scholarly journals Experimental Study on the Formation and Characteristics of Mud Filtration Cake in Large-Diameter Slurry Shield Tunneling

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Lei Kou ◽  
Jinjie Zhao ◽  
Fanglei Lian ◽  
Ronghu Miao
Keyword(s):  
Fractal Dimension ◽  
Large Diameter ◽  
Test Results ◽  
Shield Tunneling ◽  
Mud Cake ◽  
Filtration Loss ◽  
Pore Area ◽  
Mud Filtration ◽  
Slurry Shield ◽  
Penetration Tests

Multiple soil layers may be exposed simultaneously on the excavated surface of a large-diameter slurry shield. To study the formation and characteristics of mud filtration cake on the excavation surface during large-diameter slurry shield tunneling, penetration tests of mud slurries in different soils were carried out using a self-made device, and the microstructures of different mud filtration cakes were observed using scanning electron microscopy. The test results showed that there were three categories of filling forms for mud slurries permeating the soils: mud filtration cake, mud cake + permeation zone, and permeation zone; correspondingly, there were three types of filtration loss, which was mainly affected by the specific gravity of mud slurry. Finally, the porosity and the fractal dimension for the pore area of the mud filtration cake were calculated, and it is found that the fractal dimension of pore area is beneficial to classify the type of mud filtration cake.

scholarly journals Risk Analysis and Control Measures for Slurry Shield Tunneling Diagonally under an Urban River Embankment

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yu Liang ◽  
Xiangyu Chen ◽  
Junsheng Yang ◽  
Linchong Huang
Keyword(s):  
Large Diameter ◽  
Fine Sand ◽  
Urban River ◽  
Control Measures ◽  
Additional Stress ◽  
Shield Tunneling ◽  
Cross River ◽  
Sand Stratum ◽  
Slurry Shield ◽  
River Embankment

The construction of urban cross-river tunnels usually requires passing under river embankments, which inevitably disturbs the embankment substratum and causes ground deformation. Previous engineering cases have shown that embankment settlement is greater than ordinary surface settlement and that uneven settlement results in cracks of in the embankment, reducing the embankment stability. Based on a cross-river tunnel project in China, the construction risks caused by the additional stress on the embankment substratum, asymmetrical embankment load, and shield tunneling in saturated fine sand are analyzed during a large-diameter slurry shield tunneling below an urban river embankment diagonally. Additionally, relevant risk control measures, such as slurry pressure, jacking thrust setting, and driving velocity in the saturated fine sand stratum, are evaluated. The results show that during shield tunneling under a diagonal urban river embankment, the additional stress and asymmetrical load effects should be considered, and the shield slurry pressure and jacking thrust should be adjusted according to the distance between the cutter head and the embankment. Furthermore, based on settlement monitoring data, the driving velocity of the shield should be reasonably adjusted in a timely manner to avoid disturbing the fine sand stratum below the embankment.

Preliminary Study on Formation Law Simulation of Filter-Cake in Slurry Shield at Meso-Scale Level

2012 ◽  
Vol 224 ◽  
pp. 362-366
Author(s):  
Peng Wei ◽  
Xiao Dong Ni ◽  
Ti Kang Li
Keyword(s):  
Filter Cake ◽  
Bentonite Clay ◽  
Element Model ◽  
Scale Level ◽  
Shield Tunneling ◽  
Membrane Formation ◽  
Mud Cake ◽  
Preliminary Study ◽  
Slurry Shield ◽  
Meso Scale

In order to investigate the mechanism of mud membrane formation during slurry shield tunneling, mesoscopic particle flow method was carried out to examine the way of mud membrane forming in sandy soil stratum at granular level with combinations of the traits of (particle) discrete element model. This study showed that the type of mud membrane formed transit from mud cake to permeable mud cake zone with the increase of the diameter rate of strata soil and bentonite clay until an inability to form mud membrane in the same strata of the soil. Numerical simulation results and related laboratory test are in good accordance, it bear out that researching the It has been demonstrated that it is comparatively reasonable and effective to carry out research on the mechanism of mud membrane formation at a meso-scale level.

