Load bearing characteristics of a new support structure for rapid repair of damaged tunnels and related field tests.

To address the need for rapid repair and emergency support of traffic capacity in damaged tunnels, this study proposed a new structure combining arches assembled from steel plates and shotcrete with high early strength and performance (hereinafter referred to as the steel-shotcreting structure) based on the concept of "modular assembly, rapid formation, and temporary-permanent combination". It is designed to replace the traditional cast-in-place concrete arch repair technique. Based on the principle of equivalent stiffness, the load borne by the steel arches in the new support structure was analyzed.

In Situ Scanning Electron Microscope (SEM) Observations of Damage and Crack Growth of Shale.

To better understand the formation and evolution of hierarchical crack networks in shales, observations of microscopic damage, and crack growth were conducted using an in situ tensile apparatus inside a scanning electron microscope. An arched specimen with an artificial notch incised into the curved edge was shown to afford effective observation of the damage and crack growth process that occurs during the brittle fracturing of shale. Because this arched specimen design can induce a squeezing effect, reducing the tensile stress concentration at the crack tip, and preventing the brittle shale from unstable fracturing to some extent.