scholarly journals Phenomenon and Critical Conditions of Chamber Soil Sliming during EPB Shield Tunneling in Water-Rich Weathered Diorite: Case Study of Jinan Metro, China

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Lu Wang ◽  
Wei Zhu ◽  
Yongjin Qian ◽  
Chao Xu ◽  
Jiannan Hu ◽  
...  
Keyword(s):  
Pressure Chamber ◽  
Critical Conditions ◽  
Chamber Pressure ◽  
Water Volume ◽  
Seepage Water ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Rock Stratum ◽  
Effective Measure ◽  
Epb Shield

The sliming problem of chamber soil is caused by excessive groundwater seeping into the pressure chamber when an Earth pressure balance shield tunnels through a water-rich weathered rock stratum under semiopen under-pressure mode. As a solution to this problem, a calculation model was established based on field measurements of the discharged soil properties, the seepage water volume, and the seepage path in Jinan Metro, China. Chamber soil sliming is a phenomenon in which chamber soil is in a thin mud state, with no pressure balance in the pressure chamber of the EPB shield and an excessive water content of the chamber soil owing to the continuous seepage of groundwater into the chamber. The chamber pressure is relatively low, which is different from the phenomenon of spewing when the chamber pressure is relatively high. A large amount of water seepage from the stratum around the tunnel excavation surface and shield to the chamber is a significant factor leading to chamber soil sliming during the construction process. It was considered that when the moisture content of the chamber soil, w, is 2wL ≤ w ≤ 3wL, slight chamber soil sliming may occur, whereas when w ≥ 3wL, serious chamber soil sliming may occur. Moreover, some measures to prevent and control the occurrence of chamber soil sliming were discussed. Controlling the advancing time and the permeability coefficient of chamber soil during construction is the most effective measure to avoid the phenomenon of soil sliming.

scholarly journals Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

2021 ◽  
Vol 11 (6) ◽  
pp. 2551
Author(s):  
Hyobum Lee ◽  
Hangseok Choi ◽  
Soon-Wook Choi ◽  
Soo-Ho Chang ◽  
Tae-Ho Kang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Tunnel Boring Machine ◽  
Chamber Pressure ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Operational Conditions ◽  
Shield Tunnelling ◽  
Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

Research on Chamber Earth Pressure of EPB Shield Considering Soil Arching Effect

2014 ◽  
Vol 1065-1069 ◽  
pp. 373-377
Author(s):  
Jing Cao ◽  
Hai Xing Yang ◽  
Bo Liang ◽  
Hai Ming Liu
Keyword(s):  
Earth Pressure ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Soil Arching ◽  
Shield Tunneling ◽  
Arching Effect ◽  
Soil Arching Effect ◽  
Earth Pressure Balance ◽  
Tunnel Depth ◽  
Epb Shield

Chamber earth pressure is one of the significant parameters during the Earth Pressure Balance (EPB) shield construction processing. The soil arching effect is existence when the tunnel depth is enough. It is significant to consider the influence of arching effect to analyze the pressure in soil chamber in shield tunneling. In this paper, the influence of arching effect is considered to calculate the chamber earth pressure. Firstly, the soil is supposed as loose media, and the necessary buried depth of producing arching affects is deduced according to the loose media theory. Then, based on the characteristic of proper arching axis, the equation and the height of proper arch are obtained. At last, the calculation formula of minimum chamber earth pressure of EPB shield tunnel is deduced which can consider the effect of arching effect.

scholarly journals Risk Mitigation and Construction Control for Effective Underwater Recovery of an EPB Shield: A Case Study of the First Metro Tunnel in Tel Aviv

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Weiqiang Qi ◽  
Zhiyong Yang ◽  
Yusheng Jiang ◽  
Zhiyong Liu ◽  
Yinxin Guo ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Fine Sand ◽  
Diaphragm Wall ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Tel Aviv ◽  
Metro Tunnel ◽  
Epb Shield

Shield recovery in water-rich sand strata is a challenging issue in the field of shield tunnel engineering, especially when the end of the shaft cannot be reinforced by jet grouting or freezing or when the shield cannot be supported with a steel sleeve. Therefore, it is important to develop an effective recovery approach and adopt suitable techniques to control the risks. In this study, a new method based on filling the receiving shaft with water is proposed for the underwater recovery of an earth pressure balance (EPB) shield with zero end reinforcement from a metro tunnel in Tel Aviv, Israel. Several additional techniques are used to ensure safe recovery of the shield, including the design of a concrete cradle, drilling of pressure relief holes, control of excavation parameters, screw conveyor sealing, portal sealing, tail sealing, and grouting. Furthermore, according to the actual situation on site, filling the shaft with water to 1 m above the water level in the strata can prevent the fine sand from percolating into the shaft. Before the cutterhead approaches the underground diaphragm wall, the driving attitude should be strictly controlled, and the edge hob should be inspected for wear. The necessary thrust of shield tunneling in the underground diaphragm wall and shaft is calculated theoretically. In order to ensure the deformation control of the underground diaphragm wall and the smooth tunneling of the shield, the thrust of the shield excavating the underground diaphragm wall will not be larger than 12 000 kN, and the penetration degree will be limited to 3 mm/r. Qualitative observations and measurements of surface subsidence in the metro tunnel indicate that these risk mitigation techniques are effective and suitable for the underwater recovery of EPB shields in water-rich sand strata.

