• Geomechanics and Engineering
• /
• 제35권6호
• /
• pp.617-626
• /
• 2023

In this study, three-dimensional numerical parametric study was conducted to explore deformation mechanisms of grouped piled-raft-foundation due to lateral load in clays. Effects of load intensity, loading angle, soil stiffness, pile diameter, pile spacing and pile length on foundation deformations were explored. It is found that the smallest and largest movements of pile foundation are induced when the loading angles are 0° and 30°~60°, respectively. By increasing loading angle from 0° to 30°~60°, the resultant horizontal movements and settlements increase by up to 20.0% and 57.1%, respectively. Since connection beams can substantially increase integrity of four piled raft foundation, resultant horizontal movements, settlements and bending moments induced in the piled raft foundation decrease by up to 54.0%, 8.8% and 46.3%, respectively. By increasing soil stiffness five times, resultant horizontal movements and settlements of pile foundation decrease by up to 61.7% and 13.0%, respectively. It is indicated that effects of connection beam and soil stiffness on settlements of pile foundation are relatively small. When pile diameter is less than 1.4 m, deformations of piled raft foundation decrease substantially as a reduction in the pile diameter. Two dimensional groups are proposed to develop calculation charts of horizontal movements and settlements of pile foundation. The proposed calculation charts can directly estimate movements of piled raft foundation under arbitrary loading, ground and pile conditions.

• 한국지반공학회지:지반
• /
• 제5권1호
• /
• pp.35-46
• /
• 1989

사질토에 있어서의 말뚝지지력을 해석하기 위하여 아세톤 고형, 수지충진기법을 사용한 모형말뚝 실험을 하여 흙의 변형을 조사하였다. 이 결과로부터 새로운 변형형태가 가정되었으며, 구형공동확장이론을 적용하여 새로운 해석법을 제시하였다. 새로운 해석법에 의한 말뚝지지력은 극한 구형공동확장압력과 지지력 상관계수로 표시된다. 본 해석법의 결과는 공동확장이론을 근거로 한 타 해석법과 비교되었다. 비교 결과, 본 해석법은 공동확장이론에 의한 말뚝지지력 해석의 결점으로 지적되는 실제보다 높은 지지력을 주는 문제점을 해결할 수 있을 것으로 기대된다.

• 한국지반환경공학회 논문집
• /
• 제7권2호
• /
• pp.15-24
• /
• 2006

본 연구에서는 수평재하시험과 공내수평재하시험 결과를 이용하여 지반반력계수를 각각 분석하였다. 또한 이들 값과 수평재하시험 실시 위치에서의 N치를 이용하여 도로교표준시방서, 일본토목학회, Hukuoka식, 일본도로협회 제안식으로 산정한 수평방향 지반반력계수를 비교 및 분석하여 제안식별 적용성을 평가하고자 하였다. 수평방향 지반반력계수 산정시 지반의 변형계수가 큰 영향을 미치는 것으로 볼 때 합리적인 지반의 변형계수 산정이 매우 중요하며, 제안식별 변형계수 적용에 대해 재하시험 결과를 이용하여 검토하였다. 특히 공내수평재하시험 결과를 이용하여 지반반력계수를 산정하는 방법은 수평변위를 고려할 수 없는 등의 문제점이 있는 것으로 나타나 사질토 지반의 수평방향 지반반력계수 산정시 말뚝의 직경과 수평변위를 고려할 수 있는 식을 제안하였으며, 아울러 N치를 이용한 지반의 변형계수를 고려하는 제안식에 대해서는 수평재하시험과 비교하여 지반의 변형계수 추정식을 제안하였다.

• 한국기계가공학회지
• /
• 제9권6호
• /
• pp.1-6
• /
• 2010

Patterned optical components are widely used for optical products such as LCD and lighting. Since CCFL was used as a light source in the products, prism films having linear continuous optical patterns were widely used. However, LED which is a dot light source is popular recently, therefore, the optical products need new optical components having non-continuous optical patterns. Indentation machining method is a powerful method for machining of non-continuous pattern. When a copper mold and a brass mold were machined by this method, severe plastic deformation called pile-up was observed around the patterns. Since pile-up has negative relationship to ductility, this deformation can be eliminated by annealing treatment which makes the materials ductile. No plastic deformation occurred when machined after annealing at $600{^{\circ}C}$ and $575{^{\circ}C}$ for copper and brass, respectively. Finally, non-continuous optical patterns with high quality were machined on a copper mold and a brass mold successively.

