In order to clarify the key points of machine learning in surface deformation prediction of shield tunneling, the development background of machine learning was introduced, and the engineering application of machine learning was summarized from the aspects of database establishment, data preprocessing, model framework construction and model evaluation. It was pointed out that the shortcomings of the current relevant research were the lack of professional public database and the uneven quality of engineering data; for engineering with different stratum types, the model was prone to over fitting. At the same time, the further development direction of machine learning in shield tunneling surface deformation prediction was discussed, including the effective combination of algorithms could learn from each other; there was still a large research and application space for feature selection and super parameter optimization.

In many cases of shield tunnel collapse accidents occurred both domestically and internationally, the development process of the collapse showed the characteristics of progressive collapse, leading to serious economic losses and casualties. However, the research is still in its primary stage. The lack of understanding of the triggering conditions, development process, and effective prevention measures of the progressive collapse of shield tunnels restricted the high-quality development of urban rail transit in China. Based on the statistical analysis of nearly one hundred cases of tunnels accidents all over the world and focused investigation into 23 typical cases of progressive collapse from 2003 to 2020, the characteristics of progressive collapse of shield tunnels was analyzed. Using statistical methods, the initial damaged location, stratum, damage degree and other factors of shield tunnel progressive collapse accidents and their relationships were categorized and evaluated. The main characteristics were clarified. Based on the comprehensive analysis of multiple cases, the development process of the shield tunnel lining structure damage in the accident was generalized, and it corresponded to the damage degree of the tunnel structure. Finally, considering the interaction between the tunnel structure and the surrounding stratum, the response of the surrounding water and soil during the collapse was analyzed, and it was pointed out that the progressive collapse of the shield tunnels was a fluid-solid coupling dynamic problem. The research results are helpful to improve the relevant understanding of the progressive collapse of shield tunnels, and provide guidance for the prevention and control of the progressive collapse of shield tunnels.

This work systematically summarized four types of methods for predicting tunnelling induced ground movements, namely analytical solution, empirical equation, numerical simulation and model test method. The theory of four types of analytical solutions was firstly presented. The widely-used empirical equations and determination methods for the key parameters were introduced. The development of numerical analysis methods with respect to soil constitutive model and simulation technique was discussed. The 1g model test and centrifuge model test were presented in brief as well. Some suggestions on predicting tunnelling induced ground movements in China were presented according to the advantages and disadvantages of various methods.

The quantitative relationship between the seepage defects and several influencing factors was studied based on the various types of inspection data of a highway tunnel in Yunnan Province, China. Based on the survival analysis method, a Weibull damage accumulation model was established for predicting the leakage of tunnel developing with influencing factors and time. The reasonability of the physical meanings of model parameters was discussed, and followed by the validation of the accuracy of model prediction. The research found that the order of importance for the influencing factors of seepage defects were: the existence of cavity behind the lining, the grade of surrounding rock, whether neighboring the deformation joint, and operating time, respectively; in addition, according to the model prediction, the leakage of tunnel could continually increase over time, so it was suggested to adopt maintenance measures such as water sealing treatment. This research provided a new method for diagnosing the major influencing factors and predicting the future development of tunnel defects.

The prevention and treatment of tunnel drainage pipe crystal blockage is very important to the safety of tunnel structure and normal operation of tunnel. Based on the systematic review of domestic and foreign research data, the crystallization process and mechanism of tunnel drainage pipe were analyzed and summarized. The crystallization process in tunnel drainage pipe was summarized as three main stages: the penetration process of groundwater into shotcrete, the dissolution process of calcium in concrete, crystal deposition process in drainpipe. Meanwhile, based on the source of the crystalline material and the crystallization process, the factors affecting the clogging of the tunnel drainpipe were divided into internal and external factors. Internal factors include three types of groundwater quality, surrounding rock types, and shotcrete characteristics. External factors include the characteristics of the aqueous solution in the drainpipe(including the CO₂ content, pH value, salt content in the solution, flow velocity), environmental factors(temperature, pressure)and engineering factors, and elaborated in detail on them. In addition, the prevention technology of drainpipe crystallization blockage was discussed from the aspects of drainage system design, drainage pipe material and concrete mix ratio. Finally, the mechanical, physical, chemical, and biological disposal methods for the crystallization of the tunnel drain pipe were discussed and analyzed in detail. The research can provide a theoretical reference for the prevention and treatment of crystal blocking disease of tunnel drainage pipe.

