## 2 Background  
Huayuan Road and Luzhou Road are two main municipal roads in Hefei City, China, and they were both constructed in the form of open tunnel. The open trench tunnel of Huayuan Road is 2.9 km in length, ranging from Huizhou Road to Baohe Road, which is crossed by the Luzhou Road Tunnel, as shown in Figure 1. To make the construction of this crossing section of the road tunnels workable, a combined box culvert was adopted where a frame structure of the Huayuan Road Tunnel downward side was combined with an upward side frame structure of the Luzhou Road Tunnel. The crossing section was named as the \"Huayuan-Luzhou\" Crossing Point. The physical dimension of the Huayuan Road pit was about 35 m wide and 20 m deep, which was partly supported by a cast-in-place pile (supporting pile) or by natural sloping. The pit of Luzhou Road was excavated shallowly by natural sloping near the two sides of Huayuan Road. Figure 2 shows the two orthogonal sections of the \"Huayuan-Luzhou\" Crossing Point. The tunnel frame structure of Huayuan Road was constructed prior to that of Luzhou Road (see Figure 3). Consequently, the mechanical behavior of the tunnel frame structure of Huayuan Road was greatly affected by the construction of Luzhou Road as it approached the crossing section. In engineering the crossing point, the construction process of such a long tunnel was carried out from one section to another (about 25 m in length per section), and the section next to the Huayuan Road foundation pit was regarded as a connecting section that served as a connection of the Huayuan Road Tunnel and Luzhou Road Tunnel. The deformation behavior of the crossing section is a main issue for engineering the construction. In order to study the influence of the construction process on the deformation behavior of the connecting section, the whole construction process was divided into six procedures, as shown in Figure 3. Firstly, the pit of Huayuan Road around the crossing section was excavated and supported by a series of cast-in-place piles and three-row transverse support. Secondly, the tunnel frame structure of the crossing section was constructed from the bottom to the top (Huayuan Road downward sides and Luzhou Road upward sides). Thirdly, the southern pit of the connecting section was excavated in the Huayuan Road Tunnel, and the soil behind the supporting pile was removed in two steps  
Figure 1: Location and structural diagram of the crossing section of Huayuan Road and Luzhou Road: (**a**) plane layout, (**b**) three-dimensional location diagram of crossing section and (**c**) structural frame diagram of crossing section. Figure 2: Two orthogonal sections of “Huayuan-Luzhou” Crossing Point: (**a**) Huayuan Road and (**b**) Luzhou Road (unit: mm). according to the construction scheme (as shown in Figure 4). Fourthly, the part of the supporting pile above the pit bottom was cut off. Fifthly, the upper tunnel frame structure of the connecting section (tunnel frame structure of Luzhou Road) was constructed. Finally, the tunnel frame structure of the connecting section at the northern part was constructed the same way as the southern part. Figure 4: Excavation of foundation pit behind supporting pile. Figure 3: Construction process of connecting section: (**a**) pit excavation with supporting pile in Huayuan Road; (**b**) construction of frame structure in Huayuan Road; (**c**) excavation of pit in southern connecting part; (**d**) supporting pile cutting; (**e**) construction of southern connecting frame structure and (**f**) construction of northern connecting frame structure. Based on the construction process of the connecting section (see Figure 3), it can be seen that an asymmetric construction measure was adopted in the engineering, since the soil excavation of the foundation pit in the southern part was conducted prior to the soil excavation in the northern part. Large structure deformation and soil settlement might occur because of a sudden stress release and an unevenly distributed loading during asymmetric construction [31,32].