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In order to solve the problem short mining distance, slow driving speed, conflict of exploitation and mining of working face in Jining No.2 Coal Mine, pier column pressure testing, mechanical model, theoretical calculations and field test methods were applied to put forward innovatively pier structure gob-side entry retaining. The results showed that the pier column could meet the strength requirements, the required for cutting the top pressure was 21.96 MPa. When the sand and stones weight ratio in steel pipe was 1.0 : 1.6, the effect of pier column gob-side entry retainiuy was the best, the pier column not only could maintain a higher strength, but also had good scalability. The rock pressure observation showed that the maximum roof to floor convergence was 596 mm, the maximum rib to rib convergence was 299 mm, which could ensure the stability of gob-side entry retaining. [ABSTRACT FROM AUTHOR]

By using of theoretical analysis method, the structural mechanical model of roadway driving along next goaf was established, and the width expression of internal stress fields was derived, the rational position of roadway driving along next goaf was determined and the deformation of the surrounding rock was also calculated. Meanwhile, the parameter of roadway was given. At last, the control technology of roadway driving along next goaf in thick seam was put forward, and the first is high strength and pretension bolt supporting to control roof,the second is decreasing bolt interval of roadway gob-side, the last is secondary supporting to the integrated coal side of roadway, based on this, the bolt supporting parameter was determined by system information design method, and it is successfully applied to engineering practile. [ABSTRACT FROM AUTHOR]

According to the situation of gob-side entry retaining with the large and uneven deformation and poor support effects, took gob-side entry retaining in Qinxin colliery as engineering background, dealt with the numerical simulation analysis the relationship between support inside roadway, surrounding rock deformation and stress distribution, and the obtained support mechanism inside roadway of gob-side entry retaining are as follows: with the application of support with high resistance and yielding, increasing carrying capacity and deformation resistance of surrounding rock in roadway, adapting to large deformation and stress adjustment. The developed support technologies inside roadway of in gob-side entry retaining are:(1) basic support: using high-strength bolt and anchor support owning high pre-stress force, increasing carrying capacity of surrounding rock and adapting to large deformation; (2) reinforced support: within a certain range behind working face, in gob-side entry retaining, the hydraulic support with high resistance and yielding is used to strengthen roof and floor support, which means that in the intense stage of roof breakage and stress adjustment of surrounding rock of gob-side entry retaining, the hydraulic support can be used to support the roof and floor effectively and reduce the rotating, sinking of roof and floor heave, maintaining the stability of surrounding rock in gob-side entry retaining; (3) after the surrounding rock deformation stability in gob-side entry retaining, the hydraulic support used as reinforced support can be removed. [ABSTRACT FROM AUTHOR]