The widespread disposal of scrap tires has become a major environmental problem that necessitates finding an effective way of using recycled crumb rubber (CR) in concrete. Rubberized concrete, however, exhibits reduced mechanical strength compared to conventional concrete, which restricts its application in structures. This research adopted a mix design strategy based on the Taguchi method to overcome these drawbacks and improve the performance of rubberized concrete. A total of ten mixes, including one for normal concrete (NC) mix, were formulated by varying the CR content (10
This study presents an integrated experimental and numerical investigation of the bearing behaviour of single-bolt angle connections, focusing on the coupled effects of end distance (e1) and edge distance (e2). Twenty-two tests were conducted on S355 angle sections (L70×5 to L140×10) with Grade 8.8 bolts, and 816 finite-element models were developed covering 23 angle sections (L50×6 to L300×20) and steel grades S235–S420. Two failure-mode transitions were identified using an objective 95
This study investigates the impact of canyon wind characteristics on fire smoke diffusion within railway tunnel groups using an integrated approach of two-year field measurements, Empirical Mode Decomposition (EMD) analysis, and numerical simulations. Field data reveal significant diurnal and seasonal variations in canyon wind speeds, with peak velocities occurring in winter and during the afternoon, supporting a recommended maximum design yaw angle of 60°. Findings demonstrate that the critical open section length for smoke control is governed by localized canyon wind conditions. Aerodynamically, the smoke diffusion length into the tunnel correlates negatively with canyon wind speed, while smoke intrusion volume increases significantly with larger wind yaw angles due to crosswind shear. Consequently, for open section scenarios at risk of smoke intrusion, mechanical ventilation systems must be dynamically configured based on specific wind speeds (0–14.5 m/s) and yaw angles (0°-60°). Furthermore, a mechanical ventilation design framework was established for tunnel portals under four asymmetric longitudinal natural wind combinations. The results indicate that the required smoke control velocities at the portals range from 0.5 m/s to 2.5 m/s. These findings provide physical boundaries and quantitative parameters for optimizing dynamic ventilation systems in mountainous railway tunnel groups.
Layered slate tunnels commonly exhibit pronounced asymmetric deformation because excavation-induced stress redistribution interacts with weak bedding planes. This study investigates the deformation and failure mechanism of a deep-buried carbonaceous slate tunnel using laboratory triaxial tests and a three-dimensional discrete-element model. Cylindrical specimens with bedding inclinations of 0°, 30°, 60°, and 90° were tested under a confining pressure of 15 MPa, and the results were used to calibrate a 3DEC bonded-block model. The calibrated parameters were then transferred to a tunnel-scale model to examine progressive deformation, bedding-plane displacement, and plastic-zone evolution, together with the effects of bedding dip angle, layer thickness, and lateral pressure coefficient. The results show that asymmetric failure is governed by bedding-parallel shear slip coupled with flexural deformation of the layered rock toward the excavation, producing localized collapse at the upper-left spandrel. Crown settlement and invert heave generally decrease as the bedding dip angle increases. Deformation becomes markedly less asymmetric when the layer thickness increases from 1.0 to 1.25 m, and the thickness effect becomes limited above approximately 1.5 m. Increasing the lateral pressure coefficient amplifies displacement, although the deformation pattern remains primarily controlled by bedding orientation. A targeted bolting scheme combining 4.0 and 7.0 m bolts reduces settlement at the biased crown location by approximately 0.5 cm while limiting the plastic zone. These findings provide a mechanistic basis for differentiated support design in layered slate tunnels.
An elastic-theory and soil-arching-based calculation method was proposed to determine the reasonable anchorage length of a single-layer geosynthetic-reinforced embankment over shallow subsidence-induced collapse. The vertical stress distributions in the subsided and stable areas, reinforcement tensile force, and anchorage resistance were derived under plane-strain and small-deflection conditions. The method was evaluated using 1:5-scale physical model tests and two-dimensional particle flow code (PFC2D) simulations, both based on a single cohesionless sand, for the investigated ranges of H/B ≈ 2.5–5.0 and B ≈ 1–3 m. The predicted vertical stresses and maximum reinforcement tension agreed reasonably well with the measured and numerical results, with overall errors generally within 5–10
