Abstract
This paper presents a review of selected tunnel stability models that have been developed and used in calculating the minimum tunnel face pressure as described by original authors. Furthermore, this paper provides a comparison of required tunnel face pressure obtained from analytical models, based either on limit equilibrium method or the limit analysis method (upper bound theorem) and numerical models using the finite element method. The numerical results are presented in charts for the comparative study to discuss the influence of cover depth to tunnel diameter ratio (C/D), internal friction of the soil (φ), and cohesion (c) on normalized support pressure (pu/γD) for each model. To verify the accuracy of the selected models, a comparison of the results of seven tunnel stability models with the results of the physical models is carried out. In a ground composed of two layers, a comparison of the required tunnel face pressure is presented. The results show that the wedge–silo models provide higher support pressure than the conical block models. Moreover, the support pressure using the conical block models is only dependent on the friction angle and not on the C/D ratio. Finally, the results of wedge-silo models indicate more significant dependence of the required support pressure on the C/D ratio especially for the lower friction angle.
Highlights
This paper presents a review of seven tunnel face stability models that have been used to calculate the minimum support pressure, covering three different approaches, Limit
The comparative studies are performed on seven tunnel stability models, covering three different approaches—Limit Equilibrium Method (LEM), Limit Analysis Method (LAM), and Finite Element Method (FEM) calculations
The results of normalized support pressure obtained from Chambon and Corte [3], Kirsch [22] and Chen et al [47] physical models are compared with the results of the wedgesilo models by Anagnostou and Kovari [7], Broere [8], Anagnostou [11], the upper bound solution by Mollon et al [14], Leca and Dormieux [13], and the finite element method by Vermeer et al [21]
Summary
The upper bound theorem of limit analysis became an effective method for studying the stability of the tunnel face. Due to the assumptions in the upper bound theorem, it is difficult to simulate the 3D arching phenomena at the front of the tunnel face To overcome this difficultly in the analysis, one or more truncated conical sliding wedges is assumed to be the failure mechanism, leading to a reduction of the self weight and thereby to include the 3D soil arching effect in evaluation of the support pressure (e.g., Leca and Dormieux [13]; Mollon et al [14]; Tang et al [15]; Ibrahim et al [16]; Zou et al [17]; Li and Zhang [18]). In the case of a ground composed of two soil layers, a comparison of the required support pressure of these models is presented
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