Excavation in foundation pits can result in serious issues for nearby tunnel structures like deformation, differential settlement, and seepage damage, which profoundly impact project timelines and potentially endanger life and property safety. Therefore, it is imperative to investigate these impacts before and after construction and to facilitate timely adjustments of construction measures and reinforcement where possible. In this study, a foundation pit construction project near a rail transit line is employed as a case to comprehensive study the impact of on-site deep foundation pit excavation on adjacent rail transit structures by numerical simulation. A three-dimensional finite-element model of the foundation pit based on site geological characteristics and construction procedures is established to study the excavation and maintenance processes. Through analysis of key parameters including soil deformation, displacement, shear force, and bending moment of the tunnel structures, the designed protective structure is found to have effectively mitigated soil deformation, ensuring the stability of the foundation pit. As excavation progresses, lateral soil deformation and vertical uplift gradually increase but remain within specified control values. During various excavation stages, the maximum displacement of the tunnel structure gradually increases, with the increase rates of maximum settlement being 29.09%, 20.51%, and 6.45%, respectively. This indicates a gradual enhancement of the stability of the tunnel structure. Additionally, excavation of the foundation pit has a significant impact on the bending moment distribution of the tunnel structure but does not affect the axial force and shear force of the tunnel structure. The findings of this study offer crucial scientific insights for evaluating the safety and stability of construction near tunnel structures.

With diminishing natural aggregate resources and increasing environmental protection efforts, the use of recycled fine aggregate is a more sustainable approach, although challenges persist in achieving comparable mechanical properties. Exploration into the incorporation of steel fibers with recycled aggregate has led to the development of steel-fiber-reinforced recycled aggregate concrete. This study investigates the shrinkage performance and compressive constitutive relationship of steel fiber recycled concrete with different steel fibers and recycled aggregate dosages. Initially, based on different replacement rates of recycled coarse aggregate and different volume contents of steel fiber, experimental results demonstrate that as the replacement rate of recycled coarse aggregate increases, shrinkage also increases, while the addition of steel fiber can mitigate this effect. An empirical shrinkage model for steel fiber recycled concrete under natural curing conditions is also proposed. Subsequently, based on the uniaxial compression test, findings indicate that with an increasing replacement rate of recycled fine aggregate, the peak stress and elastic modulus of concrete decrease, accompanied by an increase in peak strain, and the addition of steel fiber limits concrete crack development and enhances its brittleness while the peak stress and strain of recycled fine aggregate concrete are enhanced. However, the steel fiber volume percentage has a negligible effect on the elastic modulus. A constitutive relationship for concrete considering the effects of recycled fine aggregate and steel fiber is also proposed. This finding provides foundational support for the influence patterns of steel fiber dosage and recycled aggregate ratio on the mechanical properties of steel fiber recycled concrete.

A building developed by Wuhan Shimao Group in Wuhan, China, is a high‐rise residence with 56 stories near the Yangtze River. The building is a reinforced concrete structure, featuring with a nonregular T‐type plane and a height 179.6 m, which is out of the restrictions specified by the China Technical Specification for Concrete Structures of Tall Building (JGJ3‐2010). To investigate its seismic performance, a shaking table test with a 1/30 scale model is carried out in Structural Laboratory in Wuhan University of Technology. The dynamic characteristics and the responses of the model subject to different seismic intensities are investigated via the analyzing of shaking table test data and the observed cracking pattern of the scaled model. Finite element analysis of the shaking table model is also established, and the results are coincident well with the test. An autoregressive method is also presented to identify the damage of the structure after suffering from different waves, and the results coincide well with the test and numerical simulation. The shaking table model test, numerical analysis, and damage identification prove that this building is well designed and can be safely put into use. Suggestions and measures to improve the seismic performance of structures are also presented.

Urbanization and population concentration in China’s major cities drive high land utilization demands, affecting nearby bridges during underground construction. Foundation pit construction alters the internal forces, deformation, and displacement of bridge piles. To understand these impacts and assess excavation support rationality, a case study was conducted on an ultra-deep foundation pit near an elevated ring road bridge in Wuhan. Considering the engineering geological conditions of the project site, construction sequence, and traffic load on the bridge, a three-dimensional finite element model was established to simulate the impact of foundation pit excavation on the elevated structure. And through an analysis of tracked monitoring data from the construction site, comparisons were also made with the simulation results. The findings of this case study indicated that throughout the entire construction phase of the foundation pit, the maximum horizontal and vertical displacements of the bridge foundation structure caused by the construction are 2.98 mm and −1.75 mm, respectively; the maximum change rate of the bending moment in the bridge structure due to the foundation pit construction is 6.3%, while the change in the axial forces is small, and completely within the safety control standards for bridge structure displacement. By analyzing the monitoring data over three stages within one year after the completion of the foundation pit, it is shown that the bridge structure gradually tends to stabilize. Additionally, due to soil consolidation, its displacement shows uniform rebound and tends to stabilize. The research findings provide valuable reference points for the design and construction of similar deep foundation pit projects.