Test Study on Multi Tray Bolt in Gob-Side Entry Retaining Formed by Roof Cut and Pressure Releasing

In order to obtain satisfactory effect of control of roadway-side, there is a kind of multi tray bolt developed by numerical simulation and field test in gob-side entry retaining formed by roof cut and pressure releasing. After the installation, multi tray bolt experience two working process: the bolt bolting stage and the bolt automatic pre tightening stage. Bolt rod body stress more uniform with the increase of the number of small trays and bolt forms the pre tightening force between the small tray and the large tray with the goaf roof caving by numerical simulation. Through the resistance drawing power field test of multi tray bolt, the resistance drawing power of 2113 multi tray bolt is 8.2t and 2113 multi tray bolt is 9.8t, So it is determined that 2113 type multi tray bolt is used for the field application. The roof-floor displacement is 0 mm and the two side maximum displacement is 12 mm according to the field application effect. The 2113 multi tray bolt can meet the requirement of controlling the roadway along the empty tunnel and can achieve satisfactory results.