Abstract: China has made significant progress in tunnels and underground engineering during the "13th FiveYear Plan" period. Especially, despite of the sudden outbreak of COVID19 pandemic, remarkable achievements, both in quality and quantity, were made in railway, highway and subway tunnel projects from 2019 to 2020. In this paper, tunnel construction in railways, highways, subways and other fields in China in the recent two years is compared. Analysis and discussions are made on the tunnel projects under construction, such as Shiziyang tunnel of FoshanDongguan intercity railway, Xiaosanxia tunnel of ZhengzhouWanzhou railway and Shantou Bay tunnel, and the newly started tunnel works such as Gaoligongshan tunnel of DaliRuili railway, Tianshan Shengli tunnel and Shergyla Mountain tunnel of SichuanTibet railway from the aspects of engineering characteristics,  challenges and corresponding technological innovations. The technical progress made in the field of tunnels and underground engineering in China in the recent two years and the construction technical challenges that need to be further tackled in the future are systematically summarized as follows: (1) According to the construction of Muzhailing tunnel of WeiyuanWudu expressway, Qinling tunnel of HanjiangtoWeihe diversion project, Shantou Bay tunnel, etc., great breakthroughs and successful applications have been made in control technology for soft rock deformation under high ground stress, monitoring and treatment technology for hard rock burst, and undersea tunnel construction technology in high earthquake intensity areas, etc.; the manufacturing and application technology of domestic largediameter TBMs and irregularshaped largesection TBMs have reached a new level, and domestic shield machine main bearings and completemachine remanufacturing equipment have been successfully verified and applied; attempts have been made to apply the shield TBM cruise tunneling technology based on highpressure water jet assisted rock breaking technology and the big data mining technique in tunnel industry. (2) Breakthroughs in new rock breaking methods, multifunctional hybrid TBM equipment, and construction technology for maglev system tunnels based on low vacuum pipelines are urgently needed for tunnel construction in extreme environments or complex geological conditions such as crossriver or crosssea tunnels and SichuanTibet railway. (3) Aiming at the key challenges in tunnel engineering under extremely complicated geological conditions, such as SichuanTibet railway tunnels, which can hardly be solved using the traditional tunnel engineering concepts and methods, the concept of tunnel field is put forward, and it is pointed out that the tunnel field deconstruction and reconstruction theory and method should be gradually established and improved, and the design concept for tunnels in extreme geological conditions should be innovated; and the organic integration of advanced technologies such as "Intelligent Construction" and "5G" with tunnel and underground engineering should be promoted in a targeted and systematic manner in combination with the complexity, variability, and unpredictability of tunnel and underground engineering.

Key words: tunnel and underground engineering, shield, TBM; drilling and blasting method, survey and design technology, tunnel construction technology, big data technology, intelligent construction, tunnel operation and maintenance, tunnel field, deconstruction and reconstruction theory