Slurry Shield Research Articles

Slurry Clogging Criteria for Slurry Shield Tunnelling in Highly Permeable Ground

When tunnelling using a slurry shield tunnel boring machine (slurry shield TBM), the tunnel face stability is significantly influenced by the filter cake formation during slurry injection to the chamber. In order to study slurry penetration behavior in highly permeable ground, comprehensive slurry injection tests were performed by varying the particle size distribution of the ground, the bentonite content and viscosity, and the slurry injection pressure. According to the results of these tests, the slurry penetration behavior could be classified into three types: Type A, denoting negligible slurry penetration; Type C, denoting excessive penetration; and Type B, denoting in-between penetration. Slurry clogging criteria (SCC) were proposed to classify these three types. The main superiority of the proposed SCC is that it can consider the grain size distribution of the ground, the characteristics of the slurry, and the slurry injection pressure together when assessing the penetration characteristics. The SCC value can either be obtained by performing a simple slurry penetration test; or it can be theoretically estimated by using the regression equation proposed in this paper.

Experimental study on property change of slurry and filter cake of slurry shield under seawater intrusion

During submarine tunnels construction by the slurry shield tunneling method, seawater may enter the pressure chamber from excavation surface and mix with the slurry. This will cause the physical stability of the slurry to change and will also affect the properties of the filter cake and the stability of the excavation surface. This study aims to investigate the effect of seawater on the properties of the slurry and the filter cake using laboratory experiments. Mixtures of slurry and seawater in different ratios were prepared and the physical stability, viscosity, and zeta potential of the slurries were tested. The basic properties and microstructure of the filter cake formed by the different slurries were also investigated. The results showed that the intrusion of seawater significantly reduced the physical stability and the zeta potential of the slurry. As the seawater content in the slurry was increased, the void ratio in the filter cake formed by the slurry decreased and the filter cake permeability coefficient increased from 10−8 cm/s to 10−7 cm/s. In the filter cakes formed by slurries containing some seawater, soil particles in aggregates were more tightly packed with more intra-aggregate pores and better connectivity than the seawater-free filter cake. The decrease in zeta potential was the fundamental reason for both the slurry’s change in physical stability and the changes in filter cake properties.

Slurry filtration process and filter cake formation during shield tunnelling: Insight from coupled CFD-DEM simulations of slurry filtration column test

The slurry infiltration process plays a crucial role in the slurry shield tunneling process, during which a filter cake is expected to form on the tunnel face to transmit the support pressure. This paper proposed a coupled computational fluid dynamics (CFD)-discrete element method (DEM) numerical approach to investigate the slurry infiltration and filter cake formation by modeling the slurry filtration column test, which incorporates the particles, fluid phase, and their interactions. The Simplified Johnson-Kendall-Roberts (SJKR) model was employed to consider the cohesion effect between slurry particles. The validity of the current approach was verified based on the Kozeny-Carman Equation modified by Ergun (1952). The slurry filtration process was divided into four stages with different characteristics of filter cake porosity and pressure drop. Influences of some key model parameters including externally-applied pressure, friction coefficient and cohesion energy density on filter cake formation were investigated and the underlying mechanisms were explored. The law of pressure variation within the filter cake was proposed. A linear relationship between pressure drop ratio and porosity of filter cake was established, which will be useful for predicting the effectiveness of support pressure transmission due to slurry filtration.

Numerical Study and Field Monitoring of the Ground Deformation Induced by Large Slurry Shield Tunnelling in Sandy Cobble Ground

This paper presents the ground deformation induced by the large slurry shield tunnelling with a diameter of about 12 m in urban areas, which may challenge the safety of the existing nearby constructions and infrastructures. In this study, the ground deformation is analyzed by a three‐dimensional finite difference model, involving the simulation of tunnelling advance, grouting, and grouting hardening. The transverse settlement, longitudinal settlement, and horizontal displacement of the ground are analyzed by comparing the simulation results with the field measurements in the Rapid Transit Line Project from Beijing Railway station to West Beijing Railway station in China. The numerical model proposed in this paper could well predict the ground deformation induced by large slurry shield tunnelling. The results show that the main transverse settlement occurs within the zone about 1.5 times of the excavation diameter, and the settlement during the passage of the shield and the tail void plays a most important role in the excavation process.

