Author(s): Peter Salat; Laszlo Nagy
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Abstract: Problems: Construction and strengthening of flood levees in Hungary, having been continuously made during the past 150 years, followed, as much as possible, the original first track of the levee lines. It has turned out only recently that the original layout of the earthen structures crossed several areas of unfavourable subsoil condition. The main geotechnical hazards of the flood levees in Hungary have been examined and summarised. Purposes: For the monitoring of flood levees, methods had to be developed, which allow the appropriate (i. e. reliable and exact) determination of the condition of earthworks. The selected methods are the complex geotechnical and geophysical surveys with quality control (QC) and quality assurance (QA). These integrated methods explore larger blocks of soil and serve the purposes of improving the flood defence. Principles: The joint geotechnical and geophysical investigations carried out by means of different physical instruments along a line on the earth surface are similar to those of core analysis and well logging which are carried out along the borehole axis. Consequently the routine methods of quality controlled data acquisition and evaluation of well logs can be applied to the complex surface monitoring of the condition of the levees. Results: The quality controlled monitoring was tested on some well known test sites. Statistical classification and estimation methods were applied to determine soil classes, geotechnical parameters and geometrical characteristics of layers as well as their reliability and confidence intervals or covariances. The conclusions are in agreement with the real situations within the estimated confidence limits. The surveys of flood levees, following the above principles, provided a globally unique data base for evaluating the expectable behaviour of levees under flood pressure, and for identification of sites with safety levels less than acceptable.
Year: 2002