A Study on the Fixed-Point Adjustment Factor of Opposing Horizontal Strutsin Strutted Retaining Structures

The elastic support stiffness coefficient kR of opposing horizontal struts constitutes a critical parameter in the design of strutted retaining structures for deep excavations. The determination of the fixed-point adjustment coefficient λ serves as a fundamental prerequisite for the quantitative assessment of this stiffness coefficient. To identify the fixed-point location and establish a computational approach for λ, the endpoint displacements of opposing horizontal struts are classified into four distinct scenarios. For each scenario, the relationship between the lateral earth pressures on both sides of the excavation is derived, the support mechanism of the internal strut is elucidated, and the corresponding fixed-point locations of the struts are determined. Utilizing the response curve between the support-point displacement of the retaining structure and the lateral earth pressure, and adhering to the principle of linearization, analytical formulas for λ under the four scenarios are formulated. The proposed method is employed to compute and evaluate the fixed-point adjustment coefficient of the opposing horizontal struts in a case study drawn from the literature, with the results rigorously compared against the existing published data. Furthermore, the λ values for opposing horizontal struts in a metro station excavation project are computed and contrasted with values back-calculated from monitored horizontal displacements of the retaining structure. The findings demonstrate that the proposed method for determining λ is both computationally efficient and practically applicable. The derived λ values can be effectively used to predict internal forces and deformations in retaining structures for asymmetrically loaded deep excavations. This research offers substantial theoretical insights and practical implications for the scientifically informed design and construction of deep excavation support systems.