scholarly journals Application Ranges of EPB Shield TBM in Weathered Granite Soil: A Laboratory Scale Study

2021 ◽  
Vol 11 (7) ◽  
pp. 2995
Author(s):  
Tae-Hwan Kim ◽  
In-Mo Lee ◽  
Hee-Young Chung ◽  
Jeong-Jun Park ◽  
Young-Moo Ryu
Keyword(s):  
Water Content ◽  
Upper And Lower Bounds ◽  
Shield Tunnel ◽  
Particle Crushing ◽  
Pressure Balance ◽  
Soil Conditioning ◽  
Weathered Granite ◽  
Weathered Granite Soil ◽  
Granite Soil ◽  
Epb Shield

Soil conditioning is a key factor in increasing tunnel face stability and extraction efficiency of excavated soil when excavating tunnels using an earth pressure balance (EPB) shield tunnel boring machine (TBM). Weathered granite soil, which is abundant in the Korean Peninsula (also in Japan, Hong Kong, and Singapore), has different characteristics than sand and clay; it also has particle-crushing characteristics. Conditioning agents were mixed with weathered granite soils of different individual particle-size gradations, and three characteristics (workability, permeability, and compressibility) were evaluated to find an optimal conditioning method. The lower and upper bounds of the water content that are needed for a well-functioning EPB shield TBM were also proposed. Through a trial-and-error experimental analysis, it was confirmed that soil conditioning using foam only was possible when the water content was controlled within the allowable range, that is, between the upper and lower bounds; when water content exceeded the upper bound, soil conditioning with solidification agents was needed along with foam. By taking advantage of the particle-crushing characteristics of the weathered granite soil, it was feasible to adopt the EPB shield TBM even when the soil was extremely coarse and cohesionless by conditioning with polymer slurries along with foam. Finally, the application ranges of EPB shield TBM in weathered granite soil were proposed; the newly proposed ranges are wider and expanded to coarser zones compared with those proposed so far.

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 Variation in strength owing to solidification treatment of weathered granite soil

2021 ◽  
Vol 21 (3) ◽  
pp. 163-169
Author(s):  
Sungyeol Lee ◽  
Sunggon Kim ◽  
Wonjin Baek ◽  
Sungjin Kwon ◽  
Changsung Jung ◽  
...  
Keyword(s):  
Compression Strength ◽  
Raw Material ◽  
Unconfined Compression Strength ◽  
Unconfined Compression ◽  
X Ray Diffraction ◽  
Curing Conditions ◽  
Weathered Granite ◽  
Soil Cement ◽  
Weathered Granite Soil ◽  
Granite Soil

Recently, soil-cement is being increasingly used in various applications such as road pavements, slope protection, backfilling of earth walls, and improving soft ground, in order to increase the strength of the raw material soil. Therefore, in this study, the characteristics of changes in the unconfined compression strength of soil-cement were analyzed by adding a solidifying agent targeting granite soil, which is representatively distributed in Korea. Laboratory tests were conducted to analyze the changes in strength according to 1) curing conditions and fine contents, 2) inorganic solidifying agent, and 3) repeated effects of dry and wet conditions. The unconfined compression strength of soil-cement increased as the curing period and mixing ratio increased, and it was constant after 14 days of curing. In addition, weathered granite soil with relatively low fine contents showed a large increase in the unconfined compression strength. In addition, the strength increased with an increase in the solidifying agent added. X-ray-diffraction analysis showed that vermiculite was generated by adding cement and admixtures, and the strength was increased by filling the gap between the particles. Considering the results of this study, a relationship between the unconfined compression strength and the elastic modulus of soil-cement by treatment with a solidifying agent was proposed.

scholarly journals Four-Year Monitoring Study of Shallow Landslide Hazards Based on Hydrological Measurements in a Weathered Granite Soil Slope in South Korea

Water ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2330
Author(s):  
Kyeong-Su Kim ◽  
Sueng-Won Jeong ◽  
Young-Suk Song ◽  
Minseok Kim ◽  
Joon-Young Park
Keyword(s):  
Slope Stability ◽  
South Korea ◽  
Shallow Landslide ◽  
Soil Slope ◽  
Weathered Granite ◽  
Landslide Hazards ◽  
Infinite Slope Stability Model ◽  
Geological Conditions ◽  
Weathered Granite Soil ◽  
Granite Soil

To build a comprehensive understanding of long-term hydro-mechanical processes that lead to shallow landslide hazards, this study explicitly monitored the volumetric water content (VWC) and rainfall amount for a weathered granite soil slope over a four year period. From the 12 operational landslide monitoring stations installed across South Korea, the Songnisan station was selected as the study site. VWC sensors were placed in the subsurface with a grid-like arrangement at depths of 0.5 and 1.0 m. Shallow landslide hazards were evaluated by applying an infinite slope stability model that adopted a previously proposed unified effective stress concept. By analyzing the variations in the monitored VWC values, the derived matric suctions and suction stresses, and the calculated factor of safety values, we were able to obtain numerous valuable insights. In particular, the seasonal effects of drainage and evapotranspiration on the slope moisture conditions and slope stability were addressed. Preliminary test results indicated that continuous rainfall successfully represented the derived matric suction conditions at a depth of 1.0 m in the lower slope, although this was not the case for the upper and middle slopes. The significance of a future study on cumulative field monitoring data from various sites in different geological conditions is highlighted.

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