Compaction is a critical step in asphalt pavement construction. The objective of this study is to analyze the mesoscale mechanical behaviors of coarse aggregates in asphalt mixtures during gyratory compaction through experiments and numerical simulation using the Discrete Element Method (DEM). A novel granular sensor (SmartRock) was embedded in an asphalt mixture specimen to collect compaction response data, including acceleration, stress, rotation angle and temperature. Moreover, the irregularly shaped coarse aggregates were regenerated in the DEM model, and numerical simulations were conducted to analyze the evolution of aggregate interaction characteristics. The findings are as follows: (1) the measured contact stress between particles changes periodically during gyratory compaction, and the amplitude of stress tends to be stable with the increase of compaction cycles; (2) the contact stress of particles is influenced by the shape of aggregates: flat-shaped particles are subjected to greater stress than angular, fractured or elongated particles; (3) the proportion of strong contacts among particles is high in the initial gyratory compaction stage, then decreases as the number of gyratory compactions grows, the contacts among particles tending to homogenize; (4) during initial gyratory compactions, the normal contact forces form a vertical distribution due to the aggregates’ gravity accumulation. The isotropic distribution of contact forces increases locally in the loading direction along the axis with a calibrated internal angle orientation (1.25°) in the earlier cyclic loading stage, then the local strong contacts decrease in the later stage, while the strength of the force chains in other directions increase. The anisotropy of aggregate contact force networks tends to weaken. In other words, kneading and shearing action during gyratory compaction have a positive impact on the homogenization and isotropy of asphalt mixture contact forces.

Based on the advantages of the silicone graphene composite thermal insulation board, it was used to replace traditional plywood in the external wall formwork system, and the active embedded steel wire knot form in silicone graphene composite thermal insulation structure integrated system was designed. Firstly, the theoretical model of steel wire drawing resistance was established by theoretical analysis method, and the rationality of the theoretical model was verified by combining relevant experimental data. The relationship between multiple variables and steel wire pull-out resistance was analyzed. Then, combined with the theory of wind pressure strength of the exterior wall of a building structure, the layout form and the corresponding number of embedded steel wires of thermal insulation board under different building heights were analyzed. Finally, the silicone graphene composite thermal insulation board and ordinary plywood were compared and analyzed from the force of perspective of external wall formwork. The results showed that the pull-out resistance of steel wire was directly proportional to the diameter of steel wire, embedded depth, and embedded deflection angle. With the increase of building height, the number of steel wires to be arranged also increased. When the thickness of the silicone graphene composite thermal insulation board is not less than 80 mm, the anti-deformation effect is close to that of the ordinary plywood, which can meet the construction requirements of the external wall formwork. It can ensure the energy conservation and thermal insulation of the external wall, integrate the building’s exterior wall and thermal insulation structure of the building, and achieve the purpose of exemption from formwork removal.

According to the design specifications, the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer. To address this challenge, a subterranean transfer structure spanning multiple subway tunnels was proposed. Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness, and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure, we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model. The resolved established simplified mechanical model employed finite difference technology and the Newton-Simpson method, elucidating the mechanical mechanism of the transfer structure. The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure, subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels. The established simplified analysis method can be used for stress analysis of the transfer structure, concurrently considering soil stratification, pile foundation behavior, and plate action. The pile length, pile section size, and beam section size within the transfer structure should account for the characteristics of the upper load, ensuring an even distribution of the beam bending moment.

Based on the theoretical model of a soil plug column, the stress analysis of the soil plug column during the spinning process of steel casing is carried out, and the critical depth of the soil column is determined using the stress and torsional shear ratio of the soil column. The effect of factors such as casing wall thickness, surface load, and steel casing spinning speed on the critical depth of soil columns has been explored, and more reasonable construction process parameters have been obtained quantitatively. Combined with the construction of small net distance test piles at a distance of 2.5 m from the tunnel, the impact of the construction process on the existing shield tunnel has been explored. The results indicate that during the construction process, when the wall thickness of the steel casing does not exceed 0.012 m, the surface load does not exceed 15 kPa, the spinning speed of the steel casing is maintained at 5/4/2/4 m/h or 5/3/2/3 m/h (corresponding to soil depths of 2.5/9.5/6/14 m), and the soil height of the soil column is controlled within 11 m, it is not easy to generate soil plug inside the steel casing, and the soil column has strong torsional shear resistance. According to the measured data of adjacent tunnels, it has been found that the construction method of fully rotating steel casing bored pile can effectively reduce the impact on adjacent shield tunnels, and has a good microdisturbance effect, which can control tunnel deformation not exceeding 1 mm and maintain within the warning value range.

This study proposes an improved dual shear unified strength model by introducing the plastic internal variable which reflects the collective effects of strain softening, intermediate principal stress and unequal strength under tension and compression. The improved model is then simplified into simple forms for typical stress states, including uniaxial tension and compression, plane stress pure shear and tri-axial stress states. The smooth method and conjugate gradient method are utilized to facilitate its numerical implementation, avoiding numerical singularity and non-convergence in the solution process. The physical meanings of the parameters are further clarified and their values for self-compacting concrete are determined from the results of triaxial compression tests through a combination of direct determination, equation solution and back propagation (BP) neural network optimization. Validated against the test results, the improved model gives a more accurate prediction than the traditional dual shear unified strength model and Mohr-Coulomb model, in terms of both the overall trend and representative values. Validation results show that the improved model is applicable to materials for which the compressive strength is greater than the tensile strength and the tensile strength is greater than the shear strength.

To enable real-time prediction of tunnel deformation induced by foundation pit excavation, this study develops a predictive framework that integrates an analytical solution based on a two-stage unloading method with a back-propagation neural network for parameter identification. The analytical model accounts for excavation-induced stress redistribution using Mindlin's solution, while the tunnel is modeled as a beam resting on a double-sided elastic foundation to represent its deformation behavior. Five key mechanical parameters are considered for inversion, including the initial residual stress coefficient, unloading reduction coefficient, longitudinal stiffness reduction factor, and the vertical and horizontal subgrade reaction moduli. These parameters are calibrated using field monitoring data through a trained back-propagation neural network. The proposed framework is embedded into a real-time prediction system and applied to the Gubei Road Station of Shanghai Metro Line 15, which is located adjacent to Line 10. The predicted tunnel displacements exhibit strong agreement with field measurements, with maximum relative errors of 21.82% in the vertical direction and 1.95% in the horizontal direction. Except during phases of displacement trend reversal, the system consistently maintains high predictive accuracy. These results verify the reliability of the proposed method for forecasting excavation-induced tunnel deformation and underscore its applicability in proactive risk management for urban tunneling projects.