Cyber-physical-system-based safety monitoring for blind hoisting with the internet of things: A case study

Abstract This study proposed a cyber-physical-system-based safety monitoring system (CPS-SMS) for blind hoisting in metro and underground constructions. Wuhan Metro's Sanyang road tunnel, which crosses the Yangtze River in China, was selected for this case study. A slurry shield machine with a cutter diameter of 15.76 m was designed to be hoisted for 44 m into the underground tunnel shafts. The major challenges of this hoisting were as follows: 1) complex construction environment for hoisting, 2) limited visibility of crane operator or blind hoisting, and 3) precise control of position and gesture of a giant cutter wheel in real time. To overcome these challenges, the CPS-SMS was proposed to simulate and monitor the hoisting process to avoid the unsafe status of cranes and the hoisted cutter wheel. Internet-of-things technologies, such as wireless sensor-based location and tracking, self-organized Wi-Fi, and bi-directional communication, were used to prevent accidents in the changing and dynamic hoisting process. The implementation of monitoring blind hoist in the Yangtze River, which crosses the metro tunnel construction site, was successful, that is, no collision or injury occurred. The CPS-SMS can be applied by practitioners to various construction projects, such as dams, high-rise buildings, and large-scale infrastructure projects, to decrease the likelihood of safety risks in blind hoisting in complex environments.

New testing method for the prediction of the dispersion of soil in slurry shield tunnelling

AbstractIn this contribution, we present a new testing method for the prediction of the dispersion of soil in slurry shield tunnelling. It is based on the proven slake durability test equipment but differs substantially regarding the procedure for testing and evaluation. With the results, a substantial data analysis was conducted searching for correlations with typical characteristic soil parameters. For the first time in tunnelling practice, the test enables a qualitative assessment and therefore a prognosis of the expected dispersion based on quantitative values determined in a traceable and reproducible testing method. In addition the test allows for an estimation of the dispersion tendency based on figures for the plasticity and consistency, which are usually collected anyway in the preliminary stages of a tunnelling project. Contractual recommendations are also provided concerning the topic of dispersion.

A Coupled CFD–DEM Simulation of Slurry Infiltration and Filter Cake Formation during Slurry Shield Tunneling

Tunneling in highly permeable ground using a slurry shield machine can be challenging because it is difficult to form the so-called filter cake on the tunnel face to transport the support pressure. Consequently, destructive accidents might happen, such as face instability and water inrush. How to form an efficient filter cake in time is crucial during engineering practice, especially in ground with high permeability. Various theoretical and experimental analyses regarding the formation of filter cakes have been conducted. However, due to the complexity of this problem, which has to incorporate the mechanical and hydraulic behaviors of the fluid–solid mixture system, few numerical simulations are found in the literature. In this paper, with the aid of a newly developed numerical tool, a coupled CFD (computational fluid dynamics)–DEM (discrete element method) simulation is established to study the slurry infiltration and filter cake formation during slurry shield tunneling. The slurry infiltration process is simulated by modelling the scheme of the infiltration column test, in which sedimentation behaviors of slurry particles are captured and compared with experimental results. The results show that the sedimentation behaviors of the slurry particles and filter cake formation phenomenon are well captured by simulations and in accordance with the experiments, which indicates the robustness of the coupled CFD–DEM simulation used in present work.

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

Within mechanized tunneling, slurry shields are used for excavations in soils with unstable tunnel face due to the possibility to support the tunnel face with pressurized slurry (bentonite suspension). Two key conditions have to be fulfilled to stabilize a tunnel face. These two conditions are sufficient face support pressure in the excavation chamber and the pressure transfer of slurry excess pressure, exceeding the pore pressure, onto the soil skeleton. In practice, the German standard DIN 4126 [Nachweis der Standsicherheit von Schlitzwanden (Stability analysis of diaphragm walls), Deutsche Institut fur Normung, 2013] is usually used to predict this transfer. However, DIN 4126 (2013) cannot explain increased pore water pressures measured in practice close to the slurry supported tunnel face during excavation. The increased pore water pressures reduce the efficiency of slurry face support. These pressures are explained by on-going disturbance of the pressure transfer mechanism by periodic rotating cutting tools. The characteristics of disturbance are designated as excavation scale. Another factor of influence is the timespan during which the pressure transfer mechanism can achieve a significant decrease in its own permeability, and thereby to decrease considerably the flow through the tunnel face. By scale comparison of these two processes, a prognosis about occurrence of increased pore water pressures in saturated sands can be derived. It turns out that the different combinations of penetration rate and revolutions per minute of the cutting wheel, while keeping the advance rate constant, would result in different chance for causing increased pore pressures. Consequently, an excavation strategy for reducing the chance for increased pore pressures is suggested with respect to three reference slurry shields.