Numerical Analysis of Metro Station Construction by Large-Diameter Shield and Pile-Beam-Arch Method

2011 ◽  
Vol 368-373 ◽  
pp. 2711-2715 ◽  
Author(s):  
De Yun Ding ◽  
Xiu Ren Yang ◽  
Wei Dong Lu ◽  
Wei Ning Liu ◽  
Mei Yan ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Large Diameter ◽  
Element Model ◽  
Construction Method ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Shield Tunneling ◽  
Metro Station ◽  
Dimensional Finite Element ◽  
New Construction

In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

Experimental Research on the Engineering Properties of Foam-Improved Red Clay Soil

2011 ◽  
Vol 261-263 ◽  
pp. 1831-1835
Author(s):  
Guo Gang Qiao ◽  
Da Jun Yuan ◽  
Bo Liu
Keyword(s):  
Experimental Research ◽  
Clay Soil ◽  
Soil Improvement ◽  
Engineering Properties ◽  
Screw Conveyor ◽  
Test Results ◽  
X Ray Diffraction ◽  
Shield Tunneling ◽  
Red Clay ◽  
Improvement Measures

Red clay soil is widely distributed in south China, the microstructure of red clay soil was studied applying scanning electron microscopy (SEM), and the X-ray diffraction analysis (XRD) test found that a large number of swelling inducing minerals, for example, montmorillonite, illite-montmorillonite or chlorite-smectite were contained in the red clay soil. Shield tunneling in this kind of stratum is prone to arising “cake” and “arch” phenomena and it prone to lead screw conveyor device unsmooth dumping, so soil improvement measures must be taken. Foam as the most advanced soil conditioner has been widely used in shield construction. Using self-developed foam agent, experimental research on foam conditioning red clay soil was carried out, test results show that foam can not only significantly reduce the soil shear strength, but also can greatly enhance the soil's compressibility and fluidity, which is significant for the smooth dumping and excavation face stability maintenance.

Test of Solidification Characteristics of Grouting and the Effect on Strata Deformation in Shield Tunnelling

2012 ◽  
Vol 568 ◽  
pp. 80-84
Author(s):  
Xiao Chun Zhong ◽  
Wei Ke Qin ◽  
Hai Wang
Keyword(s):  
Numerical Model ◽  
Rigid Body ◽  
Active Control ◽  
Calculation Method ◽  
Civil Engineering ◽  
Test Results ◽  
Shield Tunneling ◽  
Shield Tunnelling ◽  
Strata Deformation ◽  
Over Time

Back-fill Grouting is a key procedure for the active control of strata settlement during shield tunnelling in civil engineering. The paper studies the stress - strain characteristics of grouting and the state of grout, which changes from liquid to solid over time and is simulated by variable rigid body. The model of flowing state are divided in four phases from liquid-plastic to rigid state. The paper establish a numerical model of shield tunnelling in civil engineering with the consideration of characteristics of grout deformation, and has analyzed law of strata settlement. The test results show that the calculation method can well accord with the four stages of strata deformation, and can more accurately reflect the process of strata deformation caused by shield tunneling.

scholarly journals The Effect of Probe Geometry on Rind Puncture Resistance Testing of Maize Stalks

2020 ◽  
Author(s):  
Douglas D. Cook ◽  
Kyler Meehan ◽  
Levan Asatiani ◽  
Daniel J Robertson
Keyword(s):  
Meta Analysis ◽  
Resistance Testing ◽  
Test Results ◽  
Lodging Resistance ◽  
Puncture Resistance ◽  
Analysis Of Results ◽  
Stalk Lodging ◽  
Penetration Tests ◽  
Shape And Size ◽  
Probe Geometry

Abstract Background: Stalk lodging (breaking of plant stems prior to harvest) is a major impediment to increasing agricultural yields of grain crops. Rind puncture resistance is commonly used to predict the lodging resistance of several crop species. However, there exist no standard operating procedures or suggested protocols for conducting rind penetration experiments. In addition, experimental details of rind penetration tests such as the shape and size of the penetrating probe are rarely reported in the literature. This has prevented meta-analysis of results and has likewise prevented key findings of past studies from being replicated. As a first step towards establishing an agreed upon measurement standard for rind puncture resistance this study investigates the effect of the puncturing probe’s geometry on test results.Results: Results demonstrate that probe geometry has a significant impact on test results. In particular, results showed that a 2mm diameter chamfered probe produced stronger correlations with stalk bending strength than a 1.5mm diameter pointed probe. The chamfered probe was also more strongly correlated with geometric features of the stalk that are known to influence stalk lodging resistance (e.g., rind thickness, diameter and section modulus). In addition, several alternative rind penetration metrics were investigated, and some were found to be superior to the most common rind penetration metric of maximum load. Conclusions:There is a need in the agricultural and plant science community to create agreed-upon operating procedures and testing standards related to mechanical traits of plant stems. In particular, a standardized probe geometry and insertion rate for rind penetration studies are needed to enable greater interoperability and meta-analysis of results. Probe shape and size should be reported in any study conducting rind penetration tests as these factors significantly impact test results.

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