Aiming at the construction safety risk control problem of network construction project in underground space, five network methods including adjacent extension and construction, connection between existed structures extension, vertical direction extension,enlargingexistingunderground extension and multidirectional extension were proposed. The risk characteristics of network construction project were studied and analyzed. In planning and design stage, the safety planning and design methods and pre-redundancy design were established. In construction stage, pre-planning and design methods of quality evaluation,verification and feedback were constructed. The new planning and design technology could guarantee the safety in the whole process of network construction project. Based on the hierarchical control of the interference level, the safety pre-control measures for the four elements in construction projects including the extended structure, the existing structure, the ground and the surrounding environment were put forward. The new construction safety monitoring index system was given so that the safety risk prevention and control could be fully implemented in the construction process. The researched results provided theoretical guidance and technical support for the planning and design and safe construction of underground space network construction project.

Fire is one of the main threat for tunnel safety. Because of their long and narrow shape, fire in tunnels commonly induces fast temperature rising and smoke concentrations,with the consequent loss of life and negative economic impacts. How to control tunnel fires refers to several topics such as traffic monitoring and risk evaluation,fire recognition,emergency evacuation and system control,assisting fire extinction,and updating accident database. To improve the safety and fire emergency response capacity of the tunnel,this work was presented based on the latest metadata system,machine learning strategy,fast fire recognition method,and robot equipment. We discussed the key points for building intelligent fire emergency and evacuation system of highway tunnel, and focused on the composition and function of each sub-part of the system. The proposed ideas and routines can help the designer and engineers to design the corresponding intelligent system for specific tunnels,which will improve the safety of the structure and assure the normal working performance of the tunnels.

Traditional blasting design is mainly based on experience, and lacks systematic automatic layout algorithm for blas-thole design when smooth blasting is used for rock tunnel. Combined with the design code of blasting and the existing algorithm of blast-hole pattern, this paper introduced a programmatic automatic algorithm of blast-hole pattern suitable for various cross-section shapes from the aspects of computer graphics, simplex integration and automatic layout. Through the characterization of data structure for tunnel cross-section, calculation of geometric parameter and the streamline of division blasting, algorithm of blast-hole pattern for each area was introduced in details. The algorithm was applied to automatic blast-hole pattern design for rock tunnels with four cross-section forms of irregular trapezoid, semicircle arch, circle and ellipse, which verified the feasibility of the algorithm.

In order to fully study the research progress of the delimitation of deep and shallow loess tunnels, the research status of the delimitation of deep and shallow loess tunnels was described from four aspects: theoretical research, numerical simulation, model test and actual measurement analysis. The results showed that: the theoretical research was mostly based on the study and analysis of the changes in surrounding rock pressure and deformation pressure with the buried depth of the tunnel, and the best limit value was found in the changing rules; the numerical simulation was mostly to study the deformation and settlement laws of tunnels with different buried depths, the results were relatively intuitive, and the tunnel force and deformation could be analyzed intuitively; the model test was mainly to carry out the gravity similar simulation test on different buried depth tunnels, which could analyze the force status of the actual project; the actual measurement analysis was based on the on-site statistical results for analysis, according to experience, the boundary value of the depth of the tunnel was delineated. Based on the analysis of the four methods of dividing the depth of the loess tunnel, the factors considered when dividing the boundary between deep and shallow burial was summarized, and the problems in the existing research such as the inaccurate division of the buried depth of the tunnel and the large range of the obtained buried depth were pointed out. In combination with the engineering characteristics of the loess tunnel, it was suggested to use the improved XIE Jiaxiao Maximum Method to calculate the depth and shallow burial limit of the loess tunnel.

Natural gas, as a clean energy, is one of the main energies fueling the green economic development of China. It is one of the main tasks to develop underground gas storage facilities so as to increase the natural gas storage capacity and to improve the quick access to large volume of natural gas during high demand periods. The state-of-the-art of the three principal types of underground gas storage, i.e., in depleted oil/gas fields, aquifers and salt caverns and the basic information on underground gas storage facilities used in USA and Europe were reviewed. The development of underground gas storage facilities in China was compared with that in other countries. Root causes for three typical accidents on three underground gas storage facilities were analyzed. The statistical results on the accidents on underground gas storage facilities documented in literature were summarized. The differences on the root causes of accidents on different types of underground gas storage facilities were analyzed. Some suggestions on the plan and construction of underground gas storage facilities in China were presented according to the experiences and lessons from the review on the development in other countries.