Deformation behaviour of tunnel face reinforced with longitudinal pipes-laboratory and numerical investigation

This paper presents the results of laboratory and numerical investigations on the deformation behaviour of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests as well as 3D finite-element analyses were carried out with particular emphasis on the effects of reinforcement parameters such as density (number), length and stiffness of reinforcements on the face deformation behaviour. The results of the present study indicate among other things that the face reinforcement technique can significantly reduce not only face deformation but also ground surface settlements, suggesting that the face reinforcing technique can be effectively used as a positive means for ground movement control during urban tunneling. The study illustrates that the reinforcing effect is significantly influenced by the manner in which the reinforcements are distributed, and that there exists a critical value of each reinforcement parameter from which maximum reinforcing effect can be derived. Implications of the findings from this study are discussed in great detail.