• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1326-1333
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• 2006

Purpose of this research is a development for the curve fitted equations that can improve practical calculation and work application when seismic performance has been evaluated and this work has been made a study of the dynamic response under various boundary conditions of buried pipelines to compare the dynamic behavior of concrete pipe and steel pipe, FRP pipe. This research have been developed curve fitted equations that can be improving efficiency and practicality. Using a nonlinear least square method, and after testing several different exponential equations, Proposed the curve fitted equations to give the best result and constant value by the propagation velocities. With these results, dynamic response analysis and seismic performance evaluation have been achieved on concrete pipe, steel pipe and FRP pipe that have a various boundary conditions. Degree of a polynomial expression and coefficient value by propagation velocity have been calculated when using the curve fitting equations.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1340-1347
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a free vibration analysis. End boundary conditions considered herein consist of free ends, fixed ends, and fixed-free ends in the axial and the transverse direction. Guided ends, simply supported ends, and supported-guided ends were added to the transverse direction. The buried pipeline was regarded as a beam on an elastic foundation and the ground displacement of sinusoidal wave was applied to it. Natural frequencies and mode shapes were determined according to end boundary conditions. In addition, the effects of parameters on the natural frequency were evaluated. The natural frequency is affected most significantly by the soil stiffness and the length of the buried pipelines. The natural frequency increases as the soil stiffness increases while it decreases as the length of the buried pipeline increases. Such behavior appears to be dominant in the axial direction rather than in the transverse direction of the buried pipelines.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1165-1172
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• 2006

In this study, an aspect of settlement, developed from different ground improvement method like suction drain method using vacuum pressure and vertical drain method using overburden pressure, was compared each other. In order to analyze settlement tendency of each method exactly, the finite element analysis program was used. The analyses of vertical settlement and lateral displacement for suction drain method and vertical drain method were conducted independently during the solving stage. The initial condition of drainage zone was fixed with 25m depth and 21m width. After the program analyses, the settlement condition had a different tendency with the ground improvement method. Especially, in the results of vertical drain method, the disparity of settlement between the middle of improved zone and unimproved zone. In the case of suction drain method, however, the difference of settlement was smaller than that of vertical drain method.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.515-520
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• 2005

The behavior of jointed rock mass is much different from that of intact rock due to the presence of joints. Similarly, the characteristics of elastic wave propagation in jointed rock are considerably different from those of intact rock. The propagation of elastic waves in jointed rock is greatly dependent on the state of stress. The roughness, filling materials, and spacing of joints also affect wave propagation in jointed rock. If the wavelength of elastic waves is much larger than the spacing between joints, wave propagation in jointed rock mass can be considered as wave propagation in equivalent continuum. A rock resonant column testing apparatus is made to measure elastic waves propagating through jointed rock in the state of equivalent continuum. Three types of wave, i.e, torsional, longitudinal and flexural waves are monitored during rock resonant column tests. Various roughness and filling materials are applied to joints, and rock columns with various spacings are used to understand how these factors affect wave propagation under a small strain condition. The experimental results suggest that the characteristics of wave propagation in jointed rock mass are governed by the state of stress and influenced by roughness, filling materials and joint spacings.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1455-1460
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• 2005

This paper presents the results of an experimental study on the ground deformation by trench excavation for Diaphragm Wall construction. The model tests are performed to investigate the back ground deformation by lowering of slurry level in trench after excavating. Through these, the deformation characteristic of the back ground due to stress release of excavated space was investigated. This study considered relative density of soil mass and the distance between trench and surcharge. An experiment was performed in order to observe the failure pattern of a slurry-supported trench excavated in sandy ground. From model tests, in order to predict reasonably the deformation behavior of the adjacent ground due to the underground excavation, it is significantly recommended that the ground settlement by trench excavation should be considered.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.831-837
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• 2005

