Geotechnical Engineering Online Library

The 2008 Wenchuan earthquake resulted in a large number of fatalities and caused significant economic losses. Thousands of landslides, many of which are very large, were triggered by the earthquake. A majority of catastrophic landslides were distributed along the central Longmenshan fault system, at the eastern margin of the Tibetan Plateau. Some of the landslides resulted in sudden damming of rivers causing flooding, which in turn induced secondary sliding disasters. Among the most significant landslides, the Daguangbao landslide was the largest in volume with the maximum thickness. For this, a numerical model of the Daguangbao landslide, using the material point method (MPM), was developed to simulate the interaction of the seismic loads imposed on the slope. The numerical results then are compared with the post-earthquake profile. As a consequence of the landslide, a nearly vertical head scarp with a maximum height of about 700 m was generated. This is considered as a high risk situation that requires constant monitoring and evaluation. Finally, we propose a methodology based on Bayesian networks (BNs) to manage the risk associated with the stability of the rockwall at the Daguangbao landslide site.

With the third innovation in science and technology worldwide, China has also experienced this marvelous progress. Concerning the longwall mining in China, the “masonry beam theory” (MBT) was first proposed in the 1960s, illustrating that the transmission and equilibrium method of overburden pressure using reserved coal pillar in mined-out areas can be realized. This forms the so-called “121 mining method”, which lays a solid foundation for development of mining science and technology in China. The “transfer rock beam theory” (TRBT) proposed in the 1980s gives a further understanding for the transmission path of stope overburden pressure and pressure distribution in high-stress areas. In this regard, the advanced 121 mining method was proposed with smaller coal pillar for excavation design, making significant contributions to improvement of the coal recovery rate in that era. In the 21st century, the traditional mining technologies faced great challenges and, under the theoretical developments pioneered by Profs. Minggao Qian and Zhenqi Song, the “cutting cantilever beam theory” (CCBT) was proposed in 2008. After that the 110 mining method is formulated subsequently, namely one stope face, after the first mining cycle, needs one advanced gateway excavation, while the other one is automatically formed during the last mining cycle without coal pillars left in the mining area. This method can be implemented using the CCBT by incorporating the key technologies, including the directional pre-splitting roof cutting, constant resistance and large deformation (CRLD) bolt/anchor supporting system with negative Poisson's ratio (NPR) effect material, and remote real-time monitoring technology. The CCBT and 110 mining method will provide the theoretical and technical basis for the development of mining industry in China.

The progress of soft rock mechanics and associated technology in China is basically accompanied by the development of mining engineering and the increasing disasters of large rock deformation during construction of underground engineering. In this regard, Chinese scholars proposed various concepts and classification methods for soft rocks in terms of engineering practices. The large deformation mechanism of engineering soft rocks is to be understood through numerous experiments; and thus a coupled support theory for soft rock roadways is established, followed by the development of a new support material, i.e. the constant resistance and large deformation bolt/anchor with negative Poisson's ratio effect, and associated control technology. Field results show that large deformation problems related to numbers of engineering cases can be well addressed with this new technology, an effective way for similar soft rock deformation control.

This paper attempts to present the findings involving rockbursts classification, rockburst failure criteria, and related control measures. Experimental investigations were performed using the strainburst testing machine and impact-induced rockburst testing machine. According to the stress paths and experimental methods, rockbursts were classified into two major groups, i.e. the strainbursts and impact-induced bursts. The mechanisms and criteria of rockburst obtained from experimental investigations were discussed. Then, the developments of constant-resistance and large-deformation bolt (CRLDB), which can adapt itself to the external loading at a constant resistance by elongating continually, were introduced. The deformation energy of country rocks with large deformation can be absorbed by CRLDBs. Finally, the principles and the experimental results for control and prevention of rockburst using the CRLDBs were presented.

To better understand the mechanism of the strength weakening process of soft rocks in deep mines after interacting with water, a self-developed experimental system, Intelligent Testing System for Water Absorption in Deep Soft Rocks (ITSWADSR), is employed to analyze the hydrophilic behavior of deep calcareous shale sampled from Daqiang coal mine. Experimental results demonstrate that the relation between water absorption and time can be expressed by power functions, and the soakage rate decreases while the soakage increases with time. In order to quantitatively calculate the weight coefficients of the influential factors for water absorbing capacity of rocks, a series of testing methods are adopted, including scanning electron microscope (SEM), X-ray diffraction and mercury injection test. It is demonstrated that the effective porosity has a positive correlation with the water absorbing capacity of rocks and the contents of illite and illite/smectite. The initial water content presents a negative correlation with the water absorption capacity of rocks. According to the absolute value of weight coefficients of various influential factors, the order of magnitude from high to low is captured: initial water content, illite, illite/smectite formation (S=5%), and the effective porosity. After water absorption tests, uniaxial compressive strength (UCS) tests were performed on rock specimens allowing a linear relationship between the UCS and the water content of rock to be established, indicating that the strength of calcareous shale decreases linearly with the increasing water content.

Over the last decades, people from almost all over the world have realized that it is necessary to quickly develop strategies for the control and reduction of greenhouse gases (GHG) emissions. Among various GHGs, carbon dioxide (CO2) is the most abundant GHG. Its underground storage involves less risk and lower levels of dangerousness. The paper briefly describes the most effective technologies available in the market for background processes to storage (capture and transport) CO2, as well as the more secure solutions for its storage, in particular for the geological storage in carboniferous formations. This paper also outlines the methodologies for the risk assessment involved in storage of CO2, with a particular focus on cases where the injection is made into unminable coal seams and in abandoned coal mines. Methodologies used for risk analysis are described in detail with particular emphasis on Bayesian network (BN). Some applications regarding the risk assessment of CO2 injection processes and CO2 storage in carboniferous formations and contamination of aquifers are presented and analyzed. Finally, based on the applications of BN, several conclusions are drawn.

The most common method used to describe earthquake activity is based on the changes in physical parameters of the earth’s surface such as displacement of active fault and seismic wave. However, such approach is not successful in forecasting the movement behaviors of faults. In the present study, a new mechanical model of fault activity, considering the shear strength on the fault plane and the influence of the resistance force, is established based on the occurrence condition of earthquake. A remote real-time monitoring system is correspondingly developed to obtain the changes in mechanical components within fault. Taking into consideration the local geological conditions and the history of fault activity in Zhangjiakou of China, an active fault exposed in the region of Zhangjiakou is selected to be directly monitored by the real-time monitoring technique. A thorough investigation on local fault structures results in the selection of two suitable sites for monitoring potential active tectonic movements of Zhangjiakou fault. Two monitoring curves of shear strength, recorded during a monitoring period of 6months, turn out to be steady, which indicates that the potential seismic activities hardly occur in the adjacent region in the near future. This monitoring technique can be used for early-warning prediction of the movement of active fault, and can help to further gain an insight into the interaction between fault activity and relevant mechanisms.