After being disturbed, the regenerated rock mass is prone to looseness and fragmentation, but under the support effect, the regenerated rock mass still has a certain bearing capacity, especially with significant improvement in post peak bearing capacity, which is the foundation for controlling the stability of the regenerated rock mass roadway. To study the bearing characteristics of recycled rock mass and the influence of support on the bearing capacity of recycled rock mass, a four-factor mixed level orthogonal test was designed for uniaxial loading of recycled rock mass. The bearing mechanism of recycled rock mass is analyzed. The significance of anchor spacing, rod diameter, anchor length, and metal mesh on the post peak weakening trend and bearing capacity of recycled rock mass is tested based on orthogonal analysis of variance. The results show that: Under the conditions of no support and partial anchor support, the regenerated rock mass undergoes compression shear failure under uniaxial loading, while some anchor support regenerated rock mass undergoes splitting failure, and the metal mesh constrained regenerated rock mass specimen undergoes plastic sliding failure. The residual strength of the regenerated rock mass after fracture exhibits fluctuating characteristics. The stability of the post peak bearing stage depends on the friction effect of multiple fracture surfaces, and the support reinforcement friction effect resists the sliding and dislocation of the broken block under external loads. The metal mesh has a significant impact on the post peak bearing capacity of the recycled rock mass, while the change in anchor rod parameters only affects the weakening trend of the strength of the recycled rock mass.

In order to solve the problems such as long deformation time period, large deformation amount and insufficient support strength of carbonaceous slate tunnel with high ground stress. The viscoelastic constitutive model and large deformation control technique of carbonaceous slate are studied by laboratory experiment, numerical calculation and field test. The results show that: (1) The peak strength of the carbonaceous slate is greatly affected by the bedding inclination, exhibiting a U-shaped trend with increasing inclination, and the strength of the rocks with the bedding inclination of 45° is the weakest. (2) The unsteady Burgers creep constitutive model was constructed, and the creep parameters of the constitutive model were determined according to the triaxial creep test. (3) Six supporting conditions were established by using the creep constitutive model constructed. Considering safety and economy comprehensively, the supporting parameters of the large deformation control test section were defined in case 3 (HW175 steel frame, 0.6 m/pin, 4 m long anchor bolt set at the arch, 6m long anchor bolt set at the side wall, spacing 1.2 m×0.8 (ring × longitudinal)). (4) Through the test section, HW175 steel frame and 4 m arch top + 6 m side wall long anchor rod are used. The average arch top settlement and side wall convergence are 18.1 mm and 79.72 mm, respectively, meeting the purpose of controlling large deformation. The research results can provide reference for similar projects.

To solve the problems of waste accumulation and deep and narrow backfilling of foundation pit in the construction process, by adding polycarboxylate superplasticizer (PCE), cement, phosphogypsum (PG) and water glass (WG), the engineering residue is improved into fluid solidified soil for foundation pit backfill. The effects of various admixtures on the fluidity, strength and drying shrinkage of the improved fluid solidified soil were studied through laboratory mobility test, unconfined compressive strength test, drying shrinkage test and microscopic test, and the improvement mechanism was analyzed. The results show that: The flow property of the material can be greatly improved by adding PCE, but the flow rate decreases rapidly with the increase of cement content. PG can make the sample obtain higher strength in the later stage, while water glass can improve the early performance and drying shrinkage property of the sample. With the incorporation of cement, PG and water glass, various hydration products fill the pores in the soil, and the internal structure of the soil becomes more dense. In addition, the feasibility of using fluid solidified soil as backfill for foundation pit is verified by selecting test section for field backfill. This paper can provide reference for improving the performance of fluid solidified soil and the design of mix ratio.

