Search Results (2)

To investigate the failure mechanisms of roadway-surrounding rock in the wind oxidation zone, where the rock experiences instability under cyclic excavation-induced loading and unloading, this study conducted experiments leveraging acoustic emission analysis, scanning electron microscopy, and a digital image correlation (DIC) system. The research focused on grouting reinforcement under varying gradation indices, examining its mechanical properties, deformation characteristics, and microscopic structure post-failure. Results show that as the gradation index increases, the peak strength of the grouted solid exhibits a non-linear trend, initially decreasing to a minimum of 9.40 MPa (a 40.4% drop) before rising again to a maximum of 15.76 MPa. The hysteresis loop observed follows a pattern of ‘sparse–dense–sparse’. Additionally, the acoustic emission cumulative ringing count demonstrates a three-stage pattern of ‘rising–active–quiet’, with a similar initial decrease followed by an increase correlated with the gradation index. Using digital image correlation (DIC) technology, the study revealed the crack development characteristics of the grouting reinforcement. Higher gradation indices lead to wider localization zones, more extensive crack propagation, and greater damage. Microstructural analysis showed that PVA enhances the formation of hydration products, fostering stronger adhesion between these products and the cement matrix. This leads to a denser and more uniform microstructure, thereby enhancing the macroscopic strength of the samples. It provides a basis for practical mining engineering applications of grouting reinforcement of roadways in wind oxidation zones. Full article

The Falakra geosite is located at the northern shoreline of the island of Limnos, Greece, and exhibits an array of unusual geomorphological features developed in late Cenozoic sandstones. Deposition of the primary clastic sediments was overprinted by later, low-temperature hydrothermal fluid flow and interstitial secondary calcite formation associated with nearby volcanic activity. Associated sandstone cannonballs take center stage in a landscape built by joints, Liesengang rings and iron (hydr)oxide precipitates, constituting an intriguing site of high aesthetic value. The Falakra geosite is situated in an area with dynamic erosion processes occurring under humid weather conditions. These have evidently sculpted and shaped the sandstone landscape through a complex interaction of wave- and wind-induced erosional processes aided by salt spray wetting. This type of geosite captivates scientists and nature enthusiasts due to its unique geological and landscape features, making its sustainable conservation a significant concern and topic of debate. Here, we provide detailed geological and remote sensing mapping of the area to improve the understanding of geological processes and their overall impact. Given the significance of the Falakra geosite as a unique tourist destination, we emphasize the importance of developing it under sustainable management. We propose the segmentation of the geosite into four sectors based on the corresponding geological features observed on site. Sector A, located to the west, is occupied by a lander-like landscape; to the southeast, sector B contains clusters of cannonballs and concretions; sector C is characterized by intense jointing and complex iron (hydr)oxide precipitation patterns, dominated by Liesengang rings, while sector D displays cannonball or concretion casts. Finally, we propose a network of routes and platforms to highlight the geological heritage of the site while reducing the impact of direct human interaction with the outcrops. For constructing the routes and platforms, we propose the use of serrated steel grating. Full article