Abstract
There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata; thus, the roof is prone to delamination and falling, and it is difficult to control the surrounding rock when developing roadway in such rock strata. In deep mining, the stress environment of surrounding rock is complex, and the mechanical response of the rock mass is different from that of the shallow rock mass. For composite-roof roadway excavated in deep rock mass, the key to safe and efficient production of the mine is ensuring the stability of the roadway. The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine (Shanxi Province, China). On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions, the roof is divided into an unstable layer, metastable layer, and stable layer. The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure. A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rebar bolts and highly prestressed cable bolts is put forward. The support technology provides good application results in the field. The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.
Highlights
Coal-measure strata have a typical layered characteristic
The composite roof roadway is supported by cable bolts, and the surrounding rock is stable in the initial stage
Theoretical support and technical guidance were provided for the stability control of a roadway under similar geological conditions
Summary
Coal-measure strata have a typical layered characteristic. In the process of rock formation, owing to the sedimentary environment and geological tectonic movement, the lithology of the roof changes alternately in the vertical direction and structural planes, such as bedding, fissures, and weak interlayers, form a layered roof with a complex structure; that is, a composite roof (Peng and Meng 2002). The breaking rate of cable bolts in some coal mines is high, and roadway roof fall accidents still occur. There is an urgent need to investigate the failure mechanism and control technology of the surrounding rock of a deep roadway, so as to guarantee safety in deep coal development. The mining depth of most of the mining districts in the coal mine is more than 500 m, and the main roadways adopt cable bolts as primary support without rebar bolts. Compared with the case for shallow mining (at depths less than 400 m), the breaking rate of cable bolts is higher, the deformation of the roadways is larger, and the phenomena of roof fall and rib spalling are more common. A field application of the newly proposed support scheme is reported, and the support effect is evaluated
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