Analysis of Piezoresistive Model on an Inner-Adhesive-Type Carbon Fiber Reinforced Plastics of Restorative Tunnel

Abstract

This paper used the force-sensitive properties of embedded carbon fibre to conduct early-warning research on lining reinforcement to prevent secondary damage during tunnel lining reinforcement. The length change relationship of the single fibre was obtained on the basis of the principle that the volume of a single carbon fibre is constant during the deformation process. The resistance and strain model of the single carbon fibre under the action of external force was then established following the relationship between the resistance, the length change and the volume change of the single carbon fibre. The resistance of carbon fibre composite materials according to their production technology and  unidirectional force  properties was assumed to be a mixture of the serial and parallel resistance of the single carbon, and the piezoresistive model of  carbon  fibre composite materials was formed by using the multi-dimensional Taylor series expansion and the idea of average equivalent. The comparison between the theoretical and monitoring values of the piezoresistive model in a tunnel project in Tibet, China, reveals that the resistance of different kinds of carbon fibres increases with the radius of the  lining  reinforcement and earth pressure and decreases with the increase in the lining reinforcement thickness. Meanwhile, angles at different positions of the lining reinforcement also have certain effects on the resistance value of the carbon fibre. The variation curve of the piezoresistive model was exponential in deep- or shallow-buried tunnels, which verifies the rationality of the model.

Keywords: Warning system；Surrounding rock pressure；Carbon fiber reinforced plastics（CFRP）；Piezoresistive model；Electron tunneling effect； Internode length