• Journal of the Korean Geotechnical Society
• /
• v.30 no.11
• /
• pp.61-69
• /
• 2014

In this study, the performance of group suction anchors installed in sand and subjected to pullout loading was investigated by numerical analysis. The group suction anchors consist of two or three units rigidly connected to each other in parallel array and the pullout resistances were compared with that of a single anchor. Parametric study was performed using numerical models to study the effect of the physical conditions of the group anchor. The parameters include the skirt length to diameter ratio of a unit suction anchor, the pad-eye location, inclination of loading and the spacing between unit suction anchors. The analysis shows that the ratios of the pullout capacity of double suction anchor and triple suction anchor to that of single anchor are 1.7 and 2.4, respectively. The ratio increases with the increase in the spacing between the unit anchors. The other parameters such as the skirt length to the diameter ratio, the location of the pad-eye and the loading inclination have negligible effect on the ratio of pullout resistances of the group anchor to the single anchor.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.6
• /
• pp.459-468
• /
• 2023

In this study, an experiment on pullout capacity was conducted of rock bolts using grouting materials such as cement mortar and resin, which are widely used, and a newly proposed steel pipe friction type rock bolt using elastic restoring force, and the results were compared and analyzed. The experimental results showed that the pullout capacity on the rock bolts with cement mortar under a dry condition (no ground water) was relatively larger than the rock bolts with resin and the steel pipe. Nevertheless, the friction type steel pipe rock bolt to use elastic restoring force is expected to be useful in the field particularly where groundwater exists and it affects the loss and curing of grouting materials such as cement mortar or resin. In addition, it was found to have the advantage of being easy and quick to install.

• Geomechanics and Engineering
• /
• v.14 no.3
• /
• pp.233-240
• /
• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.

• Geomechanics and Engineering
• /
• v.18 no.3
• /
• pp.277-289
• /
• 2019

In this study, an innovative anchoring approach has been developed dealing with all relevant aspects in consideration of previous works. An ultimate pulling force calculation of anchor is presented from a geotechnical point of view. The proposed umbrella anchor focuses not only on the friction resistance capacity, but also on the axial capacity of the composite end structure and the friction capacity occurring around the wedge. Even though the theoretical background is proposed, in-situ application requires high-level mechanical design. Hence, the required parts have been carefully improved and are composed of anchor body, anchor cap, connection brackets, cutter vanes, open-close ring, support elements and grouting system. Besides, stretcher element made of aramid fabric, interior grouting system, guide tube and cable-locking apparatus are the unique parts of this design. The production and placement steps of real sized anchors are explained in detail. Experimental results of 52 pullout tests on the weak dry soils and 12 in-situ tests inside natural soil indicate that the proposed approach is conservative and its peak pullout value is directly limited by a maximum strength of anchored soil layer if other failure possibilities are eliminated. Umbrella anchor is an alternative to conventional anchor applications used in all types of soils. It not only provides time and workmanship benefits, but also a high level of economic gain and safe design.

• Journal of the Korean Society for Railway
• /
• v.14 no.3
• /
• pp.240-247
• /
• 2011

Finite element analysis was undertaken to investigate the effect of freezing force of water unexpectedly penetrated into inserts used in railway sleeper on pullout capacity of anchor bolts for fixing base-plate onto concrete sleeper. Based on the in-situ investigation and measurement of geometry of railway sleeper and rail-fastener, the railway sleeper was modeled by 3D solid elements. Nonlinear and fracture properties for the finite element model were assumed according to CEB-FIP 1990 model code. And the pullout maximum load of anchor bolt obtained from the model developed was compared with experimental pullout maximum load presented by KRRI for verification of the model. Using this model, the effect of position of anchor bolt, amount of fastening force applied to the anchor bolt, and compressive strength of concrete on pull-out capacity of anchor bolts installed in railway sleeper was investigated. As a result, it is found that concrete railway sleepers could be damaged by the pressure due to freezing of water penetrated into inserts. And the pullout capacity of anchor bolt close to center of railway is slightly greater than that of the others.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.1
• /
• pp.167-173
• /
• 2014

