An integrated approach to the preparation of general purpose engineering geological maps and the evaluation of special purpose map derivatives : with the Colle de Jou area province of Tarragona Spain used as an example for illustration Vol. I and II

1999. An integrated approach to the preparation of general purpose engineering geological maps and the evaluation of special purpose map derivatives : with the Colle de Jou area province of Tarragona Spain used as an example for illustration Vol. I and II / by T.N. Ndola. - Delft : ITC, 1999. - 128 p. ; 30 cm. - ITC MSc-thesis. ABSTRACT, supervisor(s): Hack, thesis availability: ITC Library

ABSTRACT

General- purpose engineering geological maps are often the products of preliminary site investigations used for the assessment of geotechnical terrain conditions to allow for the evaluation of the suitability of the terrain for a variety of engineering works to be executed within the framework of a major civil engineering project.

Major civil engineering projects passes through various stages from project conception, through preliminary site investigations, main (detailed) site investigations, design, construction, and post construction (maintenance) stages.

The stages between preliminary site investigations and design and construction are in the order of ascending costs and should form the time sequence to be cost-effective. Preliminary site investigations therefore often get the least in terms of project time and budget allocations. Nevertheless important decisions on project planning, feasibility studies site selections, preliminary project design and the design of detailed investigations of selected sites are based on the results of these investigations. The principle aim of preliminary site investigation should therefore be to provide as much relevant data as possible on the ground conditions in the project area, to allow for the safe design of engineering structures.

The aim of this research project is the optimisation of data stored in general-purpose engineering geological database, in order to ensure maximum benefit in posterior special purpose studies.

This calls for an integrated approach to the preparation of general purpose engineering geological maps and the evaluation of special purpose map derivatives.

To achieve this the parameters and input data requirements for rock and soil mass classification for a set of special purpose engineering applications (slope stability, excavabilty foundation engineering and construction materials-specially for aggregates and base for road construction), are established.

A qualitative ranking in terms of relative importance of the parameters and input data requirements in each category of special purpose engineering application is established as a guideline to ensure that all the important parameters are included during data acquisition. A similar ranking is established for general-purpose engineering geological mapping in accordance with the scale of mapping.

Two categories of data inputs are established, as essential requirements for the preparation of general-purpose engineering geological maps from preliminary site investigation data. These include the basic thematic map inputs (topographic, geologic geomorphologic, hydrogeologic and DEMs), which are often available or have to be prepared, and the field and laboratory data on engineering properties of rock and soil units acquired during fieldwork.

The large number of data and information layers required as inputs and to be produced in preliminary site investigation studies requires that GIS should be applied in engineering geological mapping. As such a 2D-GIS database structure for data, integration is essential. A conceptual model for the 2D-GIS database structure for an integrated approach to the preparation of general purpose engineering geological maps and the evaluation of special purpose map derivatives has developed in this research.

The database should have two essential input databases; basic thematic GIS database consisting of input GIS map data, and a field and laboratory database consisting of results of field and laboratory tests, measurements and observations on the engineering properties of rock and soil units present in a given project area. The two databases for an integral part of the general purpose engineering geological database from which classification of rock for various engineering applications may be carried out for the production of general and special purpose engineering geological maps.

The practical application of the 2D-GIS database structure model for an integrated approach to the preparation of general purpose engineering geological maps and the evaluation of special purpose map derivatives, requires a suitable GIS hard and software package, and a suitable data set for testing.

The model has been applied using available data for the Coll de Jou area in the Falset region of Spain, using the ILWIS GIS package with encouraging results. The Colldejou data set consists of both field and laboratory data from limited surface observation points on rock units found within the area, which is consistent with preliminary site investigation studies.