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Analys av deformationsutveckling under framdrift av tunnlar
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
2020 (Swedish)Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
Abstract [sv]

Idag används ofta ett samband, framtaget av Hanafy och Emery (1980), för att uppskatta deformationer vid tunnelfronten då bergförstärkning ska installeras i närheten av tunnelfronten. Sambandet visar hur deformationerna i ett referensplan utvecklas som en funktion av tunnelfrontens avstånd till referensplanet. I det här examensarbetet studerades deformationsutvecklingen i en tunnel med syftet att utvärdera hur tunnelgeometri, bergtäckning, spänningsfält och bergkvalitet påverkar deformationsutvecklingen under framdriften. I examensarbetet studerades även bergförstärkning under framdriften med syftet att jämföra resultat när hänsyn tagits till sprutbetongens härdningstid relativt när full styvhet antagits direkt vid installation samt studera belastning i bergbultar. Studien visade att analysresultat och samband framtaget av Hanafy och Emery kan återskapas med FLAC3D. Kombination av förändrat spänningsfält, tunneltvärsnitt och/eller bergtäckning medförde att deformationsutvecklingen inte följde sambandet. Resultatet kunde generaliseras till alla fall skilt från ett hydrostatiskt spänningsfält. Baserat på studien rekommenderas att sambandet enbart bör användas när hydrostatiskt spänningsfält och elastiskt materialbeteende kan antas för att uppskatta deformationer i närheten av tunnelfronten. Tredimensionell modellering i närheten av tunnelfronten rekommenderas alltid utföras när spänningsfält ej kan antas hydrostatiskt. Detta för att på ett korrekt sätt uppskatta deformationer och spänningar kring tunneln. Simulering av bergförstärkning bör genomföras baserat på verklig uttagssekvens med projektspecifika indata för att belastningshistorik och deformationer ska kunna uppskattas och användas som grund för dimensionering.

Abstract [en]

Currently, a correlation developed by Hanafy and Emery (1980), is often used to estimate deformations at the tunnel face for projects where rock reinforcement is to be installed near the tunnel face. It shows how deformations at a reference plane develops as a function of the distance to the tunnel face. In this thesis, the displacements was studied in order to investigate how tunnel geometry, rock coverage, stresses and rock quality affected the accumulation of displacements in a tunnel during excavation. Studies of rock reinforcement were conducted with purpose to compare results from simulations when the shotcrete hardening process had been considered and when maximum stiffness was assumed directly at installation. Load in bolts was also studied. The study showed that elastic analyses with FLAC3D can recreate analysis results and correlation developed by Hanafy and Emery. Combinations of changed stress field, tunnel geometry and/or rock cover resulted in three-dimensional effects which gave a different displacement ratio compared to Hanafy and Emery. This could be generalised to all cases in which the stress field differed from a hydrostatic stress field. Based on the study it is recommended to only use the correlation for estimating displacements near a tunnel face when hydrostatic stress field and elastic material behaviour can be assumed. Three-dimensional modelling should always be carried out in cases where the stress field cannot be assumed hydrostatic in order to correctly estimate displacements and stresses around the tunnel in the vicinity of the tunnel face. Simulation of rock reinforcement should be carried out based on the actual excavation sequence that will take place. Simulations should be performed with project-specific input data so that load history and displacements can be estimated properly and used in design.

Place, publisher, year, edition, pages
2020. , p. 60
Keywords [en]
Numerical, modelling, FLAC3D, simulation, excavation, rock, reinforcement
Keywords [sv]
Numerisk, modellering, FLAC3D, simulering, uttagssekvens, bergförstärkning, förstärkning
National Category
Civil Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-77468OAI: oai:DiVA.org:ltu-77468DiVA, id: diva2:1387472
External cooperation
Itasca Consultants AB
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering, master's level
Supervisors
Examiners
Available from: 2020-01-24 Created: 2020-01-21 Last updated: 2020-01-24Bibliographically approved

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