1、翻译部分英文原文A numerical approach for design of bolt-supported tunnels regarded as homogenized structuresDenise Bernaud a, Samir Maghous a,*, Patrick de Buhan b, Eduardo Couto aa Department of Civil Engineering, Federal University of Rio Grande do Sul, Av. Osvaldo Aranha, 99, 90540-041 Porto Alegre RS, B
2、razilb Unit de Recherche Navier, Ecole Nationale des Ponts et Chausses, Marne-la-Valle, FranceAbstract: This paper is devoted to the theoretical modeling and numerical simulation by homogenization approach of the behaviour of a tunnel reinforced by fully grouted bolts, regarded as periodically distr
3、ibuted linear inclusions. Owing to the fact that a direct numerical simulation would require the ground and the reinforcing bolts be separately discretized, leading thus to a highly complex and oversized problem, a homogenization procedure is developed, aimed at circumventing the difficulties connec
4、ted with the implementation of a direct simulation. The situations of reinforcement by radial bolts and horizontal anchors installed ahead the excavation face are both investigated. Considering a DruckerPrager rock material, elastoplastic constitutive equations are formulated for the bolted rock mas
5、s regarded as a homogenized anisotropic medium at the macroscopic scale. Special attention is paid to the description of the algorithm of plastic integration involved in the finite element implementation. At this respect, closed-form expressions are derived for the stress projection onto the macrosc
6、opic yield surface. The finite element procedure is thus carried out for simulating the advancement of a bolt-supported tunnel and computing the displacements of the tunnel walls and the facing as the excavation proceeds. A parametric study, varying some relevant parameters defining the bolt reinfor
7、cement scheme, is undertaken by means of the finite element tool. The combination of rock bolting with a classical lining support system such as a shotcrete layer is also examined, thus providing some guidelines for the optimal design of the reinforcement pattern.Keywords:Tunnel, Fully grouted bolts
8、, Homogenization, Elastoplasticity, Finite element method1. IntroductionDesigning appropriate support systems for tunnels together with the ability to reliably predict their contribution to controlling the deformation of the surrounding ground remain a major concern in underground engineering. In th
9、is context, the use of metallic or fiber-glass bolts is nowadays considered as an effective reinforcement technique for tunnels excavated in soft rocks, specifically in the framework of NATM tunneling or the so-called convergence-confinement approach for tunnel construction (Panet,1995). Fully grout
10、ed radial bolting contributes to controlling the radial displacements of the tunnel walls, thus maintaining the tunnel convergence within an allowable limit, compatible with subsequent operating conditions. Similarly, grouted horizontal fiberglass bolts installed ahead the excavation face play an im
11、portant role during the excavation process by improving the degree of stability of the tunnel face.Rock bolting has been successfully applied in a number of tunnel projects and the increasing use of this reinforcement technique in the field of rock tunnelling has been favoured mainly by the followin
12、g reasons: (1) it is easy to carry out, (2) it is very flexible since the bolt density can be punctually adapted to account for local geotechnical properties, and (3) it is efficient when compared for example to a classical steel frame support, which requires heavy equipment for installation. 2. The
13、 bolted tunnel as a homogenized mediumThe tunnel under consideration is a horizontal cylindrical underground opening of radius R, excavated in a homogeneous medium. This structure is reinforced by a system of bolts, introduced into the rock mass as the excavation process proceeds. Perfect adherence
14、is assumed between the bolts and the rock. The bolts are regularly disposed following the radial direction or the face (i.e., bolts placed at the tunnel face). From a practical point of view, these two kinds of bolting can be used separately or in association. The geometrical characteristics of the
15、problem are defined in Fig. 1:l Radial bolts placed around the tunnel, perpendicular to the axis z of the tunnel. They are regularly distributed along the tunnel axis (horizontal spacing pr) and within each transversal section (angular spacing r). The radial bolt length is denoted by lr.l Face bolts
16、 placed at the tunnel face, parallel to the tunnel axis z.The corresponding length is lf. They are regularly distributed at the tunnel face following a rectangular grid pf bf.Fig. 1. Geometrical characteristics of the problem.For sake of simplicity, the following abbreviations will be used in the sequel. The zone of the rock mass reinforced by radial bolts is referred to by (ZR), whi