The embedded suction anchor, ESA, is one type of mooring anchor systems which utilizes the suction pile or caisson to penetrate the anchor into the sea bed and develops its capacity under pullout load. In this study, the numerical analysis using ALE (Arbitrary Lagrangian Eulerian) Adaptive Meshing technique was performed to simulate the pullout behavior of the ESA, and the results were compared to those of the previous research, centrifuge model tests and the analytical method based on limit equilibrium theory. The pullout behaviors of the ESA under horizontal, vertical, and inclined loading were evaluated. The analysis results showed that the maximum horizontal pullout load was developed when the location of loading point was at the mid-point, and the each vertical pullout load gave the similar value regardless of the locations of the loading points. The pullout load decreased as the load inclination angle increased at the mid-point of the anchor.

• Geomechanics and Engineering
• /
• v.8 no.6
• /
• pp.801-810
• /
• 2015

The ultimate pullout capacity under inclined dynamic loading is an important measure of the destruction degree of vertical screw piles (anchors) under dynamic actions. Based on the static and dynamic tests on two kinds of model screw piles, the ultimate bearing capacity was researched considering different distance-width ratio of blade (D/W) and preloading ratio. The results compared well with other experimental data available in the literature. This research reveals that D/W might determine the failure model of the piles (anchors), for example D/W = 3.14 or 5; a critical dynamic-static loading ratio (DSLR) existed in the experiments. The critical DSLR was reached under the conditions of 40%~60% preloading (D/W = 3.14) or 20%~40% preloading (D/W = 5), respectively.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.277-284
• /
• 2000

Using the large diameter (D ＝ 2,500mm, L ＝ 40m) batter steel pipe piles, designed as compression piles but used as reaction piles during the static compression load test of socketed test piles (D ＝ 1,000mm, L ＝ 40m), static pile load tests for large diameter instrumented rock-socketed piles were performed. The reaction steel pipe piles were driven 20m into the marine deposit and weathered rock layer and then l0m socketed with reinforced concrete through the weathered rock layer and into hard rock layer. Steel pipe and concrete in the steel pile part, and concrete and rebars in the socketed parts were instrumented to measure strains in each part. The pullout amounts of reaction pile heads were also measured with LVDT. During the static pile load test, total compressional load of about 20MN was loaded on the head of test piles, but load above 20MN was not loaded due to lack of loading capacity of loading system. Over the course of the study, maximum pullout amount up to 7mm was measured in the heads of reaction piles when loaded op to 10MN and 1mm of pullout amount was measured. More than 85% of pullout load was transfered in the residual weathered rock layer and about 10% in the soft rock layer, which was somewhat different transfer mechanism in the static compressional load tests.

• Earthquakes and Structures
• /
• v.5 no.5
• /
• pp.527-552
• /
• 2013

Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1286-1293
• /
• 2010

The ground anchor used in domestic area, which resists by adhesion between anchor body and the ground to the external force, seems not to be adequate for soft ground and urban area where the boundary between structures is close because the ground is disturbed and lost its strength during boring. In order to overcome such a shortcoming an expanded anchor system has been developed. The ground expansion is accomplished by means of Pulse Discharge Technology. In this technology, a high voltage of electricity is stored and discharged in milliseconds which induces high pressure acting on the ground. By making a couple of bulbs, a passive resistance as well as shaft resistance are mobilized, and therefore a higher pullout resistance comparing existing ground anchors is developed.In this study, a couple of full scale tests were conducted in order to figure out how much the resistance of an expanded anchor increases comparing to the straight. As a result, it was found that a remarkable increase in ultimate pullout capacity is observed for the soft ground and as the number of bulb increases. In addtion, as a result of applying to a cut slope reinforcement, it appeared that the length of fixed zone of anchor can be reduced effectively.