The effectiveness of geogrid reinforcement, placed at the base of a layer of granular fill on the surface of soft clay, has been studied by small-scale model tests in the laboratory. In the tests, monotonic loading was applied by a rigid footing, under plane strain conditions, to the surface of reinforced and unreinforced systems, using a range of fill thicknesses and subgrade strengths. Continuous measurements were made of footing load and footing displacement, and deformations of the subgrade and of the geogrid reinforcement were measured from photographs. From these measurements the different mechanisms of failure in the unreinforced and reinforced system were established. Performance of reinforced systems was found to be superior even at small deformations, owing to the significant change in the pattern of shear forces acting on the surface of the clay, brought about by the presence of the reinforcement. Membrane action of the reinforcement only became significant at large deformations.A finite element computer program has been specially formulated to allow inclusion of a thin reinforcing layer, and to handle correctly the large deformations and strains induced in the physical models. This formulation is able to reproduce satisfactorily the main features of behaviour observed in the models, and may now be used with some confidence to perform accurate predictions for full-scale structures. Key words: bearing capacity, clays, finite elements, foundations, geotextile, granular materials, model tests, reinforced soil, roads.
A new escalator tunnel and associated passageways have been constructed at Waterloo station in London, passing only a few metres beneath two sensitive masonry structures. Compensation grouting was undertaken in the ground between the tunnels and the overlying structures to limit settlements to acceptably small levels. This comprised injections of grout during tunnelling in response to detailed observations of ground and structure movements. The observational method was used in the control of the compensation grouting operations. This was achieved by comparison of field observations with defined limits of acceptable behaviour, and by planned contingencies in the event that these limits were approached. The extensive instrumentation installed to monitor the movements of the ground and the structures during tunnelling is described. Details are given of the performance of the instrumentation, of the measurements made and of the interpretation of the observations required to evaluate the soil-structure interaction behaviour. The specified requirements for compensation grouting and a summary of the grouting operations are presented. Settlements of the structures due to tunnelling were restricted to less than 15 mm. The relatively novel technique of compensation grouting has proved very successful in limiting settlements. Un nouveau tunnel d'escalator et les couloirs associés ont été construits à la gare de Waterloo, à Londres. Ils passent quelques mètres seulement au dessous de deux structures de maçonnerie particulièrement sensibles. Un coulis compensateur a été injecté dans le terrain entre les tunnels et les structures sus-jacentes pour limiter le tassement à des valeurs faibles acceptables. Ceci consiste à injecter du coulis lors du percement du tunnel en fonction d'observations minutieuses de mise en mouvement du terrain ou des structures. La méthode d'observation a été utilisée pour contrôler la mise en place du coulis compensateur. Ceci a été réalisé en comparant les observations de terrain à des limites définies de comportement acceptable, et en parant à l'imprévu au cas où ces limites seraient approchées. On décrit l'instrumentation mise en place pour enregistrer à la fois les mouvements du terrain et ceux des structures. On détaille les performances de cette instrumentation, les mesures réalisées et l'interprétation des observations permettant d'évaluer l'interaction sol-structure. On présente également les conditions requises et le résumé des opérations de mise en place du coulis compensateur. Le tassement des structures dû au tunnel a été inférieur à 15 mm. La technique du coulis compensateur s'est donc révélée efficace pour limiter les tassements.
This paper introduces the concept of settlement reducing piles (SRPs), describing how they may be usefully employed to improve raft performance in certain ground conditions. A simple method of soil–structure interaction analysis for the incorporation of SRPs is proposed, and a successful case history is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.