Research On Application Of Shaped Charge Technology In Blasting Of Subway Shield Boulders

In recent years,the construction of subways in our country has developed rapidly.The shield tunneling method boasting assured safety and high efficiency,is widely used in subway construction.However,the complex and changeable geological conditions often bring difficulties to the construction with shields.Among them,the boulders are considered typically unfavorable.In the shield construction process,the boulders can easily cause adverse effects.In order to eliminate the hidden trouble brought by the boulders,the drilling and blasting method is often applied to treat the boulders in the project.However,the vibration shock generated by the blasting may damage the shield machine or the adjacent buildings.Because of their random distribution,boulders are not easily found.Thus,there may be omissions in the survey process.When encountering these without pretreated boulders during the construction process,it is usually impossible to employ blasting method,for the shield machine,adjacent to the boulders,will be affected by the blasting;but rather,other comparatively more conservative measures are adopted to deal with the boulders.These measures are,however,often inefficient and costly.Therefore,it poses great challenges to efficiently tackle boulders without affecting the shield machine and surrounding buildings.In view of the special working conditions of encountered boulders in the shield tunneling process,combined with the "Research on Xiamen Metro Shield Boulders and Prominent Rock Blasting Technology",proposes a new technology for the tackling boulders,i.e.shaped charge blasting method.More specifically,detonated by shaped charge with less explosive,the accumulative effects of the energy are produced,which can improve the crushing effect on the rock while reduce detriment to the surrounding area.In this paper,through theoretical analyses,field tests and numerical simulation methods,exploratory research on the application of shaped charge technology in boulders processing was conducted.The research contents mainly include:first,the principle of the action of shaped charge,the jet formation theory and the penetration theory are introduced.Second,through field tests,verifying the feasibility of shaped charge technology to deal with boulders,the blasting treatment of the granite was carried out by means of a shaped perforation projectile.It can be seen from the results of the drilling and coring based on the blasting treatment of the shaped charge that the block size and RQD value meet the passing requirements of the shield machine.Compared with traditional columnar charges,the single-hole dosage can be reduced by more than 60%.Finally,the process of forming and penetrating the rock target by numerical simulation was simulated and analyzed.The effects of the coating cone angle,wall thickness,bore diameter and blast height on the rock fragmentation were studied.On the basis of orthogonal test,evaluated by the criteria,i.e.the depth of penetration and the number of cracks,structural parameters of shaped charges were optimized.