• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2005.10a
• /
• pp.349-354
• /
• 2005

In this study, settlement characteristics of 23 CFRD was investigated from monitoring data and the method to estimate the crest settlements considering internal settlement during constructions was proposed. Moreover, crest settlement smaller than 20cm and deflection of face slab smaller than 20cm are not considered to be critical to the stability of large dam whose height is over 40m. Therefore, we assigned the region as safe zone that can be used as a guideline of maintenance of dam. These estimated data can be used in the design, construction and long-term maintenance in domestic CFRD hereafter.

• Geomechanics and Engineering
• /
• v.2 no.1
• /
• pp.57-69
• /
• 2010

A major consideration in the design of tunnels in urban areas is the prediction of the ground movements and surface settlements associated with the tunneling operations. Excessive ground movements can damage adjacent building and utilities. In this paper, a neural network model is used to predict the maximum surface settlement, based on instrumented results from three separate EPB tunneling projects in Singapore. This paper demonstrates that by coupling the trained neural network model to a spreadsheet optimization technique, the reliability assessment of the settlement serviceability limit state can be carried out using the first-order reliability method. With this method, it is possible to carry out sensitivity studies to examine the effect of the level of uncertainty of each parameter uncertainty on the probability that the serviceability limit state has been exceeded.

• The Journal of Engineering Geology
• /
• v.12 no.1
• /
• pp.1-21
• /
• 2002

Recently, the rapid industrialization and urbanization of the country due to a high economic growth, require optimization, usage and the expansion of underground space. Therefore the consturction of large and deep basements takes place in braced excavated area where their earth retaining structures cause many problems such as settlement and damages of nearby buildings and underground utilities. this study deals with the influence distance of settlement and the amount for settlement based on the measurement which were obtained at five excavation construction sites. Maximum ground surface settlement, (0.28∼0.3)(%)H utilizing depth, is similar to the measurement and the value by Clough's method. It was found that the settlement and the influence distance of settlement calculated by Clough's method were rational.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2007.09a
• /
• pp.363-372
• /
• 2007

The residual settlement due to difference between predicted and observed settlement is one of the social problems during reclaiming construction in the soft ground having a deep depth such as Busan and Gwangyang province. Prediction error for the secondary compression settlement makes the construction much harder. To examine characteristics of the secondary compression settlement, the secondary compression index is the most important factor. In this study, various empirical methods for determining the secondary compression index are evaluated. And errors applied to the design case practically are also explained. The pre loading method is the only way to reduce the secondary compression settlement and reduction ratio of the secondary compression should be investigated correctly. Hence, research results on the reduction ratio of the secondary compression are analyzed in this paper. Moreover, decrement of the secondary compression index due to over consolidation ratio is examined closely by laboratory consolidation test using clay in the Gwangyang area.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.4
• /
• pp.61-69
• /
• 2012

A high rock embankment by means of phased dynamic compaction has hardly carried out in Korea. Settlement of each layer is measured in order to verify the settlement behavior of dynamically compacted high rock embankment. A high rock embankment is generally constructed by dividing into several sub-embankments. Such a sub-embankment and dynamic compaction may induce an increase of pressure at the lower part of embankment and cause a different behavior of ground from initial status. In this study, settlement of a high rock embankment is estimated using a hyperbolic model taking into construction history. The results from prediction are compared with those obtained from field measurements. And second creep settlement is predicted using pre-loading test.

