Practical Estimate of Deformations and Stress Relief Factors for Deep Tunnels Supported by Shotcrete

Summary.Even though ground-support interaction in the vicinity of the tunnel face is a typical 3D problem, tunnel support design is usually based on simplified plane strain models, which are strongly dependent on the assumed degree of ground stress relief at the time of lining installation. The paper focuses on tunnels supported by shotcrete close to the face, where the interaction between the loading process and progressive hardening of the green shotcrete makes the problem time-dependent. A constitutive law characterized by the time-dependent stiffness and strength of the shotcrete is employed herein. The results of an extensive parametric study based on 3D axisymmetric models are presented in the form of non-dimensional design charts, which can provide guidance to a preliminary evaluation of convergences and support loadings.Moreover a strategy is proposed to enhance the capability of simplified design methods (2D models, Convergence-Confinement Method). This consists in a “guided estimate” of stress relief factors, which again is based on the results of 3D time-dependent analyses. Finally, by way of example, the proposed method is applied to two well-documented case-histories.

[1]  Evert Hoek,et al.  Big Tunnels in Bad Rock , 2001 .

[2]  F. Corbetta,et al.  Contribution à la méthode convergence-confinement par le principe de la similitude , 1991 .

[3]  G. Barla,et al.  Tbm Tunnelling In Difficult Ground Conditions , 2000 .

[4]  E. T. Brown,et al.  Underground excavations in rock , 1980 .

[5]  G Lombardi.  DIMENSIONING OF TUNNEL LININGS WITH REGARD TO CONSTRUCTIONAL PROCEDURES , 1973 .

[6]  Håkan Stille,et al.  Support of weak rock with grouted bolts and shotcrete , 1989 .

[7]  A. Guenot,et al.  Analysis of convergence behind the face of a tunnel : Tunnelling 82, proceedings of the 3rd international symposium, Brighton, 7–11 June 1982, P197–204. Publ London: IMM, 1982 , 1983 .

[8]  Rudolf Pöttler,et al.  Time-dependent rock—Shotcrete interaction a numerical shortcut , 1990 .

[9]  C. Carranza-Torres,et al.  Dimensionless Graphical Representation of the Exact Elasto-plastic Solution of a Circular Tunnel in a Mohr-Coulomb Material Subject to Uniform Far-field Stresses , 2003 .

[10]  Daniela Boldini,et al.  Simplified behavior models of tunnel faces supported by shotcrete and bolts , 2001 .

[11]  H. Einstein,et al.  SIMPLIFIED ANALYSIS FOR TUNNEL SUPPORTS , 1979 .

[12]  P Tedd,et al.  THE KIELDER EXPERIMENTAL TUNNEL: FINAL RESULTS , 1983 .

[13]  E. T. Brown,et al.  Ground Response Curves for Rock Tunnels , 1983 .

[14]  D. Bernaud,et al.  The `NEW Implicit Method' for Tunnel Analysis , 1996 .

[15]  D Bernaud,et al.  LA "NOUVELLE METHODE IMPLICITE" POUR L'ETUDE DU DIMENSIONNEMENT DES TUNNELS , 1992 .

[16]  R. C. K. Wong,et al.  Performance Assessment of Tunnels in Cohesionless Soils , 1991 .

[17]  Wulf Schubert,et al.  Dealing with squeezing conditions in Alpine tunnels , 1996 .

[18]  Yasuaki Ichikawa,et al.  An Experimental Study on the Mechanical Properties of Shotcrete , 1989 .

[19]  Pierpaolo Oreste,et al.  A Procedure for Determining the Reaction Curve of Shotcrete Lining Considering Transient Conditions , 2003 .

[20]  K Y Lo,et al.  EFFECTS OF DILATANCY AND YIELD CRITERIA ON DISPLACEMENTS AROUND TUNNELS , 1987 .

[21]  C. Vogt,et al.  Analyses of Natm-Tunnels with 2-D And 3-D Finite Element Method , 1998 .

[22]  H. Duddeck,et al.  Stress-strain fields at the tunnelling face—Three-dimensional analysis for two-dimensional technical approach , 1991 .

[23]  Georgios Anagnostou,et al.  Significant Parameters in Elastoplastic Analysis of Underground Openings , 1993 .