Praktijkonderzoek Boortunnel Groene Hart: Liggerwerking van boortunnels in de bouwfase: Eindrapport F512

Praktijkonderzoek Boortunnel Groene Hart: Liggerwerking van boortunnels in de bouwfase: Eindrapport F512

De Rijke, Q.C.

2009-03-26

Behind the tunnel boring machine (TBM) the rings form a tunnel lining that is embedded in grout and soil. The TBM exerts a normal force, a bending moment and a shear force on the lining. The tunnel rings behind the TBM experience a load through the grout, ground and ground water, but the ground also acts as a support medium. A ring that has just left the TBM floats in the fluid grout that has hardly any stiffness and offers resistance to tunnel displacements due to downward grout flow. Furthermore, resistance is offered by force transfer to the TBM and the adjacent rings of the tunnel lining and the hardened grout further down the tunnel. The rings thus have to cooperate to create equilibrium. This cooperation is called beam action. The focus of the research of COB-committee F512 was aimed at the beam action behind the TBM during the construction phase of the Boortunnel Groene Hart (bored tunnel in the Groene Hart in the Netherlands). Important issues in the research were the displacements and deformations of the tunnel, stresses in the tunnel lining and the grout pressure at the exterior of the tunnel tube. The research consisted of the following phases: 1. Execution of predictions of the vertical displacements of an escape shaft in the planned route of the tunnel; 2. Composition of a measuring plan, placement of the measuring instruments, execution of the measurements and composition of the measuring reports; 3. Assessment and check on the measurement results; 4. Evaluation of the measurement results by means of modelling; 5. Composition of the final report. The executed predictions (phase 1, see above) forecasted only small displacements and thus only little beam action was expected to occur. Therefore it was decided to aim the research at beam action in the tunnel behind the TBM. Beam action in the tunnel is researched by carrying out several measurements: • displacements and tilt angles of the lining; • ovalisation of the lining; • strains in de tunnel segments; • grout loads at the tunnel lining; • water pressures in the surroundings of the tunnel; • deformations of ground level. The results of the measurements are summarized in measurement reports. Not all measurements appeared to have impeccable results due to both execution aspects and the reliability of the measurement instruments. Recommendations on the execution of the measurements are discussed. A pre-evaluation is executed to assess and perform a check on the consistency of the measurement results for consistence. Furthermore the measurement results have been evaluated. On the one side, by studying several types of results and searching for explanations for phenomena found. Especially the result of the tilt and strain measurement appeared to be much more informative than would be expected beforehand. On the other side several types of measurering results are evaluated using models. Two models were used to analyse beam action: • A finite element method model, in which the tunnel is modelled as a 1D shear and bending beam (partly) on an elasto-plastic support. Also phased construction of the tunnel rings is implemented; • An analytic model, implemented in an Excel worksheet. The tunnel is modelled as a 1D bending beam (partly) on an elastic support. Phased construction of the tunnel rings is implemented also in this model. Several models for the behaviour of grout are used to investigate the consolidation of the grout (for instance the influence of ground water flow), the formation of the grout cake, the flow of grout directly behind the TBM and the uplift loading of the grout on the tunnel. In the end of the report an evaluation of the research is given and the most significant conclusions and recommendations are summarized.

tunnelboormachine
Groene Hart
Liggerwerking
boortunnel
grout
tunnel
tunnel boring machine
beam action
F512-07-03
CT01.10
Beheerste Boren
CT01.11.13
Beheerste zakkingen - GHT
Delft Cluster

http://resolver.tudelft.nl/uuid:393138a5-ab14-470b-89a0-03936803de8a

Delft Cluster

9789077374214

Institutional Repository

report

(c) 2009 De Rijke, Q.C.