###### Abstract  
Based on the semi-rigid characteristics of a double-cell prefabricated utility tunnel composed of groove-shaped elements (PUTCGE), this paper proposes an extended study of a stiffness reduction method for PUTCGEs by introducing the stiffness reduction and bending moment adjustment coefficients of the sidewalls. The effects of the joint stiffness ratio, the aspect ratio of width to height, the coefficient of subgrade reaction, and the embedment depth of the utility tunnel on the stiffness reduction and bending moment adjustment coefficients were investigated, and calculation formulas were established. The results showed that the stiffness reduction coefficient increased with the increase in the joint stiffness ratio, while the bending moment adjustment coefficient decreased with the increase in the joint stiffness ratio. The stiffness reduction coefficient increased with the decrease in the aspect ratio of width to height, while the effect of the aspect ratio of width to height on the bending moment adjustment coefficient was found to be very small. It was also found that neither the coefficient of subgrade reaction nor the embedment depth had a significant effect on the stiffness reduction and bending moment adjustment coefficients. The stiffness reduction method for the PUTCGE was validated through comparison with a full-scale physical model test. The proposed method can provide a reference for designing PUTCGEs for underground construction. v 20221 2 20221 20  
engineering industry should continue to be improved and fine-tuned so that underground facilities are quicker and cheaper to build with much less impact on nearby facilities and residents. Prefabricated concrete utility tunnels have three types: prefabricated utility tunnels composed of composite slabs (PUTCCSs), integrated prefabricated utility tunnels (IPUTs), and prefabricated utility tunnels composed of groove-shaped elements (PUTCGEs) [10; 11; 12]. A PUTCCS is composed of double-sided composite sidewalls, a composite top slab, and a cast-in-situ bottom slab, which are then connected to an overall structure by post-cast concrete on site. It has the characteristics of light weight and assemblage flexibility, but it involves wet operations, leading to inconvenience during construction, and its double-sided composite sidewalls are very complex to produce. The main feature of an IPUT is overall prefabrication in the horizontal direction, and there is no wet operation on site. However, due to the weight of the monomer, it is difficult to transport and hoist. The main feature of a PUTCGE is characterized by the fact that it is divided into upper and lower groove-shaped members in the horizontal direction, which are connected by prestressed tendons or bolts on site. Compared with the other two types of prefabricated utility tunnels, a PUTCGE has the advantages of reducing the volume and weight of prefabricated components and, therefore, the difficulty of transportation and hoisting and of improving construction efficiency and saving energy through its dry operation, thereby making it more environmentally friendly. However, due to the existence of prestressed tendon connection joints, PUTCGEs have semi-rigid characteristics that increase the complexity in terms of structural calculations and analysis. The mechanical performance and the calculation method of such a structure have attracted considerable attention in recent years. [PERSON] et al. [13] divided the types of prefabricated structural connection joints into two types: one was equivalent to cast-in-situ with rigid connections, and the other was nonequivalent to cast-in-situ with semi-rigid connections. The main feature of semi-rigid connections is that the connected components not only rotate relative to each other but also transmit bending moments. The prestressed tendon connection is a typical semi-rigid connection.