The ERFA system prevents a collapse and protects ... - Geobrugg AG

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ERFA sinkhole protection system / System description / March 2010 Fig.2: Photos from the full-scale fi eld test in Goldach SG, Switzerland 4 ERFA SINKHOLE PROTECTION SYSTEM The ERFA sinkhole protection system is characterized by linear, rigid bearing elements combined with a high-strength diamond-shaped steel mesh acting as a fl at force spreading element. Serving for load transfer in the road longitudinal axis are standard reinforcement steel strands of high-tensile steel wire. As a result of the high deformation rigidity, the linear load bearing elements can transfer considerable forces with very slight defl ection. A force transfer of 2 000 – 2 500 kN/m is possible without problems. The system rigidity plus the load bearing capacity is directly infl uenced by the choice of the number of strands per running meter and their cross-sectional area. By this means, the system can be optimally adapted to the project-specifi c requirements and boundary conditions. The linear load bearing elements are held together by means of the hightensile steel wire mesh which is placed over them, exerting a spreading effect. This prevents the breakage of individual strands through the pavement. Due to optimal interaction with the rubble the anchoring section of the combi product can be considerably reduced longitudinally. Through the choice of diameter of the reinforcement steel strands and their mutual spacing, the load bearing capacity and the maximum defl ection in the case of an event is adaptable to the project-specifi c requirements.
Linear load bearing elements According to the supplier data the linear main load bearing elements used in the standard ERFA sinkhole protection system possess the following characteristics: Parameter Value Nominal diameter in inches D = 0.6’’ Nominal diameter in mm D = 15.7 mm Nominal cross-section A = 150 mm P 2 Weight G = 1180 g/m Yield stress f = 1590 N/ mm y 2 Minimum tensile strength f = 1770 N/ mm tk 2 Fracture force P = 266 kN tk Number of wires 6 + 1 Diameter of the outer wires 5.20 mm Diameter of the inner wire 5.35 mm Elongation at maximum load 3.5 % Contraction Ψ = 30 % E-modulus (mean value) E = 195’000 N/ mm P 2 Relaxation over 1 000 h, 20°C, 0.70 ftk max. 2.5 % The following illustration shows a schematic tension-elongation diagram for a reinforcement steel strand according to the specifi cation in Table 1. Flat load bearing element The high-tensile steel wire mesh used with the ERFA system as a force spreading load bearing element, for instance TECCO ® G65/4, was specially developed by Geobrugg AG for applications with high demands. It possesses the following characteristics: Tab. 1: Characteristics of a reinforcement steel strand as a linear main load bearing element Fig. 3: Tension-elongation diagram for a reinforcement steel strand with nominal cross-section A p = 150 mm 2 5
Page 1 and 2: ERFA sinkhole protection system Sin
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Page 7 and 8: Connectors In the full-scale fi eld
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Page 11 and 12: When using the ERFA system, the thi
Page 13 and 14: The maximum grain size of the prefe
Page 15 and 16: Reinforcing of the boundary zone In

The ERFA system prevents a collapse and protects ... - Geobrugg AG

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