In this study, a computer program to predict the behavior of laterally loaded single pile and pile groups was developed by using a beam-column analysis in which the soils are modeled as nonlinear springs by a family of p-y curves for subgrade modulus. The special attention was given to the lateral displacement of a single pile and pile groups due to the soil condition and the cap rigidity. The analysis considering group effect was carried out for $2\;{\times}\;2\;and\;3\;{\times}\;3$ pile groups with the pile spacing 3.0B, 4.0B and 5.0B. Based on the results obtained, it is found that the overall distributions of deflection, slope, moment, and shear force in a single pile give a reasonable results irrespective of cap connectivity conditions. It is also found that even though there are some deviations in deflection prediction compared with the observed ones, the prediction by present analysis simulates much better the general trend observed by the centrifuge tests than the numerical solution predicted by PIGLET.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1159-1166
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• 2005

In the present study, a series of laboratory tests with sands of different silt contents, are conducted and methods to assess non-linear behaviors based on in-situ test results are proposed. Modified hyperbolic stress-strain model is used to analyze non-linearity of silty sands in terms of non-linear degradation parameters f and g as a function of silt contents and relative density $D_R$. Stress-strain relationship results were obtained from a series of triaxial tests on sands containing different amounts of silt. Initial shear modulus which was applied to normalize modulus degradation of silty sands were determined based on the resonant column test results. From the laboratory test results, it was observed that, as the relative density increases, values of f decrease and those of g increase. Cone resistance $q_c$ for silty soil condition used in the triaxial tests were estimated based on the cavity expansion analysis. A suggestion to make an estimation of degradation parameters f and g as a function of fine contents is addressed in terms of cone resistance $q_c$ .

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.286-293
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• 2005

In soft ground the settlement criterion usually governs. Therefore, it is very important not only reasonable assessment of the allowable bearing capacity of the soil but also reasonable assessment of settlement. In the previous studies by many other researchers, load concentration ratio and settlement reduction factor are usually proposed for estimating the settlement of granular compaction piles. In the previous studies, the reinforced ground with granular compaction piles is simplified as composite ground and the analysis is performed with in the basis of this assumption. However, the lateral deformation of granular compaction pile could not be considered and only the relative vertical strength between pile and soils could be considered in the analysis. In this study, a method adapting the Tresca failure criterion is proposed for calculating settlement of granular compaction pile. Proposed method can be considered the strength of pile material, pile diameter, installing distance of pile and the deformation behavior of vertical and horizontal directions of pile. In the presented study, large-scale field load test is performed and the results are described. Also, predictions of settlements from the proposed method are compared with the results of the load test. In addition, a series of parametric study is performed and the design parameters are analyzed.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1205-1210
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• 2005

The behavior of rock mass and solute(e.g. groundwater, radioactivity) flow in fractured rock can be directly influenced by joint roughness. The characteristics of joint roughness is also a main factor for the rock classification(e.g. RMR, Q system) which is usually used in tunnel design. Nevertheless, most of JRC estimation has been carried out only by the examination with the naked eye. This JRC estimation has a lack of objectivity because each investigator judges JRC by his subjective opinion. Therefore, it will be desirable that the assessment of JRC is performed by a numerical analysis which can give a quantitative value corresponding to the characteristics of a roughness curve. Meanwhile, roughness curves for joint surfaces which are observed in drill cores have been obtained only along linear profiles. Although roughness curves are measured in the same joint surface, they can frequently show diverse aspects in a standpoint of roughness characteristics. If roughness curves can be measured along the elliptical circumferences of joint surfaces from core scanning images or Televiewer images, they will certainly be more comprehensive than those measured along linear profiles for roughness characteristics of joint surfaces. This study is focus on dealing with (1) extracting automatically roughness curves from core scan image or Televiewer image, (2) improving the accuracy of quantitative assessment of JRC using fractal dimension concept.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.924-931
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• 2005

In this study, we intended to compare and examine several settlement management methods by analyzing measurement results of a site of the industrial complex at ${\bigcirc}{\bigcirc}$ province. We predicted and analyzed the amount of final settlement by using generally used final settlement methods as like Hyperbola method, Hoshino methods and Asaoka method. And then, We compared the predicted results with that of measurement. On the basis of comparison of the three methods, Hyperbola method was the most convenient and accurate method of the three methods and if a sufficient time was given enough after embankment construction, the use of Hoshino method was possible. In the case of the Asaoka methods, it was possible to know that it had an approaching tendency to the measured one with increasing time interval spent on analysis. Therefore, in order to predict settlement behavior more accurately it is needed to understand their advantages and shortcomings sufficiently and pay attention to application to the real site.