Slurry Shield Tunneling: New Methodology for Simplified Prediction of Increased Pore Pressures Resulting from Slurry Infiltration at the Tunnel Face Under Cyclic Excavation Processes

Zizka, Zdenek; Schößer, Britta; Thewes, Markus; Schanz, Tom

doi:10.1007/s40999-018-0303-2

Cited by 41 publications

(23 citation statements)

References 15 publications

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“…Actually, the theory of displacement earth pressure means that there is a close association between the earth pressure (i.e., the stress in soil) and the induced displacement during the movement of the retaining structure, which also involves the coupling process of external force, seepage action [27,28], soil microstructure damage [7,29], and even thermal loading [23,30]. In the existing theory, the relationship between displacement and earth pressure is generally described from three aspects: (a) the displacement earth pressure curve is fitted according to the experimental data to obtain a certain functional relationship between earth pressure and displacement [31]; (b) the association between the internal friction angle and the displacement is obtained from the backfilling of retaining structure, to obtain the variation of earth pressure with the corresponding displacement; (c) in view of the stress-strain constitutive law of the soil behind the retaining structure, the calculation model of the relationship between displacement and earth pressure is established.…”

Section: Displacement Earth Pressure Theorymentioning

confidence: 99%

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A Displacement‐Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

Guang

Han

Zhang

et al. 2021

Advances in Civil Engineering

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Due to the poor stability of the loose sandy soil layer, if the support force is not properly controlled during the construction process of the shield tunnel using the earth pressure balance method, it is easy to cause the ground to collapse or uplift. Therefore, understanding the support force of the excavation surface of shield tunneling in sandy soil layer is very vital to ensure the stability of the excavation surface. Firstly, it is assumed that the damaged soil is a three-dimensional wedge and a modified three-dimensional wedge in the active and passive failure modes, respectively. The shallow soil pressure theory and the soil plastic limit equilibrium theory are derived by analyzing the stress distribution on the damaged soil. The equation for revealing the inner essence between the support force of the shield excavation surface and excavation surface displacement under the condition of sand-covered soil is used. Secondly, the numerical simulation method analyzes the displacement of the excavation surface when the support force changes under different working conditions, and the relationship curve between the excavation surface support force and the shield tunneling displacement is obtained. The comparison and analysis between the numerical simulation calculation and the theoretical analysis indicate that the deduced calculation equation for the excavation surface support force based on the displacement earth pressure is reasonable.

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Section: Displacement Earth Pressure Theorymentioning

confidence: 99%

“…According to this theory, the soil takes on a static state at the beginning. Due to the external disturbance and the change of soil microstructure [29,30], a certain deformation occurs.…”

Section: Displacement Earth Pressure Theorymentioning

confidence: 99%

A Displacement‐Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

Guang

Han

Zhang

et al. 2021

Advances in Civil Engineering

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“…Technical Editor: Daniel Onofre de Almeida Cruz, D.Sc. 3, more than 90% of the holes and openings of cutterhead are blocked by the caked mud, with the faceplate fully covered with mud, the central part completely blocked, and the inside space filled up with silt ( Fig. 1).…”

Section: Bid Of Wuhan Metro Linementioning

confidence: 99%

“…As a specialized machine for tunnel construction, the slurry shield has become essential equipment for the development of high-water tunnels such as large-scale trans-ocean or river-crossing projects [1][2][3][4]. However, with the great appliance of the slurry shield machine, prominent problems emerging in the process have posed severe challenges to us, and many scholars at home and abroad have carried out relevant research on these issues.…”

Section: Introductionmentioning

confidence: 99%

Effect of the nozzle structure of the large-diameter slurry shield cutterhead on the scouring characteristics

Xiao

Xia

Mao

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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The mud cake of the large-diameter slurry shield severely affects the tunneling efficiency and construction safety, the avoidance and elimination of which largely depends on the scouring characteristics of the nozzle. Based on the solid-liquid twophase flow theory and dynamic mesh technology, this paper establishes a mud flow model of the nozzle on a slurry shield cutterhead and a cutterhead rotation model and builds a simulation model of the cutterhead nozzle scouring process with CFD. By verifying the simulation model with the self-developed 1 Mpa pressure-bearing scouring test bench, the paper conducts an analysis on how the convergence angle, outlet diameter, and length-diameter ratio of the 12 m large-diameter slurry shield cutterhead affect the scouring characteristics of the nozzle. The results show that when the convergence angle is 13°, the flow fields will be more uniformly distributed inside the nozzle, the average flow rate will be maximized, reaching 3.29 m/s, and the pressure loss will be minimized, thus leading to a relatively good scouring performance. With the assurance of both high flow speed and low pressure loss, the nozzle outlet diameter can be set between 30 and 60 mm for optimal flushing effect; at this point, the average mud flow rate is no less than 3 m/s, and the pressure loss is no more than 10 6 pa, which can help solve the caking problem to some extent. With the increase in length-diameter ratio, the loss of static pressure and total pressure witnessed a relatively high rise, as result of which a smaller long-diameter ratio will be more appropriate, also considering the mud flow rate reaches a maximum value of 3.24 m/s when the ratio is 3 and satisfying results could be achieved when the above ratio has the value of about 3.

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“…Efficiency of the pressure transfer mechanisms for different interaction at the tunnel face during excavation stage, illustrated for the elevation at the tunnel axis after[28]: a) Case A; b) Case B-1; c) Case B-2…”

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confidence: 99%

Influence of stagnation gradient for face support calculation in Slurry Shield Tunnelling

Zizka

Kube

Schößer

et al. 2020

Geomechanics and Tunnelling

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In slurry shield tunnelling, a reliable face support is presumed if a sufficient support pressure is transferred and the slurry excess pressure provides efficient support pressure on the soil skeleton. The required support pressure is calculated in reference to the groundwater pressure and the earth pressure. In this paper, the sliding wedge mechanism is applied. To ensure face stability, the support pressure transfer needs to be provided within the theoretical sliding wedge at the tunnel face. Therefore, the penetration depth of the bentonite suspension as a support medium has to be kept within limits. Research shows that certain penetration is required.The stagnation gradient defines the relation of the support pressure and the penetration depth of the suspension. The gradient has a described minimum, but also an undefined but existing maximum. The German standard DIN 4126 describes two cases for the minimum at each trench depth: Either the pressure losses due to the pressure acting outside the sliding wedge are less than 5 % or the stagnation gradient is at least 200 kN/m3. If the supporting pressure gradient is below 200 kN/m3, DIN 4126 defines rough reduction factors. For a more precise observation of the stagnation gradient, this paper presents a detailed supplement to the DIN 4126 approach taking the tunnel diameter and the angle of the sliding wedge into account. The aim is to determine the minimum recommended stagnation gradient for which no increase of the slurry excess pressure is necessary due to too deep penetration.

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Slurry Shield Tunneling: New Methodology for Simplified Prediction of Increased Pore Pressures Resulting from Slurry Infiltration at the Tunnel Face Under Cyclic Excavation Processes

Cited by 41 publications

References 15 publications

A Displacement‐Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

A Displacement‐Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

Effect of the nozzle structure of the large-diameter slurry shield cutterhead on the scouring characteristics

Influence of stagnation gradient for face support calculation in Slurry Shield Tunnelling

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