Experimental investigation of 15.5-m prototype segment lining structures: The load equivalent method and in-situ verification

Abstract

Super-large cross-sections are an important trend and the main focus in the current development of shield technology. However, at present, little attention is being paid to the mechanical behavior of super-large segment lining structures (SL-SLS), resulting in their design being blind and still relying on the experience from tunnels with smaller cross-sections. In view of this, a series of prototype tests of a 15.5 m SL-SLS were conducted in this study, in which the load-equivalent relationship between the prototype test and the theoretical model was proposed based on a joint-included numerical model and a neural network. Subsequently, in-situ tests were performed to verify the reliability of the proposed load-equivalent method. Finally, the influence of the local structural stiffness and stagger effect on the mechanical behavior of the SL-SLS were analyzed. The following conclusions have been drawn from this study: (i) The proposed load equivalent method is reasonable and the prototype test can accurately reflect the mechanical behavior of the SL-SLS. (ii) The local structural stiffness has a significant influence on the bending moment and radial displacement, and its influence decreases with increasing water pressure. (iii) The radial displacement of the staggered joint assembly structure is not always smaller than that of the straight joint assembly structure due to the decrease in the overall stiffness of the SL-SLS. (iv) For an SL-SLS, the bearing state of positions near the ± 45° direction might be the most unfavorable and thus should be paid more attention to during the design of the SL-SLS.