Outburst orientation of sandstone under gravitational field

The characters of outburst sandstone in rocks from Yongchuan Coal Mine were studied on the base of experimental investigation on its physical and mechanical properties. The outburst orientation of sandstone at the-350 m horizontal in this coal was analyzed and the criterion of outburst orientation was proposed. The results show that outburst sandstone has the physical characteristics of big porosity and big blowhole volume, and the mechanical characteristics of low Young's modulus, low strength, and not easy to produce plastic deformation. The launch process of rocks and gas outburst has uniformity with the rockburst characteristic, and the rockburst theory can be used to study the outburst orientation of sandstone, which depends on many kinds of factors. In these factors the mechanical factor is primary. The assessment method of outburst orientation of sandstone was established based on the energy criterion, strength criterion, and impact orientation criterion.