• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5C
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• pp.155-162
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• 2011

Settlement prediction based on field monitored data, which is used to control subsequent surcharges, is very important in construction management for soft ground improvement with the preloading method. Observational settlement prediction methods, which are suggested for an instantaneous loading, have been widely used in fields. However, they have difficulties in the settlement prediction with subsequent surcharge change. In this paper, a simple method to predict the settlement with subsequent surcharge change is suggested. The suggested method adopts assumptions to simplify the complex field condition and utilizes observational methods. The suggested method is applied to a large consolidation test result, FDM analysis results, and field monitored settlement data to confirm its practicability. From the applications, the suggested method produces reasonable prediction results with various subsequent surcharge changes.

• Geotechnical Engineering
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• v.13 no.2
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• pp.137-154
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• 1997

Piling engineers in limit state design should consider both capacity of a pile and settlements of pile for stability of a structure. This paper analyzes the prediction of the settlements of single piles and nine-group piles installed at an overconsolidated clay site by common prediction methods and cone penetrometer test data obtained closely at pile locations. The effects of Young's modulus, which varies spatially in soil profile, on estimating the set tlements of piles have been investigated briefly. The predicted settlements for single piles and nine-pile group by using simple linear elan tic methods, Vesic's method and Poulos's method, overestimated overalls the measured valroes, and the assumption of Youngs modulus, which are to be varied linearly through the soil layers. did not significantly affect the settlement predictions.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.59-70
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• 2002

Horizontal drains are sometimes installed on the ground together with vertical drains in order to drain excess pore water. Taking into account the discharge capacity of horizontal drains, a new analytical method is developed in this paper, and then a new formula for the discharge capacity of horizontal drains is proposed. It is known from the analysis that the effect of the rate of surcharge loading is negligible in determining horizontal discharge capacity. This formula is described as the function of coefficient of consolidation, space of vertical drain, compression index, length of horizontal drains, and thickness of the compressible layer.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.317-327
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• 2001

For soils with high void ratios, the inverse method of utilizing results obtained from centrifuge model test was used to find the constitutive relation of effective stress - void ratio - permeability whereas conventional oedometer test and constant rate of strain consolidation test were also used to fine its relation at ranges of relatively low void ratio. Results of column test about settlement of interface and pore pressure and distribution with time were compared with numerically estimated values to confirm such a constitutive relation as obtained from the inverse method. Consolidational settlement in dredged and reclaimed ground, where the consolidation was in progress, was predicted by using the numerical technique implemented with the finite strain consolidation theory.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.51-56
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• 2004

The sand compaction pile (SCP) method, which forms a composite ground by driving sand piles into clay deposit, is the most commonly used soil improvement techniques in many countries for more than 30 years. Installation of sand compaction piles reduces the amount of consolidation settlement and increases the bearing capacity of soft clay deposit. In this paper, field survey conducted to investigated the consolidation behavior of the composite ground improved by SCPs. It is suggested that the measured consolidation velocity is later than design theory, however measured consolidation settlement is higher than design theory.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.433-452
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• 2018

The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.17-23
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• 2003

Accurate prediction of consolidation behaviors of the soft ground improved by plastic board drains is not easy because the consolidation characteristics of the improved ground has not been fully elucidated yet. The shape of drains is one of the most important factors which affect the consolidation characteristics of the improved ground. In this paper, a series of model consolidation tests of soft clay ground improved by plastic board drain were carried out, in order to investigate the effect of both plastic board width and stress level on consolidation characteristics of the improved ground. As the results, behaviors of both settlement and excess pore pressure dissipation were elucidated. Also, the non-uniform distribution of water content in the model ground was obtained. Then, in order to investigate the effect of vertical drainage on the consolidation behavior in the model tests, the comparison between experimental consolidation behaviors and Barron's theoretical ones were carried out. As the results, it was elucidated that the consolidation behavior in the model tests was affected not only by radial drainage but also by vertical drainage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.229-238
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• 2006

Observed field behaviors are frequently different from the behaviors predicted in the design state due to several uncertainties involved in soil properties, numerical modeling, and error of measuring system even though a sophisticated numerical analysis technique is applied to solve the consolidation behavior of drainage-installed soft deposits. In this study, genetic algorithms are applied to back-analyze the soil properties using the observed behavior of soft clay deposit composed of multi layers that shows complex consolidation characteristics. Utilizing the program, one might be able to appropriately predict the subsequent consolidation behavior from the measured data in an early stage of consolidation of multi layered soft deposits. Example analyses for drainage-installed multi-layered soft deposits are performed to examine the applicability of proposed back-analysis method.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.486-490
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• 2005

Fine recycled-concrete aggregates(RCAs) instead of natural sand were tested for a foundation material under sewage conduit system, which was evaluated based on foundation settlement at various conditions. To obtain this applicability of RCAs, the settlement behavior was simulated with FLAC program based on the difference of material properties, and immediate settlement behaviors and the change of material properties under the simulated drainage conditions also tested at the various loading conditions in the laboratory. Finally, large-scale settlement test in the field was conducted to prove the above feasibilities. Subsequently, the amount of settlement from the FLAC simulation was calculated under $5.0{\times}10^{-6}\;m$ and the extent of settlement and property changes (porosity, permeability and waster absorption) was not noticeable from the laboratory experiments. Also, settlement monitoring from the field experiment showed the consistent results with laboratory experiments except for the consolidation settlement(=5 mm) of the round below the foundation. In summary, adopting fine RCAs as a foundation material for sewage conduit system was resonable based of geotechnical point of view.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.59-68
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• 2009

In this study, it was developed that the software could be used to estimate consolidation settlement by curve fitting method according to Terzaghi's consolidation theory on the condition of gradual incremental loading, and the method of estimating settlement caused by lateral displacement was suggested, in which the settlement was calculated from the difference between the settlement calculated with the developed software using the early part of measured data and the settlement measured for the short duration from the beginning of embankment in the field. The verification of the suggested method of estimating settlement caused by lateral displacement showed good results.