Development Of Expandable Control Anchor And Study Of Its Performance

The expansive control type anchor rod is developed and developed based on the principle of the deformation of the soft soil layer under the pressure of injection.A new type of anchor structure expansion control greatly improves the bearing capacity of inflatable anchor is too small,the large displacement of the shortcomings of the structure mainly by squeezing device,expansion device,transmission device and control circuit of four parts,the main structure features in expansive soil compaction device package expansion device lateral pressure or expansion device the hydraulic anchor(along the axial section of steel tube,etc.)by squeezing device in contact with the peripheral soil extrusion,resulting in anchoring force.Control type bolt has the advantages of free grouting,anchoring force can be controlled and completely recycling and expansion.However,in the actual construction process,a large number of grouted stone bodies remain in the soil,which is not only a waste of resources,but also unsafe.It is not only an important theoretical and practical guiding value but also a good economic benefit for the research of the expanded control type anchor rod.First of all,based on the research status of the expansion control bolt with the end of the baffle and the expansion control bolt with the side guard plate,this paper puts forward the specific requirements for the performance of each component.All components are selected from different materials or different structures were analyzed and compared in a series,fully meet the excellent mechanical properties,simple component production conditions,determine the selection of materials and fabrication method of the final structure,each component of the anchor.Then,starting from the full-scale field test,through the soft soil pullout test verifies the rationality of structure control expansion bolts,anchor pullout control in the whole process that is expanding,squeezing the optimized device effectively solves the expansion device and soil contact problem,fundamentally changed the way dowel bolt.On the basis of a series of verification tests,the results show that the control type anchor structure reasonable expansion force compared with ordinary grouting bolt,with end baffle type expansion bolt and control with side plate has greatly improved the ultimate bearing.Then a series of comparative experiments,experimental results show that the expansion of the main influence factors of bearing capacity of anchor control air pressure,depth,anchorage length and compacting steel sheet thickness,one of the most significant influencing factor for inflation pressure,a certain ratio of growth;then the length of anchoring section,bearing there is a linear relationship between the force and the length of anchoring section;increasing the buried depth and soil compaction steel sheet thickness on the bearing capacity of anchor increase to a certain extent,but the effect is not significant.Based on field test,the expansion anchor mechanism and load control type anchor displacement curve is analyzed in detail,the expansion force control type anchor process is divided into three stages,elastic stage,plastic stage and failure stage.The third stage bolt and common grouting bolt are obviously different,specific performance in the common grouting anchor after destruction of the bearing capacity of anchor in the control disappeared,and after the failure of expansion,there are still up more than 86.14% of the residual strain.Finally,by simplifying the anchor mechanics model,based on cavity expansion theory,deduced the expansion anchor bolt control simplified calculation formula,the calculation results were compared with the experimental measured values,obtained errors are within 10%,to verify the reliability of bearing capacity calculation formula.On the basis of the above,the failure mode of the expansion control bolt is summarized.