Foreword by Qihu Qian

Since entering the 21st century，with the continuous development of economy，the continuous improvement of comprehensive national strength and the continuous application of high and new technology，China's tunnel and underground engineering have achieved unprecedented rapid development.China has become the country with the largest scale，the largest number，the most complex geological conditions and structural forms，and the fastest development of construction technology in the world.At the same time，with the continuous increase of urban subway construction，the number of cross-river and cross-sea tunnel projects continues to increase.National key construction projects such as long-distance water supply，underwater transportation，West to East Gas Transmission and other projects will involve the problem of crossing rivers.The construction of railway，highway，municipal administration，water supply，gas supply，flood control，hydropower and other tunnel projects will greatly increase the number of tunnels.

In the aspect of tunnel construction technology，the technical system of high-speed railway tunnel has been basically formed；the construction technology of long large tunnels with complex geological conditions in difficult and dangerous mountainous areas has made continuous progress；the construction technology of large section soft surrounding rock tunnels has made great progress；the construction technology of urban large-span shallow buried tunnels and river crossing underwater tunnels has made breakthroughs；the research and development and manufacture of tunnel boring machines have made great progress，these marks the tunnel construction technology in China has reached a new level of development.In particular，China has a vast territory，complex geological conditions，and extremely complex geological conditions are the main factors restricting the safe and efficient construction of tunnels，which are recognized as the difficulties of tunnel construction.Relying on a large number of key and difficult projects，such as Guanjiao tunnel of Qinghai-Tibet railway，West Qinling Tunnel of Lanzhou-Chongqing railway，immersed tunnel of Hong Kong-Zhuhai-Macao Bridge，Gaoligongshan tunnel of Dali-Ruili railway，Yangtze River Tunnel of Sanyang road in Wuhan，etc.，China has made great achievements and more innovative achievements in tunnel and underground engineering，especially in tunnel construction under complex geological and environmental conditions.Therefore，in view of the complex geological conditions such as complex terrain and landform type，complex geological structure and poor engineering geology of rock and soil mass，based on the breakthrough and innovation achievements of key and difficult projects，the editorial board of the series and Shanghai Science and Technology Press jointly planned the series.

From the perspective of geological exploration，early warning and risk control，design，construction and digital application，the series systematically sorts out the key technologies of tunnel construction under complex geological and environmental conditions，such as mountains，underwater，soft and hard uneven strata.In the form of academic monographs，it introduces the innovative achievements and core technologies formed in the process of complex geological tunnel construction in recent years.The innovative achievements and technologies involved and introduced in the series are at the leading level in China，some of which have formed core technologies with independent intellectual property rights，and have been applied in major projects，making the series have the characteristics of cutting-edge，original，innovative and leading.For example，Kairong Hong's Shield Tunneling Technology in Hard-Soft Uneven Strata and Extremely-Soft Strata expounds shield treatment technology of soft and hard uneven stratum and extremely soft stratum of underwater tunnel from theory，technology and engineering cases，which represents the latest theory and practice of soft and hard uneven stratum tunnel and underground engineering；based on the scientific research project“National Defense Engineering Geological Prediction and Quality Nondestructive Testing System”presided over by the author，and combined with the research and application results of the team for many years，Guohou Cao and Hao Liu's Three-Dimensional Exploration Technology of Tunnel Geology comprehensively introduced the new theory，new method and new technology of tunnel complex geological geophysical exploration；Shucai Li's Monitoring Method and Early Warning Technology of Tunnel Water Inrush relying on the national major scientific research instrument and equipment development project“Comprehensive Geophysical Exploration Instrument for Quantitative Advance Prediction of Tunnel Unfavorable Geology Used in the Roadheader Construction”，the National Natural Science Foundation for outstanding young scientists project“Mechanism and Disaster Control of Tunnel Water Inrush and Mud Inrush”and other major scientific research projects，introduces the advanced prediction technology of water inrush and mud inrush disaster source in complex geological tunnels and its application in large tunnel engineering，etc.The application cases in the series also include yuelongmen tunnel of Chengdu-Lanzhou Railway in Sichuan，Yellow River Tunnel Project in Jinan，Qiyueshan Tunnel of West Hubei expressway，Jiaozhou Bay Tunnel in Qingdao，Yangtze River Tunnel in Nanjing，and river crossing tunnel in Wuhan.

Under the strategic background of vigorously promoting the“One Belt and One Road”construction，implementing the innovation-driven development strategy and building a powerful transportation nation，we hope that the publication of the series will not only better summarize the above technological achievements and promote the popularization and application of innovative technologies，but also play a catalytic role in the breakthrough of basic theoretical research and common key technologies，and can play a positive role in the cultivation of technological innovation mode and professional talents.In the process of discussion，planning，organization，compilation and review，the series has been greatly supported by relevant large enterprises，colleges and universities，research institutions，societies and associations.Many experts have put forward many very good suggestions and ideas for the series in their busy schedule.Thank you all.

Guangzhou City，P.R.China　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Qihu Qian

August 2018

Mr.Qihu Qian Professor of the Army Engineering University of the Chinese people's Liberation Army and academician of the Chinese Academy of Engineering.Director of the editorial board of“Series of Key Technologies for Tunnel Construction under Complex Geological and Environmental Conditions”.