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.

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.

With the rapid development of underwater shield tunnel construction in China, the waterproof problem of segment joints is becoming more and more prominent, and the hydraulic pressure on shield tunnel is also increasing, which poses a severe challenge to the waterproof safety of the tunnel. The waterproofing of shield tunnel with high hydraulic pressure has gradually become a hot topic at home and abroad. Aiming at the possible problems in the design stage, construction stage and long-term operation stage of segment joint waterproofing of shield tunnel with high hydraulic pressure, the relevant important research at home and abroad were summarized, mainly including: material selection, section design, corner processing, arrangement of multi-channel sealing gasket, waterproof of bolt hole, numerical simulation and test analysis of sealing gasket, waterproof performance of sealing gasket under earthquake action and long-term durability evaluation of aging sealing gasket material. The existing problems and the research trend of related waterproof problems were discussed.

With development of railway transportation, shield tunneling technology has been widely used. As a key component of shield tunneling, the working efficiency and failure form of hob were directly related to the geological conditions and had an important influence on construction schedule and safety. Based on a subway tunneling project, its geology related was analyzed firstly, then the failure types and corresponding causes of the disc cutters were also explained. Finally, a brief discussion was given about the material properties of disc cutters. The results showed that the failure forms were mainly partial grinding, edge curl, fracture of disc cutter ring, cutter ring off, fracture of cutter shaft.

The main academic thoughts and achievements of Academician Mengshu Wang in the tunnel and underground engineering were summarized. The new Austrian tunnelling method(NATM)was introduced and innovated, and successfully applied in Dayaoshan Tunnel and thus forming the shotcrete anchor construction method of railway, breaking through the outdated tunnel construction technologies, which had milestone significance in the history of tunnel development. The shallow underground excavation method for the urban subway engineering was established, which changed the construction status of subway construction that must be “open cut” from the ground, and could effectively protect the safety of the building structures and promote the rapid development of urban subway construction. In terms of undersea tunnel construction, the determination method of minimum roof thickness and design value of hydraulic pressure of the tunnel were established, and the waterproof and drainage technology and corresponding key construction technologies of undersea tunnel were put forward, all of which could provide technical support for the construction of the first undersea 2019年 - 第1卷第2期 谭忠盛:隧道与地下工程建设理念及关键技术——记王梦恕院士的主要学术思想和科研成就 \=-tunnel in China. A new mode of tunnel construction by TBM+ drilling and blasting method was put forward, and the auxiliary tunnelling technologies were established, compression concrete shield with a diameter of 7.3 m cutter head was firstly developed in China, which promoted the nationalization of shield. For the complexity of geology and environment in our country, the construction concept and basic principle of tunnel and underground engineering were put forward. Academician WANG Mengshus academic thoughts and scientific research contributions have had a profound impact on the development of the discipline, and has made a significant historical contribution in promoting the development of tunnel and underground engineering technology in China.

With the rapid development of shield technology, more and more shield tunnels pass through sensitive environments. Due to the complicated construction conditions of shield tunnels, stratum disturbances will inevitably occur during the construction process, resulting in settlement on the surface and serious damage to surrounding buildings. Therefore, it is especially important to control the construction settlement effectively when the subway tunnel passes through settlement sensitive areas such as high-density shantytowns. The project of Wuhan Metro Line 8 project, Huangpu Road Station to Xujiapeng Station tunneling through high-density shantytown project was taken as the project support. The perturbation control technology of super-large diameter mudwater shield in the construction process was studied. On the basis of a brief analysis of the engineering background and the difficulties, the article optimizes the excavation parameters, including the pre-excavation building evaluation and the excavation process, so as to achieve the final adjustment of the cutting water pressure, the excavation speed and the cutter head torque during the construction process. The implementation of key technologies such as mud membrane control and secondary grouting ensured the smooth progress 2019年 - 第1卷第2期王焕: 大直径泥水盾构穿越无加固条件沉降敏感带扰动控制技术研究 \=-of excavation. The parameter control of excavation process provides reference and basis for analyzing the construction control of large-diameter shields under the old shantytown.

