Jing Cui

Based on the Zhengzhou–Xuchang Intercity Railway tunnel project passing beneath Terminal 1 of Xinzheng International Airport, this study employs a three-dimensional numerical analysis model to investigate the effects of tunnel depth and pile foundation structure on ground surface settlement and pile foundation response during twin-line shield tunnelling in typical cohesive soils under tunnel side-crossing and under-crossing conditions. The results indicate that during tunnel side-crossing, the ground surface settlement profiles evolved from V-shaped to W-shaped before and after twin-tunnel breakthrough. With increasing tunnel depth, the lateral displacement profiles of the left-row and right-row piles transformed from spindle-shaped to X-shaped. With increasing pile count, the maximum axial force per pile decreased from 320.1 kN in the single-pile configuration to 197.4 kN in the six-pile configuration, a reduction of 38.3%. During tunnel under-crossing, the lateral displacement profiles of both left-row and right-row piles exhibit X-shaped profiles at different tunnel depths, and the pile-top displacement varies slightly with a maximum of 1.1 mm. With increasing pile count, the maximum axial force per pile decreased from 202.2 kN to 132.1 kN, a reduction of 34.7%. The findings provide valuable reference for design and construction control of twin-line shield tunnels crossing existing airport pile foundations in cohesive soil.

In response to the issues of microcrack susceptibility, high brittleness, and unstable mechanical properties of desert sand recycled aggregate concrete (DSRAC), this study experimentally investigated the mechanical performance of DSRAC reinforced with hybrid steel–FERRO fibers. By testing macroscopic properties (compressive, splitting tensile, and flexural strengths) under different desert sand replacement ratios and fiber dosages, combined with microscopic analysis, the fiber-matrix interfacial behavior and toughening mechanism were clarified. The results showed that (1) DSRAC achieved optimal compressive strength when desert sand replaced 30% natural sand, with an obvious early strength enhancement; (2) both steel fibers and FERRO fibers independently improved DSRAC’s mechanical properties, while their hybrid combination (especially F0.15-S0.5 group) exhibited a superior synergistic strengthening effect, significantly outperforming single-fiber groups; (3) the established constitutive model accurately described the stress–strain response of hybrid fiber-reinforced DSRAC; (4) microscopic observations confirmed fibers inhibited crack propagation via bridging and stress dispersion, with hybrid fibers exerting multi-scale synergistic effects. This study provided theoretical–technical support for resource utilization of desert sand and recycled aggregates, and offered practical references for localized infrastructure materials (e.g., rural road subgrades and small-span culverts) in desert-rich regions and high-value reuse of construction waste in prefabricated components, advancing eco-friendly concrete in sustainable construction.

Thermal expansion of a member can affect structural bearing capacity when one or more members are subjected to fire. To explore the developmental rule of member internal force in latticed shell structure, a computation method of member sensitivity is presented based on the alternate path method. Taking a K8 single-layer latticed shell structure as the analysis object, finite element models are established by ANSYS, applying temperature loads on radial and circumferent ribs, calculating the sensitivity of each member during heating, and exploring the rule of member sensitivity at different temperatures. It is revealed from the numerical results that when one member is in fire, member sensitivity is proportional to temperature and inversely proportional to the distance from the member subjected to fire. Taking the member sensitivity coefficient as an index, the internal force will be transmitted along the member with high sensitivity, the rule of load path and internal force redistribution is given when the latticed shell structure is under elevated temperature.