• Journal of the Korean Geotechnical Society
• /
• v.23 no.7
• /
• pp.17-25
• /
• 2007

Various geotechnical problems due to insufficient bearing capacity or excessive settlement are likely to occur when constructing roads or large complexes on soft ground. Accurate predictions of the magnitude of settlement and the consolidation time provide numerous options of ground improvement methods and, thus, enable to save time and expense of the whole project. Asaoka's method is probably the most frequently used one for settlement prediction and the empirical formulae such as Hyperbolic method and Hoshino's method are also often used. To find an elaborate method of predicting the embankment settlement, two recurrent type neural network models, such as Jordan model and Elman-Jordan model, are adopted. The data sets of settlement measured at several domestic sites are analyzed to obtain the most suitable model structures. It was shown from the comparison between predicted and measured settlements that Jordan model provides better predictions than Elman-Jordan model does and that the predictions using CPT results are more accurate than those using SPT results. It is believed that RNN using cone penetration test results can be a highly efficient tool in predicting settlements if enough field data can be obtained.

• Geotechnical Engineering
• /
• v.13 no.6
• /
• pp.5-12
• /
• 1997

Predictions of settlements under preloading for the improvement of soft soil is a very important element of construction management. Due to the non uniformity, difficulty of estimating resonable soil properties, predictions of settlements and settlement velocities at the design stage seldom agree with the actual future settlements. To overcome this problem, the prediction methods based on the settlement observation of initial preloading stage such as hyperbolic method and Asaoka method have been employed frequently. However the estimating method for the reliability of these predictions at the time of prediction has not been suggested. In this study, comparisons of predicted settlements by hyperbolic met hed and observed settlements are explored through case studies. And a stratagem of estimating reliability of settlement predictions by hyperbolic method is suggested as the result of investigation on the relationship between the initial observed time and error of settlement prediction by hyperbolic method.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.948-955
• /
• 2005

In this case of study, Incheon International Airport 2nd phase site preparation 1st section estimated final settlement to improve soft ground. Final settlement is very important in preloading method. Recently, Hyperbolic method, Hoshino method and Asaoka method are used mostly in prediction of final settlement and this paper, Comparing a result of Final settlement, used to Artificial Neural Network. The structure of Dynamic Artificial Neural Network which predicted Final settlement, has application to Young_Jong Island other site, If new investigation data will be added. Also, It is expected to save measuring_system cost in soft ground.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.10
• /
• pp.29-38
• /
• 2019

In stability and settlement management of soft ground, the settlement prediction technology has been continuously developed and used to reduce construction cost and confirm the exact land use time. However, the preexistence prediction methods such as hyperbolic method, Asaoka method and Hoshino method are difficult to predict the settlement accurately at the beginning of consolidation because the accurate settlement prediction is possible only after many measurement periods have passed. It is judged as the reason for estimating the future settlement through the proportionality assumption of the slope which the preexistence prediction method computes from the settlement curve. In this study, ARIMA technique is introduced among time series analysis techniques and compared with preexistence prediction methods. ARIMA method was predictable without any distinction of ground conditions, and the results similar to the existing method are predicted early (final settlement).

• Geotechnical Engineering
• /
• v.13 no.6
• /
• pp.25-36
• /
• 1997

A degree of consolidation at any time can be evaluated by using cone penetration test after soil improvement. In this case, after stopping the penetration of a piezocone, pore pressure dissipation(PPD) best is carried out until the pore pressure remains constant. Since the hydraulic conductivity of soft ground is very small, it takes very long time to finish the PPD test. This research is performed to develop a method overcoming this problem of the PPD test and reducing the test time. The analyses are carried out in the following ways : an equilibrium pore pressure can be determined by using pore pressure measured in the middle of the test, which is predicted by hyperbolic, Asaoka and Hoshino methods. And this equilibrium pore pressure is compared with the one measured in a test of long duration. As a result of the study, it is found that Hoshino method is the best way to predict the equilibrium pore pressure in a teat of short duration. And it is proposed as a methodology to fond a minimal time in which we can get an equilibrium pore pressure.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.38 no.1
• /
• pp.116-127
• /
• 1996

