Investigations on the transient support pressure transfer at the tunnel face during slurry shield drive Part 2: Case B – Deep slurry penetration exceeds tool cutting depth

2021 ◽  
pp. 104169
Author(s):  
Zdenek Zizka ◽  
Britta Schoesser ◽  
Markus Thewes
Keyword(s):  
Support Pressure ◽  
Cutting Depth ◽  
Tunnel Face ◽  
Slurry Shield ◽  
Tool Cutting

scholarly journals Face Stability Analysis of Shield Tunnels in Homogeneous Soil Overlaid by Multilayered Cohesive-Frictional Soils

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Kaihang Han ◽  
Chengping Zhang ◽  
Wei Li ◽  
Caixia Guo
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Support Pressure ◽  
Tunnel Face ◽  
Arch Effect ◽  
Theory Approximation ◽  
Homogeneous Soil ◽  
Frictional Soils

In order to better interpret failure features of the failure of soil in front of tunnel face, a new three-dimensional failure mechanism is proposed to analyze the limit support pressure of the tunnel face in multilayered cohesive-frictional soils. The new failure mechanism is composed of two truncated cones that represent the shear failure band and a distributed force acting on the truncated cones that represents the pressure arch effect. By introducing the concept of Terzaghi earth pressure theory, approximation of limit support pressures is calculated using the limit analysis methods. Then the limit support pressures obtained from the new failure mechanism and the existing approaches are compared, which show that the results obtained from the new mechanism in this paper provide relatively satisfactory results.

Study on Chip Breaking of HSS Tool with Convex Stripe

2014 ◽  
Vol 685 ◽  
pp. 90-93
Author(s):  
Zhong Liang Wu ◽  
Jie Zhao ◽  
Yan Lin Wang
Keyword(s):  
Aluminum Alloy ◽  
High Speed ◽  
Cutting Tool ◽  
Experimental Results ◽  
Manufacturing Processes ◽  
Cutting Depth ◽  
Chip Breaking ◽  
On Chip ◽  
Tool Cutting ◽  
Cutting Experiments

Chip breaking is important during manufacturing processes. A method of chip breaking is described. Common high speed tool was selected as cutting tool. The convex stripe was made by the laser instrument on the rake of cutting tool. Cutting experiments of aluminum alloy were carried out with this kind of tools. Experimental results show that chip breaking of tools with convex stripe is easier than ordinary tools. And the chip shape is always arc. The chip created by tools with convex stripe breaks more easily when cutting depth is less than 0.5mm. There is no damage on cutting tool with this method which is simple for manufacture.

scholarly journals Investigation on the Influence Caused by Shield Tunneling: WSN Monitoring and Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Hao Liu ◽  
Jinjiang Shi ◽  
Jiasen Li ◽  
Chao Liu
Keyword(s):  
Signal Transmission ◽  
Monitoring Data ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Shield Tunneling ◽  
Tunnel Face ◽  
Wireless Monitoring ◽  
Mems Sensor ◽  
Grouting Pressure ◽  
Transmission Test

Traditional monitoring techniques are faced with the problems of low acquisition frequency and easy to be affected by the construction environment during the shield tunneling, which cannot meet the actual needs of timeliness monitoring of surrounding environmental impact on shield tunnel construction. Based on this actual demand, a wireless sensor network (WSN) system was used to monitor the response of shield tunnel segments and surrounding buildings during the shield tunneling in this study. According to the result of the signal transmission test, an optimization scheme of microelectromechanical system (MEMS) sensor layout is designed to improve the monitoring efficiency of the WSN system. Through the comparative analysis of WSN system monitoring data and traditional monitoring data, it is found that, with the increasing distance between the monitoring section and the tunnel face, the convergence value of tunnel lining clearance gradually tends to be stable, and the wireless monitoring results of transverse clearance convergence of the tunnel in this section are consistent with the overall deformation trend of the convergence gauge monitoring results. This study also simulated the shield tunneling adjacent buildings using a nonlinear finite element method. A parameter sensitivity analysis of the support pressure of the excavation face and the grouting pressure at the tail of the shield is carried out. The results show that the surface settlement can be reduced by properly increasing the grouting pressure and the support pressure of the excavation face. Moreover, increasing the support pressure of the excavation face has a better inhibition effect on the settlement of the surface soil than increasing the grouting pressure.

