• Journal of the Korean Geosynthetics Society
• /
• v.15 no.2
• /
• pp.65-75
• /
• 2016

In this study, we constructed a database by collecting field pullout test data of the soil nailing using pressurized grouting, and suggested a method to estimate the ultimate pullout resistance using nonlinear regression analysis to overcome the problems of ultimate pullout resistance estimation using graphical methods. The load-displacement curve estimated by nonlinear regression showed a very high correlation with the field pullout test data. Estimated ultimate pullout load by nonlinear regression method was average 29% higher than estimated ultimate pullout load using previous graphical method. A sigmoidal growth model was found to be the best-fitting nonlinear regression model against rapid pullout failure. Further, an asymptotic regression model was found to be the best fit against progressive nail pullout. The unit ultimate skin friction suggested in this research reflected in the domestic geotechnical characteristics and the specifications of the pressurized grouting method. This research is expected to contribute towards establishing an independent design standard for the soil nailing by providing solutions to the problems that occur when using design charts based on foreign research.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.32 no.4
• /
• pp.71-80
• /
• 1990

Model tests for the ultimate pullout resistance of anchorages and investigation of failure behaviors in cohesionless soil have been conducted. The factors affecting the anchorage are mostly the geometry of the system, and soil properties of sands. The main conclusions of the experimental work were as follows. 1. The load - displacement relationship can be a form of parabolic curve for all plates. 2. The change in ultimate pullout resistance of anchor is mostly affected by embedment ratio and size of anchor, and influenced to a lesser degree by its shape. 3. Critical embedment ratio which is defined as the failure mode changes from shallow to deep mode is increased with increasing height of anchor. 4. For a constant anchor height, as the width of anchor increases the ultimate pullout resistance also increases. However, considering the efficiency of anchor for unit area, width of anchor does not appear to have any sigrnificant contribution on increasing anchor city. 5. Anchor capacity has a linear relation to sand density for any given section and the rate of change increases as the section increases. Critical depth determining the failure patterns of anchor is decreased with a decrease of sand density. 6. With increasing inclination angle, size of anchor, and decreasing embedment ratio, the ultimate pullout resistance of anchor under inclined loading is significantly decreased. 7. The ultimate pullout resistance of double anchor, a method of improving single of anchor capacity, is influenced by the center - to - center spacing adjacent anchors. It is also found that tandem and parallel anchor rigging arrangements decrease the anchor system capacity to less than twice the single anchor capacity due to anchor interference.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.1240-1249
• /
• 2008

Jacket anchor was developed to increase the pullout resistance of general ground anchor in soft ground, and the mechanism of pullout resistance of jacket anchor was analyzed. Also, the ultimate bond stress of jacket anchor was estimated by ultimate resistance which is determined by field tests. Grout milk was injected into the jacket to make grout bulb of jacket anchor. The formation of grout bulb of jacket anchor increases the diameter of grout bulb, ground strength and confining pressure between anchor grout and soil. From the twelve field test results, it was observed that the pullout resistance of jacket anchor is 15.38~295.02%(average 83.53%) greater than that of general ground anchor, and plastic deformation of jacket anchor is 20.78~1,496.45%(average 288.78%) smaller than that of general ground anchor at the same load cycle. Especially, it was investigated that the increase of ultimate resistance over 200% and the reduction of plastic deformation over 600% was obtained in gravel layer. It means that the jacket anchor is superior to the general ground anchor in gravel layer. Finally, the ultimate bond stress was proposed to design jacket anchor.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.10
• /
• pp.5-16
• /
• 2015

Considering the conversion of the Korea Construction Standards to Limit State Design (LSD), we analyzed the resistance bias factor for pullout resistance, as a part of the development of the Load and Resistance Factor Design (LRFD) for soil nailing; very few studies have been conducted on soil nailing. In order to reflect the local characteristics of soil nailing, such as the design and construction level, we collected statistics on pullout tests conducted on slopes and excavation construction sites around the country. In this study a database was built based on the geotechnical properties, soil nailing specifications, and pullout test results. The resistance bias factors are calculated to determine the resistance factor of the pullout resistance for gravity and pressurized grouting method, which are the most commonly used methods in Korea; moreover, we have relatively sufficient data on these methods. We found the resistance bias factors to be 1.144 and 1.325, which are relatively conservative values for predicting the actual ultimate pullout resistance. It showed that our designs are safer than those found in a research case in the United States (NCHRP Report); however, there was an uncertainty, $COV_R$, of 0.27-0.43 in the pullout resistance, which is relatively high. In addition, the pressurized grouting method has a greater margin of safety than the gravity grouting method, and the actual ultimate pullout resistance determined using the pressurized grouting method has low uncertainty.

