Active and passive arching stresses outside a deep trapdoor
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RESEARCH PAPER
Active and passive arching stresses outside a deep trapdoor Yuri D. J. Costa1
•
Jorge G. Zornberg2
Received: 12 July 2019 / Accepted: 10 April 2020 Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The classic trapdoor configuration has been useful to examine the changes in stresses expected on buried structures. However, the primary focus of previous studies has been on investigating the loads on the surface of the trapdoor, while stresses outside the trapdoor boundaries have generally been overlooked. This paper presents and discusses results of threedimensional laboratory model tests conducted to investigate changes in the vertical soil pressure measured at various locations within a granular soil mass surrounding a deep rectangular trapdoor acting in both active and passive modes. The study aimed at investigating stress changes within the portion of the soil mass beyond the boundaries of the trapdoor. Redistributions of soil pressure were found to occur in a large zone of the soil outside the trapdoor under both active and passive conditions. Results indicate that active conditions induced the development of an unloading region in the soil, which includes the collapsing mass above the trapdoor and a portion of the soil surrounding the trapdoor. A stable loadtransfer region could be identified in farther portions of the backfill. In passive conditions, the development of a loadtransfer region above the trapdoor and an unloading region extending to farther zones in the backfill was also identified. The soil relative density, soil confinement and trapdoor shape were found to affect soil pressure distributions outside the trapdoor limits. Keywords Sand Soil arching Soil stress Trapdoor tests Underground structure List of symbols B Width of the trapdoor or buried structure (m) Dr Soil relative density (%) Es Young’s modulus of the soil (kPa) H Height of soil above the trapdoor (m) He Vertical distance from the trapdoor (m) L Length of the trapdoor or buried structure (m) q Applied surface pressure (kPa) x Horizontal distance from the center of the model (m) d Trapdoor vertical displacement (m) w Dilatancy angle of the soil ()
& Yuri D. J. Costa [email protected] Jorge G. Zornberg [email protected] 1
Department of Civil Engineering, Federal University of Rio Grande do Norte, Av. Sen. Salgado Filho, 3000, Natal, RN 59072-970, Brazil
2
Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, E. Dean Keeton St., Stop C1792, Austin, TX 78712-1174, USA
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Axial strain change Volumetric strain change Poisson’s ratio of the soil Effective confining pressure (kPa) Vertical pressure in the soil (kPa) Vertical pressure prior to yielding of the buried structure (kPa) Critical state friction angle of the soil () Internal friction angle of the soil () Peak friction angle of the soil ()
1 Introduction The arching phenomenon in soils results from the
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