BEHAVIOUR MONITORING OF DRIEKOPPIES DAM DURING CONSTRUCTION AND FIRST FILLING : PROBLEMS AND LESSONS

摘要

Construction of Driekoppies Dam in South Africa was completed in April 1998 and the dam spilled for the first time in March 1999. During construction a variety of instrumentation systems were installed to monitor the long-term behaviour of the structure. These systems included piezometers, settlement cells, earth pressure ceiis and extensometers. This paper describes problems and lessons which have arisen during the installation of these instruments and the subsequent processing, reporting and evaluation of the results obtained. The problems described include difficulties during installation, damage to cables and instruments during construction, electrical problems arising from lightening induced power surges and unreliable readings from the instruments themselves. A particular aspect discussed in the paper is the development of a procedure to processing the data using commercially available computer spreadsheet software (Microsoft Excel). The primary purpose of this approach was to be able to present the enormous quantity of data generated by the instrument systems into graphic images which was readily understandable. The graphic images produced by the process include line diagrams, contour plots and bar plots. This procedure has been extended to enable contour plots generated on a (say) monthly intervals to be transferred to a presentation package (Microsoft Powerpoint) and in this way a "movie" of changes with time can be displayed.