After 24 consecutive days and nights of intensive work, the "Xingsheng" shield machine on the Changsha Xiangya Road river-crossing tunnel project safely exited a roughly 170-meter-long fault zone beneath the river on the 10th. This means the project has overcome a series of difficulties including high water pressure, deep overburden and complex geology, successfully crossing the longest fractured-zone risk source in the section in one go, and accumulating valuable construction experience for later crossing the overlapping area of shallow cover and fault zone. It is reported that the Xiangya Road river-crossing tunnel achieved shield launch at the end of March; the north-line shield tunnel has advanced 880 meters and is planned to achieve single-line breakthrough before the Spring Festival.

The Xiangya Road river-crossing tunnel is one of the city's "Five Top Ten" infrastructure construction projects. The project starts at Yuehua Road in Yuelu District in the west and ends at Furong Road in Kaifu District in the east, with a total length of about 4.18 kilometers, of which the riverbed shield section is about 1.4 kilometers. The riverbed shield section needs to cross geological fault zones four times, with a total length of about 440 meters, mainly cataclastic rock, rich groundwater, and uneven hardness, posing very high construction risks.

When the shield machine crosses fault zones, blowouts and face collapses are likely to occur. At the same time, due to uneven distribution of soft and hard strata, it is difficult to control the shield tunneling attitude, which can easily lead to shield deviation and cutter breakage. During shield construction, the stability of the fault-zone face is poor and the rock has a high clay content. During crossing, the clay particles in the muck increased, causing the specific gravity of the shield tunneling slurry to rise too quickly and reducing shield construction efficiency. Under normal conditions, it can advance 10 meters per day, but when crossing the fault zone it can only advance six or seven meters per day.

In response to a series of problems, all parties in the project planned ahead and deployed carefully, replacing cutters in a timely manner before reaching the fault zone; when crossing the fault zone, increasing the frequency of fresh slurry preparation at the slurry plant, strictly controlling cutterhead rotation speed and advance speed to reduce disturbance to the stratum; controlling synchronous grouting pressure and grouting quality to prevent segment uplift; and carrying out secondary grouting in a timely manner to fill the gaps between segments and rock strata, ensuring safety and quality.

It is introduced that in order to reduce the risk of the shield crossing the fault zone, personnel from project construction, contracting, design, supervision, monitoring and inspection units stayed at their posts during the National Day holiday and conscientiously performed their duties to safeguard project construction. All parties cooperated fully and communicated in a timely manner, while optimizing and adjusting shield tunneling parameters to ensure safe and stable shield tunneling.