Automatic roadway formation method by roof cutting with high strength bolt grouting in deep coal mine and its validation

Surrounding rock control is a big challenge in high stress mining roadway of deep coal mine.To address this issue,Suncun Coal Mine,the coal mine with the largest mining depth in China,is taken as engineering background to monitor and analyze the traditional gob side entry driving with bolt and cable supporting.The result shows that the surrounding rock deformation is large and the surrounding rock damage scope is wide.Most of the bolt body is in the strength degradation zone,which makes it difficult to play its bolting role.The stress of anchor cable is large,which is close to the ultimate bearing capacity of the anchor cable.For the above problems,the numerical tests of different pillar width,in situ stress level,strength of roof surrounding rock and roof cutting height were systematically carried out.The quantitative evaluation indexes such as roof stress release rate,side abutment pressure increase rate and surrounding rock deformation control rate were established.The variation law of mining pressure and the surrounding rock control mechanism in both the automatically formed roadway by roof cutting and traditional gob side entry driving under various factors were compared and analyzed.On this basis,the automatic roadway formation method by roof cutting with high strength bolt grouting in deep coal mine was proposed.This method improves the integrity of the roof surrounding rock by high strength bolt grouting and cuts off the stress transfer between the goaf roof and roadway by roof pre splitting crack,making the roadway in the stress reduction zone.In order to validate the rationality of this method,a model test was carried out by using the geomechanical model test system independently developed.The average stress of surrounding rock in automatically formed roadway by roof cutting with high strength bolt grouting is 20.8% lower than that in gob side entry driving,and the surrounding rock deformation is 45.1% of that in gob side entry driving.The effect of stress release and surrounding rock control in automatically formed roadway by roof cutting with high strength bolt grouting is obvious.Based on the above research,the corresponding engineering recommendations were put forward and the method was applied to the 2215 working face of Suncun Coal Mine.The field application and monitoring show that the method can effectively control the deformation of surrounding rock and achieve coal mining with no pillar.