3D Finite Element Simulation on During Shield Tunneling

2011 ◽  
Vol 90-93 ◽  
pp. 1950-1955
Author(s):  
Yi Liu ◽  
Ji Shun Li ◽  
Bao Lian Wang
Keyword(s):  
Finite Element ◽  
Numerical Procedure ◽  
Ground Surface ◽  
Element Model ◽  
Small Strain ◽  
Ground Movement ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Epb Shield

Based on the comprehensive analysis on the primary components of ground movement associated with earth pressure balance (EPB) shield tunneling, a three-dimensional nonlinear finite element model for simulating EPB shield tunneling is proposed. The proposed modeling techniques are applied to simulate a tunneling project. The distributions of soil displacement on the ground surface associated with the advance-ment process of shield tunnel are analyzed. According to the comparisons of numerical results with field measurements, the proposed numerical procedure is found to be an effective approach for predicting the deformation dun to shield tunneling. The further analysis shows that the computed results of the small-strain constitutive model are more reasonable, and the small-strain mechanical behaviors of soils should be taken into account

scholarly journals A Data-Driven Method for Predicting the Cutterhead Torque of EPB Shield Machine

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Kairong Hong ◽  
Fengyuan Li ◽  
Zhenjian Zhou ◽  
Feng Li ◽  
Xunlin Zhu
Keyword(s):  
Linear Regression ◽  
Short Term Memory ◽  
Thrust Force ◽  
Change Point Detection ◽  
Linear Regression Method ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Start Up ◽  
Shield Machine ◽  
Epb Shield

The prediction of cutterhead torque of earth pressure balance (EPB) shield machine is mainly studied. First, the idea of shield tunneling stage division is proposed. The process of shield tunneling from start to stop (or pause) is divided into start-up and stationary driving stages. Using the change point detection method based on linear regression, the separation points between start-up stage and stationary driving stage are identified from the original construction data, and the datasets of the two stages are extracted, respectively. Then, for the start-up stage, the linear regression method is suggested for the cutterhead torque prediction, since there is a strong linear correlation between the key parameters such as the cutterhead torque and the thrust force. Meanwhile, for the stationary driving stage, considering the fact that the key parameters vary smoothly and show obvious inertia, the long short-term memory (LSTM) network method can be used to establish the relationship model between cutterhead torque and other key parameters, such as the thrust force. Through the test experiments of construction data in Zhengzhou, Luoyang, and Dalian shield projects, the results show that the proposed segmented modeling method possesses good adaptability and the cutterhead torque prediction model has high prediction accuracy.

scholarly journals Experimental Study on the Soil Conditioning Materials for EPB Shield Tunneling in Silty Sand

2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Chi-Hao Cheng ◽  
Shao-Ming Liao ◽  
Xiao-Bo Huo ◽  
Li-Sheng Chen
Keyword(s):  
Earth Pressure ◽  
Test System ◽  
Cutting Performance ◽  
Silty Sand ◽  
Test Results ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Soil Conditioning ◽  
Sand Stratum ◽  
Epb Shield

Earth pressure balance (EPB) shield tunneling in a silty sand stratum is frequently faced with the wear of rotary cutter disc, clogging, or even collapse of workface due to its noncohesive and discrete properties of silty sand material. Soil conditioning is an effective way to reduce the discrete and friction properties of silty sand and to increase its rheology and fluidity, thus improving the cutting performance of EPB machines. However, soil conditioning materials were generally prepared and injected based on past limited field experiences or lab tests which were far from reality. In this article, a ground suitability test system for simulating shield tunneling in a conditioned ground was specially developed and used in a series of tests to investigate the influences of key factors of soil conditioning on the shield cutting performance. In addition, a field experiment of shield tunneling in silty sand of Wuhan Metro was conducted for verification. The major findings were obtained as follows. (1) The proposed test system performed well in simulating and assessing the cutting performance of EPB shield in conditioned soils, and the test results agreed well with the field test. (2) The soil conditioning materials can significantly reduce the cutting torque of shield tunneling in silty sand by up to 60%–70%. (3) The optimal foam and slurry parameters are suggested in the paper for shield tunneling in silty sand, respectively. (4) The test results reveal that the slurry conditioning is better than the foam in decreasing the cutter torque in silty sand. To achieve the same effect of soil conditioning, the injection ratios of foam and slurry should be 45% and 10%, respectively, to achieve the torque reduction ratio of 60%. These findings can provide a practical reference for engineers to determine the best-fit conditioning materials and construction parameters in the silty sand stratum.

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