| With the in-depth development of urban areas,the available space is relatively limited.In order to meet people’s increasing demand for transportation,underground space development has become a major trend in urban development worldwide.As the main construction method for the development and construction of underground space,the shield method is widely used in urban highway or rail transit construction due to its own advantages of high construction efficiency,low surface disturbance,and safe working surface.However,shield machines,especially large-diameter shields,in the process of underground excavation,complex geological conditions such as uneven soft and hard,excessively high content of abrasive minerals/caking minerals and other complex geological conditions cause rapid wear of the tools,which greatly reduces the number of tools.The efficiency of disk cutting brings serious difficulties to shield tunneling.The tool wear of large-diameter shields has become an urgent problem to be solved.At this stage,the detection and evaluation methods of worn tools in engineering are still relatively rudimentary.The choice of tools depends more on experience and lacks theoretical support.The law of tool wear mostly stays at the level of two-dimensional theoretical derivation,and the soil parameters during construction are not effectively used.Structure parameters,construction parameters to explore the internal relationship between these important parameters and the existing wear data.Therefore,this paper studies methods and technologies such as point cloud-based reverse engineering modeling and wear detection,discrete element-based shield tool wear analysis and shield tool wear prediction,focusing on tool wear status evaluation,wear mechanism and law,and wear volume Relevant research has been carried out in the forecast,and the main work includes:(1)An efficient and high-precision evaluation method for service tool wear based on laser scanning point cloud multi-feature point registration is designed.A comprehensive method that first uses point cloud multi-point features for coarse alignment,and then uses the ICP method based on feature-free registration for fine alignment is proposed,which improves the drawbacks of using an algorithm alone,and significantly improves point cloud splicing.Quality improves the reliability of tool wear analysis.Use a three-dimensional laser scanner to scan the worn tools in batches to obtain point cloud data,carry out retrograde modeling and comprehensively compare with the designed tools,and realize a comprehensive assessment of the tool wear parts,wear trends and wear volume.The case analysis results show that the average tool wear amount is 13 mm,and the maximum wear amount is 15.02 mm,and the wear on the soil-facing surface of the tearing knife is extremely serious.There are grooves on the soil-facing surface of the tool,and the soil-facing surface of the tool is changed from the original non-planar surface.The wear becomes almost flat,realizing accurate modeling and condition assessment of in-service tool wear.(2)Constructed a large-scale discrete element model for cutting sand with a largediameter shield cutter,and innovatively realized the simulation calculation and analysis of the wear process of multi-tools mixed with old and new tools.Based on Solidworks 3D modeling software and EDEM discrete element software,the rock-breaking wear simulation of four combined forms of full double-edged,full single-edged,outer double-edged inner single-edged,and outer single-edged inner double-edged hob was carried out,and compared The rock-breaking effect and wear of the tearing knife and the hob were studied,and the influence of the forward and reverse rotation of the cutter head on the tool wear was studied.The main conclusions are drawn that the full double-edged hob is more stable and has less eccentric wear compared to the single-edged hob,but the rock breaking ability is the worst and the wear is the highest;the single-edged and outer double-edged inner single-edged rock breaking ability is strong,The wear amount is small but the partial wear is serious;the wear amount of the tearing knife is larger than that of the full double-edged hob,that is,the tearing knife is more suitable for soft rock and sandy soil;the facing surface of the tool and the frontal wear of the tool in contact with the soil The highest degree and all tool types have eccentric wear in the tunneling process.After the cutter head of the shield machine is reversed,the average wear of the tool will increase slowly,but the maximum wear will still increase rapidly;the wear of the tool through the lower half of the tunnel is high This is due to the phenomenon of the wear of the tool passing through the upper half of the tunnel;the wear of the tool will increase with the installation radius of the tool,but not linearly with the installation radius of the tool.(3)Relying on the analysis of engineering case data,a method for predicting the wear of large-diameter shield cutters was established.The distribution and wear amount of replaceable tools on the shield machine are counted,and the relationship between the tool path distance and tool wear amount is deduced.Then,the tool wear coefficient of the tunneled ring is analyzed by the least square method,and the wear curve of the tool is fitted.After the classic algorithm GA-BP is trained,the wear model is obtained and then the tool wear prediction is carried out.The results show that the wear coefficient of the leading knife and the hob is extremely stable in the front area and the arc area,but the difference in the wear coefficient in the center area is obvious;the wear coefficient of the scraper is extremely stable on the entire cutter head during the tunneling process,The prediction stability is relatively high;in the composite stratum,the tool wear is more seriously affected by the proportion of each soil layer,and the wear prediction of the shield section after the wear coefficient is uniformized can not get a better prediction effect. |
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