• Geotechnical Engineering
• /
• v.13 no.3
• /
• pp.33-52
• /
• 1997

A three dimensional nonlinear finite element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with the shell elements, and the soil with solid 3D nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation, and the placement and stressing of the anchors. The numerical model is calibrated against a full scale instrumented tieback wall at the National Geotechnical Experimentation Site (NGES) on the Riverside Campus of Texas A&M University. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior : location of the first anchor, length of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, stiffness of the wood lagging, and of the piles. The implications in design are discussed.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.1 no.3
• /
• pp.10-16
• /
• 2010

In construction industries, new construction materials are needed to overcome some problems associated with the use of conventional construction materials due to the change of environmental and social requirements. Accordingly, the requirements to be satisfied in the design of civil engineering structures are diversified. As a new construction material in the civil engineering industries, fiber reinforced polymeric plastic (FRP) has a superior corrosion resistance, high specific strength/stiffness, etc. Therefore, such properties can be used to mitigate the problems associated with the use of conventional construction materials. Nowadays, new types of bridge piers and marine piles are being studied for new construction. They are usually made of concrete filled fiber reinforced polymeric plastic tubes (CFFT). In this paper, a new type of FRP-concrete composite pile which is composed of reinforced concrete filled FRP tube (RCFFT) is proposed to improve compressive strength as well as flexural strength. The load carrying capacity of proposed RCFFT compression member is discussed based on the result of experimental and analytical investigations.

• Journal of the Korean Geosynthetics Society
• /
• v.8 no.4
• /
• pp.19-25
• /
• 2009

In this study, field pull-out tests were performed for steel pipe nailing installed foldable wedge and non-wedge type steel pipe nailing under the same test conditions. This is to evaluate pull-out resistance improvement effect of steel pipe nailing installed foldable wedge. Evaluating for field pull-out characteristics of steel pipe nailing installed foldable wedge was performed through analysis of ultimate pull-out resistance ($T_L$), ultimate unit skin friction ($q_s$, $u_{max}$), tensile normal stiffness ($K_{\beta}$), tension of nail. As a result, the steel pipe nailing installed foldable wedge have an effect of pull-out resistance increased about 30% in comparison with non-wedge type steel pipe nailing.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.3
• /
• pp.126-136
• /
• 1991

This study is concerned with the nonlinear dynamic behaviors of guyed towers for wave loadings. In order to analyze the nonlinear responses of guyed towers efficiently, the main tower is modeled as an equivalent stick, the guyline system is idealized as a spring with nonlinear stiffness in the horizontal direction. and the pile foundation system is represented as a linear spring in the rotational direction. The wave forces on the main tower are evaluated by using Morison's equation. In order to consider adequately the nonlinearities of the guying system and drag forces due to fluid viscosity. the analyses are performed in the time domain. The mode superposition method is adopted for solving the nonlinear equation of motion efficiently. which is based on the Newmark integration scheme. Numerical analyses are carried out to investigate the sensitivity of two major design parameters for guyed towers. i.e., the clump weight conditions and the base renditions of the tower.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.5
• /
• pp.27-36
• /
• 2016

This paper presents the investigation of the major influence factors on the degree of soil plugging for open-ended piles based on the Coupled Eulerian-Lagrangian (CEL) numerical technique. The main objective of this study was to investigate the effect of soil plugging on the response of piles in various conditions. Through comparison of the results of field load tests, the CEL methodology was found to be in good agreement with the general trend observed by in situ measurement. Additionally, the parametric studies were performed by controlling the soil conditions, soil elastic moduli, end-bearing conditions and multi layers. It was found that the degree of soil plugging for sand layers was greater than that of clay layers. Also, the degree of soil plugging increased with an increase in both the soil stiffness and length of pile embedded in the bearing layer.

• International Journal of Highway Engineering
• /
• v.12 no.4
• /
• pp.139-145
• /
• 2010

An integrity testing for stone columns was attempted using crosshole S-wave logging. The method is conceptionally quite similar to the crosshole sonic logging (CSL) for drilled piers. The critical difference in the logging is the use of S-wave rather than P-wave, which is used in CSL, because swave is the only wave sensing the stiffness of slower unbounded materials than water. An electro-mechanical source, which can generate reversed Swave signals, was utilized in the logging. The stone column was delineated using the S-wave travel times across the stone column, the S-wave velocity profile of the crushed stone($V_{cs}$-profile) and that of surrounding soil($V_s$-profile). In the calculation of $V_{cs}$-profile of the crushed stone, its friction angle and Ko (coefficient of lateral earth pressure at rest) are recommended to be used. The calculation of the column diameter is not much affected by the values of friction angle and Ko.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.8
• /
• pp.67-75
• /
• 2010

