scholarly journals Experimental Study of the Influence of Excavation Surface Stability and Sand Flowability Caused by Dense Slurry–Earth Pressure Balance Shield Tunneling in Silty Sand Stratum

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Yongjin Qian ◽  
Fanlu Min ◽  
Zhenze Mo ◽  
Xihui Fan
Keyword(s):  
Pore Pressure ◽  
Filter Cake ◽  
Earth Pressure ◽  
Rate Of Change ◽  
Silty Sand ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Earth Pressure Balance ◽  
Sand Stratum ◽  
Epb Shield

Silty sand is highly permeable and has a large internal friction angle. To ensure the stable and efficient construction of the Earth pressure balance (EPB) shield in silt stratum, it is necessary to reduce the disturbance to the stratum during tunneling and reduce the risk of spewing and blocking during soil discharge. Thus, a new type of dense slurry-EPB shield construction technology is proposed. Using a custom-made test device, the consolidation tests were conducted on sand after mixing it with different amounts of slurry to study the change in the pore pressure in the mixed soil and sand stratum and analyze the stress transmission rule. In addition, slump tests were conducted on the mixed soil to study the change in the fluidity. Based on the laboratory test results, a field investigation was carried out to study the effects of the amount of slurry addition on the pore pressure in the stratum, the driving parameters, and the sand’s flowability during shield tunneling. The results show that when the amount of slurry reaches a certain value, the filter cake effect occurs. The greater the amount of slurry added during the shield tunneling, the smaller the rate of change of the pore pressure in the stratum. When the amount of BC2 slurry added reached 8 m3 per ring, the rate of change was reduced by 57%, and the slump value improved by 93%. The type of filter cake of the DS-EPB shield was only internal filter cake during tunneling, which reduced the disturbance of the excavation face and improved the flowability of the sand. These results are of great significance to the application and promotion of DS-EPB shields in sandy cobble strata.

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.

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.

Online Fault Prediction for EPB Shield Tunneling Based on Neural Network

2012 ◽  
Vol 457-458 ◽  
pp. 1287-1293 ◽  
Author(s):  
Bu Hai Shi ◽  
Wei Qing Li
Keyword(s):  
Neural Network ◽  
Earth Pressure ◽  
Risk Process ◽  
Fault Prediction ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
The Neural Network ◽  
Earth Pressure Balance ◽  
Artificial Neural Network Ann ◽  
Epb Shield

For the complex earth conditions and uncertain factors, the earth pressure balance (EPB) shield tunneling is a complicated and high-risk process. There would cause some faults, such as earth caking, soil occluding in the capsule, water spewing, surface settlement. To avoid them, this paper applies artificial neural network (ANN) to predict the common shielding faults. The neural network is trained by several samples about the tunnel boring machine’s (TBM) parameters, and then it will have self-learning to identify the fault. With the parallel computing ability, the network could detect and predict abnormal behaviors online. This paper includes three parts, firstly, the introduction of EPB, and four usual blockings; and then the principle of BP neural network is present, for the defect of BP algorithm, two kinds of improved BP algorithms are applied in the network; finally, an simulation is given to illustrate the prediction.

Geological Adaptive Cutterhead Selection for EPB Shield Based on BP Neural Network

2014 ◽  
Vol 607 ◽  
pp. 118-123
Author(s):  
Lai Kuang Lin ◽  
Yi Min Xia ◽  
Fei He ◽  
Qing Song Mao ◽  
Kui Zhang
Keyword(s):  
Neural Network ◽  
Bp Neural Network ◽  
Earth Pressure ◽  
Training Model ◽  
Structure Design ◽  
Pressure Balance ◽  
Selection For ◽  
Earth Pressure Balance ◽  
Set Up ◽  
Epb Shield

In view of complex and fuzziness of geological adaptive cutterhead selection for earth pressure balance (EPB) shield, a cutterhead selection method based on BP neural network is put forward. Considering the structure characteristics of EPB shield cutterhead, typical cutterhead types are classified and summarized based on cutterhead topology structure and number of spokes. After analyzing the determinants of cutterhead selection, one-to-many mapping relation between cutterhead type and geological parameters is put forward, and then core geologic parameters related to cutterhead selection are concluded. The feasibility of using neural network method to choose the cutterhead type is analyzed, and a BP neural network training model for cutterhead selection is set up and tested in testing sample data. The result shows that the selected cutterhead and the construction cutterhead are basically consistent. The feasibility of this method is proved and it can be theoretical basis for the cutterhead structure design which will improve scientific of cutterhead selection.

Performance Simulation Analysis and Design of the Scale Model for the Earth Pressure Balance Shield

2011 ◽  
Vol 346 ◽  
pp. 364-371 ◽  
Author(s):  
Xu Chen ◽  
Zhu Feng Shao ◽  
Xiao Qiang Tang ◽  
Ping Fa Feng
Keyword(s):  
Optimization Design ◽  
Driving Forces ◽  
Simulation Analysis ◽  
Earth Pressure ◽  
Scale Model ◽  
Pressure Balance ◽  
Analysis And Design ◽  
The Earth ◽  
Earth Pressure Balance ◽  
Epb Shield

Referring to the Earth Pressure Balance (EPB) shield with the diameter of 6.25m, a new experiment station of EPB shield is proposed, which is loaded with mechanical structure instead of traditional soil box. The structure of the experiment model is designed for the performance analysis of the EPB shield. The mechanical loading device, which is called the soil simulator, can simulate different geological environments. The soil simulator is capable of realizing three work states, such as earth balance pressure, earth under pressure, and earth over pressure. By adopting virtual prototype technology, parametric model of the shield station is established and the co-simulation scheme is determined. Besides, the kinematic analysis as well as variation principles between the displacement and driving forces of the propulsion system are obtained, which build the foundation for optimization design and control of the shield prototype.

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