In order to enhance the prediction accuracy of surrounding rock deformation, enable real-time monitoring of deformation status, prevent deformation failure, and ensure construction safety, a novel underground cavern surrounding rock deformation temporal prediction method based on GRU neural network is proposed to tackle the low training efficiency, slow convergence, and poor generalization of traditional methods, along with the establishment of a corresponding prediction framework. Utilizing monitoring data of surrounding rock deformation from the underground powerhouse on the right bank of the Baihetan Dam, predictions are made and subsequently compared and analyzed with the forecasting results generated by the Long Short-Term Memory (LSTM) neural network algorithm. The results indicate that the GRU neural network model effectively addresses the prediction challenges associated with underground cavern surrounding rock deformation, offering advantages such as simplified structure, relatively fewer parameters, rapid training and convergence rates, and high prediction accuracy. Compared to the predictions derived from the LSTM neural network algorithm, the GRU model demonstrates a reduction in training duration by over 70%, with a corresponding decrease in prediction error of more than 50%. The relative error for cumulative maximum deformation is less than 0.3%, the probability of absolute error less than 0.9 mm is as high as 95%, and the maximum absolute error is only 2.05 mm.

With the global population aging, urban public transportation systems, particularly subway stations, face significant challenges. This paper outlines the basic concepts of age-friendly design for subway stations, analyzes the behavioral characteristics of elderly passengers, and examines their specific needs regarding barrier-free facilities, information signage systems, and station environments. The paper then reviews recent research advancements, including adaptations of facilities for elderly use, integration of smart technologies, and the development of assessment frameworks tailored to age-friendly criteria. Finally, it identifies key challenges in age-friendly renovations, such as insufficient user research, inadequate data analysis, incomplete evaluation systems, a single-scheme verification mechanism and uneven overall development. The paper also outlines future directions in enhancing intelligent systems and evaluation frameworks to better accommodate the needs of elderly passengers and improve their overall travel experience.

In order to investigate the plastic yielding mode of surrounding rock caused by the excavation of shallow twin tunnels, the displacement and additional surface force joint controlling the Schwarz alternation method and complex function method are adopted to solve the elastic stress function of surrounding rock of shallow twin circular tunnels through iterative cycles as an example. The expression of plastic stress components of surrounding rock is obtained based on Mohr-Coulomb failure criterion. The elastoplastic solution of the radius of the plastic zone is determined preferentially by using the stress continuity condition at the interface of the elastic-plastic zones around the shallow twin circular tunnels. The analytical solution for the distribution range of the plastic zones around the shallow twin circular tunnels is established, according to the interconversion relationship between polar coordinates and right-angle coordinates. The rationality and applicability of the analytical solution are verified by numerical simulation results and field measurement results of engineering application. The influence of the center spacing of the twin tunnels on the plastic zones around shallow twin circular tunnels are also analyzed. The results show that the analytical solution in this study can be used to solve the problem of predicting the distribution range of the plastic zones around shallow twin tunnels in actual engineering, and meets the requirement of 20% engineering accuracy, fits well with the numerical simulation results, and has a high calculation accuracy. The distribution range of the plastic zones around shallow twin circular tunnels are positively correlated with the center spacing s of the twin tunnels. Based on the distribution pattern of the plastic zone around shallow twin circular tunnels under the influence of this factor, when the plastic zone reaches the critical state of penetration, the reasonableness of the calculation results of the distribution range of the plastic zones is preliminarily judged. It provides theoretical guidance for similar tunnel engineering design calculation and deformation control of surrounding rock.

A large number of different inclinations of tectonic fracture exist for the Sichuan-Tibet Railway along the tunnel peripheral rock, and often in the high ground temperature and high stress coupling environment. In order to study the influence of fracture inclination on the unloading failure characteristics of hard rock under high temperature and high stress coupling, this paper analyzes the unloading rupture characteristics of granite specimens of a tunnel of Sichuan-Tibet Railway under 50 ℃ real-time temperature field through unloading test by adopting indoor test and numerical simulation method. The results show that: the unloading strength decreases with the increase of fracture inclination angle, when the fracture inclination angle is 0°, the unloading strength of the specimen under the 50 ℃ real-time temperature field is obviously smaller than the unloading strength at room temperature; the fracture specimen under the unloading condition has strong tensile damage characteristics, and the dilatancy phenomenon of the specimen under the 50 ℃ real-time temperature field is more obvious when the fracture inclination angle is 30°; When the fracture inclination angle is 0°, a penetrating fracture through the center of the pre-fracture is generated; under the real-time temperature field of 50 ℃, the larger the fracture inclination angle is, the more dispersed microcracks are developed in the unloading process of the specimen, and the smaller the inclination angle is of the pre-fracture, the earlier the accelerated point of fracture development occurs.

