• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.227-243
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• 2015

In this paper, the effects of nonlinear soft clay on dynamic embedment of offshore pipeline were investigated. Seabed embedment by pipe-soil interactions has impacts on the structural boundary conditions for various subsea structures such as pipeline, riser, pile, and many other systems. A number of studies have been performed to estimate real soil behavior, but their estimation of seabed embedment has not been fully identified and there are still many uncertainties. In this regards, comparison of embedment between field survey and existing empirical models has been performed to identify uncertainties and investigate the effect of nonlinear soil parameter on dynamic embedment. From the comparison, it is found that the dynamic embedment with installation effects based on nonlinear soil model have an influence on seabed embedment. Therefore, the pipe embedment under dynamic condition by nonlinear parameters of soil models was investigated by Dynamic Embedment Factor (DEF) concept, which is defined as the ratio of the dynamic and static embedment of pipeline, in order to overcome the gap between field embedment and currently used empirical and numerical formula. Although DEF through various researches is suggested, its range is too wide and it does not consider dynamic laying effect. It is difficult to find critical parameters that are affecting to the embedment result. Therefore, the study on dynamic embedment factor by soft clay parameters of nonlinear soil model was conducted and the sensitivity analyses about parameters of nonlinear soil model were performed as well. The tendency on dynamic embedment factor was found by conducting numerical analyses using OrcaFlex software. It is found that DEF was influenced by shear strength gradient than other factors. The obtained results will be useful to understand the pipe embedment on soft clay seabed for applying offshore pipeline designs such as on-bottom stability and free span analyses.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.233-240
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• 1999

The laboratory tests on geogrid-reinforced sand were conducted with considering embedment effect. The relative densities of sand are 60% and 80%, respectively. The embedment depths of foundation were varied as D$\_$f/B=0, 0.5, 1.0. Based on the model test results, (u/B)$\_$cr/, BCR$\_$u/, and (b/B)$\_$cr/, were determined. The optimum depth of reinforcement was determined. The embedment depth of foundation is greatly contributed on the bearing capacity of geogrid-reinforced sand.

• 대한토목학회논문집
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• 제7권3호
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• pp.175-181
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• 1987

개단 강관말뚝의 선단지지력은 폐색 효과에 의하여 발생되는데 이 폐색 효과는 말뚝의 직경에 대한 관입깊이의 비 즉, 상대 관입깊이와 밀접한 관계가 있는 것으로 알려져 있다. 이에 본 연구에서는 폐색 효과를 종합적으로 평가하기 위하여 지반의 상대밀도와 모형말뚝의 상대 관입 깊이를 달리하여 재하시험을 수행하였으며 개단 말뚝의 유효직경을 축소시킬 목적으로 십자 모양의 칸막이 판을 선단에 부착한 모형말뚝에 대한 시험도 병행하였다. 그 결과로서 개단 말뚝은 말뚝의 극한 지지력을 기준으로 폐색효과를 평가할 때 말뚝 타설 지반이 단단할수록 작은 상대관입깊이에서 큰 폐색효과를 얻을 수 있으나 100%의 폐색효과는 지반의 상대밀도에 상관없이 대략 상대관입깊이 25 정도에서 발휘된다는 사실을 알았다. 그리고 칸막이 판의 설치로 인한 폐색효과의 증대는 기대하기 어려운 것으로 판단된다.

• 한국철도학회논문집
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• 제8권4호
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• pp.367-371
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• 2005

Pile foundations are utilized when soil is so weak that shallow foundations are not suitable or point load is concentrated in small area. Such soil can be formed by the land reclamation works which have extensively been executed along the coastal line of southern and western parts of the Korean Peninsula. The working load at pile is sometimes subjected to not only compression load but also lateral load sad uplift forces. But in most of the practice design, uplift capacity of pile foundation is not considered and estimation of uplift capacity is presumed on the compression skin friction. This study was carried out to determine that the effect of embedment ratio and loading rate on uplift adhesion factor of concrete pile driven in clay. Based on the test results, the critical embedment ratio is about 9. Adhesion factor is constant under the critical embedment ratio, and decreasing over the critical embedment ratio. Also, adhesion factor is increased with the loading rate is increased.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1477-1482
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• 2015

기초의 근입비가 보상기초의 극한지지력과 침하량에 미치는 영향을 살펴보고자 수치해석을 수행하였다. 수치해석에 의한 극한지지력비는 이론식에 의한 극한지지력비보다 컸으며 전체적으로 극한지지력비가 근입비에 비례하는 결과를 보였으나 정사각형기초에 대한 수치해석결과만 극한지지력비가 근입비에 따라 급격하게 증가하는 양상을 보였다. 모래지반에 놓인 띠기초의 경우 근입비에 따른 극한지지력비는 수치해석과 Meyerhof 방법에 의한 경우가 비슷하였으며 대체로 근입비의 제곱에 가까운 값을 나타내었으며 점토지반에 놓인 띠기초의 경우 이론식에 의할 경우 극한지지력비는 근입비의 영향을 크게 받지 않았고 수치해석결과에 따르면 근입비를 약간 상회하는 값들을 보였다. 수치해석결과에 따르면 근입비에 따른 정사각형기초의 극한지지력비가 띠기초의 그것에 비하여 크게 계산되었다. 수치해석결과를 통해 볼 때 전체적으로 근입비가 1인 경우 침하량비는 0.4 정도의 값을 보이다가 근입비가 커짐에 따라 침하량비가 감소하는 양상을 보였으며 느슨한 모래의 경우 상대적으로 침하량비가 가장 작았다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.598-613
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• 2013

