The design of internal bracing is critical for controlling deformations in soft-soil foundation pits, especially in congested urban areas where ground anchors are prohibited. This study investigates a novel combined support system consisting of 45° inclined H-beam strength composite piles (SCPs) and triaxial deep-mixing columns (TDCs). A full-scale field investigation was conducted in a 6.15-7.10 m deep excavation in Nanjing mucky silty clay, adjacent to sensitive metro tunnels and dense underground utilities. Field load tests on three inclined SCPs demonstrated ultimate vertical capacities of 1,350-2,090 kN, with total settlements limited to 14.07-15.17 mm. Regression analysis using a power-function model (s = aQ^b) predicted extrapolated ultimate capacities of 2,299-3,682 kN, indicating that current technical specifications (JGJ/T 327) provide reliable but conservative estimates (approximately 62%-84%). Continuous field monitoring revealed that the maximum lateral wall deflection was confined to 6.36 mm (less than 0.1%H), significantly superior to conventional cantilever systems. These results validate a structural system transformation from a quasi-cantilever to a quasi-simply supported configuration enabled by the inclined bracing. This study provides a practical benchmark and quantified performance data for the application of inclined SCPs as a low-carbon, high-efficiency alternative to traditional internal bracing in complex soft-soil environments.

For ground with trapezoidal distributed subgrade reaction coefficients caused by natural sedimentation, a calculation model for pile(wall) deflection deformation under lateral loads was established. Based on the theory of power series solution of differential equations, a power series solution for pile(wall) deflection deformation that considers the trapezoidal distribution of lateral loads and subgrade reaction coefficients was proposed. The power series solution can be degraded into the traditional K-method and m-method formulas for calculating pile(wall) deflection deformation. The results show that when the number of calculation terms of the power series solution is taken as 20, the maximum relative truncation error of the horizontal displacement is 0.19%, and the calculation accuracy can meet the requirements of theoretical analysis and engineering calculation. For long pile(wall) with a converted depth $\overline{h}$ greater than 5 m, it is suggested to calculate at 5 m. The analysis of engineering examples demonstrates the validity. The proposed power series calculation method solves the problem of pile(wall) deflection deformation with trapezoidal distributed subgrade reaction coefficients under lateral loads, which the traditional K-method and m-method cannot solve. Compared with the finite element method, the computational efficiency of the deterministic method is improved. Therefore, the proposed method can support the establishment of calculation methods for complex problems such as pile(wall) deflection deformation in multi-layered ground and anti-slide piles under local lateral loads.

The blasting-induced environmental impact of tunneling is a major concern in drill and blast excavation practice, particularly in urban areas. The present paper carries out comprehensive numerical modeling to study the vibration attenuation at the soil surface away from the blasting source as well as the resulting interactions between a historical structure and the surrounding soil, with particular attention to the effects of a millisecond delay. Special attention is given to the interpretation of the role of the local site effects in terms of the frequency-dependent changes of the vibration attenuation mechanism and the response of the historical structure. The velocity responses along the ground surface generally exhibit higher-frequency suppression and low-frequency amplification for both instantaneous blasting and millisecond delay blasting cases in the layered soil–rock site. The millisecond delay blasting can effectively avoid excessive vibration velocity and thus reduce the vibration amplitude at the ground surface by 60–70% (compared with instantaneous blasting), with the predominant frequency mainly concentrated in the high frequence band of 400–500 Hz. The empirical formulae for predicting the vibration attenuation along the scale distance in a soil–rock site has been proposed for both instantaneous blasting and millisecond delay blasting. Through the HHT spectral analyses of the velocity response of the historical structure, it is seen that the difference of structure properties between the wood-frame tower and the base masonry structure has a remarkable influence on the structural vibration. The numerical results can provide a reliable reference for the practical blasting scheme and the systematic study of the dynamic responses of historical structures subjected to blasting-induced vibrations.