OPTIMIZATION OF ROCKFILL AND EARTHFILL DAMS MONITORING SYSTEMS

摘要

A lot of instruments have been installed in new dams and measurements performed. However, few conclusions about the optimization of the instrumentation have been made and still less shared and published. Some need exists to summarize the analyses and all the experience gained in evaluating the separate phenomena for different types of dam in order to optimize the monitoring system. On the basis of realized observations and analyses, the dam monitoring system can be optimized to minimum quantity of instruments and at the same time sufficient to guarantee the dam safety at the lowest cost. Here part of Bulgarian practice in the monitoring of fill dams and in more detail of rockfill dams with a clay core is briefly presented. For the safety control of rockfill dams that are properly constructed on a solid ground, all what is necessary is monitoring of the seepage discharge through the dam and the displacements of dam surface points. Determining the phreatic surface is also required, but only for earthfill dams. All other measurements are not directly connected with the dam safety. They are mostly used for a verification of the engineering concepts and for research purposes. The analyses of 11 Bulgarian rockfill dams with a plasticity index of the core sandy clay from 0.10 to 0.18, leads to the inference that at such plasticity index the pore pressure at the end of construction is much lower than the same later at a full reservoir. For this reason its measuring is not necessary for the safety control. Installation of pore pressure cells is not required. It is sufficient, with some allowance for the core compaction from the load of the soil above and eventual hydraulic fracturing, to determine the dam stability with a pore pressure coefficient of 0.30 for the entire core.