In this study, a series of 1 g shaking table tests were carried out for a single pile in soft clay with various input acceleration amplitudes and frequencies. Based on the results, dynamic p-y curves were drawn and, in turn, the dynamic p-y backbone curve was formed by connecting the peak points, corresponding to the maximum soil resistance, of the dynamic p-y curves. In order to represent the p-y backbone curve numerically, Matlock's p-y formulations for clay was used to find the initial stiffness ($k_{ini}$) and the ultimate capacity ($p_u$) of the clay, both of which are required to formulate the p-y backbone curve as a hyperbolic function. The suggested p-y backbone curve was verified through comparisons with currently available p-y curves as well as other researchers' centrifuge test results and numerical analysis results.

• The Journal of Engineering Geology
• /
• v.19 no.4
• /
• pp.475-482
• /
• 2009

The behavior of earth retention wall installed in cut slope is different from the behavior of retention wall applied in urban excavation. In order to establish the design method of anchored retention walls in cut slope, the behavior of anchored retention wall can be investigated and checked in detail. In this study, the behavior of anchored retention wall was investigated by instrumentation installed in cut slope for an apartment construction stabilized by a row of piles. The horizontal displacement of anchored retention wall was larger than the displacement of slope soil behind the wall at the early stage of excavation. As the excavation depth became deeper, the horizontal displacement of slope soil was larger than the displacement of anchored retention wall. It means that the horizontal displacement of anchored retention wall due to excavation is restrained by soldier pile stiffness and jacking force of anchor. Jacking force of anchor was mainly influenced in the horizontal displacement of anchored retention wall. The displacements of anchored retention wall and slope soil were affected mainly by an rainfall infiltrated from the ground surface. Meanwhile, the horizontal displacement of anchored retention wall with slope backside was about 2-6 times larger than the displacement of anchored retention wall with horizontal backside of excavation.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.11
• /
• pp.93-101
• /
• 2012

SCP is a construction method that maximizes the effects of ground improvement by creating sand piles, which are formed by the compaction within soft ground. SCP is mainly used for consolidation and drain effects in clayey soils, and as a liquefaction countermeasure through effects such as compaction in loose sandy soils. In the design of SCP, if the sand piles with high stiffness are not taken into account, it can become a design that overly considered safety, and increased construction costs are highly likely to cause economic disadvantages. The changes in stress conditions and compaction mechanisms in the subsurface have been identified to a certain extent by study findings to date. However, the studies that considered SCP and in-situ ground as composite ground are fairly limited, and therefore, those studies have not achieved enough results to fully explain the relevant topics. In this study, the ground improved by SCP was regarded as the composite ground that consists of SCP and in-situ ground. Moreover, employing a CID test, this study examined the changes in the stress conditions of in-situ ground according to the installation of SCP through the relations between $K_0$ and SCP replacement ratio. At the same, whether the SCP installation procedure can be recreated in a laboratory was examined using a cyclic triaxial test. According to the test results, the changes in the stress conditions of the original ground occurred most largely in an initial stage of SCP installation, and after a certain time point, the vibration for SCP installation did not have a great influence on the changes in the stress conditions of the ground. Moreover, in order to recreate the behaviors of in-suit ground according to SCP in a laboratory, cyclic loading, which corresponds to casing vibration, was concluded to be essentially required.

• The Journal of Engineering Geology
• /
• v.15 no.2 s.42
• /
• pp.155-168
• /
• 2005

The behavior of earth retention wall installed in a cut slope is different from the behavior of retention wall applied in an urban excavation. In order to establish the design method of anchored retention wall in the cut slope, the behavior of anchored retention wall needs to be investigated and checked in detail. In this study, the behavior of anchored retention wall was investigated by the instrumentation installed in the cut slope, where was stabilized by a row of piles in an apartment construction site. The horizontal displacement of anchored retention wall was larger than the displacement of slope soil behind the wall at the early stage of excavation. As the excavation depth became deeper, the horizontal displacement of slope soil was larger than the displacement of anchored retention wall. It means that the horizontal displacement of anchored retention wall due to excavation is restrained by soldier pile stiffness and jacking force of anchor at the early stage of excavation. lacking force of anchor was mainly influenced on the horizontal displacement of anchored retention wall. The displacements of anchored retention wall and slope soil were affected mainly by rainfall infiltrated from the ground surface. Meanwhile, the horizontal displacement of anchored retention wall with a sloped backside was about $2\~6$ times larger than the displacement of anchored retention wall with a horizontal backside of excavation.