This paper dealt with FEM analysis of foundation improved with pack drain. The theory on pack drain was scrutinized and observed values in the field were compared with numerical results. Work site of Kwangyang container pier was selected as a ease study in which measurement of settlement and pore water pressure was accurately carried out. Biot's consolidation equation was selected as governing One, coupled with modified Camclay model as constitutive one. Christian and Boehmer's numerical technique was adopted. Behavior of foundation with pack drain is not simple but very complicated. Discontinuity resulted from rigidity difference between adjacent materials, smear effect and complicated boundary conditions should be considered in the behavior analysis of foundation behavior. The results of numerical analysis were influenced by smear zone. In relevant to this effect, finite element analysis was carried out using the reduced horizontal coefficient of permeability in the smear zone; The numerical results were compared with observed values in surface settlement. including pore water pressure. However only lateral di5plaoement by numerical ana1Ysis was shown since its measurement was not performed in the field. The predication of settlement to be developed later can be effectively employed for the obtimization of construction. The predication of residual settlement using the data measured in the field was made by Hoshino, Asaoka and hyperbolic method. Among them, the hyperbolic method proved best one. Settlements accorded well between numsrical and observed values while pore pressure showed a slight difference. Lateral displacement showed largest values at constant distance from ground surface. The validation of foundation analysis improved with pack drain by computer program employed in this study selecting modified Cam-clay model was satisfactorily secured.

• Journal of the Society of Disaster Information
• /
• v.3 no.1
• /
• pp.37-53
• /
• 2007

Various difficult problems occur due to insufficient bearing capacity or excessive settlements when constructing roads or large complexes. Accurate predictions on the final settlement and consolidation time can help in choosing the ground improvement method and thus enables to save time and expense of the whole project. Asaoka's method is probably the most frequently used for settlement prediction which are based on Terzaghi's one dimensional consolidation theory. Empirical formulae such as Hyperbolic method and Hoshino's method are also often used. However, it is known that the settlement predicted by these methods do not match with the actual settlements. Furthermore these methods cannot be used at design stage when there is no measured data. To find an elaborate method in predicting settlement in embankments using various test results and actual settlement data from domestic sites, Back-Propagation Neural Network(BPNN) and Recurrent Neural Network(RNN) were employed and the most suitable model structures were obtained. Predicted settlement values by the developed models were compared with the measured values as well as numerical analysis results. Analysis of the results showed that RNN yielded more compatible predictions with actual data than BPNN and predictions using cone penetration resistance were closer to actual data than predictions using SPT results. Also, it was found that the developed method were very competitive with the numerical analysis considering the number of input data, complexity and effort in modelling. It is believed that RNN using cone penetration test results can make a highly efficient tool in predicting settlements if enough field data can be obtained.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.6
• /
• pp.31-41
• /
• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.6
• /
• pp.23-30
• /
• 2015

This study analyzed degree of disturbance, using specimens by laboratory test with large block specimens and piston samplers collected from the Korea's two typical soft ground districts: South coast Gwangyang and Yangsan. To assess the characteristics of compression index of laboratory test incurred by disturbance, the compression index of laboratory test was compared with the back analysis compression index resulting from the analysis of the measured settlement. The analysis of specimen disturbance of the laboratory test results with the piston specimens of the two districts found that the qualities of most specimens were poor and the settlement predicted by the laboratory test compression index was underestimated. The analysis of test material taken from nearby areas proved that the disturbance degrees of large block specimens were lower than that of the piston specimens. The hyperbolic method, Hoshino method, Asaoka method, and ${\sqrt{S}}$ method, all of which are predictive methods using measured settlement, were employed to reach a conclusion that reliabilities of each predictive method except predictive material of a few points were the same. To compensate the disturbance effects on compression index of the piston specimens, we suggested a new modification formula that estimates compression index of piston specimens, using Schmertmann's corrected compression index, and back analysis compression index from the analysis of predictive settlement.