scholarly journals A Theoretical Calculation Method of the Unsupported Span for the Shallow Tunnel in the Soft Stratum

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xiaoxu Tian ◽  
Zhanping Song ◽  
Guannan Zhou ◽  
Xiaowei Zhang
Keyword(s):  
Soft Rock ◽  
Friction Angle ◽  
Soil Mass ◽  
Calculation Model ◽  
Support Pressure ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Rock Stratum ◽  
The Stability ◽  
Shallow Buried Tunnel

During the construction of the tunnel in soft stratum, it is often found that the unsupported span is too large, resulting in instability of the tunnel face and collapse of the vault. However, the unsupported span was often selected according to the experience of engineers in the actual construction process, which was lack of the theoretical basis. Therefore, based on the calculation model of the surrounding rock pressure of shallow buried tunnel, this paper analyzed the stability of the tunnel face and the vault and then obtained the calculation formula of the unsupported span of the shallow buried tunnel in soft rock stratum. It was pointed out that the unsupported span is not determined by the arch crown stability or the tunnel face stability alone, but by both. The rationality of the formula was verified by a centrifugal test and an engineering case. The analysis and discussion showed that the unsupported span is sensitive to the cohesion and internal friction angle of the rock-soil mass, especially the cohesion. The unsupported span of the shallow buried tunnel in the soft rock stratum is a linear function of the support pressure. The support pressure has a more significant contribution to the increase of the unsupported span by the centre cross diaphragm (CRD) method, and the unsupported span increases linearly with the increase of the support pressure. The research results provide a theoretical reference for the determination of the unsupported span for the shallow tunnel in the soft stratum.

scholarly journals Upper Bound Solution for the Face Stability of Shield Tunnel below the Water Table

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Xilin Lu ◽  
Haoran Wang ◽  
Maosong Huang
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Fe Simulation ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
The Face ◽  
Upper Bound Limit Analysis

By FE simulation with Mohr-Coulomb perfect elastoplasticity model, the relationship between the support pressure and displacement of the shield tunnel face was obtained. According to the plastic strain distribution at collapse state, an appropriate failure mechanism was proposed for upper bound limit analysis, and the formula to calculate the limit support pressure was deduced. The limit support pressure was rearranged to be the summation of soil cohesionc, surcharge loadq, and soil gravityγmultiplied by their corresponding coefficientsNc,Nq, andNγ, and parametric studies were carried out on these coefficients. In order to consider the influence of seepage on the face stability, the pore water pressure distribution and the seepage force on the tunnel face were obtained by FE simulation. After adding the power of seepage force into the equation of the upper bound limit analysis, the total limit support pressure for stabilizing the tunnel face under seepage condition was obtained. The total limit support pressure was shown to increase almost linearly with the water table.

Improvement of Surface Flatness in Face Milling by Varying the Tool Cutting Depth and Feed Rate

2009 ◽  
Author(s):  
Bruce L. Tai ◽  
David A. Stephenson ◽  
Albert J. Shih
Keyword(s):  
Feed Rate ◽  
Tool Path ◽  
Face Milling ◽  
Mirror Image ◽  
Cutting Depth ◽  
Surface Flatness ◽  
Local Compliance ◽  
Automatic Tool ◽  
Tool Cutting ◽  
Cutting Path

This paper explores two approaches to improve the flatness of face milled surfaces by modifying the tool cutting depth and feed rate based on the 3D holographic laser measurement. The tool cutting depth compensation method generates a cutting path which is the mirror image of the measured error profile to reduce the flatness errors. Issues of back-cutting and the interference due to cutter size limit the range of applicability of this approach. The feed rate is varied to match the axial force on the cutter with the local compliance of the workpiece to further improve the surface flatness. Using a flat plate workpiece and 50.8 mm diameter face milling cutter, the surface flatness can be reduced from around 15 μm without compensation to lower than 10 μm by varying tool cutting depth. Modification of feed rate further reduces the flatness errors from 10 μm to 6 μm. Automatic tool path compensation based on holographic feedback is also discussed.

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