• Geotechnical Engineering
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• v.4 no.3
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• pp.19-26
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• 1988

A stochastic numerical model for predictions of differential settlement of foundation Eoils is developed in this Paper. The differential settlement is highly dependent on the spatial variability of elastic modulus of soil. The Kriging method is used to account for the spatial variability of the elastic modulus. This technique provides the best linear unbiased estimator of a parameter and its minimum variance from a limited number of measured data. The stochastic finite element method, employing the first-order second-moment analysis for computations of error Propagation, is used to obtain the means, ariances, and covariances of nodal displacements. Finally, a reliability model of differential settlement is proposed by using the results of the stochastic FEM analysis. It is found that maximum differential settlement occurs when the distance between two foundations is approximately same It with the scale of fluctuation in horizontal direction, and the probability that differential settlement exceeds the allot.able vague might be significant.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.361-375
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• 2007

This paper presents the results of investigation on tunnelling-induced ground surface settlement characteristics in water bearing ground using finite element (FE) stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of the coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as rock type, thickness of soil layer, permeability of shotcrete lining, among others. The results indicate that the tunneling-induced groundwater drawdown results in a deeper and wider settlement trough than without groundwater drawdown, and that the Error function approach does not yield satisfactory result in predicting a settlement profile. The results of analysis are summarized so that the relationship between the settlement and the influencing factors can be identified.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.635-642
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• 2018

Braced excavation systems are commonly required to ensure stability in construction of basements for shopping malls, underground transportation and other habitation facilities. For excavations in deposits of soft clays or residual soils, stiff retaining wall systems such as diaphragm walls are commonly adopted to restrain the ground movements and wall deflections in order to prevent damage to surrounding buildings and utilities. The ground surface settlement behind the excavation is closely associated with the magnitude of basal heave and the wall deflections and is also greatly influenced by the possible groundwater drawdown caused by potential wall leakage, flow from beneath the wall, flow from perched water and along the wall interface or poor panel connections due to the less satisfactory quality. This paper numerically investigates the influences of excavation geometries, the system stiffness, the soil properties and the groundwater drawdown on ground surface settlement and develops a simplified maximum surface settlement Logarithm Regression model for the maximum ground surface settlement estimation. The settlements estimated by this model compare favorably with a number of published and instrumented records.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.1-9
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• 2019

This study investigated settlement and scouring characteristics of artificial reef reinforced with various reinforcement types to reduce settlement and scouring. Three reinforcement types were prepared: geogrid, geogrid-bamboo mat (GBM) and seaweed-pile mat (SPM). Various laboratory tests such as bearing capacity test, large size settlement test, two-dimensional flow scour test were performed according to different soil types (sand, silt, clay). Laboratory test results indicated that bearing capacity of seabed with a reinforced artificial reef increased and its settlement and scour depth reduced for all reinforcement types. Especially, reinforcement effect tends to be greater in clay soft ground rather than sand and silt grounds.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.67-75
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• 2024

In the case of the Pohang earthquake, which had a magnitude of 5.4 in 2017, geotechnical damages such as liquefaction and ground settlement occurred. The need for countermeasures has emerged, and experimental research in the Pohang area has continued. This study collected undisturbed samples from damaged fine-grained soil areas where ground settlement occurred in Pohang. Cyclic tri-axial tests for identifying the dynamic characteristics of soils were performed on the undisturbed samples, and the results were analyzed to determine the cause of ground settlement. As a result of the study, it was determined that in the case of fine-grained soils, ground settlement occurred because the seismic load as an external force was relatively more significant than the shear resistance of the very soft fine-grained soils, rather than due to an increase in excess pore water pressure.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.31-40
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• 2003

Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as the method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus, it is practically impossible to take into account these factors reasonably with the only group efficiency. In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement fur structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result to verify the validity of the proposed method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.94-108
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• 1988

