Use of BCN test for controlling tension capacity of fiber reinforced shotcrete in mining works

Abstract

Fiber reinforced shotcrete (FRS) is widely used for tunnel construction. However, the systematic control of FRS properties is hampered by the complexities of the experimental procedures used. The experiments are normally based on the load-deflection response obtained from flexural tests with third-point loading performed under displacement control. These types of tests are characterized by instability when the cracking load is reached and, subsequently, errors occur in the deflection measurements, increasing the dispersion of the results. An alternative test, the Barcelona test, has some experimental advantages for FRS control as the use of much smaller specimens, an easy procedure and a lower scatter.Using the mean crack opening, correlations were established between the Barcelona test and the flexure test to estimate the toughness and residual strengths at a deflection of 3.0 mm. Equivalences between the two tests were obtained based on the laboratory results and were validated based on work site results, with differences of less than 5% of the residual strength.These relationships and advantages have allowed the Barcelona test to be proposed to control the properties of the FRSs used in the Chuquicamata Underground (Chuquicamata Subterránea) Project developed by the mining company CODELCO-Chile.