• Geomechanics and Engineering
• /
• v.15 no.3
• /
• pp.851-859
• /
• 2018

There are two primary causes of the ground movement due to tunnelling in urban areas; firstly the lost ground and secondly the groundwater depression during construction. The groundwater depression was usually not considered as a cause of settlement in previous research works. The main purpose of this study is to analyze the combined effect of these two phenomena on the transverse settlement trough. Centrifuge model tests and numerical analysis were primarily selected as the methodology. The characteristics of settlement trough were analyzed by performing centrifuge model tests where acceleration reached up to 80g condition. Two different types of tunnel models of 180 mm diameter were prepared in order to match the prototype of a large tunnel of 14.4 m diameter. A volume loss model was made to simulate the excavation procedure at different volume loss and a drainage tunnel model was made to simulate the reduction in pore pressure distribution. Numerical analysis was performed using FLAC 2D program in order to analyze the effects of various groundwater depression values on the settlement trough. Unconfined fluid flow condition was selected to develop the phreatic surface and groundwater level on the surface. The settlement troughs obtained in the results were investigated according to the combined effect of excavation and groundwater depression. Subsequently, a new curve is suggested to consider elastic settlement in the modified Gaussian curve. The results show that the effects of groundwater depression are considerable as the settlement trough gets deeper and wider compared to the trough obtained only due to excavation. The relationships of maximum settlement and infection point with the reduced pore pressure at tunnel centerline are also suggested.

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

• Geomechanics and Engineering
• /
• v.21 no.6
• /
• pp.583-598
• /
• 2020

This study is attempted to propose a new hybrid artificial intelligence model called integrative genetic algorithm with multivariate adaptive regression splines (GA-MARS) for settlement prediction of shallow foundations on sandy soils. In this hybrid model, the evolution algorithm - Genetic Algorithm (GA) was used to search and optimize the hyperparameters of multivariate adaptive regression splines (MARS). For this purpose, a total of 180 experimental data were collected and analyzed from available researches with five-input variables including the bread of foundation (B), length to width (L/B), embedment ratio (D_f/B), foundation net applied pressure (q_net), and average SPT blow count (N_SPT). In further analysis, a new explicit formulation was derived from MARS and its accuracy was compared with four available formulae. The attained results indicated that the proposed GA-MARS model exhibited a more robust and better performance than the available methods.

• Journal of the Korean Geosynthetics Society
• /
• v.23 no.2
• /
• pp.9-17
• /
• 2024

When constructing on soft ground, managing ground settlement and safety is crucial. However, there often exists a significant disparity between the actual behavior of the ground and the design plans. In this study, we aimed to compare and analyze the difference between the predicted settlement based on theoretical formulas and the measured settlement during construction, in order to predict settlement. For this purpose, we analyzed settlement data from 18 construction sites. The results indicated that the back analysis settlement values were similar to the measured settlement values, whereas the design settlement values were significantly higher compared to the measured settlement values. Specifically, the design settlement values were 1.2 to 1.4 times higher than those derived from back analysis using measured values. The RMSE analysis revealed a value of 0.6212m for the design settlement and 0.1697m for the back analysis settlement. The difference between the back analysis settlement and the measured settlement was more than 70% lower than the difference between the design settlement and the measured settlement. This indicates that the back analysis settlement values exhibit lower error rates compared to the design settlement values.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.291-300
• /
• 2022

Tunnel boring machines combined with the earth pressure balanced shield method (EPB shield TBMs) have been adopted in urban areas as they allow excavation of tunnels with limited ground deformation through continuous and repetitive excavation and support. Nevertheless, the expansion of TBM construction requires much more minor and exquisitely controlled surface settlement to prevent economic loss. Several parametric studies controlling the tunnel's geometry, ground properties, and TBM operational factors assuming ordinary conditions for EPB shield TBM excavation have been conducted, but the impact of excessive excavation on the induced settlement has not been adequately studied. This study conducted a numerical evaluation of surface settlement induced by the ground loss from face imbalance, excessive excavation, and tail void grouting. The numerical model was constructed using FLAC3D and validated by comparing its result with the field data from literature. Then, parametric studies were conducted by controlling the ground stiffness, face pressure, tail void grouting pressure, and additional volume of muck discharge. As a result, the contribution of these operational factors to the surface settlement appeared differently depending on the ground stiffness. Except for the ground stiffness as the dominant factor, the order of variation of surface settlement was investigated, and the volume of additional muck discharge was found to be the largest, followed by the face pressure and tail void grouting pressure. The results from this study are expected to contribute to the development of settlement prediction models and understanding the surface settlement behavior induced by TBM excavation.