There are large numbers of roadway intersections constructed annually in Chinese coal mines with various geometries, such as, three-way intersection, four-way intersection, two dimensional roadway intersection and three dimensional roadway intersection, etc. With continually increasing the depth of cover, the stability of roadway intersection is susceptible to ground control problems due to inherently wide roof spans and complicated intersection geometry used. The paper presents the comprehensive results obtained from the field monitoring and numerical modeling related to the stability of the roadway intersection in coal mine. Firstly, the basic geomechanical behavior of roadway intersection has been determined by using underground monitoring in great depth of cover, and then the numerical modeling is conducted to determine the stability behavior of intersection associated with the different geometrical shapes, the depth of cover, and construction sequence and direction on the stability of intersection. The results clearly indicated that large span of the opening and great depth of cover are major factors, which may influence the stability of the roadway intersections. Comparing different geometrical shapes of the two-dimensional intersections, the most unstable one is the cross-intersection, and results indicated that the construction sequence and direction are also sensitive factors for the stability of roadway intersection.
From the statistical data, it is noted that the roof failure mainly occurred around the large span of underground opening, and the situation is getting worth, when the complex geometrical structures and deep mining conditions are encountered. This paper is describes the stability and failure characteristics of intersection on the basis of literature review and study of the stability and failure behaviour of different geometrical structure of intersection, which commonly used in underground of coal mine in China, associated with various depths of cover using numerical simulation.
It is noted that the geometrical shapes used in China coal mining industry is much complex, comparing with major coal mining countries in overseas, such as Australia and USA. With increasing the depth of cover, it is susceptible to ground control problems due to the complex geometries of underground structure.
Stability of underground intersection had been paid attention previously, even in the shallow condition. The investigations had been conducted to study the structural characteristics, stability and failure bahaviour in the shallow condition by former US Bureau of Mine (Hanna, 1991).
In 1976, Balachandra studied the stability of intersection using underground monitoring and computer simulation.
The department of mining engineering from West Virginia University studied the stability of three-way intersection with different geometrical parameters, and it found that the tensile stress is the main reason to cause the failure of the intersection. Comparatively, the threeway intersection is more likely having shear failure than the cross intersection. It is concluded that the tensile and shear failure on the roof strata increased with the reducing of angle between two roadways (Peng, 1978).
The department of mining engineering from University of Wollongong also studied the stability of the T-intersection (Singh, 2001).