Keywords: world wide web, data representation, geotechnical, dam, retaining wall, foundation.

This paper describes the development of GeotechML, a mark-up language for representing geotechnical data on the web. GeotechML is a version of XML (Extensible Mark-up Language) specifically targeted at geotechnical engineering. The representation of geotechnical entities (or structures) such as dams, foundations, retaining walls etc in GeotechML is presented. Other work on defining GeotechML is also underway. Some examples are given on the Durham University GeotechML website (http://www.dur.ac.uk/~des0www4/geotechml/).

XML allows simple text files to be `marked up' by including `tags' within the file. These tags can be recognised by an XML compliant web browser (e.g. Microsoft Internet Explorer 5.0) and can be used to give meaning to the contents of a file. The concept of GeotechML is illustrated with a very simple example of a dam, with a Java program to produce a graphical representation.

In order to be able to exchange information about different geotechnical projects it is necessary to be able to represent, in a standard form, the different types of geotechnical entities that may be involved in a project e.g. dams, foundations, retaining structures, slopes, ground improvement etc. A data structure is proposed that allows an entity to be made up of different elements and materials. Examples of Foundation entities might be: Pad foundation; Strip foundation; Raft foundation; Piled foundation or Dam entities might be: Earth dam; Rockfill dam; Gravity dam; Arch dam. Examples of Elements making up an entity could be: Slab; Beam; Pile; Wall; Gabion; Berm; Zone; Drain etc. Examples of Materials could be: Soil; Rock; Fill; Grout; Geosynthetic; Concrete etc.

Although XML compliant browsers can display XML data directly, the browser produces only a simple text-based display. To make the GeotechML format useful to users, it is necessary to have the ability to transform the XML file into different display formats. Stylesheets written in XSL (Extensible Stylesheet Language) provide the simplest way to achieve this by transforming the XML into HTML. Although HTML does not have any graphical capabilities it can display predefined image files (gif, jpg, bmp etc). This ability has been used to provide default representations of GeotechML files, using XSL, so that a default representation is presented to users rather than the simplistic text-based display.

An example of XSL style sheets is given for retaining walls. XSL is used to check the type of retaining wall represented in the GeotechML file and uses a different image file for each to convey the type of wall. Information about surcharge loadings and anchors is then superimposed. Tables are provided to convey the wall dimensions and the properties of the soils in front and behind the wall.

Although stylesheets are useful to provide a default view of a GeotechML entity they can only convey the type of entity, not a true representation. Therefore a Java application has been written to provide a way of viewing GeotechML files. This program allows the full details of a GeotechML entity (made up of different component elements) to be displayed. It provides a display of sections through the entity and also a three dimensional representation. It is illustrated using a raft foundation (comprising a slab and ground beams) as an example.

The potential for GeotechML is enormous as it provides all the possibilities that XML provides. Tools are available for XML for displaying the data (e.g. XSL and Java). However, perhaps the major advantage of GeotechML is that it will make it possible to search all geotechnical data available on the web. For instance, it would be possible to locate GeotechML files that contain projects within a particular geographical location or having particular types of entity or where particular soil properties have been used. In this way the World Wide Web will become an international repository of geotechnical information, available to the whole community. This avoids the necessity to establish national or international geotechnical databases; each data owner can make their data directly available on their own web server.

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