Design of geosynthetic reinforcements for platforms subjected to localized sinkholes

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Date: Feb. 2008
From: Canadian Geotechnical Journal(Vol. 45, Issue 2)
Publisher: NRC Research Press
Document Type: Report
Length: 6,171 words
Lexile Measure: 1520L

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Abstract: Construction of road and railway platforms in areas subject to localized sinkholes requires the use of specific reinforcements, for example, geosynthetics. The current design method for these structures is based on the assumption that there is no displacement of the geosynthetic in the anchorage areas on either side of the cavity. A new analytical method is proposed that takes into account the displacements and deformation of the geosynthetic reinforcement in the anchorage areas and the increase in stress at the edge of the cavity. To validate this new analytical method, a full-scale experiment was carried out; the use of optical fibre sensors integrated into the geosynthetic sheet made it possible to accurately measure the strain of the geosynthetic reinforcement. Comparison of the results obtained by this new analytical method with measurements of a full-scale experiment and the results of a finite element model confirmed the relevance of these new developments.

Key words: localized sinkhole, geosynthetic reinforcement, analytical design, full-scale experiment.

Resume: La construction de plates-formes routieres et ferroviaires dans les zones a risque d'effondrements localises necessite la mise en oeuvre d'un renforcement specifique qui pent etre de type geosynthetique. Le dimensionnement actuel de ces structures est base sur des hypotheses simplificatrices fortes comme le non-dipacement du geosynthetique dans la zone d'ancrage situee de part et d'autre de la cavite. Une nouvelle methode analytique proposee prend en compte les deplacements et les deformations de la nappe geosynthetique dans la zone d'ancrage et "augmentation de la contrainte an bord de la cavite. Pour valider cette nouvelle methode analytique, une experimentation en vraie grandeur a ete realisee; l'utilisation de capteurs a fibres optiques integres a la nappe geosynthetique a permis de mesurer exactement les deformations de la nappe. La comparaison des resultats obtenus par cette nouvelle methode avec les mesures de l'experimentation en vraie grandeur et les resultats d'une modelisation par elements finis a confirme la pertinence de ces nouveaux developpements.

Mots-cles : effondrements localises, renforcement geosynthetique, dimensionnement analytique, experience en vraie grandeur.

Introduction

Due to the current difficulties of locating voids in areas at risk (small and (or) deep cavities), it is often necessary to implement reinforcements in the construction of highways or railway lines to prevent localized sinkholes. A commonly adopted solution is the use of reinforcement techniques; those with one or several geosynthetics can be attractive because they are easy to implement and they are inexpensive.

Experimental and theoretical research into this topic (Kinney and Connor 1987; Kempton et al. 1996; Giraud 1997; Gourc et al. 1999) has given rise to the formulation of analytical design methods (British Standards Institution 1995 (BS 8006); Villard et al. 2000, 2002). Using simple assumptions, it is possible to calculate geosynthetic shape and surface settlement based on geosynthetic stiffness and cavity size. It is generally assumed that the geosynthetic is fixed at the edge of the cavity.

To improve the current design method, a new approach has been developed; it is based on the existing method for the membrane effect (Giroud et al....

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Gale Document Number: GALE|A180471815