| In order to solve the difference between the impact action of the inner ring roller cutters and the outer ring roller cutters of the large cross-section drilling machine,resulting in the mismatch of the drilling parameters of the inner ring roller cutters and the outer ring roller cutters,and the lack of a method to quickly evaluate the drilling efficiency of the large cross-section drilling machine at present,In order to reduce the mismatch of drilling parameters,it will cause low service life and abnormal loss of TCI roller cutters,so as to improve the rock drilling efficiency of roller cutters and reduce the rock drilling cost.We need to optimize the drilling parameters of the roller cutters of the large section drilling machine and evaluate the rock drilling efficiency.Firstly,taking MSJ5.8/1.6D mine shaft boring machine as an example,this paper studies the movement,stress and rock drilling mechanism of large section shaft drilling machine,roller cutters and cutter bits,analyzes the operation process of roller cutters and the basic law of rolling rock breaking,expounds the process of rock deformation and crushing,and calculates the stress of roller cutters,Finally,the difference of rock drilling mechanism between inner ring roller cutters and outer ring roller cutters is analyzed.Then,the rolling mechanism of the inner ring roller cutters and the impact mechanism of the outer ring roller cutters are studied;The drilling speed and specific energy of inner ring roller cutters under different drilling pressure and rotating speed are studied;And through the minimum specific energy method of the roller cutters and the impact effect test of the outer ring roller cutters,the optimal drilling pressure and optimal speed of the large section drilling machine are discussed respectively,and the optimization method and theory of the drilling parameters of the large section drilling machine are obtained.Finally,by analyzing the rock drilling efficiency evaluation mechanism of large section shaft drilling machine with roller cutters based on characteristic particle size theory,the theoretical basis of characteristic particle size is formed,and through the linear rock breaking test of conical roller cutters breaking marble and granite,as well as the industrial test of a slag chute project on the left bank of Baihetan Hydropower Station,Verify the reliability of characteristic particle size theory and the feasibility of implementation.The following conclusions are obtained through the study:1.Theoretical research:the main rock drilling mechanism of inner ring roller cutters is to squeeze and shear rock,and the impact effect of outer ring roller cutters is more significant while squeezing and shearing rock;At the same time,there is no obvious distinction between inner ring roller cutters and outer ring roller cutters;The mathematical model based on continuum mechanics is difficult to solve the practical calculation problem of rock fragmentation,so the principle of energy dissipation needs to be used to analyze the process;The dissipative energy,energy dissipation rate and specific energy in the process of rock breaking can be used as the indexes for the optimization of rock drilling parameters of large section drilling machine;In order to define the inner ring roller cutters and the outer ring roller cutters,the loading rate of the cutter bits on the rock drilling surface can be calculated by the rolling linear speed of the roller cutters.By comparing the loading rate range in the SHPB test,the outer ring roller cutters and the inner ring roller cutters can be defined by the loading rate;To sum up,according to the rock drilling mechanism analysis of the outer ring roller cutters of the large section drilling machine,it is proposed to establish a b-shpb theoretical model to study the optimal speed of the large section drilling machine.2.Study on the optimization of drilling parameters of large section drilling machine:the relationship between the penetration depth of roller cutters in the inner ring of large section drilling machine and drilling pressure are approximately linear,but the increase rate shows a downward trend in a certain range;The relationship between drilling speed and drilling pressure is also approximately exponential,and the fitting curve can well describe the exponential change of drilling speed and pulling force.In addition,with the increase of pulling force,the drilling speed will rise faster,which shows that for the rock drilling mechanism of inlaid hob rolling drilling,increasing drilling pressure can increase the drilling speed exponentially.There is a linear relationship between drilling speed and rotating speed.With the increase of rotational speed,the drilling speed increases linearly.The effect of speed contrast energy is not significant.It is found in the impact mechanism test of outer ring roller cutters,grey sandstone,red sandstone and marble all have dynamic enhancement effect.With the increase of rock static compressive strength,the higher the dynamic compressive strength,the less sensitive the dynamic compressive strength to the change of strain rate.Marble is most sensitive to the change of dynamic compressive strength,while red sandstone is less sensitive to the change of dynamic compressive strength.The dissipated energy of grey sandstone,red sandstone and marble samples increases with the increase of strain rate or incident