• 한국해양공학회지
• /
• 제22권6호
• /
• pp.1-6
• /
• 2008

Anchors have been commonly used to as foundation systems of the structures that require the uplift resistance. Recently anchors have been used in ocean sediment for mooring systems to stabilizeoffshore structures. In the saturated clayey soil however suction developed between the soil and andchor and affects the uplift capacity of anchor. To estimate the uplift capacity of the andchor accurately, the failure mechanisms of the andchor by the uplift force should also be correctly assumed. The uplift capacity is usually expressed in terms of breakout factors with respect to embedment ratio. In this paper, a two-dimensional plane strain numerical investigation into the vertical uplift capacity of a plate andchor in a clayey soil is described. The breakout factor against their corresponding values of embedment ratio was calculated and plotted along a single curve. The modes of failure mechanism at shallow and deep andchors are also presented.

• Geomechanics and Engineering
• /
• 제17권2호
• /
• pp.165-173
• /
• 2019

Plate anchors are generally used for structures like transmission towers, mooring systems etc. where the uplift and lateral forces are expected to be predominant. The capacity of anchor plate can be increased by the use of geosynthetics without altering the size of plates. Numerical simulations have been carried out on three different sizes of square anchor plates. A single layer geosynthetic has been used as reinforcement in the analysis and placed at three different positions from the plate. The effects of various parameters like embedment ratio, position of reinforcement, width of reinforcement, frequency and loading amplitude on the pull out capacity have been presented in this study. The load-displacement behaviour of anchors for various embedment ratios with and without reinforcement has been also observed. The pull out load, corresponding to a displacement equal to each of the considered maximum amplitudes of a given frequency, has been expressed in terms of a dimensionless breakout factor. The pull out load for all anchors has been found to increase by more than 100% with embedment ratio varying from 1 to 6. Finally a semi empirical formulation for breakout factor for square anchors in reinforced soil has also been proposed by carrying out regression analysis on the data obtained from numerical simulations.

• Geomechanics and Engineering
• /
• 제27권5호
• /
• pp.497-509
• /
• 2021

A large deformation FEM (Finite Element Method) based numerical analysis has been performed to study the behaviour of the bell-shaped anchor embedded in undrained saturated (cohesive) soil with the help of finite element based software ABAQUS. A typical model anchor with bell-diameter of 0.125 m, embedded in undrained saturated soil with varying cohesive strength (from 5 kN/m² to 200 kN/m²) has been chosen for studying the characteristic behaviour of the bell-shaped anchor installed in cohesive soil. Breakout factors have been evaluated for each case and verified with the results of experimental model tests for three different types of soil samples. The maximum value of breakout factor was found as about 8.5 within a range of critical embedment ratio of 2.5 to 3. An explicit model has been developed to estimate the breakout factor (F_c) for uplift capacity of bell-shaped anchor within clay mass in terms of H/D ratio (embedment ratio). It was also found that, the ultimate uplift capacity of the anchor increases with the increase of the value of cohesive strength of the soil and H/D ratio. The empirical equation developed in the present investigation is usable within the range of cohesion value and H/D ratio from 5 kN/m² to 200 kN /m² and 0.5 to 3.0 respectively. The proposed model has been validated against data obtained from a series of model tests carried out in the present investigation. From the stress-profile analysis of the soil mass surrounding the anchor, occurrence of stress concentration is found to be generated at the joint of anchor shaft and bell. It was also found that the vertical and horizontal stresses surrounding the anchor diminish at about a distance of 0.3 m and 0.15 m respectively.

• Geomechanics and Engineering
• /
• 제11권5호
• /
• pp.691-711
• /
• 2016

In this study, the uplift capacity of anchor plates embedded in sand was investigated by conducting model tests. Square shaped anchors were used in the tests and parameters such as relative density of sand, embedment ratio (H/B), spacing ratio between anchors (S/B) and anchor configuration affecting the uplift capacity were investigated. Breakout factor and group efficiency which are dimensionless parameters were used to show the results. A series of finite element analyses and analytical solutions were additionally performed to ascertain the validity of the findings from the laboratory model tests and to supplement the results of the model tests. It can be concluded that the embedment depth in dense sand soil condition is the most important parameter with respect to the other parameters as to influencing the uplift capacity of group anchors.

