To prevent the appearance of localized sinkholes under roads and railway lines in areas at risk, a research program testing a geosynthetic reinforcement solution was carried out by a group of laboratories. The aim of the reinforcement is to limit surface deformation after the appearance of a sinkhole by making the surface settlement as compatible as possible with the geometrical safety criteria of the road or railway line until earth filling and repair works can be scheduled. Full-scale tests were carried out on reinforced, instrumented road and railway structures subjected to localized collapse. At the same time, a numerical study was carried out to gain a better understanding of the mechanisms involved (arch effect, membrane effect, and collapse mechanisms). The experimental results of the full-scale tests were analyzed and compared with the results of three-dimensional finite element modeling.Key words: localized sinkhole, karstic cavity, reinforcement, geosynthetic.

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Due to increased land use, road or rail infrastructure is more and more frequently being built on ground that is weak or risks collapse. To avoid any damage or dis ruption (closure to traffic), reinforcements made from geotextile sheets are cur rently being studied. To understand the three-dimensional behavior of textile sheets acting as membranes under pressure, an original finite element calculation method is discussed and compared with analytical solutions in simple cases. A sizing nom ograph and some practical solutions are presented in more complex cases of rein forcement.

The technique for constructing geosynthetic-reinforced soil retaining structures is now in widespread use. Since its first use in the late 1960s, construction processes have become more technologically advanced, and the number of alternatives has reduced, with most of the construction techniques being standardised. This type of reinforced structure has been in use for nearly 30 years, during which time its reliability has been proved. At the same time, work is in progress to standardise the design of these structures using the new international format of Ultimate Limit States and Serviceability Limit States calculations and associated partial factors. This study presents the procedure currently being prepared for the future standard in France. First, a preliminary parametric calibration based on typical structure profiles is described, comparing different stability calculation methods and different partial factor combinations. Second, design validation of instrumented case histories is performed.

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