• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.888-895
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• 2006

In this study, anisotropically consolidated undrained shear(CAU) test was performed to examine the variation of the shear strength according to the stress history. The specimen having 30% relative density was homogeniously prepared, and 200KPa of back pressure was applied to increase the B value more than 0.95. To make NC specimens, the vertical stress was applied on the specimen by 100KPa, 200KPa and 400KPa, and to make OC specimens, the vertical stress was applied upto 400KPa and was reduced to 200KPa and 100KPa resulting in OCR 2 and 4 respectively. The test result indicates the shear strength for the OC specimens are slightly higher then that of the NC specimens at the same confining pressure. The elastic modulus varies according to the confining stress and considerably affected by preconsolidation stress.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.424-433
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• 2006

This paper studies the field applicability of the Special Chemical grouting Method(SCM) in reinforcing and reducing permeability of the back of an existing continuous wall. SCM uses double rod which imposes intermediate pressure$(981\sim9,810kPa)$ to disturb, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Uniaxial compression tests, test for chemical properties and fish poison test are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1295-1302
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• 2006

Controlled low-strength material(CLSM) which is easily excavated and also known as flowable material, is commonly used as a backfill in utility trenches and other applications. In this study, a rapid-setting flowable material a kind of CLSM made with a field soil were evaluated by an experimental study. The properties ordinarily desired from the mix are: (a) flow under gravity; (b) hardening for early workability(after 4 hours)and cover; and (c) ultimate strength low enough to allow ready excavation. Fluidity of fresh material is evaluated using a simple spread test. Hardening is measured by a mortar penetrometer, and these values are correlated with unconfined compressive strength. It is desirable to keep the ultimate strength to less than $5.6kg/cm^2$ somewhat less target strength is selected for the 28-day value.

• 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.552-561
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• 2006

The purpose of this study is to propose a pavement analysis system which considers dynamic effects resulted from the various vehicle speeds. Vehicle loading effects were estimated by loading frequency and dynamic loads under various vehicle speeds. In addition, a proposed analysis model takes the non-linear temperature using a predictive model for dynamic modulus in asphalt layer and the non-linear stress in the unbound material. To examine adequacy of existing multi-layer elastic analysis of non-linear temperature in asphalt layer and non-linear stress conditions in unbound material, this study divided layers of asphalt pavement structures with 10 layers in asphalt, 2 layers in subbase and 1 layer in subgrade. In order to verify the pavement analysis system that considers various speeds, deflections of pavement calculated using ABAQUS, a three dimensional finite element program, were compared with the results of field tests under various speeds.

• 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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• 2006.03a
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• pp.590-599
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• 2006

In this study, Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal loading, increasing wedge loading, and real earthquake loading were investigated focusing on the dissipated energy. From the results of cyclic triaxial test, liquefaction resistance strength was calculated by the concept of energy according to the type of input loading. Liquefaction resistance strength was expressed in accumulated dissipated energy calculated from stress-strain curve(hysteresis loop). The dissipated energy according to loading type was compared and the energy-based evaluation was proposed. The procedures are presented in terms of normalized energy demand(NED), normalized energy capacity(NEC), and factor of safely, where NED is the load imparted to the soil by the loading(both amplitude and duration), NEC is the demand required to induce liquefaction, and factor of safely is defined as the ratio of NEC and NED.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1014-1023
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• 2006

Soil nailing is a reinforcement method used for stabilizing excavated wall or slope. Due to its many advantages such as ease of construction and economical efficiency, use of soil nailing is increased. However, the soil nail can't trespass on the neighbor private land, which pays rent for use. For this reason, removable soil nailing system was developed. However, the removal rate of this system is just about $50\sim70%$. To solve this, the Fiber Reinforced Polymer (FRP) soil nailing system, which does not need to be removed and allows for the trespass on the private land, is developed. In this paper, through theoretical and experimental studies in laboratory and field, we evaluate the stability and behavior characteristics of the FRP nail system. Besides, numerical analyses using FLAC2D were performed for various soil conditions, where the simulations for pullout tests were carried out. As a result, compared with the conventional removable soil nailing system, the FRP soil nailing systems show similar behavior characteristics.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.553-560
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• 2005

An experimental investigation was carried out to study recycling possibility of waste oyster shells, which induce environmental pollutions from piling up out at the open or the temporary reclamation. The purpose of this paper is to develop eco-friendly binder using waste oyster shells, and to investigate their reinforcing effects for dredged soil improvement. A series of laboratory tests including compressive strength tests were performed to evaluate strength characteristics of soils treated by developed binder with varying water content of dredged soils, mixing rates of binder, and different curing days. Based on laboratory test results, eco-friendly binders developed here using waste oyster shells were found as good resource materials for soft soil improvements.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.65-70
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• 2005

In this study, the large scale model tests were executed to estimate the Load Sharing Ratio(LSR) of raft in a piled footing under various conditions. The conditions such as the subsoil type, pile length, pile spacing, array type and pile installation method etc. were varied in the pile loading tests about the free-standing group piles and a piled footing. As the results of this study, it was found that there were no differences of the load-settlement curves, along with the pile installation method and subsoil type. The piles supported most of the external load until a yielding load of the piled footing, but the raft supported a considerable load after a yielding load. And it was also found that the LSR didn't be affected by the pile installation method and the subsoil type. As the relative density of sands increased, the LSR decreased. As the pile spacing was wider and the pile length increased, there was a tendancy for the LSR to increase.