By K Z Andrawes, A McGowan and M M Al-Hasani, University of Strathclyde
This paper was first publsihed in GE’s September 1978 issue and is based on s lecture presented by the authors at last year’s TRRL/Heriot-Watt University symposium on reinforced earth
The strengthening effect of placing metal strips and woven fabrirc membranes in soils has been utilised in a variety of soil structures following the concept of reinforced earth put forward by Vidal (1966). The analysis of such reinforced earth structures has recently been investigated by many researchers; however, the operational soil reinforcement interaction mechanisms have yet to be fully agreed upon.
The placement in soils of quite different types of materials has grown in recent years, particularly the use of non-woven fabric membranes which are very extensible. The main functions of these nonwoven fabrics has been separation and filtration, ‘but a reinforcement function has also been suggested for them by McGown & Ozelton (1973.
To further the understanding of the strengthening effect of all these types of materials an investigation of the mechanisms operating in both reinforced earth and non-woven fabric and soil systems has been undertaken at Strathclyde University in conjunction with ICI Fibres and has led to an appreciation of the relationships between the properties of the material embedded in the soil and their resulting alterations to the soil be’haviour.
A clear conclusion of the work so far completed is that materials placed ‘in soil should not be referred to as reinforcements; rather they should be termed “inclusions”, as their influence may not always be simply one of strengthening soil structures (McGown Ik Andrawes, 1977).
The investigations at Strathclyde University are very widely based in terms of the variety of inclusion types considered and the variety of engineering structures investigated. In this Paper, however, only the inclusions most commonly used in reinforced earth end non-woven fabric soil systems will be referred to and then only in relation to very simple soil systems. Nevertheless, from this a basic understanding of the functions of inclusions and of the relative importance of their various physical properties will be illustrated.