Technical advances, innovation and challenges of developing high-speed rail in China

After little more than a decade of development, China’s 29 000 km high-speed railway network is by far the largest in the world. This paper describes the technological advances and innovations regarding trains, stations, ballastless track, automatic train operation and signalling that made such rapid development possible, as well as setting new global standards for safety, efficiency and reliability. The engineering challenges of building and operating high-speed railways in diverse environments are also discussed, including areas with high winds, low temperatures, underground caverns and debris flows.

Numerical Simulation of the Stability of Rock Mass around Large Underground Cavern

Geotechnical problems are complicated to the extent and cannot be expected in other areas since non-uniformities of existing discontinuous, pores in materials and various properties of the components. At present, it is extremely difficult to develop a program for tunnel analysis that considers all complicated factors. However, tunnel analysis has made remarkable growth for the past several years due to the development of numerical analysis method and computer development, given the situation that it was difficult to solve formula of elasticity, viscoelasticity, and plasticity for the dynamic feature of the ground when the constituent laws, yielding conditions of ground materials, geometrical shape and boundary conditions of the structure were simulated in the past. The stability of rock mass around an underground large cavern is the key to the construction of large-scale underground projects. In this paper, the stability analysis was carried out based on those parameters by using 2D FEM RS2 program. The calculated stress and displacements of surrounding rock and rock support by FEM analysis were compared with those allowable values. The pattern of deformation, stress state, and the distribution of plastic areas are analyzed. Finally, the whole stability of surrounding rock mass of underground caverns was evaluated by Rock Science - RS2 software. The calculated axial forces were far below design capacity of rock bolts. The strong rock mass strength and high horizontal to vertical stress ratio enhanced safe working conditions throughout the excavation period. Thus wide span caverns and the system of caverns could be stability excavated sedimentary rock during the underground cavern and the system of caverns excavation by blasting method. The new method provides a reliable way to analyze the stability of the caverns and the system of caverns and also will help to design or optimize the subsequent support. Doi: 10.28991/CEJ-2022-08-01-06 Full Text: PDF

Four Ways to Store Large Quantities of Hydrogen

Hydrogen can be stored in underground caverns or geological structures in one of four ways. The easiest way to store hydrogen is in salt caverns. These are created by injecting fresh water or water with low salt content into a well down to a salt geological layer, with the extraction of salt-saturated brine. The caverns measure between 50 and 100 metres in diameter and up to several hundred meters tall where the salt formation is thick enough. Salt caverns are not lined, as the salt itself acts as a sealant. This type of storage is suitable for storing hydrogen at extremely high pressures where the salt layer is deep enough. The second way to store large quantities of hydrogen is to inject pure hydrogen or a hydrogen-methane mix into porous rock, in a depleted oil or gas field, or an aquifer. The hydrogen content may vary from a few per cent to 100 per cent. Reservoir and biochemical testing/modelling are to be performed accordingly. The hydrogen-methane mix can be withdrawn and injected into the network. Alternatively, hydrogen can be separated from methane at the well head, for example using pressure swing adsorption technology. Hydrogen can also be stored underground by converting it into a liquid carrier, such as ammonia, which can then be stored in a Lined Rock Cavern. A liner is required to prevent contact between ammonia and water. The pressure and temperature are adapted to optimise the entire supply chain. The advantage of using ammonia is that proper storage conditions can be fulfilled without the need for excessive pressure or temperature. Lastly, hydrogen can be stored underground by directly injecting it into a Lined Rock Cavern. This may take the form of compressed storage (gaseous hydrogen) or cryogenic storage (liquid hydrogen), the choice once again depending on the supply chain as a whole. A liner is required owing to extremely high pressures or extremely low temperatures. It should be noted that storing hydrogen in a Lined Rock Cavern involves a few technical difficulties that have yet to be resolved. These four underground hydrogen storage techniques differ in terms of their technology readiness level (TRL) and cost. All four will likely be required in the coming years to satisfy the needs of a booming market.

Rockburst Inducement Mechanism and Its Prediction Based on Microseismic Monitoring

The rockburst disaster in the hard rock caused by excavation and unloading of deep underground caverns threatens the safety of engineering construction. In recent years, the microseismic monitoring technology, which can dynamically monitor the whole process of progressive failure of rock mass in real time, has been widely used in rockburst monitoring and early warning of underground engineering. In view of the slight rockburst in local surrounding rock during the excavation of underground powerhouse of Huanggou Pumped Storage Power Station, a rockburst microseismic monitoring system is constructed. And through the analysis of the temporal and spatial activity of microseisms during the monitoring period, the potential risk areas of rockbursts are identified and delineated. The monitoring results show that the microseismic system can effectively capture the blasting and microseismic signals during construction. The microseismic activity is closely related to the intensity of field blasting disturbance. The potential risk areas of rockburst are the upstream side arch shoulder and the intersection between lower drainage corridor and workshop installation room. The research results can provide technical support for later excavation and support of underground powerhouse caverns of Huanggou Hydropower Station.

Rockburst Precursors and the Dynamic Failure Mechanism of the Deep Tunnel: A Review

With the rapid development of underground caverns in the fields of hydraulic engineering, mining, railway and highway, the frequency, and intensity of rockburst and dynamic instability have gradually increased, which has become a bottleneck restricting the safe construction of deep caverns. This paper presents a review of the current understanding of rockburst precursors and the dynamic failure mechanism of the deep tunnel. Emphasis is placed on the stability of the surrounding rock of the deep tunnel, the rockburst prediction method, and the dynamic failure characteristics of the surrounding rock of the deep tunnel. Throughout the presentation, the current overall gaps in understanding rockburst precursors and the dynamic failure mechanism of deep tunnels are identified in an attempt to stimulate further research in these promising directions by the research community.

Influence of Discontinuities on Rock Failure under Blasting at Shuangjiangkou Hydropower Station

The underground caverns of Shuangjiangkou hydropower station are under complex geological conditions. During excavation, the stability of the tunnels is severely affected by problems, such as blasting impact and excavation unloading, resulting in abnormal deformation at different locations. On the basis of on-site measurement, the characteristics of rocks at the main powerhouse and the main transformer room are compared through dynamic tests, and a numerical model is established using discrete element method (DEM) to analyze the special influence of fault SPD9-f1 on the deformation after excavation. It is revealed that the surrounding rock of the main powerhouse has stronger impact resistance than that of the main transformer room and that the existence of fault SPD9-f1 accounts for the abnormal deformation. In this study, the failure characteristics and mechanism of surrounding rock deformation controlled by stress and fault are revealed, providing important references for the subsequent excavation and support design of underground projects.