A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field m...A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.展开更多
The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the su...The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the surrounding environment is very sensitive to the fluctuation of slurry pressure.In this study,an optimal control method for slurry pressure during shield tunnelling is developed,which is composed of an identifier and a controller.The established identifier based on the random forest(RF)can describe the complex non-linear relationship between slurry pressure and its influencing factors.The proposed controller based on particle swarm optimization(PSO)can optimize the key factor to precisely control the slurry pressure at the normal state of advancement.A data set from Tsinghua Yuan Tunnel in China was used to train the RF model and several performance measures like R2,RMSE,etc.,were employed to evaluate.Then,the hybrid RF-PSO control method is adopted to optimize the control of slurry pressure.The good agreement between optimized slurry pressure and expected values demonstrates a high identifying and control precision.展开更多
泥水平衡盾构机气垫仓内岩屑的快速排出对于保证施工安全和提高掘进效率至关重要,已有研究主要集中在岩屑在排浆管中运输的运动特性,而从气垫仓进入排浆管直至排出的完整过程却往往被忽略,因此现有研究对于指导实际工程还存在局限性。基...泥水平衡盾构机气垫仓内岩屑的快速排出对于保证施工安全和提高掘进效率至关重要,已有研究主要集中在岩屑在排浆管中运输的运动特性,而从气垫仓进入排浆管直至排出的完整过程却往往被忽略,因此现有研究对于指导实际工程还存在局限性。基于CFD-DEM(computational fluid dynamics-discrete element method)计算流体力学-离散单元耦合计算方法并结合实际工程建立了可以完整反映气垫仓内岩屑排出的数值计算模型,对比了不同冲刷管布设情况下(垂直距离h1、水平距离h_(2)和转角β)岩屑的排出情况,总结了不同因素对岩屑排出率的敏感度。研究结果表明排出率随着h1的增加而减小,随着h_(2)和β的增加而增加,三个因素的平均敏感度排序从大到小依次为h1(1.6)>h_(2)(0.79)>β(0.61),因此在实际工程中降低冲刷管高度是提高岩屑率最有效的措施。研究结果可为优化冲刷管的布设和制定相关施工措施提供实用参考。展开更多
The rapid discharge of cuttings from the air cushion chamber is crucial for the construction safety and excavation efficiency of the slurry shield.Previous studies have mainly focused on the transport characteristics ...The rapid discharge of cuttings from the air cushion chamber is crucial for the construction safety and excavation efficiency of the slurry shield.Previous studies have mainly focused on the transport characteristics of cuttings in the slurry discharge pipe,while the complete process of cuttings entering the slurry discharge pipe from the air cushion chamber until they are discharged was often overlooked.Based on the CFD-DEM coupling method and combined with actual engineering,this paper established a numerical model that can more completely reflect the cuttings discharge process during slurry shield tunneling,and the effects of the slurry velocity at slurry gate and scouring pipes,inclination angle of slurry discharge pipe,cuttings diameter and shape coefficient were investigated by analyzing the variation in the mass flow rate,mass of discharged cuttings,and discharged ratio.The results revealed that increasing the slurry velocity can promote the discharge of cuttings.To keep the discharged rate at a high level,it is recommended that the slurry velocity at the slurry gate should be greater than 0.15 m/s.Reducing the inclination angle of the discharge pipe is conducive to the rapid discharge of cuttings.Cuttings with large diameter or small shape coefficient are more prone to accumulate in the air cushion chamber and cause clogging risk.The research results not only help to improve engineers'understanding of cuttings discharge in slurry shield,but also provide practical guidance for formulating relevant construction measures.展开更多
基金Project(41202220) supported by the National Natural Science Foundation of ChinaProject(2011YYL034) supported by the Fundamental Research Funds for the Central Universities,China
文摘A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.
基金This work was supported by the Fundamental Research Funds for the Central Universities(2020YJS141)the Key Project of High-speed Rail Joint Fund of National Natural Science Foundation of China under Grant No.U1834208.
文摘The control of slurry pressure aiming to be consistent with the external water and earth pressure during shield tunnelling has great significance for face stability,especially in urban areas or underwater where the surrounding environment is very sensitive to the fluctuation of slurry pressure.In this study,an optimal control method for slurry pressure during shield tunnelling is developed,which is composed of an identifier and a controller.The established identifier based on the random forest(RF)can describe the complex non-linear relationship between slurry pressure and its influencing factors.The proposed controller based on particle swarm optimization(PSO)can optimize the key factor to precisely control the slurry pressure at the normal state of advancement.A data set from Tsinghua Yuan Tunnel in China was used to train the RF model and several performance measures like R2,RMSE,etc.,were employed to evaluate.Then,the hybrid RF-PSO control method is adopted to optimize the control of slurry pressure.The good agreement between optimized slurry pressure and expected values demonstrates a high identifying and control precision.
文摘泥水平衡盾构机气垫仓内岩屑的快速排出对于保证施工安全和提高掘进效率至关重要,已有研究主要集中在岩屑在排浆管中运输的运动特性,而从气垫仓进入排浆管直至排出的完整过程却往往被忽略,因此现有研究对于指导实际工程还存在局限性。基于CFD-DEM(computational fluid dynamics-discrete element method)计算流体力学-离散单元耦合计算方法并结合实际工程建立了可以完整反映气垫仓内岩屑排出的数值计算模型,对比了不同冲刷管布设情况下(垂直距离h1、水平距离h_(2)和转角β)岩屑的排出情况,总结了不同因素对岩屑排出率的敏感度。研究结果表明排出率随着h1的增加而减小,随着h_(2)和β的增加而增加,三个因素的平均敏感度排序从大到小依次为h1(1.6)>h_(2)(0.79)>β(0.61),因此在实际工程中降低冲刷管高度是提高岩屑率最有效的措施。研究结果可为优化冲刷管的布设和制定相关施工措施提供实用参考。
基金support from the National Natural Science Foundation of China(grant number 52278403)the Natural Science Foundation of Shandong Province(grant number ZR2021ME135).
文摘The rapid discharge of cuttings from the air cushion chamber is crucial for the construction safety and excavation efficiency of the slurry shield.Previous studies have mainly focused on the transport characteristics of cuttings in the slurry discharge pipe,while the complete process of cuttings entering the slurry discharge pipe from the air cushion chamber until they are discharged was often overlooked.Based on the CFD-DEM coupling method and combined with actual engineering,this paper established a numerical model that can more completely reflect the cuttings discharge process during slurry shield tunneling,and the effects of the slurry velocity at slurry gate and scouring pipes,inclination angle of slurry discharge pipe,cuttings diameter and shape coefficient were investigated by analyzing the variation in the mass flow rate,mass of discharged cuttings,and discharged ratio.The results revealed that increasing the slurry velocity can promote the discharge of cuttings.To keep the discharged rate at a high level,it is recommended that the slurry velocity at the slurry gate should be greater than 0.15 m/s.Reducing the inclination angle of the discharge pipe is conducive to the rapid discharge of cuttings.Cuttings with large diameter or small shape coefficient are more prone to accumulate in the air cushion chamber and cause clogging risk.The research results not only help to improve engineers'understanding of cuttings discharge in slurry shield,but also provide practical guidance for formulating relevant construction measures.
