frequently fulfilled. Not suprisingly given the number of papers, there tends to be a voluminous Discussion section at the end. The following brief selection from the February and April 2002 issues gives a flavour of the Journal.

The following are summaries of papers published in other parts of ICE Proceedings that readers of Geotechnical Engineering may find of interest, covering the period September 2001 to May 2002.