Analysis of the evolution of road tunnels equilibrium conditions with a convergence–confinement approach

Abstract

Since both lining structure and rock mass exhibit delayed behaviour, tunnel equilibrium conditions evolve with time. After discussing existing work done on different aspects of long-term tunnel behaviour, the aim of this paper is to ''understand'' the influence of rock mass and lining degradations on the long-term stability conditions of the tunnel by means of the convergence-confinement method. In order to represent the effects of degradation on tunnel long-term conditions, specific degradation models are selected according to the disorders identified during principal inspections of road tunnels in Switzerland. By simulating the reduction of the mechanical properties of both the rock mass and the lining or by using creep models, it is possible to assess the influence of the main degradation processes on tunnel stability. The results are interpreted in terms of tunnel safety factor. The presented approach for the determination of the long-term behaviour of tunnels, although valid for simple tunnel geometry and field stress conditions, allows to roughly estimate the influence of significant degradation processes that affect the rock mass and the supporting structure. Though this approach results in some simplification, it may be generalised and adopted with more refined numerical analyses for improving the assessment of tunnel long-term conditions.

Identification and analysis of Swiss National Road tunnels pathologies

“…For moving towards a degradation diagnosis and a maintenance planning, it is necessary to integrate successive inspections results and to predict the tunnel behaviour with time by means of degradation models (Sandrone and Labiouse, 2010). The importance of updating the collected data is prescribed by guidelines of several countries (Dir.…”

“…All these processes may change the tunnel equilibrium conditions with time (Sandrone and Labiouse, 2010) and contribute to the changes in tunnel serviceability, stability and safety conditions.…”

“…All these processes may change the tunnel equilibrium conditions with time (Sandrone and Labiouse, 2010) and contribute to the changes in tunnel serviceability, stability and safety conditions. During operation, the tunnel owner should perform regular preventive maintenance to avoid major deficiencies and reduce pathologies development.…”

“…Various chemical, physical and mechanical processes may determine the deterioration of exposed surfaces of the rock mass and the lining. It is possible to distinguish between:• the chemical action, properly named weathering, caused by the chemical interaction of the tunnel with the surrounding environment;• the physical action, ageing, ruled by time dependent changes affecting the characteristics of concrete lining and rock mass;• the other actions, mainly mechanical, such as pore water pressure redistribution, ice and frost, fires and car collisions.All these processes may change the tunnel equilibrium conditions with time (Sandrone and Labiouse, 2010) and contribute to the changes in tunnel serviceability, stability and safety conditions.During operation, the tunnel owner should perform regular preventive maintenance to avoid major deficiencies and reduce pathologies development. Tunnel pathologies may appear in the form of several disorders depending on the building materials (e.g.…”

PADTUN - Using Semantic Technologies in Tunnel Diagnosis and Maintenance Domain

“…Regarding the causes of the degradation (the origin of the problem), two general groups of pathologies were identified distinguishing based on its origin. They were ground degradation pathologies (if pathologies occur underground) and lining degradation pathologies (if pathologies occur with lining)( [7,8]). Fig.…”