Influence of the slurry-stabilized tunnel face on shield TBM tool wear regarding the soil mechanical changes – Experimental evidence of changes in the tribological system

The wear of slurry shield TBM excavation tools is a challenging topic that has been discussed over many years, Due to the complexity of the tribological system that defines the tool wear, no sufficient approach to determine the wear in a specific tunneling project has been developed up to now. The elementary step to display the application-oriented tribological system is one of the main issues regarding laboratory scale test methods. Therefore, the RUB Tunneling Device has been developed at the Ruhr-University Bochum (Germany). With this apparatus, several influencing factors regarding the tribological system of a TBM-tool can be analyzed. A unique feature of the device is the experimental simulation of a slurry shield excavation, including a realistic tunnel face support. This paper focuses on the experimental simulation of slurry shield excavation and the influence of face support on tool wear. Changes in the soil mechanical properties due to slurry penetration at the tunnel face are regarded and correlated with the tribological system of a slurry shield excavation. It is proven that the tribological system, and thus the tool wear, changes significantly due to slurry injection.

TBM tunnelling under the Suez Canal – Port Said tunnels in challenging ground conditions

AbstractThe Port Said Tunnels Project consists of twin road tunnels crossing the Suez Canal with a planned capacity of 2,100 mixed vehicles/hour in each direction. The dual carriageway tunnels are an important part of the Suez Canal Region Development Plan, which will connect the Sinai with other Egyptian provinces to provide a gateway for investment opportunities and speed up the development of Sinai province. The project is located 19 km south of Port Said city, near the northern entrance of the Suez Canal. The tunnels are constructed using slurry shield TBMs in difficult ground conditions, including the presence of methane gas. This paper demonstrates the main challenges encountered during tunnelling and the measures taken to mitigate potential risks during construction and to control long‐term differential settlements in the upper, very soft soil. The tunnels are connected by two cross passages which are being constructed using ground freezing and conventional tunnelling.

Lake Mead Intake No 3 Tunnel – Design considerations and construction experience

AbstractThis paper presents the pre‐construction evaluation of the ground for the Lake Mead Intake No 3 Tunnel and the experience gained from the project, which had the aim of maintaining water supplies for the Las Vegas greater metropolitan area. The construction of this tunnel using a dual‐mode slurry shield represents a major engineering achievement, which pushed back the boundaries of closed shield tunnelling: Overcoming an extended fault zone under high hydrostatic pressure in the metamorphic rocks and mucking‐out difficulties associated with high rates of water inflow in the sedimentary rocks necessitated closed‐mode operation over about 2 km at unprecedentedly high face pressures of up to 14 bar.

Numerical simulation of slurry fracturing during shield tunnelling

The slurry type shield method is an important tunnelling method, especially for underwater tunnels in soft soil. If the slurry pressure is too high, it may lead to slurry fracturing of the stratum in front of the excavation face and cause water inrush accidents. Controlling the face stability of shallow shield tunnels is difficult owing to the inadequate understanding of the slurry induced fracturing mechanism. Most importantly, understanding the details of the slurry fracturing propagation process is not enough, as the process is especially complicated. However, the propagation process cannot be directly observed in the field or in small-scale laboratory tests because it occurs in bodies of soil. Thus far, an effective approach to investigate the slurry fracturing mechanism in the surrounding stratum of a slurry shield tunnel has not been reported. In this paper, a numerical simulation method for evaluating tunnelling-induced slurry fracturing is presented. The developed numerical model considered the couplings of stress distribution, fluid flows, and fracturing. The fracture initiation, branching, and propagation in the stratum could be reproduced numerically. A series of simulations for different ratios of cover depth to tunnel diameter were carried out to investigate the propagation process of slurry fracturing. The effects of slurry pressure at the tunnelling face and the cover depth above the tunnel were investigated. The results of the fracturing process induced by slurry, such as the fracture propagation velocity, slurry pressure distribution along the fracture, fracture initiation pressure, fracture extending pressure, and stratum deformations, were analyzed.

