• 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 the Korean GEO-environmental Society
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• v.13 no.2
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• pp.19-26
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• 2012

In this study, characteristics of consolidation settlement of soft grounds adapting preloading method and vertical drain method were compared. A real measurement settlement is compared with predicted one by the future settlement prediction method like the Asaoka's method, the Hyperbolic method and the Hoshino method. A accuracy of predicted future settlement by the Asaoka's method is relatively higher than the Hyperbolic method or the Hoshino method generally. But in the area conducted with the vertical drain method, settlement prediction accuracy of three methods is similar unlike popular beliefs; Asaoka's is the better method for prediction than others. The study area is also confirmed by investigation of the drainage system after applying the change through the N values, soil physical and mechanical properties were investigated, and physical properties are improved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.137-143
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• 2020

This study proposes an improvement plan for the evaluation of the bearing capacity and settlement of sewer pipe bases for the improvement of design methods for determining pipe breakage. Under the same conditions, the safety of crushed stone foundation was the lowest. Concrete VR pipe and prefabricated plastic foundations were found to be safe at most excavation depths. The bearing capacity of a rigid pipe foundation was determined by the shape of the foundation, soil conditions, and groundwater, irrespective of the type of foundation. As the depth of the excavation increases, the settlement tends to decrease immediately, and as the diameter of the pipe increases, the settlement tends to increase immediately at the same depth. It is thus reasonable to consider the bearing capacity and the instant settlement amount to solve the problems caused by the settlement of a rigid sewer pipe.

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.33-40
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• 2009

In earthwork projects, the designer considers cut and fill balance for minimizing earthwork which may significantly decrease construction costs. Despite carrying out considerable earthwork design, the decrease in volume of earth occurs in construction sites because of embankment settlement under self-weight, consolidation settlement of soft ground, cavity filling and soil loss due to rainfall-runoff. To reflect the decrease in volume of earth, the specifications for road construction just give shrinkage factors in embankment for soils without consideration of embankment settlement under self-weight. In this study, the computational method is used to estimate the amount of embankment settlement under self-weight developed by Iseda (1972) and Ishii (1976). This research shows that the total compression settlements are between 3 to 10 percent of embankment height according to the property of embankment material and embankment height. As a result, the designer should consider the compression settlement on embankment material under selt-weight.

• Geotechnical Engineering
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• v.12 no.5
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• pp.41-54
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• 1996

In this paper, the consolidation settlement of the landfill foundation during and after the period of disposal is analyzed using the program CONSOL which can include the influence of waste load and the leachate level into the analysis. the stability analysis of the embankment is also performed under the varied strength of foundation soil which results from the increase of effective stress due to consolidation of the clay under the landfill. The predicted settlement from CONSOL is compared with the field measured settlement. The results show that, when the leachate level increases with the increase of waste height, the increase of the effective stress of foundation clay is negligible and the stability of the slope of the landfill may not be secured as the disposal of the waste proceeds. Several complementary repairworks, e. g. the reduction of current slope of the fill, application of drain methods to stop or reduce !he leachate level are recommended. The predicted settlement consists moderately with the field measured settlement.

• 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.14 no.1
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• pp.5-14
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• 1998

In refuse landfill, long-term settlement is considerably dependent upon the biological decomposition of refuse which is distinguished from typical soil behavior. Two equations are combined in order to model long-term settlement behavior of refuse landfill caused by mechanical secondary compression and secondary compression caused by the decomposition of biolegradable refuse. It is suggested that mechanical secondary compression is linear with respcet to the logarithm of time. In order to estimate the settlement that occurs due. to the decomposition of biodegradable refuse, a mathematical model is used which theoretically conoiders the decomposition process related to the solubilization stage of biodegradable refuse solid. This model is based on hydrolysis process and expressed as first order kinetics. The proposed model is applied to Lysimeter compression data of an old refuse. This paper intends to propose the simplest mathematical model which effectively represents settlement caused by the solubilization stage of biodegradable refuse solid on decomposition process.

• Journal of the Korean Geotechnical Society
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• v.26 no.10
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• pp.39-47
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• 2010

In order to investigate the effect of variation characteristics of compression index on the spatial distribution of consolidation settlement, this study presents the estimation methods of the distribution of consolidation settlement and compares the estimated settlements. When the variation of compression index is considerable, the ordinary cokriging is more reliable in estimating the compression index than ordinary kriging because smoothing effect of ordinary cokriging is smaller than that of ordinary kriging. The spatial distribution of consolidation settlement estimated by considering both the variation of compression index and void ratio (CASE-1) is different from that estimated by using the mean value of all soil properties (CASE-2). The settlement of CASE-1 shows the larger variation at short distances rather than that of CASE-2. Whereas the spatial settlement distribution of CASE-1 is affected by the spatial distributions of compression index as well as the thickness of consolidation layer, that of CASE-2 is significantly influenced by the distribution of consolidation layer thickness.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.199-210
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• 2012

The effects of tunnelling in weak weathered rock on the behaviour of a pre-existing single pile and pile groups ($3{\times}3$ and $5{\times}5$ pile groups) above a tunnel have been studied by carrying out three-dimensional (3D) elasto-plastic numerical analyses. Numerical modelling of such effects considers the response of the single pile and pile groups in terms of tunnelling-induced ground and pile settlement as well as changes of the shear transfer mechanism at the pile-soil interface due to tunnelling. Due to changes in the relative shear displacement between the pile and the soil at the pile-soil interface with tunnel advancement, the shear stresses and axial pile force distributions along the pile change drastically. Based on the computed results, upward shear stresses are induced up to about Z/L=0.775 from the pile top, while downward shear stresses are mobilised below Z/L=0.775, resulting in a reduction in the axial pile force distribution with depth equivalent to a net increase in the tensile force on the pile. A maximum tensile force of about $0.36P_a$ developed on the single pile solely due to tunnelling, where $P_a$ is the service axial pile loading prior to tunnelling. The degree of interface shear strength mobilisation at the pile-soil interface was found to be a key factor governing pile-soil-tunnelling interaction. Overall it has been found that the larger the number of piles, the greater is the effect of tunnelling on the piles in terms of pile settlement, while changes of the axial pile forces for the piles in the groups are smaller than for a single pile due to the shielding effect. The reduction of apparent allowable pile capacity due to tunnelling-induced pile head settlement was significant, in particular for piles inside the groups.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.53-66
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• 2007

A series of model tests were performed to investigate the soil arching effect in embankments supported by piles with geosynthetics. In the model tests, model piles with isolated cap were inserted through the holes in a steel plate, which could be operated up and down. Then geosynthetics was laid on the pile caps below sand fills. The settlement of soft ground was simulated by lowering the plate. As the plate was lowered, the soil arching was mobilized in the embankments. The deformation of both the sand fills and geosynthetics were captured by camera. Also the loads acting on pile cap and the tensile strain of geosynthetics were monitored by data logging system. Model tests showed that the embankment loads transferred on pile cap by soil arching Increased rapidly with settlement of the soft ground. In case of the absence of geosynthetics, the loads acting on pile caps dropped to residual value after peak value, whereas loads on pile caps gradually increased until constant value in case of geosynthetic-reinforced. This illustrated that reinforcing with the geosynthetics has a good effect to restrain the settlement of embankments. Also, the deformation shape of geosynthetics between pile caps was circular. The embankment loads transferred on pile caps can be estimated by considering both soil arching and tensile strain of geosynthetics in embankments supported by piles with geosynthetics.