The project is for a tunnel with a full length of 1.2km, an excavation section width of 4.6m, and a height of 6.6m. Above the tunnel are residential buildings and pavement, buried for a depth of about 4m. These buildings have strict requirements on the disturbance on surrounding rock and noise control. The tunnel stratum is all rock roadways. The rocks are limestone and granite with saturated uni-axial compressive strength of 90-110MPa, or over 110MPa partially. The project started in 2015, with the tunnel entrance and the tunnel exit commenced at the same time. The entrance was opened up with a hydraulic hammer, while drilling and blasting was used at the other end. However progress was slow and after a few months, the construction team withdrew due to low construction efficiency. Instead the team opted to utilise a tunnelling machine and selected the XTR7/360 from XCMG. This machine has a weight of 145tonnes, a cutting power of 360/280kW and can deliver cutting heights and widths of more than 7m. The machine is said to offer reliability and strong rock breaking ability. The machine can be adapted in various configurations to suit use in different stratum. It is also equipped with advanced features such as smart roll cable, sound and light alarms, soft start, and remote control.
XTR7/360 tunnel boring machine works in the full cross-section of the project. It has withstood hard rock formation and landslide since construction and shown stable performance. The tunneling efficiency has been significantly improved since its entry.
