Study On The Manufacture And Properties Of An Expandable Bolt's Anchoring Layer

Expandable bolt, which has a unique anchoring mechanism, is one kind of friction bolt. It is different from traditional bolt in anchoring action, overcoming the shortage of common bolts--bad adaptability to soft rock and large deformation tunnel. It has lower cost, excellent anchoring capability and can be called back then reused. So the study has both an important academic meaning and engineering meaning, as well as good social and economic values.The main work of the author is to manufacture expandable bolt and study its various capabilities. Firstly, according to dimensions of expandable bolt and the largest expansion diameter, the author designed the C section shape of anchoring layer; then gathered and analyzed all plastic molding methods of the C section steel. After comparing, the author decided to machining the C section steel composing the anchoring layer of the new bolt with cold roll-forming method, designed the forming process, made a set of roll forming dies and manufactured the C section steel.Secondly, to guide the design and manufacture of expandable bolt, the author analyzed the deformation of the bolt under the inner pressure and contact stress between the bolt and the rock with the FEM software ANSYS. The main work: (1) analysis of the expansion capability of the bolt(including analyzing the expansion capability of the airproof layer, the sliding and deformation of C ring composing the anchoring layer, to obtain the largest expansion diameter and the largest inner pressure that the bolt can bear).(2) analysis of the impact of rock diameter on the contact stress(getting the rock diameter at which the stress between the rock and the bolt will change little, to prepare for the analysis of bolt anchoring capability, as well as for the bolt distributing design).(3) analysis of the anchoring capability of expandable bolt(analyzing the relation between the contact stress and inner pressure under different anchoring diameter, getting the largest contact stress the expandable bolt can supply).(4)analysis of the bolt body's drawing resistance of the expandable bolt(inspecting whether the strength of the bolt body is enough under different anchoring diameter while anchoring capability is available.)The numerical simulation show that: the expandable bolt can support the wall rock effectively and overcome the shortages of fitting badly to soft rock and large deformation tunnel of common bolts. Its structure is reasonable and its performance is credible.