• Computers and Concrete
• /
• 제32권5호
• /
• pp.499-511
• /
• 2023

Anchor channels are commonly used for façade, tunnel, and structural connections. These connections encounter various types of loadings during their service life, including high rate or impact loading. For anchor channels that are placed close and parallel to an edge and loaded in shear perpendicular to and towards the edge, the failure is often governed by concrete edge breakout. This study investigates the transverse shear behavior of the anchor channels under quasi-static and high rate loadings using a numerical approach (3D finite element analysis) utilizing a rate-sensitive microplane model for concrete as constitutive law. Following the validation of the numerical model against a test performed under quasi-static loading, the rate-sensitive static, and rate-sensitive dynamic analyses are performed for various displacement loading rates varying from moderately high to impact. The increment in resistance due to the high loading rate is evaluated using the dynamic increase factor (DIF). Furthermore, it is shown that the failure mode of the anchor channel changes from global concrete edge failure to local concrete crushing due to the activation of structural inertia at high displacement loading rates. The research outcomes could be valuable for application in various types of connection systems where a high rate of loading is expected.

• 한국지반환경공학회 논문집
• /
• 제9권1호
• /
• pp.5-10
• /
• 2008

본 연구에서는 표면거칠기와 근입비, 직경에 따른 파이프형 앵커의 인발거동을 평가하기 위하여 실내모형실험이 시행되었다. 수직방향의 지반 변형에서 매입된 파이프형 앵커의 설계는 파이프에 부과된 힘의 크기에 의해 지배받는다. 본 논문에서는 모형실험의 분석을 통하여 파이프 직경과 표면 거칠기, 근입비와 지반상태로 야기된 파이프형 앵커의 변위 특성과 극한 저항력을 비교하고 평가하였다. 실험결과는 상대밀도의 증가에 따라 극한 인발력이 20%가량 증가하고 있음을 보여주고 있다. 지반의 상대밀도와 파이프의 지름, 표면거칠기의 변화에 따른 파이프형 앵커의 파괴시 변위는 근입비가 2에서 8로 증가함에 따라 약 5배 정도의 증가 경향을 보였다. 또한 앵커이론에 근거한 이론식들은 인발계수를 과대평가하는 것으로 나타났다.

• 한국수산과학회지
• /
• 제31권5호
• /
• pp.685-694
• /
• 1998

To evaluate the water quality characteristic after construction of Keum river estuary barrage, water quality analysis were conducted on August October in 1995 and January, May in 1996 respectively. The results were summarized as follows. The concentrations of COD were in the range of 1.01~5.10 (mean 2.50)mg/$\ell$ for surface water and 0.51$\~$6.68 (1.88)mg/$\ell$ for bottom water. The concentrations of dissolved inorganic nitrogen (DIN) were in the range of 1.26$\~$105.91 (29.66)$\mu$g-at/$\ell$ for surface water and 1.42$\~$68.38 (19.12)$\mu$g-at/$\ell$ for bottom water. The concentrations of phosphate phosphorus were in the range of ND$\~$0.99 (0.34)$\mu$g-at/$\ell$ for surface water and 0.17$\~$1.04 (0.49)$\mu$g-at/$\ell$ for bottom water. The nitrogen ratio to the phosphorus were as high as 3.5$\~$849.5 (146.5). Therefore, Phosphate phosphorus was playing an important role in phytoplankton growth as limiting factor in Keum river estuary. The correlation coefficient of salinity and DIN according to COD was shown to -0.757 and -0.874 respectivity. Mean values of eutrophicaton indies were calculated to 9.7, 7.2 for surface and bottom water, these values were exceeding 1, the value of eutrophication criteria. Especially station 1$\~$3 were shown over 10 as eutrophication indices. Therefore, Keum river estuary could be evaluate to possibility area for breakout of red tides.