The use of geotextile as reinforcing materials in soil structures has become widespread throughout the world. Geotextile reinforcement has been used in retaining walls, roadbed, embankment stabilization and especially reinforcement of soft foundation, and so on, In the past, however, its design and construction have been performed empirically. In this study, laboratory model tests were carried out in order to investigate the effects of geotextile rein- forcement on vertical and horizontal displacement and other characteristics in soft founda- tions. The experiments were executed in eight treatments ;no geotextile between embank - ment and subsoils, and seven geotextiles with different tensile strength. And such factors as the loading conditions, the tensile strength of geotextiles, the ingredient of geotextiles and the elapsed time were investigate in this study. And the analytical method were executed in order to study the stress and behavior of geotextile - reinforced soil structure by the nonlinear elasto - plastic finite element model. The following conclusions were drawn from this study. 1. Geotextile reinforcement reduced the effects of banking loads on subsoils more effectively with the increase of their tensile strength. 2. As the tensile strength of geotextiles was increase, the rate of the initial vertical disp - lacements of loading plate was reduced inverse proportional to loads, Rowever, the effect of loading was reduced when the loads exceed a certain limits, 3. The effect of reinforcement of nonwoven geotextile was 1.5-4.5 times larger than that of the woven geotextile with equivalent tensile strength. 4. The increased bearing capacity and the reduced settlement are proportioned as the tensile strength of geotextile. 5. The settlement at the long time loading were developed almost all, were completed after 10 days and the additional settlement were not developed since then. 6. The nonlinear elasto - plastic finite element method are accurate to predict the stresses and behayior of geotextile - reinforced soil structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.85-91
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• 2011

This study aims at evaluating feasibility of Bottom ash-mixed Foam Cement Banking(BFCB) Method on the enhancement of soft soil, which is developed to reduce self-weight of banking by applying bottom ash and foam. to cement slurry. In order to measure the behavior of soil when BFCB layer was covered to soft ground, a testing equipment for mock-up test was fabricated and phased loads were applied up to measurement of yielding and ultimate strengths as well as movement of ground particles. In addition, these measured values such as settlement and heaving were compared with ones of surface-hardening method prevailing on soil improvement. As the result through mock-up test, BFCB showed lower values of ground deformation, while wider range of deformation was observed in compare to the other method. And settlement and heaving were measured lower, which implies the method developed is very effective to applicability of soft ground.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.319-327
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• 2002

In this research, problems of recent design methods and their improvement for SIP(Soil-Cement Injected precast Pile) in domestic areas were studied by using the properties of load-settlement curves and bearing capacity from field loading tests. Elastic and plastic settlement for total settlement in each loading step of loading tests conducted in domestic areas has been shown to have a tendency. From this tendency and bearing capacity determined by loading tests, it could be ascertained that empirical chart could be an assistant tool in SIP design. It was shown that SIP design using N-value in domestic area with soil condition of granitic type resulted in very conservative hearing capacity. On the other hands, in soil with unfitted geological conditions, the design could be insecure. Also, we could ascertain that Meyerhof's bearing capacity using modified N-value on the tip part of pile was more applicable than recent design method where tip bearing capacity was 20NA$_p$ N-value limited to 50. These results showed that modified design method could be more economic than those in the past because it used pile's bearing capacity unto tolerable load of pile material.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.529-545
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• 2012

Three-dimensional (3D) finite element analyses have been performed to study the behaviour of a single pile to open face tunnelling in stiff clay. Several key factors such as tunnelling-induced ground and pile settlement, and shear transfer mechanism have been studied in detail. Tunnelling resulted in the development of pile settlement larger than the Greenfield soil surface settlement. In addition, due to changes in the shear transfer between the pile and the soil next to the pile with tunnel advancement, axial force distributions along the pile change drastically. The apparent allowable pile capacity was reduced up to about 30% due to the development of tunnelling-induced pile head settlement. The skin friction on the pile was increased with tunnel advancement associated with the changes of soil stresses and ground deformation and hence axial pile force distribution was reduced. Maximum tunnelling-induced tensile force on the pile was about 21% of the designed pile capacity. The zone of influence on the pile behaviour in the longitudinal direction may be identified as ${\pm}1$-2D (D: tunnel diameter) from the pile centre (behind and ahead of the pile axis in the longitudinal direction) based on the analysis conditions assumed in the current study. Negative excess pore pressure was mobilised near the pile tip, while positive excess pore pressure was computed at the upper part of the pile. It has been found that the serviceability of a pile experiencing adjacent tunnelling is more affected by pile settlement than axial pile force changes.