The objective of this research is to investigate the characteristics of the deformation response in adjacent subway tunnels caused by deep foundation excavation of reclaimed land. Focusing on a deep foundation excavation project situated in proximity to Line 11 of the subway in Shenzhen, this study employs theoretical analysis, numerical simulation, and on-site measurements to thoroughly investigate the deformation issues induced by the unloading of the excavation. The research results are as follows: using the energy method to calculate the uneven deformation of adjacent subway tunnels caused by the excavation can overcome the limitations of traditional algorithms, which treat the subway tunnel as a uniformly elastic foundation beam, resulting in more reasonable calculation results. Increasing the self-stiffness (EI)_eq of the tunnel can effectively reduce the maximum displacement (w_max) of the tunnel, and as (EI)_eq increases, its “weakening effect” on w_max gradually diminishes. Underground continuous walls can effectively control tunnel deformation, with tunnel displacement decreasing as the thickness and concrete strength of the continuous walls increase. “Long excavation” deep foundation excavations can impact the displacement and uplift range of the tunnel, with the maximum tunnel displacement showing a nonlinear decrease with increasing excavation depth. Tunnel displacement decreases as geotechnical parameters (elastic modulus E, internal friction angle φ, and cohesion C) increase, with the elastic modulus being the most sensitive parameter. The research findings can be applied to tunnel construction, maintenance, and safety evaluations, providing valuable references for similar engineering projects in the future.

In order to study the deformation characteristics of the retaining structure under the coupled effect of excavation and dewatering in the affected area of fault zones, this paper takes a deep excavation project in the F1322 fault zone influence area in Shenzhen as an example. The research methods of theoretical analysis, numerical simulation and field measurement are used to conduct in-depth research on the deformation of the retaining structure caused by the excavation and dewatering of the foundation pit. The results show that considering the coupled effect of dewatering in the foundation pit, the energy method based on elastic theory is more accurate in solving the deformation of the retaining pile. By comparing and analyzing the theoretical calculation results, numerical analysis results, and field measurement values, we found that the numerical laws of the three are basically the same. Simplified calculations that only consider rotational deformation and ignore the translational deformation of the wall lead to large deviations between the theoretical calculation results and the measured values of the wall bottom deformation. In order to reduce the deviation between numerical results and measured values, the construction of the foundation pit should strictly adopt measures such as “sectional excavation, avoiding peripheral loads, and optimizing construction deployment”, strengthen construction monitoring, and reduce the impact on the deformation of the retaining pile. The maximum deformation growth rate k (ΔS_max/Δ) of the retaining pile decreases approximately exponentially with the increase of the structural stiffness parameters (E and I) and the embedment ratio within a certain range. The sensitivity analysis of the lateral displacement of the retaining pile to different geological parameters is conducted, and the sensitivity factors of the geological parameters to the deformation of the retaining structure are obtained, namely the maximum internal friction angle, followed by the cohesion, and the elastic modulus is the smallest. Based on the original design plan, an optimization of the excavation design is proposed by reducing the stiffness of the support structure. Therefore, the research findings in this paper have significant theoretical and practical implications for the engineering design of excavation projects located in fault zones. By optimizing the excavation support system, not only can standardized construction procedures be achieved, but also investment costs can be reduced, and construction time shortened, which fully aligns with the current safety, economic, and sustainable design principles of excavation projects aiming to conserve resources.

The theoretical calculation of a counterweight double-row pile supporting structure is deduced and studied in this paper. The derived calculation method is applied to a Midas GTS NX simulation calculation. A case study of a deep foundation pit project in Shenzhen City is used to verify and analyze the simulation results and the field monitoring results. On this basis, the influence law of deformation parameters such as the row distance, pile diameter of back-row piles and load of the pit top on the pile of a double-row pile is further discussed. The results show that both the front- and back-row piles of counterweight double-row piles are overturning deformation, and the characteristics of the horizontal displacement are basically the same. The maximum value of the horizontal displacement of the pile is at the top and the minimum value is at the bottom. With the increase in the row distance and pile diameter, the horizontal displacement of the pile becomes smaller, and the change in the pile horizontal displacement under a top load is contrary to that. Moreover, the change in the row distance has a great influence on the horizontal displacement of the pile, followed by the load of the pit top, and the pile diameter of the back-row piles has the least influence. Due to the connection effect of the horizontal plate of the counterweight platform, the whole supporting structure is in the form of a hyperstatic structure. The back-row piles can withstand most of the lateral earth pressure, which effectively reduces the deformation of the front pile and improves the overall stiffness of the supporting structure, which is conducive to the excavation stability of the deep foundation pit. Therefore, its extensive use in the Linhai soft soil project can not only effectively reduce the number of internal supports and achieve the purpose of cost saving but also increase the construction face, which is beneficial to the development of dry construction organization and management, in line with the construction concept of green environmental protection and sustainable development advocated at present.