The Observational Method in Projects

The approach advocated in this paper is based on the use of the observational method, first described by Terzaghi and Peck.

We believe that all of Peck's items (a) to (h) are needed for the approach to be classed as the Observational Method (OM).

For the method to be workable, all parties need to pay particular attention to contract arrangements and relationships that will influence the OM's implementation. Variations of the OM are being increasingly used on 'design and build' (i.e. engineer, procure and construct) contracts. Such contracts often do not have a clause about unforeseen ground conditions and may have only a little on-site involvement from the designer's geological/geotechnical specialist. We believe that these variations are often not true OM: the term OM may be used to obscure, or as an excuse for, or as compensation for, the inadequate skills and resources being put into a project's investigation and design.

For the method to be applicable, the character of the project must be such that it can be altered during construction. He also distinguishes between situations where the use of the OM is envisaged from the inception of the project, and those where the method is introduced part way through a project as offering almost the only hope of success. In the latter situation, there may be contractual problems to overcome.

In our experience, for those contracts where the Contractor is not taking all the ground condition risk:

The implications from the above are that each site requires a reliable preliminary model on which to build subsequent investigations which will, of necessity, modify and improve the model. It is the early development of this model, by consideration of all the reasonably possible geological and geomorphological characteristics of the site, which becomes the first objective. It is essential to have an understanding of the site acquired from knowledge of the fundamental basics of earth-building and surface-modifying processes, to help in the anticipation of the likely geology/geomorphology. The second objective is to substantially improve the understanding of the geology during the remaining investigation and construction.

Thus, this approach becomes the thread that runs through the paper: how anticipation of the site geology and geomorphology allows for better engineering at all stages - the desk study, the ground investigations and the construction.