KNOW-HOW Warp knitting technology Geotextiles: essential reinforcement The structural geometry of warp-knitted geotextile materials is either of the “thin plate” type or of the “sheet” type. These materials are used mainly for their tensile properties because of their membrane mechanical behavior. GERMAIN AURAY CIVIL ENGINEER DAMIEN SIMONS, PROJECT MANAGER TEXINOV S oils consist of granular materials; under tensile-shear stress conditions, certain soil configurations risk crumbling. For example, the block shown below is breaking loose under the weight of the earth, due to the slope gradient (Fig. 1): Fig. 2: Longitudinal section of Saint Saturnin bridge. The bridge deck has a span of sixteen metres and an average above-stream height of eight metres. The nearly vertical buttress wall consists of non-grouted concrete blocks. Geotextiles are used to reinforce the structure. Fig. 1: Example of slip-circle The use of a reinforcement geotextile helps to maintain the block in equilibrium in the following manner: the geotextile is blocked by the normal stress due to above ground and the friction between the geotextile grid and the soil anchors the geotextile in the granular soil matrix, contributing to create tensile stress in the geotextile layer. We can establish a parallel between geotextiles and the archetypal composite material used in civil engineering, reinforced concrete, as they both operate on the same reinforcing principles. Texinov applications are not limited to the reinforcement of earthworks. The company also develops this type of solution for the reinforcement of asphalt pavements and of concrete. A typical example is the earth abutment for the Saint Saturnin bridge (Fig. 2 and Fig. 3): Fig. 3: Saint Saturnin bridge at the end of work. The abutment was also instrumented with fibre optic sensors (in cooperation with TenCate Geosynthetics France, Fig. 4). The fibres are incorporated directly into the geotextiles during Fig. 4: Optical fibre instrumentation of the geotextile. JEC Composites Magazine / No35 September 2007