High prestress truss cable support principle and its application in large cross section coal roadway

With the enlarge of cross section of roadway, the radius of plastic area and broken area increase, and the tensile stress and shear stress distributing in roof coal-rock layers relevantly increase, which induce support effect not obvious for ordinary bolt（cable）. While bounding point and support structure of the truss cable is in vertex angle of roadway, and supplies coal-rock layers in bounding area with the horizontal and vertical pressure, so it settles the support problems in large cross section coal roadway. From the point of view of mechanics, gave emphasis on the invalid mechanics of ordinary bolt （cable） in large cross section coal roadway and supported mechanics of prestress truss cable. The author successfully used this technique in Wuyang Mine, and had the huge economic efficiency and the social benefit.

Multi-factor influence of cross-sectional airflow distribution in roadway with rough roof

The wall surface roughness renders a significant impact on ventilation of roadways and cross-sectional wind speed distribution.Herein,the wall roughness(Ra)in the roadway has been defined theoretically.Moreover,three-center arched roadway models for different situations are established based on the normal distribution of roof roughness.The influence of inlet velocity,roof roughness and roadway height on wind speed distribution is systematically studied by using Fluent software.At Ra=0.1 m,the simulation results reveal that the wind speed is negatively related to the distance from the wall to the point where 80%of the central wind speed is reached(DA).Also,the wind speed distribution is significantly influenced by increasing the roof roughness.However,the wind speed distribution becomes asymmetric at Ra=0.2 m and 0.3 m.Furthermore,the low-speed area(v≤1 m/s)started to concentrate on the roof with the increase of roadway height.Overall,an Ra value of<0.1 m can reduce the influence of wall roughness on wind speed distribution of the roadway,which is suggested in practical applications.

Influence of anchorage length and pretension on the working resistance of rock bolt based on its tensile characteristics

In coal mining roadway support design,the working resistance of the rock bolt is the key factor affecting its maximum support load.Effective improvement of the working resistance is of great significance to roadway support.Based on the rock bolt’s tensile characteristics and the mining roadway surrounding rock deformation,a mechanical model for calculating the working resistance of the rock bolt was established and solved.Taking the mining roadway of the 17102(3)working face at the Panji No.3 Coal Mine of China as a research site,with a quadrilateral section roadway,the influence of pretension and anchorage length on the working resistance of high-strength and ordinary rock bolts in the middle and corner of the roadway is studied.The results show that when the bolt is in the elastic stage,increasing the pretension and anchorage length can effectively improve the working resistance.When the bolt is in the yield and strain-strengthening stages,increasing the pretension and anchorage length cannot effectively improve the working resistance.The influence of pretension and anchorage length on the ordinary and high-strength bolts is similar.The ordinary bolt’s working resistance is approximately 25 kN less than that of the high-strength bolt.When pretension and anchorage length are considered separately,the best pretensions of the high-strength bolt in the middle of the roadway side and the roadway corner are 41.55 and 104.26 kN,respectively,and the best anchorage lengths are 1.54 and 2.12 m,respectively.The best anchorage length of the ordinary bolt is the same as that of the high-strength bolt,and the best pretension for the ordinary bolt in the middle of the roadway side and at the roadway corner is 33.51 and 85.12 kN,respectively.The research results can provide a theoretical basis for supporting the design of quadrilateral mining roadways.