• Geomechanics and Engineering
• /
• 제37권2호
• /
• pp.167-178
• /
• 2024

The natural frequency shift under cyclic environmental loads is a key issue in the design of monopile-based offshore wind power turbines because of their dynamic sensitivity. Existing evidence reveals that the natural frequency shift of the turbine system in sand is related to the varying foundation stiffness, which is caused by soil deformation around the monopile under cyclic loads. Therefore, it is an urgent need to investigate the effect of soil deformation on the system frequency. In the present paper, three generalized geometric models that can describe soil deformation under two-way cyclic loads are proposed. On this basis, the cycling-induced changes in soil parameters around the monopile are quantified. A theoretical approach considering three-spring foundation stiffness is employed to calculate the natural frequency during cycling. Further, a parametric study is conducted to describe and evaluate the frequency shift characteristics of the system under different conditions of sand relative density, pile slenderness ratio and pile-soil relative stiffness. The results indicate that the frequency shift trends are mainly affected by the pile-soil relative stiffness. Following the relevant conclusions, a design optimization is proposed to avoid resonance of the monopile-based wind turbines during their service life.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2000년도 봄 학술발표회 논문집
• /
• pp.151-158
• /
• 2000

The lateral deformation of one row pile groups was investigated based on analytical study and a numerical analysis. The emphasis was on quantifing the load transfer of pile groups subjected to lateral soil movement. An analytical method to consider pile-soil interaction in weathered soil was developed using load-transfer curve methods. Through the comparative study, it is found that the prediction by present approach is in good agreement with the general trend observed by in-situ measurements.

• 한국농공학회지
• /
• 제44권1호
• /
• pp.142-154
• /
• 2002

This study was performed to investigate constraint effects of deformation (heaving, lateral displacement) of clayey foundation reinforced with sheet pile at the tip of banking on soft ground, under intact state (natural) and the state of vertical drain respectively. The following results are obtained. 1. In view of reduction in heaving or lateral displacement, sheet pile is not supposed to be of use. 2. Sheet pile is effective only when vertical drain is installed for acceleration of consolidation and gradual loading is applied.

• 한국환경복원기술학회지
• /
• 제9권5호
• /
• pp.10-21
• /
• 2006

For analyze of the bearing capacity, skin friction and settlements of pile on axial compressive loading, both Load transfer tests of pile and pile loading test in field have application to commonly before pile installing. A bearing capacity of pile was affected by the characteristics of surrounding ground of pile. Especially, that is very different because of evaluation of settlement due to each soil conditions of ground depths. The ground characteristics using evaluation of bearing capacity of pile through load transfer analysis depends on N values of SPT, and then a bearing capacity of pile installed soft ground and refilled area may be difficult to rational evaluation. An evaluation of bearing capacity on pile applied axial compressive loading was effected by strength of ground installed pile, unconfined compressive strength at pile tip, pile diameter, rough of excavated surface, confining pressure and deformation modules of rock etc and these are commonly including the unreliability due to slime occurred excavation works. Load transfer characteristics considered ground conditions take charge of load transfer of large diameter pile was investigated through case study applied load transfer tests. To these, matrix analytical technique of load transfer using finite differential equation developed and compared with the results of pile load test.

• 농업과학연구
• /
• 제24권2호
• /
• pp.226-236
• /
• 1997

The results obtained by elasto-plastic analysis method about the displacement, deformation and stability on the soft ground excavation using sheet pile were summarized as follows ; 1. In the case of strut 1 step, the maximum wall displacement value in the first and the second excavation was small, but it increase remarkably after the third excavation and when the excavation depth was 8m, the point of maximum wall displacement was shown 0.75H~0.8H. 2. The value of safety factor(Fs) was increased with increasing of the penetration depth of sheet pile, cohesion and internal friction angle of ground. Safety factor was mostly effected by penetration depth of sheet pile and more effected by cohesion than internal friction angle of ground. 3. Since the deformation of sheet pile of this ground from the results of analysis and measurement increased remarkabaly after 6m excavation depth, it was desirable that the point of strut installation was GL-6m. 4. Safe excavation depth on ground by analysis considered penetration depth, cohesion and internal friction was shown at the table 3.

• Geomechanics and Engineering
• /
• 제21권3호
• /
• pp.279-288
• /
• 2020

The permeation grouting is a commonly used technique to improve the engineering geology condition of the soft ground. It is of great significance to predict the permeation range of the grout so as to ensure the effects of grouting. This paper conducts a theoretical analysis of jet-grouting effects in ground improvement and rotary grouting pile installation by utilizing deformation-permeation coupled poroelastic solutions based on Biot's theory and Laplace-Fourier integral transform technique. The exponential function and the intermittent trigonometric function are chosen to represent time-dependent grouting pressure usually encountered in ground improvement and rotary grouting pile installation process, respectively. The results, including the radial displacement, the hoop stress, the excess pore fluid pressure, the radial discharge, and the permeation radius of grout, are presented for different grouting time, radial positions and grouting lengths. Parametric study is conducted to explore the effects of variation of the exponent in the exponential grouting pressure-time relationship on grouting-induced responses. It is expected that the proposed solutions can be used to estimate the permeation range of grouting in ground improvement and rotary grouting pile installation.