• Land and Housing Review
• /
• v.7 no.4
• /
• pp.281-289
• /
• 2016

Structural experiment result showed that PHC(d=600mm) Pile used as a common compression member could resist 83.6 ~ 91.6 tonf of ultimate tension force, if the adhesion of P.C. bar of PHC pile to the concrete foundation is strengthened. Considering a proper safety factor to ultimate tension strength, PHC pile can substitute the anti-floating anchor, or reduce the number of anchors. For this purpose, pullout resistance behavior of a Bored pile embedded in real ground as well as structural tension strength of PHC pile must be evaluated. This study performed the static pullout tests to evaluate the pullout behavior of bored pile, and compared the test results with design value of side resistance. To evaluate the pullout resistance easily, static pullout test results were compared with dynamic loading test results using PDA. As a result, cement paste of the bored pile was hardened which is after 15 days, LH side resistance design value corresponded well to the Static pullout test results, also to the side resistance evaluated by dynamic loading test.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.1
• /
• pp.87-97
• /
• 2014

In this study, the model tests were conducted on the short piles installed in sands under a horizontal pullout load to investigate their behavior characteristics. From the horizontal loading tests where dimensions of the pile diameter and length, and loading point were varied, the horizontal pullout resistance and the rotational and translational movement pattern of the pile were investigated. As a result, the horizontal pullout resistance of the pile embedded in sands was dependent on the pile length, diameter, loading point, etc. The ultimate horizontal pullout load tended to increase as the loading point (h/L) moved to the bottom from the top of the pile, regardless of the ratio between the pile length and diameter (L/D), reached the maximum value at the point of h/L = 0.75, and decreased afterwards. When the horizontal pullout load acted on the upper part above the middle of the pile, the pile rotated clockwise and moved to the pullout direction, and the pivot point of the pile was located at 150-360mm depth below the ground surface. On the other hand, when the horizontal pullout load acted on the lower part of the pile, the pile rotated counterclockwise and travelled horizontally, and the rotational angle was very small.

• Geotechnical Engineering
• /
• v.6 no.1
• /
• pp.43-58
• /
• 1990

In order to get ultimate pullout resistance of ground anchor, the position of failure surface, normal stress and friction angle on the failure surface should be known. In this study, the position of failure surface is obtained by observing deformation of ground around anchor, and stresses on the anchor surface are analyzed by measuring normal and shear stresses on the anchor surface through model anchor test in plane strain. In addition, the relationship between lateral earth pressure and the position of failure surface is analyzed and the formula for calculating ultimate pullout resistance of anchor is proposed by using non-dimensional coefficient of ultimate pullout resistance.

• 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.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.4
• /
• pp.5-11
• /
• 2007

In this study, several pullout tests were carried out under various field conditions to evaluate the pullout force of the end fixed nails. Pullout resistance force, displacement and friction force between the grouting and nail were measured in end fixed nails installed in soft rock, weathered rock and weathered soil. Furthermore, the field test were also carried out under the same condition using the conventional type nails. Based on the test results, it is concluded that the end fixed nails showed larger ultimate resistance force compared with conventional types nails, approximately two times in weathered soil and 1.6 times of weathered rock, respectively. The skin friction is also increased in end fixed type about 1.8~3.0 times. Finally, it is concluded in the base of the force transfer properties that using the end fixed nails could decrease the displacement and show a uniform resistance in entire length of nails.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.5 no.3
• /
• pp.15-22
• /
• 2002

To analysis of the embanked slope stability using a jointed reinforcement, the internal stability and the external stability have to be satisfied, respectively. But, because the lengths of ready-made steel-grid were limited, the reinforcements must be connecting themselves to the reinforcing. In this study, the mechanical test was carried out to investigate the tensile failure and the pullout failure at the joint parts of them, which was based on the analysis of reinforced slope in field. Through the tensile tests in mid-air for the jointed steel-grid, the deformation behavior was seriously observed as follows : deformation of longitudinal member, plastic deformation of longitudinal member and of crank part. Those effects were due to the confining pressure and overburden pressure of the surrounding ground. The bearing resistance at jointed part of jointed steel-grid was due to the latter only. The maximum tensile forces were higher about 20kN~27kN than ultimate pullout resistance, but, the results of those was almost the same in mid-soil. The failures of steel-grid occurred at welded point both of longitudinal members and transverse members and of jointed parts. The strength of jointed parts itself got pullout force about 20kN, which was about 65% for ultimate pullout force of the longitudinal members N=2. To the stability analysis of reinforced structure including the reinforced slope, the studying of connection effects at jointed part of reinforcement members must be considered. Through the results of them, the stability of reinforced structures should be satisfied.