Due to its insufficient cover thickness, the excavation face of shallow-shield tunnels is susceptible to passive instability. Tunnel longitudinal slope lead to sudden changes in cover thickness, making the passive failure mechanism of tunnel faces more complicated. There is an urgent need to explore analytical methods for excavation face stability in shallow-buried longitudinal slope shield tunnels. Based on upper bound analysis, a two-dimensional rotation-translation mechanism is proposed that simultaneously considers tunnel longitudinal slope and local instability at the excavation face. The mechanism is comprised of two rigid translation blocks and one rigid rotation block. The ultimate support pressure and failure mode of passive instability at the excavation face are obtained. Finally, the effects of longitudinal slope δ and partial failure ratio η on ultimate support pressure and failure mode of tunnel faces are analyzed, and the reasonableness of proposed models is verified by combining with engineering cases. The results indicate that: Partial failure range of excavation faces gradually increases with the increase of longitudinal inclination angle δ. As the cover depth ratio C/D increases, partial failure of the excavation face evolves into global failure. The rotation angle θ of the rigid rotating block decreases with the increase of the longitudinal inclination δ, and the longitudinal inclination δ has a significant effect on the rotation angle θ.

Aiming at the geological characteristics of loess overlying red-bedded mudstone in the Gansu area, two kinds of industrial solid wastes, namely steel slag and mineral powder are adopted to carry out the research on the mechanical properties and the constitutive model of the modified loess-red bedded mudstone mixed fill by compacting and triaxial CU test. The results show that: (1) The maximum dry density of the mixed fill is the largest when the mass ratio of loess: red mudstone is 1 ∶ 3. (2) The shear strength of steel slag is maximum when the mass dosing of steel slag is 7.5%. The larger the mass dosing of mineral powder is, the larger the shear strength is. (3) It is verified that the strain hardening process of soil samples before and after steel slag improvement could be accurately fitted by the Duncan-Zhang model. (4) For the problem that the hyperbolic model promoted by Shen Zhujiang can not fit the strain hardening well, this paper proposes to use the staged fitting method with positive and negative solutions, and it is verified that this method can accurately fit the strain hardening process of the mineral powder amended soil.

With the excavation of tunnels, the surrounding rock is disturbed and damaged, resulting in changes in its geotechnical parameters. To obtain dynamic variation laws of geotechnical parameters accurately, an inversion method for mechanical parameters of tunnel surrounding rock based on updated boundaries particle swarm optimization (UBPSO) algorithm is proposed. Due to the large fluctuation of optimization results with the particle swarm algorithm, an updated boundaries particle swarm algorithm is proposed. By updating the upper and lower limits of search boundaries dynamically, performing reversal and mutation operations on individual historical optimal values, and updating inertia weights adaptively, the updated boundaries particle swarm algorithm achieves high-precision and fast optimization. The stability test of the Ackley function indicates that compared to the particle swarm optimization algorithm, the updated boundaries particle swarm algorithm has the following advantages, fast optimization speed, high accuracy of results, small fluctuation of outcomes, and less sensitivity to getting stuck in local optima. Based on the updated boundaries particle swarm optimization algorithm, a reverse analysis model for mechanical parameters of tunnel surrounding rock using MATLAB-PYTHON-ABAQUS and on-site monitoring data is established. Taking the YK76+470 to YK76+502.5 section of the Tongluoshan tunnel as an example, the model was used to analyze the on-site monitoring data of the tunnel arch settlement. It was found that the elastic modulus of the colluvial soil layer decreased from 0.200 GPa to 0.106 GPa, the internal friction angle dropped from 14° to 12.072°, and the cohesion value fell from 22 kPa to 19.373 kPa.