Application of BCN test for controlling fiber reinforced shotcrete in tunnelling works in Chile

S Carmona,C Molins

doi:10.1088/1757-899x/246/1/012010

Abstract

In many tunnelling projects currently under construction in Chile, the quality of fiber reinforced shotcretes (FRS) is controlled by means of its energy absorption capacity determined by testing squared panel following the EFNARC recommendation. Nevertheless, this test requires large and heavy specimens, which have to be filled when concrete is sprayed into the tunnel and does not allow testing the concrete actually placed onto the support. Due to these difficulties, the quality of fiber reinforced shotcretes used in some projects has been controlled by means of the Barcelona (BCN) test, which is an indirect tension test, using cores drilled from the hardened tunnel support. To apply the BCN test, the dissipated energy measured by means of this test has been correlated with the energy absorption capacity of the fiber reinforced shotcretes using experimental data obtained from works. The aim of this paper is presenting this correlation and it application.

Highlights

In different tunnel construction projects in Chile, fiber reinforced shotcretes (FRS) used in the supports are controlled by their energy absorption capacity determined by means of the square panel tests according to EFNARC of 1996 [1]
This test requires large size and weight test specimens, which must be filled during the projection of the concrete into the tunnel. This often causes the panel to present defects or damages that disturb the results, increasing their scatter, with coefficients of variation (CoV) between specimens of the same sample greater than 20%. In view of these difficulties, the use of the Barcelona (BCN) test [2],[3], has been proposed as an alternative for controlling fiber reinforced shotcrete, because this test is characterized for requiring a small specimen, with a large specific surface of cracking, which reduces the scatter of the results, and the specimens can be obtained by drilling cores from the hardened tunnel supports
In order to use the Barcelona test in the control of the fiber reinforced shotcretes in the tunnel construction works of different projects, a correlation between the energy absorption capacity determined by EFNARC panels and energy dissipated in the BCN tests was developed

Summary

Introduction

In different tunnel construction projects in Chile, fiber reinforced shotcretes (FRS) used in the supports are controlled by their energy absorption capacity determined by means of the square panel tests according to EFNARC of 1996 [1] This test requires large size and weight test specimens, which must be filled during the projection of the concrete into the tunnel. This often causes the panel to present defects or damages that disturb the results, increasing their scatter, with coefficients of variation (CoV) between specimens of the same sample greater than 20% In view of these difficulties, the use of the Barcelona (BCN) test [2],[3], has been proposed as an alternative for controlling fiber reinforced shotcrete, because this test is characterized for requiring a small specimen, with a large specific surface of cracking, which reduces the scatter of the results, and the specimens can be obtained by drilling cores from the hardened tunnel supports.

Absorption energy capacity of fiber reinforced shotcrete

Findings

Conclusions