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Centrifuge Modelling Of Compensation Grouting In Dense Dry Sand
Lee, S.W. (Cambridge University Engineering Department) | Bolton, M.D. (Cambridge University Engineering Department) | Dasari, G.R. (Cambridge University Engineering Department) | Mair, R.J. (Cambridge University Engineering Department) | Soga, K. (Cambridge University Engineering Department) | Sugiyama, T. (Nishimatsu Construction Co.Ltd) | Ano, Y. (Nishimatsu Construction Co.Ltd) | Hagiwara, T. (Nishimatsu Construction Co.Ltd) | Nomoto, M. (Nishimatsu Construction Co.Ltd)
ABSTRACT: In the London Docklands Light Railway (DLR) Lewisham Extension tunnelling project, the contractor has utilised compensation grouting to remedy building settlements due to twin tunnel construction. However, the contractor needed to demonstrate that grout injection would not damage the tunnel lining. At the Schofield Centrifuge Centre, Cambridge, physical modelling of compensation grouting in dense dry sands was commissioned to clarify the effects of grouting depth, grouting width, and separation between grouting depth and tunnel crown on segmental lining deformations and ground movements above the grouted areas. The measured ultimate uplift resistance is compared with an upper bound plastic solution. An approximate pressure distribution mechanism is also presented to calculate lining deformations due to grouting. DLR PROJECT The DLR Lewisham Extension was constructed in South East London where ground strata are Made Ground underlain by Terrace Gravel, Woolwich & Reading Beds (now known as Lambeth Beds), and Thanet Sands. A Slurry Shield Tunnel Boring Machine was employed to excavate twin tunnels of 5.85m diameter. The tunnel cover (C) ranged from 9 to 15m, and the separation (Y) between grout injection and the tunnel crown is 2 to 5m. More details about the construction site can be found from Lee et al. (1999) and Sugiyama et al. (1999). Figure 1 and Figure 2 show the site layout and the typical compensation grouting array beneath a building, Royal Hill Court. The contractor, Nishimatsu Construction Ltd, used compensation grouting to remedy settlements and tilting of buildings due to twin tunnel construction. In order to understand the effects of compensation grouting on ground movements and tunnel lining deformation, a series of centrifuge tests in dense dry sand was conducted. The measured ground movements and lining deformations from various centrifuge tests are presented in this paper.
Experimental And Numerical Investigation Of Compensation Grouting In Clay
Jafari, M.R. (The University of Cambridge) | Au, S.K. (The University of Cambridge) | Soga, K. (The University of Cambridge) | Bolton, M.D. (The University of Cambridge) | Karim, U.F.A. (The University of Twentee) | Komiya, K. (Chiba Institute of Technology)
ABSTRACT: Compensation grouting is an effective way to reduce surface settlement induced by construction activities in urban areas. However, the long-term behaviour of the compensated area is still not known very well. Grout injection in clayey soils was performed in the laboratory to measure both short and long-term deformation of the clay around the grout and to investigate the fundamental behaviour of the compensation grouting process, which includes hydraulic fracture and cavity expansion mechanisms. The experimental results indicate the growth of a fracture plane in soil in a very fast manner both in normally and overconsolidated clays. Finite element analyses of compensation grouting have been performed to assess its ability to model the complex behaviour of compensation grouting observed in the laboratory. The finite element analyses clearly show that the long-term behaviour of compensation grouting is greatly dependent on the overconsolidation ratio of the clay. The finite element analysis agreed reasonably well with the long-term behaviour of the grouted clay in the experiments INTRODUCTION In recent years, compensation grouting has been applied successfully in many major tunneling projects to limit ground settlement (e.g. Mair, 1994). For example, during tunnel construction projects in Lisbon and for the underground construction of the Jubilee Line Extension Project in London, extensive compensation grouting systems were applied to protect the surface structure around the area influenced by tunneling construction activities (Harris et al, 1996; Schweiger and Falk, 1998). Compensation grouting can involve two different modes;compaction grouting and fracture grouting. The possible factors that affect the occurrence of different modes of behavious are: type of grout, soil type, stress history of the soil, stress state, boundary conditions and rate of injection. Because of the complex behaviour of grouting in soils, a conceptual modelling of compensation grouting in clayey soils is necessary.