Browsing by Author "Fang, Yung-Show"

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An estimation of subsurface settlement due to shield tunneling
(2014-09-01)
Fang, Yung-Show
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Wu, Chun-Te
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Chen, Shen-Feng
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Liu, Cheng
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交大名義發表
An empirical method based on the normal distribution function is proposed to estimate the magnitude and extent of subsurface settlement associated with shield tunneling. Based on field measurement data, empirical relationships are established between surface and subsurface settlement troughs. Assuming the surface settlement due to tunneling could be obtained by the analytical, numerical, or field monitoring method, based on these relationships, the range of subsurface-settlement can be easily estimated. Twenty three sets of measured subsurface settlement profiles associated with tunneling with open, slurry and earth-pressure-balance shields are compared with the predicted curves. It is concluded that the application of normal probability function can be extended to estimate the subsurface settlement due to shield tunneling. The width of the subsurface settlement trough decreases with increasing depth, and the maximum subsurface settlement increases with increasing depth. The subsurface settlement curves calculated using the proposed method are in fairly good agreement with field measurements for various types of shield machines, depths and diameters. (C) 2014 Elsevier Ltd. All rights reserved.
Double-O-Tube shield tunneling for Taoyuan International Airport Access MRT
(2012-07-01)
Fang, Yung-Show
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Kao, Chung-Cheng
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Shiu, Yu-Fen
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土木工程學系
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Department of Civil Engineering
From 1989 to 2010, 20 tunneling projects have been carried out with the Double-O-Tube (DOT) shield tunneling method in the world. In this paper, the DOT shield tunneling for the construction of Taoyuan International Airport Access (TIAA) Mass Rapid Transit (MRT) system is introduced. A 6.42 m-diameter, 11.62 m-wide DOT shield machine was used to build the first DOT tunnel in Taiwan. Field data indicated that, throughout the tunneling operation, the rolling angle of the DOT shield varied between +0.23 degrees and -0.39 degrees, which was within the limiting design values of +0.6 degrees and -0.6 degrees proposed by both TIAA MRT and Shanghai Metro. For the six surface settlement troughs collected from Tokyo, Shanghai and Taipei, the ground loss due to DOT shield tunneling ranged from 0.23% to 1.30%, and the average ground loss was 0.78%. As compared with the ground loss due to single-circular Earth-Pressure-Balance (EPB) shield tunneling in cohesive soils, the range of ground loss due to DOT shield tunneling was relatively narrow, and the peak ground loss value was significantly less. Underground excavation with the DOT tunneling method would increase the tunneling duration for about 32%. The cost per meter of tunnel constructed with a DOT shield was about 1.5 times that constructed with single-circular shields. The cost of shield machine and segment lining were 23% and 53% of the total tunneling costs respectively. The expensive DOT shield machine and the complicated manufacturing and assembly of DOT lining segments are the main reasons for higher cost of tunneling. However, it would cost a lot more budget and it would be much more risky to excavate three cross-passages between the single-circular tunnels under the river. (c) 2012 Elsevier Ltd. All rights reserved.
Earth pressure due to vibratory compaction
(2008-04-01)
Chen, Tsang-Jiang
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Fang, Yung-Show
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工學院
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土木工程學系
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College of Engineering
This paper presents experimental data on the variation of lateral earth pressure against a nonyielding retaining wall due to soil filling and vibratory compaction. Air-dry Ottawa sand was placed in five lifts and each lift was compacted to achieve a relative density of 75%. Each compacted lift was 0.3 m thick. The instrumented nonyielding wall facility at National Chiao Tung University in Taiwan was used to investigate the effects of vibratory compaction on the change of stresses at the soil-wall interface. Based on the experimental data it has been found that, for a compacted backfill, the vertical overburden pressure can also be properly estimated with the traditional equation sigma(upsilon) = gamma z. The effects of vibratory compaction on the vertical pressure in the backfill were insignificant. On the vertical nonyielding wall, extra horizontal earth pressure was induced by vibratory compaction. After compaction, the lateral earth pressure measured near the top of the wall was almost identical to the passive Rankine pressure. It is concluded that as the cyclic compacting stress applied on the surface of the backfill exceeded the ultimate bearing capacity of the foundation soil, a shear failure zone would develop in the uppermost layer of the backfill. For a soil element under lateral compression, the vertical overburden pressure remained unchanged, and the horizontal stress increased to the Rankine passive pressure. It was also found that the compaction-influenced zone rose with the rising compaction surface. The horizontal earth pressure measured below the compaction-influenced zone converged to the Jaky state of stress.
Earth pressure on an unyielding wall due to a strip surcharge
(2007)
Fang, Yung-Show
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Tzeng, Shi-Han
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Chen, Tsang-Jiang
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土木工程學系
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Department of Civil Engineering
The horizontal pressure acting on a non-yielding wall due to a strip loading was studied in this paper. Based on the experimental results, the following conclusions were made. If the strip surcharge was located near the face of the wall, the surcharge loading would induce a decrease of lateral pressure in the upper part of the compacted backfill. It may be deduced that the surcharge applied on the top of the soil near the wall would compress the soil element vertically. The induced lateral deformation would make the compacted soil "less passive" and the lateral soil thrust to decrease. This phenomenon would disappear if the surcharge loading was removed. The experimental lateral soil thrust induced by surcharge loading was apparently smaller than the theoretical predictions.
Numerical solution of active earth pressures on rigid retaining walls built near rock faces
(2010-11-01)
Fan, Chia-Cheng
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Fang, Yung-Show
;
土木工程學系
;
Department of Civil Engineering
For retaining walls built in mountainous regions, narrow backfill spaces are often encountered. The space to fully develop the active wedge is restricted for walls with a limited backfill space. This paper presents a numerical study on the behaviour of active earth pressures behind a rigid retaining wall with limited backfill space of various geometries. The active earth pressure for a wall built with limited backfill space is considerably less than that of the Coulomb solution, and the location of the resultant of active earth pressures is noticeably higher than one-third of the wall height. The coefficient of active earth pressures is as low as 0.5-0.6 times the Coulomb solution and the h/H value reaches up to 0.4-0.37 if aspect ratio of the fill space is in the range from 0.1 to 0.2. A clear trend between the ratio of the coefficient of active earth pressures at constrained fill conditions over the Coulomb K(a) value and the aspect ratio of the fill-space geometry is obtained. (C) 2010 Elsevier Ltd. All rights reserved.
Numerical solution of active earth pressures on rigid retaining walls built near rock faces
(2010-11-01)
Fan, Chia-Cheng
;
Fang, Yung-Show
;
土木工程學系
;
Department of Civil Engineering
For retaining walls built in mountainous regions, narrow backfill spaces are often encountered. The space to fully develop the active wedge is restricted for walls with a limited backfill space. This paper presents a numerical study on the behaviour of active earth pressures behind a rigid retaining wall with limited backfill space of various geometries. The active earth pressure for a wall built with limited backfill space is considerably less than that of the Coulomb solution, and the location of the resultant of active earth pressures is noticeably higher than one-third of the wall height. The coefficient of active earth pressures is as low as 0.5-0.6 times the Coulomb solution and the h/H value reaches up to 0.4-0.37 if aspect ratio of the fill space is in the range from 0.1 to 0.2. A clear trend between the ratio of the coefficient of active earth pressures at constrained fill conditions over the Coulomb K(a) value and the aspect ratio of the fill-space geometry is obtained. (C) 2010 Elsevier Ltd. All rights reserved.