Preparation And Static Test Of Piston-type Self-expanding Bolt Rod

With the increasing demand for mineral resources,deep resource exploitation has become an inevitable trend.Deep high ground stress,strong mining disturbance and other engineering environment can easily induce large deformation of surrounding rock,rock burst,goaf instability and other engineering rock disasters.In deep complex environment,conventional bolt support is easy to corrode,brittle fracture of rod body,cracking and bending of tray,and failure of anchor head;The existing energy absorbing bolts still have the defects of high load and small displacement or low load and large displacement.Therefore,the research and development of effective supporting elements with large deformation and high anchoring force is of great significance for the stability control of deep complex rock mass.Through literature review,theoretical analysis,indoor experiment and field experiment,this paper carried out the design of new piston type self expanding bolt,optimization of bolt structure parameters,static performance test,and finally carried out the comparison and verification of bolt anchoring performance based on field experiment.The main research work is as follows(1)The piston type self expanding bolt is designed,and the indoor preparation of the piston type self expanding bolt is carried out.The working mechanism and large deformation characteristics of the piston type self expanding bolt are analyzed.(2)The pull-out test was carried out to measure the strength of self expanding piston bolt;Based on the outer tube method,the expansion pressure of self expanding anchorage agent was measured,and the friction force of piston body was measured.(3)The results show that the amount of self expanding anchoring agent,sleeve taper and material properties are the main influencing factors of bolt sliding resistance.The sleeve selection test and the static performance optimization test of bolt with different charging length are carried out,and the optimal parameters and parameters of three types of piston self expanding bolt are obtained It is verified that the piston self expanding bolt has the static characteristics of large deformation and medium high anchoring force.(4)Relying on Hongling lead-zinc mine,the active pull-out test of anchor rod was carried out,the on-site installation method of piston type self expanding anchor rod was established,the anchoring characteristics of piston type self expanding anchor rod with large deformation were verified by multiple loading method,and the optimal structural parameters of piston type self expanding anchor rod under actual working conditions were determined.The indoor and field test results show that the displacement of the piston type self expanding bolt developed in this paper can reach 450-500 mm,the sliding resistance of the bolt body with 16 mm rebar can reach 90-100 kN,the sliding resistance of the bolt body with 18 mm rebar can reach 110-120 kN,and the sliding resistance of the bolt body with 20 mm rebar is about 100 kN when drilling 42 mm and 1.8 m long casing,If the length of drilling hole and charge is changed to 20 mm,the piston type self expanding bolt can reach 180-200 kN.