The interaction between the hob and the rock mass is the core of TBM technology, and numerical simulation plays an important role in studying this process. In this paper, a hob and a soft-strong inter-bedded rock model was built based on further development of discrete element software MatDEM, which contained 502 thousand particles. By simulating the process of the rock breaking by a hob, as well as recording and analyzing, including boundary and hob force, particle connection, energy conversion, heat distribution and so on. The simulation results showed that, when strong rock breaked, the force of boundary and hob changing obviously, and the particles had greater force in the direction perpendicular to the hob and layer, but when weak rock layer was breaking, the inner boundary and the hob bore less stress, and the force of the hob was uniform; There were a few of broken joints in strong rock layer, and breaking volume of rock mass was small; During this process a lot of frictional heat was produced, and the accumulate of energy in strong rock was larger. MatDEM could simulate rock breaking process by hob effectively. By modifying the shape of hob and parameter of rock, this method could be further used for simulation of large-scale rock breaking by hob in other engineering conditions. It also provided a new way for numerical simulation of large-scale hob breaking rock.

In this review, the tunnel engineering geological disasters were firstly reported, and then the simulation applications of tunnel engineering related to RFPA were summarized. The following main conclusions were that during the construction of tunnel engineering, the tunnel engineering of main geology disaster types including solid geological disasters, quasi fluid geological disasters and fluid geological disasters; the RFPA numerical methods in tunnel engineering construction related rock mechanics and failure characteristics of acquiring, under the condition of excavation of tunnel damage simulation, bedding rock tunnel excavation simulation, dynamic tunnel under the condition of failure simulation, simulation and partition of deep surrounding rock fracture under the action of seepage tunnel stability analysis were carried out in such aspects as widespread application; at present, RFPA has made important progress in the aspects of calculation accuracy, calculation scale and calculation speed, parallel computation of large-scale solution process, construction of numerical computing cloud platform and so on. It is believed that with the continuous development of technology and program, RFPA numerical calculation method will be more widely used in tunnel engineering simulation.

The outstanding achievements of fully mechanized(top coal caving)mining, backfilling mining, marine mining and non-chain-pillar mining in China were introduced. The scientific connotation of practical pressure control theory as well as its application and development in coal mass resource mining and disaster pre-control were also clarified clearly. Based on the current statu of coal resources exploitation, the establishment of the model or theory of prediction and control decision on the important disaster in coal mines is the fundament for its effective control, thus achieving the 2019年 - 第1卷第2期宋振骐:我国采矿工程学科发展现状及其深层次发展问题的探讨 \=-development of coal mine disasters pre-control from qualitative to quantitative. And further it also contributes to the accomplishment of the informatization, intelligent and visualization of decision-making and monitoring in coal mining engineering.

With the development of railway, water conservancy, mining and other projects, increasing caverns need to be excuvated in the deep. Dynaimic loads includying blasting excavation and fault-ship burst seriavsly affect the stability of surrounding rockmass of undergroud cavern. The finite difference software FLAC3D was used to simulate the surrounding rockmass stability of underground cavern under blasting and fault-slip burst conditions. The peak ground velocity(PGV)was used, and the mathematical relationship of the surrounding rock PGV under different focal mechanisms was obtained by fitting the Sadovs formula and the McGarrs formula. It was concluded that under the blasting load condition, the distance between the underground cavern and the source had a significant influence on the stability of the cavern. The Sadovs deformation formula could well characterize the PGV of the surrounding rockmass response, but the McGarrs deformation formula was not applicable. Under the condition of fault-slip, the Sadovs deformation formula and the McGarrs deformation formula did not have high goodness of fit, the slip angle had a greater influence on the stability of the cavern. Based on the above analysis, it was recommended that deep underground cavern support should consider the influence of the source, such as PGV. For the source of fault-slip, the influence of the slip angle on PGV should be considered. The above conclusions provide data support and technical basis for the excavation and support of geotechnical engineering underground cavern.