Statistical and Numerical Study of Chipping and Cracking in Segmental Lining

Abstract

Some of the most frequent damages of concrete segments in shield tunnels are chipping and cracking, which are followed by degradation of lining system. In this paper, these types of damages are studied in four subway and two water conveyance tunnels. More than 2100 concrete rings are examined for chipping inspection and another 3000 for determination of the cracking. Statistical analysis of the research data showed that corners of the key and counter-key segments carry the highest number of chipping, while most of the cracking occur in the middle zones and shape of the segments and number of trust jacks affect the cracking pattern. Two kinds of numerical models are used to examine the underlying damages, which are based on geometrical characteristics of tunnel lining and boring machine besides operational mistakes. Findings of the numerical simulation revealed that installation of segmental lining with the least amount of erection tolerances results in low amount of chipping, this is while using key-segments with 12–17 degrees of insertion angle reduces total magnitude of damage due to tensile and compressive stresses. Furthermore, the deviation angle of TBM’s jack and segment’s axis should never be more than 5 degrees; otherwise even high-quality concrete segments wouldn’t remain undamaged. Employment of boring machines with articulated system is proposed in this case.

Coal and Rock Dynamic Disasters: Advances of Physical and Numerical Simulation in Monitoring, Early Warning, and Prevention - Volume II

“…The deviation angle of the hydro-cylinder can cause damage and cracks to the pipe segments (Mohtadinia et al, 2020;Dai et al, 2022). Dai et al (2022) mainly focused on segment damage caused Frontiers in Earth Science frontiersin.org 15 by incorrect assembly angles during the assembly process, which mainly occurs at the joints and is different from the simulated working conditions in this article.…”

“…Dai et al (2022) mainly focused on segment damage caused Frontiers in Earth Science frontiersin.org 15 by incorrect assembly angles during the assembly process, which mainly occurs at the joints and is different from the simulated working conditions in this article. Mohtadinia et al (2020) suggest that when the cylinder deflection angle is 5 °, cracks will appear when the cylinder thrust reaches over 5 MPa, and the cracks are mainly distributed in the middle of a single pipe segment, which is Frontiers in Earth Science frontiersin.org cracks, indicating that the angle between the hydro-cylinder and the segment during the pushing process is highly likely caused by posture adjustment, and the angle adjusted by posture is likely to exceed 3 °. In the vast majority of cases, the clearance between the shield tail was above 50 mm, and the value of the clearance cannot reflect the contact between the pipe segment and the guidance bars.…”

“…Therefore, many experimental studies have focused on the single factor, such as jack eccentricity and limit thrust (Hemmy, 2001;Plizzari and Tiberti, 2007;Nogales and Fuente, 2020). Due to the simplicity of the numerical simulations, more factors like the effect of rotation between segments, uneven support, uneven thrust, jack eccentricity, and jack deflection, have been selected for investigation in the scientific literatures (Mohtadinia et al, 2020;Krahl et al, 2021;Tian et al, 2021).…”

Secondary Grouting Pressure Limit of Shield Tunnels in Loess Strata Based on Bolt Shear Behavior

“…In the process of numerical analysis [33,34], the strength criterion of loess is the selected M-C strength criterion; that is, the unified strength criterion parameter b is 0. The basic parameters of the soil layers are listed in Table 1.…”

Theoretical Study on Relaxed Surrounding Rock Pressure on Shallow Bias Neighborhood Tunnels under Seismic Load

“…The rugged landscape in those areas leads to the inevitable existence and rapid development of bias tunnels [1,2]. Due to their special form of load, bias tunnels are clearly distinguished from common tunnels in design and support [3][4][5]. For this reason, Yang et al [6] conducted researches on the theoretical calculation of the rock pressure acting on three shallow tunnels subjected to unsymmetrical loads.…”