Tolerances for TBM thrust load based on crack opening performance of fiber-reinforced precast tunnel segments

Abstract

In the past twenty years, several precast tunnels were constructed using Fiber-Reinforced Concrete (FRC). Also, it has been reported that concrete segments experience damage during TBM operations due to factors as load eccentricity and uneven supports. Simulating in a laboratory such conditions together with interactions between elements, as in a field, is challenging. So numerical models can provide essential guidance for the design. Therefore, the current research presents a broad investigation considering three usual tunnel diameters, different number of TBM shoes by segments, shoe dimensions, and configurations (German and French). Also, FRC classes, determined according to the fib Model Code, are tested. It was found that the French distributions of shoes presented the best performance for all studied cases when compared to the German one. Tunnels with an internal diameter of Di = 6 m were the only ones sensitive to the increase from two to three shoes by segment. In the case of four pads, all tunnel diameters increased the load capacity. The FRC class change from 1.5a to 3a significantly enhanced the load capacity relative to the crack opening of tunnels with Di of 6 m and 10 m. For changing class from 1.5a to 4a, all tunnels had enhanced performance. For Di = 10 m, the increases in load capacity were 2.23, 2.18, and 2.60 for segments with 2, 3, and 4 shoes, respectively. Also, the best aspect ratios found for the shoes’ geometry are reported in the paper.