| The rapid development of economy and society brings about a faster pace of life,and also put forward a higher demand for the convenience of transportation.Under the background that the country is vigorously expanding the space for infrastructure construction and increasing investment,urban subways,as well as highway and railway construction projects in full swing across the country spawn a large number of tunnel projects.Full-face tunnel boring machine(TBM)is widely used due to its significant construction advantages.However,with the continuous advancement of tunnel construction,the hard rock environment begins to increase,and the disc cutter therefore frequently failed,resulting in low tunneling efficiency and high construction costs.Therefore,it is of significant engineering significance and economic value to study the load and wear reduction technology of disc cutter to improve the tunneling efficiency of hard rock roadways.For this reason,the rock breaking method of abrasive slurry jet(ASJ)assisted disc cutter was proposed,thereby forming rock breaking system of water jet-cutter head based on hydraulic and mechanical combining.And the method of combining theoretical analysis,numerical simulation and laboratory test was used to study the effect of ASJ system parameters and its position parameters relative to disc cutter on the combined rock breaking performance.Based on this,the structural design scheme of water jet-cutter head was put forward,and the relevant cutting performance analysis was carried out,which provides a reference for the engineering popularization and application of the rock breaking system of water jet-cutter head for hard rock TBM.Based on the theory of rock fragmentation,rock breaking mechanism of disc cutter and breaking process were analyzed,and the load characteristics of the disc cutter were studied.The stress distribution model of single abrasive slurry particle and jet beam impacting rock surface was established sequentially on the basis of Boussinesq problem,elastic mechanics and fluid mechanics.And combined with the relevant theory of rock fracture mechanics,the stress intensity factor expression of type II crack was deduced according to the principle of maximum circumferential stress.Then,the load reduction percentage model of disc cutter in the process of ASJ assisted was established.Taking the average depth of the kerf as the index,the effect of the composition ratio parameters of ASJ(abrasive concentration,high molecular polymer concentration)on its cutting performance was analyzed,and then combined with the specific energy index,the effect of working parameters(jet pressure,jet target distance,and transverse speed)was studied.On this basis,the effect degree and significance level of each working parameter were clarified by orthogonal analysis method,and the optimal working parameter combination was mastered.At the same time,the regression model between the kerf depth and each working parameter was established.On the basis of replacing the ASJ cutting process with regular kerf,the effect of kerf depth and its relative lateral distance to disc cutter on the combined rock breaking performance was studied from multiple dimensions combined with its cutting load,specific energy and temperature.And the action mechanism of the cutting speed of disc cutter during this period and its interaction with the above parameters were analyzed,and the adjustment direction of kerf parameters in the process of matching disc cutter with larger installation radius was obtained,which revealed the optimal layout strategy of the ASJ relative to the disc cutter.Based on ANSYS/LS-DYNA,the numerical model of rock breaking with ASJ assisted disc cutter was established,and the combined rock breaking mechanism was discussed.Meanwhile,the action mechanism of kerf parameters and cutting speed of disc cutter on stress evolution in rock was analyzed.On this basis,a more comprehensive analysis of the effect of relevant parameters on the combined rock breaking performance was carried out,and the optimal range of kerf depth and lateral distance suitable for disc cutter with various installation radius was obtained,and a regression model for cutting load of disc cutter was also established,which provides a theoretical basis for the structural optimization design of water jet-cutter head.Combined with the disc cutter arrangement scheme of rock tunneling project with similar uniaxial compressive strength,a simple cutter head structure that can be used to simulate tunneling was designed,and the arrangement scheme of ASJ nozzles on it was proposed.Then,a series of cutting tests on concrete rock specimens were carried out,and the influence of compressive strength,jet pressure,rotational speed and propulsion speed during this period and the correlation between various factors were discussed,which revealed the weakening effect of ASJ on the torque and propulsion resistance of the cutter head and dust reduction performance.The dissertation has 114 figures,37 tables,and 211 references. |
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