| With the implementation of major national strategies such as transportation power and the Belt and Road Initiative,China has become the country with the largest number,scale and difficulty of tunnel construction in the world.The tunnel construction process is often faced with complex geological conditions,water and mud burst,surrounding rock collapse and other major disasters occur from time to time,which often cause casualties,property losses and construction delays.After the disaster occurs,the cave is often not equipped with the conditions for disaster disposal.At the same time,the pre-grouting work needs to be carried out in front of the face of the palm.Ground grouting is an effective technical means to control water gusher instability disaster and bad geological prereinforcement in tunnel engineering.It has the advantages of low construction risk coefficient,low construction difficulty and saving construction period.Long distance directional drilling is needed for ground grouting.The problems of low rock breaking efficiency and poor drillability of hard rock stratum are faced in the implementation of traditional kilometer directional drilling.Therefore,this paper,aiming at a new type of composite percussion drill in directional drilling equipment,based on the continuous discontinuous analysis method(CDEM),carried out a systematic study on the mechanism of composite percussion rock breaking in kilometer directional drilling,the optimization of drill tooth parameters and the optimization analysis of drilling parameters.Supported by the National Key Research and Development Program(2022YFC3005600),the following achievements have been achieved:(1)In terms of rock breaking mechanism of compound impact,based on the rock breaking theory of single drill tooth intrusion under axial impact and torsional impact,the rock breaking law of PDC single drill tooth intrusion under compound impact is analyzed.A simplified drill bit motion model considering drill string system is established.Based on the simplified model,rock breaking mechanism of drill bit under axial impact,torsional impact and compound impact is revealed.(2)In terms of numerical calculation model,based on the basic theory of BlockDyna and PDyna modules in GDEM software,a FEM-DEM coupling model based on shared nodes is established.This model organically combines the advantages of finite element and discrete element,and can realize the precise transition of solid materials from continuous media to discontinuous media.(3)In terms of parameter optimization of drill teeth,the rock breaking model of single drill teeth under compound impact was established,and the simulation of rock breaking process of single drill teeth by compound impact was realized through JavaScript secondary development.On this basis,different cutting depth,forward Angle of drill teeth and impact velocity amplitude were optimized.(4)In terms of drilling parameters optimization of the whole bit,based on the core algorithms such as the single point integration algorithm,virtual quality algorithm and unit dissolution algorithm in the continuous-discontinuous analysis method(CDEM),through the secondary development of JavaScript,PDC full bit compound impact rock breaking process simulation was realized.The law of rock breaking by combined impact of whole bit is summarized and the influence of axial impact velocity and impact period on rock breaking efficiency is analyzed.Based on a diversion inclined well project in No.2 construction tunnel of Tiantaishan pumped storage power Station in Zhejiang Province,some optimization suggestions are made on its drilling parameters.(5)In combination with the realization of directional drilling and grouting integration equipment,through the investigation of the existing data,the engineering requirements and equipment structure are analyzed,the packer device that can realize the integration of grouting is improved,and a structural design that can realize the integration of drilling and injection is proposed.The structure can realize the free setting of different positions in the drilling hole by adjusting the ground grouting pressure,so as to realize the integration function of sealing the drilling hole and drilling and injection. |
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