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Integrated Measuring Technique for Rock Pressure Determination (short version)

Abstract:

The Integrated Measuring Technique enables the determination of the cross-sectional forces in and the loads acting on a tunnel lining based on deformations measured at its intrados. The basic idea of the technique relies on inverting the procedure of beam analysis, well known in structural engineering. Here, in successive positions along the intrados of a lining, the changes in length of the chord and the rise for a base length of 50 cm are measured. From these values the state of deformation, expressed by axial strain, curvature and shear strain, may be determined. In the elastic case without shear forces purely kinematical considerations are sufficient, otherwise the stress-strain relation of the lining must also be taken into account. Based on the state of deformation and the constitutive equations, the cross-sectional forces may be found and, together with equilibrium conditions, the external load may be back-calculated.

It should be remembered that, when applying the technique on precast concrete dowels or even on shotcrete, the uncertainties and the scatter of the material properties and/or of the geometry reduce the accuracy of the results dramatically or even rule out any back-calculation. On the other hand, the state of deformation may be determined (without considering shear strains) purely kinematically from the measured quantities f and l only. Because the actual technique allows measurements on a linewise basis and not only locally at individual points, these deformations may provide valuable hints regarding the behavior of the lining under loads.

Authors:

Kovári, Kalman and Amstad, Christian and Fritz, Pit

Index Terms:

rock pressure; measurements; lining; tunnel; rock; TunnelingGroup

Remarks:

See also "Slope Stability with Plane, Wedge and Polygonal Sliding Surfaces" by Kovári and Fritz, 1978, and "Recent Developments in the Analysis and Monitoring of Rock Slopes" by Kovári and Fritz, 1984.

Further Information:

Date published: 1978