This paper deals with the dynamic effect of pipeline installation and embedment for the on-bottom stability design of offshore pipelines on soft clay. On-bottom stability analysis of offshore pipelines on soft clay by DNV-RP-F109 (DNV, 2010) results in very unreasonable pipe embedment and concrete coating thickness. Thus, a new procedure of the on-bottom stability analysis was established considering dynamic effects of pipeline installation and pipe-soil interaction at touchdown point (TDP). This analysis procedure is composed of three steps: global pipeline installation analysis, local analysis at TDP, modified on-bottom stability analysis using DNV-RP-F109. Data obtained from the dynamic pipeline installation analysis were utilized for the finite element analysis (FEA) of the pipeline embedment using the non-linear soil property. From the analysis results of the proposed procedure, an optimum design of on-bottom stability of offshore pipeline on soft clay can be achieved. This procedure and result will be useful to assess the on-bottom stability analysis of offshore pipelines on soft clay. The analysis results were justified by an offshore field inspection.

• KCI Concrete Journal
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• 제11권3호
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• pp.201-210
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• 1999

An experimental study was carried out to determine pullout behavior of a new type of anchor bolt that used deformed reinforcement and a commercial adhesive. Concrete slabs and columns with about 20-MPa compressive strength were used for 136 pullout tests performed. Test variables included anchor diameter (10 mm ~ 32 mm). embedment depth (10$\Phi$ or 15$\Phi$), edge effect. and Presence of transverse reinforcement in existing concrete. In Tyre-S test. where the edge or reinforcing steel effect was not included, the anchor Pullout strengths increased with increasing anchor diameters. Anchors with 15$\Phi$ embedment depth had higher Pullout strengths than those with 100 embedment depth The largest average Pullout load of 208 kN was determined for anchors made with D25 reinforcement and with 15$\Phi$ embedment depth. In Type-E tests, where the anchors were installed close to the edge of existing concrete, there were reductions in pullout strengths when compared to those determined in Type-S tests. In Type-ER tests, influence of the reinforcement in existing concrete on the anchor pullout strengths was examined using reinforced concrete and plain concrete columns Test results indicated that existing transverse reinforcement (column ties) did not help increase the pullout strength. The overall pullout test results revealed that the new anchor bolt can develop large pullout strengths while the anchors can be made of materials that are readily available in the market.

• Structural Engineering and Mechanics
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• 제21권1호
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• pp.1-18
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• 2005

Foschi's connector model is used as a basic component in the development of nonlinear analysis programs for timber structures. This paper presents the extension of the model to include the effect of shaft frictional forces. The wood medium is modeled using the Foschi embedment model, while shaft friction is modeled using an elastic Coulomb-type friction model. The initial confining pressure for the case of driven fasteners is accounted for by a lateral shift of the load-embedment curve. The model is used to compute the cyclic response of both driven and inserted fasteners. The results obtained from the cases studied indicate that initial confining pressure and friction do not have a significant effect on the computed hysteretic response, however, they significantly affect the computed amount of fastener withdrawal. This model is particularly well-suited for modeling the hysteretic response of shear walls with moderate fastener withdrawal under lateral cyclic or earthquake loading.

• Structural Engineering and Mechanics
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• 제59권2호
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• pp.209-226
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• 2016

Integral bridges are typically designed with flexible foundations that include one row of piles. The construction of integral bridges solves difficulties due to the maintenance of expansion joints and bearings during serviceability. It causes integral bridges to become more economic comparing with conventional bridges. Research has been focused not only to enhance the seismic performance of newly designed bridges, but also to develop retrofit strategies for existing ones. The local performance of the pile to abutment connection will have a major effect on the performance of the structure and the embedment length of pile inside the abutment has a key role to provide shear and flexural resistance of pile-abutment connections. In this paper, a simple method was developed to estimate the initial value of embedment length of the pile for retrofitting of specimens. Four specimens of pile-abutment connections were constructed with different embedment lengths of pile inside the abutment to evaluate their performances. The results of the experimentation in conjunction with numerical and analytical studies showed that retrofitting pile-abutment connections with CFRP wraps increased the strength of the connection up to 86%. Also, designed connections with the proposed method had sufficient resistance against lateral load.

• Geomechanics and Engineering
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• 제15권6호
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• pp.1193-1205
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• 2018

A footing located on slopes possess relatively lower bearing capacity as compared to the footing located on the level ground. The bearing capacity further reduces under seismic loading. The adverse effect of slope inclination and seismic loading on bearing capacity can be minimized by proving sufficient setback distance. Though few earlier studies considered setback distance in their analysis, the range of considered setback distance was very narrow. No study has explored the critical setback distance. An attempt has been made in the present study to comprehensively investigate the effect of setback distance on footing under seismic loading conditions. The pseudo-static method has been incorporated to study the influence of seismic loading. The rate of decrease in seismic bearing capacity with slope inclination become more evident with the increase in embedment depth of footing and angle of shearing resistance of soil. The increase in bearing capacity with setback distance relative to level ground reduces with slope inclination, soil density, embedment depth of footing and seismic acceleration. The critical value of setback distance is found to increase with slope inclination, embedment depth of footing and density of soil. The critical setback distance in seismic case is found to be more than those observed in the static case. The failure mechanisms of footing under seismic loading is presented in detail. The statistical analysis was also performed to develop three equations to predict the critical setback distance, seismic bearing capacity factor ($N_{{\gamma}qs}$) and change in seismic bearing capacity (BCR) with slope geometry, footing depth and seismic loading.