Construction World September 2019

GEOTECHNICAL ENGINEERING

with the corresponding design of the project. Standardisation for rockfall, debris flow, shallow landslides and slope stabilisation exists. In the European Assessment Document (EAD) for 'flexible facing systems for slope stabilization and rock protection', several tests are described for flexible facing which have been used worldwide for decades. They are available in two different qualities: mild steel and high tensile steel wire. For both qualities of steel, in combination with soil nailing/rock bolting there exist three key characteristics for the products. • Puncturing at the nail head plate (shearing-off resistance at the upslope edge of the spike plate) • Slope parallel load transfer into the nail with interaction of the soil (tensile strength) • Deformation/elongation of the mesh under load in percent What does this mean for users? The performance of the flexible facing is tabulated. These tables can be used to compare different products in terms of bearing resistance. Based on these tables, the three characteristics of flexible

I f this is possible, simple greening aids such as erosion control mats are usually enough to protect against washouts. These are however, not enough when steeper embankments must be secured or when there are superficial or even global stability problems. There are a variety of erosion control mats and geotextiles available to support the greening of loose rock slopes. In principle, there are two different starting materials: synthetic geotextiles (i.e. made of polypropylene), and natural geotextiles made of organic materials such as jute or coconut fibres. Organic material products can be used for flatter slopes. In steeper slopes, synthetic products offer advantages thanks to their low weight. Flexible slope stabilisation systems made of steel wire meshes in combination with a soil nailing system are now widely used to secure loose ground and rock slopes. These systems have proven to be very effective if applied correctly. For slope stabilisation using flexible facings it is necessary to have a certain value of tensile strength to hold a bigger volume of material back together with a deformation which should be as small as possible so that no erosion problems can start and will occur. The load distribution by a local impact is much more favourable with rhomboidal meshes such as those that Geobrugg supply. So why are Geobrugg’s products superior to the rest? Investors, designers and contractors should look at test results of products in detail to ensure that they are getting the right products with the expected performance for the job in hand. To avoid failures in installations and liability risks, it is important to make sure that the parameters in the Declaration of Performance (DoP) or European Technical Assessment (ETA) are in accordance

facings can be clearly defined in tender documents. Different products can be compared on a unique level. Geobrugg is proud of the fact that many of its rockfall barriers as well as the high-tensile wire mesh systems carry the necessary certification which makes it stand out. Factory production control are well documented and evaluated to ensure compliance with the conditions laid down in the technical specifications. Standardisation in the European Union helps to achieve a certain quality standard. The letters CE are the abbreviation of the French phrase 'Conformité Européene' which literally means 'European Conformity'. CE marking is a certification mark that indicates conformity with health, safety and environmental protection standards for products sold within the European Economic Area (EEA). The CE marking is the manufacturer’s declaration that the product meets requirements. The responsibility for the CE marking lies with whoever puts the product on the market in the EU. Stainless steel There is more evidence that standard galvanised products do not stand the test of time. To achieve prolonged design life, Tecco stainless are to be considered. Stainless steel can be used for aggressive and severe environments with low pH values, close to the seashore or in areas with direct contact with salt spray. The mesh has a tensile strength of 1 650 N/mm 2 . When one evaluates the installation cost, replacement and maintenance of conventional systems, then the high cost of the Tecco stainless steel system is not out of line.

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CONSTRUCTION WORLD SEPTEMBER 2019