Study on the deformation mechanism and application of trench cutting re-mixing deep walls

Trench cutting re-mixing deep walls can effectively mitigate water ingress and seepage; however, their low tensile strengths prevent them from serving as independent primary support structures for open-cut foundation pits. Therefore, they must be combined with concrete bored piles to form composite primary support systems. However, the wall stiffness can be effectively enhanced by replacing the concrete bored piles with H-section steel beams; this replacement results in an integrated wall–pile primary support structure. The deformation of the primary support structure is one of the key parameters of foundation-pit excavation. Using the elastic foundation-beam principle, mathematical expressions for the stress, bending moment, rotation angle, and horizontal displacement of the steel beams were derived for two boundary conditions: a scenario in which the top ends of the steel beams are free and a scenario in which the top ends are constrained by a capping beam. Using reasonable parameter assignments, the effects of both the active and passive earth pressures, the excavation depth, the steel-beam spacing, and the foundation-pit depth on the horizontal displacements of the steel beams were investigated.