energy.The greater the static compressive strength of grey sandstone,red sandstone and marble samples,the lower the energy dissipation rate.Compared with grey sandstone and marble,increasing the input energy of red sandstone can significantly improve the energy utilization rate.The parameters of stress peak,dissipated energy and energy dissipation rate obtained from b-shpb test can be used to evaluate the rock breaking efficiency of cutter bits.Under the condition that only low-power drilling machine can be used,such as limited space,the installation of pick cutter bits on the drilling tool is more conducive to the rock breaking of low-power drilling machine under the action of low impact force.Under emergency rescue and other conditions requiring rapid drilling,the installation of conical cutter bits on drilling tools can output more energy per unit time to ensure construction efficiency.Under the condition of balancing the service life and construction speed of cutter bits and giving priority to cost-effectiveness,the installation of conical cutter bits on drilling tools can improve the energy utilization rate of broken rock and improve the economy of drilling.Therefore,for the inner ring roller cutters of the large section shaft drilling machine,increasing the drilling pressure can significantly improve the rock drilling speed and reduce the specific energy within a certain range,but the effect of increasing the rotating speed on the specific energy is not significant;Increasing the rotating speed of the outer ring roller cutters can approximately linearly reduce the difficulty of rock drilling,and in most cases,it can reduce the energy dissipation rate of the roller cutters and improve the energy utilization rate.Therefore,in order to optimize the drilling parameters of large cross-section shaft drilling machine,we should find the lowest drilling pressures of specific energy and improve the speed of bit as much as possible.3.Research on rock drilling efficiency of large section drilling machine:through the linear rock breaking test of conical inserted roller cutters breaking marble and granite,it is clear that the cumulative probability of rock slag particle size distribution conforms to rosin Rammler distribution,and the characteristic particle size of rock under different drilling pressures is obtained;According to the test results,the characteristic particle size distribution law is analyzed,and it is determined that the optimal drilling pressure of granite sample is 30 kN and that of marble sample is 34.45 kN;Through the test,it is determined that the marble sample broken by the conical roller cutters conforms to the new surface theory of lijinge.According to the relationship between specific energy and drilling pressures,the optimal drilling pressures is 35.19 kN.Through the linear rock breaking test of marble and granite samples with multi row pick shaped roller cutters,the cumulative probability of rock slag particle size distribution conforms to rosin Rammler distribution,and the characteristic particle size of rock under different drilling pressures is obtained;According to the test results,the characteristic particle size distribution law is analyzed,and it is determined that the optimal drilling pressures of marble sample is 184.53 kN and that of granite sample is 117.25 kN;According to the relationship between specific energy and drilling pressures,the optimal drilling pressures of marble sample is 175 kN and that of granite sample is 120 kN.Through the industrial test of a slag chute project on the left bank of Baihetan Hydropower Station,it is clear that the cumulative probability of rock slag particle size produced by the bit of raise boring machine during rock drilling conforms to the rosin Rammler distribution;Within the test range,according to the characteristic particle size theory,it is fitted that when the rock drilling efficiency of bmc200 raise boring machine is the highest,the corresponding hydraulic system pressure for applying drilling pressures is 12.00 MPa;Combined with the parameters of drilling machine and drilling tool,the optimal drilling pressures can be calculated,which verifies the feasibility and guiding significance of the characteristic particle size theory.Therefore,through the straight-line rock breaking test of different rocks with different tooth profile roller cutters,it can be obtained that the optimal drilling pressures value obtained by characteristic particle size and specific energy is basically the same.The two methods can be used in actual construction.If conditions permit,the characteristic particle size theory method is preferred to obtain a more accurate optimal drilling pressure.The characteristic particle size theory can be used as a convenient method to evaluate the rock drilling efficiency of large section drilling machine.The larger the characteristic particle size value of rock slag produced in the drilling process,the higher the rock drilling efficiency of large section drilling machine.4.In this paper,while the determination method of drilling pressures and rotational speed for the optimization of drilling parameters of large section drilling machine roller cutters is obtained,the characteristic particle size theoretical evaluation method of rock drilling efficiency of large section drilling machine roller cutters is established. |
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