泥水盾构砂层掘进防止泥浆箱砂子沉淀装置技术应用——以中俄原油管道二线盾构穿越工程为例

泥水盾构砂层掘进防止泥浆箱砂子沉淀装置技术应用——以中俄原油管道二线盾构穿越工程为例

泥水盾构循环泥浆制备工艺技术——以甬台温天然气输气管道瓯江盾构工程为例

泥水盾构循环泥浆制备工艺技术——以甬台温天然气输气管道瓯江盾构工程为例

泥水盾构隧道施工环境保护技术措施的应用

泥水盾构隧道施工环境保护技术措施的应用

浅谈泥水盾构卵石层加压进舱技术

浅谈泥水盾构卵石层加压进舱技术

Analytical methods in predicting excess pore water pressure in front of slurry shield in saturated sandy ground

During mechanized tunnelling with a slurry shield in saturated sand, excess pore water pressures will generate in front of slurry shield. These excess pore water pressures can influence the stability of the tunnel face. The magnitude of the excess pore water pressures thus becomes of importance for the stability of the tunnel face. In this paper, two theories solutions are presented to describe the development and decline of the excess pore water pressures in front of slurry shield in saturated sandy ground. The first theory considers transient flow in a semi-confined aquifer with elastic storage, while the second one assumes different conditions of unconfined steady-state flow governed by the penetration of slurry into the soil in front of the tunnel face. Both methods are tested at different positions around the tunnel, during both drilling and standstill and compared with measurements performed at the Green Hart Tunnel and North/South line in the Netherlands. It is shown that both analytical theories can predict the excess pore water pressures in front of slurry shield. The second one seems more appropriate because it reflects the effect of slurry penetration. Furthermore, the measurements seem to indicate that the influence of elastic storage is not so big as assumed in the first theory.

Numerical investigation of pipeline transport characteristics of slurry shield under gravel stratum

In order to grasp the pipeline transport characteristics of slurry shield under gravel stratum, with a cross-river tunnel construction of Lanzhou metro as the research background, the numerical simulation method is adopted, and a slurry-stone two-phase flow model is established based on multiphase flow theory by considering the rheological properties of slurry. Besides, corresponding simulation models validated by experiment are established using CFD and DEM softwares, and the impacts of inlet slurry velocity, stone volumetric concentration and pipe inclination angle on pressure drop and transport capacity of the pipeline are investigated. The results show that stones are mainly distributed at the bottom of the pipeline for horizontal straight pipes. The pressure drop and transport capacity increase exponentially with the increase of inlet slurry velocity and stone volumetric concentration. For inclined straight pipes, the pressure drop of the pipeline increases slowly with the pipe inclination angle increasing from 0° to 60°, but increases rapidly when the pipe inclination angle increases from 60° to 90°; the transport capacity reduces slowly at first and then increases rapidly with the increase of pipe inclination angle, and the lowest value appears at 45–60°.

Numerical investigation of tunneling in saturated soil: the role of construction and operation periods

This paper numerically investigates the slurry shield tunneling in fully saturated soils with different hydraulic conductivities in short- and long-term scales. A fully coupled hydromechanical three-dimensional model that accounts for the main aspects of tunnel construction and the hydromechanical interactions due to tunneling process is developed. An elasto-plastic constitutive model obeying a double hardening rule, namely hardening soil model, is employed in the numerical simulations. The research mainly focuses on assessing the influence of soil hydraulic conductivity and the method to simulate backfill grouting in the tail void on the evolution of ground subsidence, excess pore water pressure and lining forces. Two different consolidation schemes have been taken into account to computationally address the tunnel construction in soil with low and high hydraulic conductivities. In addition, different methods are employed to simulate the tail void grouting as a hydromechanical boundary condition and to study its effects on the model responses. Finally, the influences of infiltration of the fluidized particles of grouting suspension into the surrounding soil and its corresponding time–space hydraulic conductivity evolution on the displacements and lining forces are studied.

해수의 영향에 따른 이수식 TBM의 슬러리 관리를 위한 기초적 연구

해수의 영향에 따른 이수식 TBM의 슬러리 관리를 위한 기초적 연구