Manchao He

Studies on classification, criteria and control of rockbursts

Abstract 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.

Risk assessment of CO2 injection processes and storage in carboniferous formations: a review

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.

Hydrophilic and strength-softening characteristics of calcareous shale in deep mines

Abstract 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 (Sxa0=xa05%), 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.

A new early-warning prediction system for monitoring shear force of fault plane in the active fault

Abstract 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 6xa0months, 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.