Abstract: With 22.1 km length, the Shengli tunnel crossing Tianshan mountain ("Shengli tunnel" in short) on Urumqi-Yuli highway under construction is the longest highway tunnel in the world. The tunnel crosses Tianshan mountain from the south to the north. The construction of the tunnel is faced with complex engineering geological conditions and hydrogeological conditions, very cold and high-altitude environment, high seismic intensity and strict environmental protection requirements. So far, there is no completed highway tunnel with up to 20 km length in China and abroad. The tunnel is faced with many technical challenges in terms of the structural safety and the operation safety. Critical aspects of the tunnel, such as exploration by means of the long-distance horizontal directional drilling, determination of the overall tunnel pattern, design of dual-mode TBMs with injected concrete lining function, aseismic design of the tunnel sections in active fracture zones, disaster prevention and rescue, and health monitoring, operation and maintenance, are studied on basis of the features, construction environment and hydrogeological conditions of the tunnel. In terms of the prospecting and surveying for the tunnel, 3D UAV laser scanning surveying technology, high-precision remote sensing technology and longdistance horizontal directional drilling exploration technology are used to quickly and accurately obtain the geological parameters and to shorten the prospecting and surveying period; in terms of the design of the tunnel, the overall pattern of "twin main tunnel tubes + one service tunnel tube" and the design of dual-mode TBMs with injected concrete lining function are adopted to improve the safety during the construction and operation of the tunnel and to shorten the construction period, and the aseismic design of the tunnel sections in the active fracture zones and the design of the underground high-position fire-fighting water tanks are adopted to improve the toughness of the tunnel structure; in terms of the operation and maintenance of the tunnel, intelligent disaster prevention and rescue, intelligent tunnel health monitoring, intelligent tunnel operation, intelligent tunnel maintenance, and illumination scenery in the tunnel are adopted to improve the safety and quality of the tunnel operation, realizing alarming within seconds, responding immediately and the emergency on-duty persons′ arriving at the accident position within five minutes so as to perform timely rescue.

Key words: Shengli tunnel crossing Tianshan mountain ("Shenli tunnel" in short), aseismic design, horizontal directional drilling, dual-mode TBM with injected concrete lining function, disaster prevention and rescue