Experimental and Numerical Study on Mechanical Properties of Threaded-Sleeve-Type Disconnectable Coupling for Foundation Pit Engineering

To overcome the performance shortcomings of disconnectable couplings in foundation pit support systems, a threaded-sleeve-type disconnectable coupling was designed and developed in this study. An axial loading test was performed to investigate the bearing capacity of the coupling. Its yield load, initial compression stiffness, load–displacement curve, stress distribution, and failure mode were determined. A finite element analysis parametric study was performed and formulae for calculating the yield load and compressive stiffness proposed. The following conclusions were drawn from the results: (1) The coupling has good bearing performance. The yield load is 10,509.96 kN, the ultimate load is 12,980.2 kN, and the initial compression stiffness is 4215.17 kN·mm−1. The failure of the coupling is characterized by an outward bulging of the nut part and shearing of the thread. (2) The coupling has good ductility. Strain concentration occurs at the screw. (3) The bearing capacity of the coupling is positively correlated with the outer diameter of the nut, nut thickness, and screw thickness and linearly inversely related to the elongation and screw pitch. (4) The established calculation formulae can accurately estimate the yield load and initial compression stiffness of the coupling.