Concrete mattresses have been commonly used since more than 50 years. Installations at navigable waterways have been documented at the Canal de Jonage (France) in 1993 or by the Federal Waterways and Research Institute (BAW) in the early eighties in Germany. After their application has become very unpopular during the last years the concrete mattress system is currently experiencing a comeback. Recently executed research projects (such as ice load testing at the Samara State University of Architecture and Civil Engineering, Samara, Russia or the hydraulic roughness investigations at the RWTH Aachen University, Aachen, Germany) have gained new insights in the concrete mattress technology which accelerate this development.
The objective of the study at the RWTH Aachen University in 2016 was to determine the hydraulic roughness of geosynthetic concrete mattresses as a basis for the design in practice-oriented applications such as canal linings. For this purpose, a hybrid model approach was used, that combined physical model tests and numerical modelling. The skin and form roughness of full-scale uniform mattresses were investigated in the laboratory flume of the Institute of Hydraulic Engineering and Water Resource Management at RWTH Aachen University. As the tests were performed in real scale, model effects could be eliminated and neglected. The experimental tests provided a data base to calibrate and validate a numerical model for analyzing the influence of the geosynthetic mattress shape on the hydraulic roughness. As a result, the hydraulic roughness of geotextile mattresses was quantified.
In order to describe and analyze the ice load resistance of the concrete mattress system large scale field trials were conducted at the shore of the Saratov Reservoir, which is an impoundment of the river Wolga. The field work was scientifically supervised by the Samara State University of Architecture and Civil Engineering (SSUACE), Samara, Russia. During the winter period of 2014/2015 the climate conditions and the ice thickness were continuously monitored. In addition to the field trials laboratory tests were carried out. Based on the insights of these two investigations in consideration of the existing gost standards a new design method for the ice load resistance of geoysynthetic concrete mattresses was derived.
The scope of the paper is to present a summary of the findings of the two different research projects. Furthermore the paper will illustrate the applicability and practicability of the system by showing some recently executed projects like the repair works at a German waterway. Due to the leakage of the existing asphalt revetment maintenance at the Main-Donau-Canal was required. Water reed rhizomes had perforated the lining layer. The mattress system was selected because of the potential installation under water while the ship traffic could continue. Another large scale example with the installation of approximately 150,000 m² mattress is the rehabilitation of a hydro-electric power plant canal close to Munich.
In summary the scientific research in combination with the long term experience and the recently executed projects will demonstrate the reliability of the rediscovered system.