• Geomechanics and Engineering
• /
• 제8권4호
• /
• pp.615-630
• /
• 2015

The use of helical anchors has been extensively beyond their traditional use in the electrical power industry in recent years. They are commonly used in more traditional civil engineering infrastructure applications so that the advantages of rapid installation and immediate loading capability. The majority of the research has been directed toward the tensile uplift behaviour of single anchors (only one plate) by far. However, anchors commonly have more than one plate. Moreover, no thorough numerical and experimental analyses have been performed to determine the ultimate pullout loads of multi-plate anchors. The understanding of behavior of these anchors is unsatisfactory and the existing design methods have shown to be largely inappropriate and inadequate for a framework adopted by engineers. So, a better understanding of helical anchor behavior will lead to increased confidence in design, a wider acceptance as a foundation alternative, and more economic and safer designs. The main aim of this research is to use numerical modeling techniques to better understand multi-plate helical anchor foundation behavior in soft clay soils. Experimental and numerical investigations into the uplift capacity of helical anchor in soft clay have been conducted in this study. A total of 6 laboratory tests were carried out using helical anchor plate with a diameter of 0.05 m. The results of physical and computational studies investigating the uplift response of helical anchors in soft clay show that maximum resistances depend on anchor embedment ratio and anchor spacing ratio S/D. Agreement between uplift capacities from laboratory tests and finite element modelling using PLAXIS is excellent for anchors up to embedment ratios of 6.

• Geomechanics and Engineering
• /
• 제28권2호
• /
• pp.197-207
• /
• 2022

The seismic holding behaviors of plate anchor embedded into submerged coarse-grained soils were investigated considering different anchor inclinations. The limit equilibrium method and the Pseudo-Dynamic Approach (PDA) were employed to calculate the inertia force of the soils within the failure rupture. In addition, assuming the permeability of coarse-grained soils was sufficiently large, the coefficient of hydrodynamic force applied on the inclined plate anchor is obtained through adopting the exact potential flow theory. Therefore, the seismic holding resistance was calculated as the combination of the inertia force and the hydrodynamic force within the failure rupture. The failure rupture can be developed due to the uplift loads, which was assumed to be an arc of a circle perpendicular to the anchor and inclines at (π/4 - φ/2). Then, the derived analytical solutions were evaluated by comparing the static breakout factor N_γ to the published experimental and analytical results. The influences of soil and wave properties on the plate anchor holding behavior are reported. Finally, the dynamic anchor holding coefficients N_γd, were reported to illustrate the anchor holding behaviors. Results show that the soil accelerations in x and z directions were both nonlinear. The amplifications of soil accelerations were more severe at lower normalized frequencies (ωH/V) compared to higher normalized frequencies. The coefficient of hydrodynamic force, C, of the plate anchor was found to be almost constant with anchor inclinations. Finally, the seismic anchor holding coefficient oscillated with the oscillation of the inertia force on the plate anchor.

• 한국가스학회지
• /
• 제21권3호
• /
• pp.17-25
• /
• 2017

최근 화석연료 사용에 따른 지구 온난화 현상에 대한 우려로 대체에너지 자원 개발의 필요성이 대두되고 있다. 이에 알래스카와 시베리아 같은 극한지에 매장된 천연가스에 대한 관심도 증가하고 있다. 하지만 국내 기업은 국내 건설환경과 상이한 극한지에서의 가스배관 공사의 시공 경험과 매뉴얼이 부족하다. 특히 시공 중 트렌치의 안정성이 보장되지 않으면 트렌치 사면의 붕괴로 인한 인부들의 낙상, 건설 장비들의 파손, 공기 증가 등을 야기할 수 있기 때문에 극한지의 트렌치 안정성 연구가 필수적이다. 본 연구에서는 러시아 야쿠츠크(Yakutsk) 지역을 동토지역의 계절별 지반조건의 기준으로 정하였으며, 직경 30 in.와 40 in.의 파이프라인 내리기 시공과정을 가정하였다. 지반조건은 여름과 겨울, Silt와 Peat, 사면의 각도($0^{\circ}$, $10^{\circ}$, $20^{\circ}$)별로 다양한 조건을 고려하였다. 파이프라인 시공 사례 분석을 통해 Pipelayer의 장비하중이 트렌치 안정성에 영향을 줄 수 있는 요소임을 알 수 있었고, 이에 Pipelayer 장비가 트렌치에 미치는 영향을 분석하기 위하여 Pipelayer 장비 종류별, 트렌치와 Pipelayer 장비 사이의 거리별, Pipelayer의 종방향 간격별로 Case를 나누어 수치해석을 시행하였다. 수행결과 사면경사가 클수록, 장비와 트렌치 사이의 거리는 가까울수록 사면의 안전율이 감소하였다. 특히 경사가 $20^{\circ}$일 때는 사면의 예상 파괴면이 Pipelayer 장비에서 트렌치까지 이어지는 것을 확인할 수 있었다. 사면경사가 $20^{\circ}$이하인 겨울철 지반에서는 트렌치 안정성의 문제는 없는 것으로 판단되었다.