• 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 the Korean Geotechnical Society
• /
• v.30 no.2
• /
• pp.5-18
• /
• 2014

Depending on the underground load support mechanism, anchors are classified as friction anchors, bearing plate anchors and the recently developed combined friction-bearing plate anchors which combine the characteristics of both the friction and bearing plate type anchors. Even though numerous studies have been performed on bearing plate anchors, there were only few studies performed to observe the failure surface of bearing plate anchors. Furthermore most of the soil materials used on these tests were not real sand but carbon rods. In this study, sand was placed in the soil tank and laboratory tests were performed with bearing plate anchors installed with an embedment depth (H/h) ranging from 1~6. The variation in the pullout capacity and the behaviour of soil with the embedment depth (H/h) were observed. Ground deformation analysis program was also used to analyze soil displacement, zero extension direction, maximum shear strain contours. It was determined from the analysis of the results that at ultimate pullout resistance the deformation was 5 mm and the failure surface occurred in a narrower area when compared with results of the previous researches. It was also observed that the width of the fracture surface gradually becomes wider and expands up to the surface as the deformation increases from 10 mm to 15 mm.

• Geomechanics and Engineering
• /
• v.11 no.1
• /
• pp.141-160
• /
• 2016

This study elucidates the uplift behaviors of the straight-sided and belled shafts. The field uplift load tests were carried out on 18 straight-sided and 15 belled shafts at the three collapsible loess sites under an arid environment on the Loess Plateau in Northwest China. Both the site conditions and the load tests were documented comprehensively. In general, the uplift load-displacement curves of the straight-sided and belled shafts approximately exhibited an initial linear, a curvilinear transition, and a final linear region, but did not provide a well defined peak or asymptotic value of the load, and therefore their uplift resistances should be interpreted from the load test results using an appropriate criterion. Nine representative uplift resistance interpretation criteria were used to define the "interpreted failure load" for each of the load tests, and all of these interpreted uplift resistances were normalized by the failure threshold, $T_{L2}$, obtained using the $L_1-L_2$ method. These load test data were compared statistically and graphically. For the straight-sided and belled shafts, the normalized uplift load-displacement curves were respectively established by the plots that related the mean interpreted uplift resistance ratio against the mean displacement at the corresponding interpreted criteria, and the comparisons of the normalized load-displacement curves were made. Specific recommendations for the designs of uplift belled and straight-sided shafts in the loess were given, in terms of both capacity and displacement.

• Geomechanics and Engineering
• /
• v.8 no.4
• /
• 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.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.2
• /
• pp.15-22
• /
• 2010

A series of field pull-out tests were carried out to investigate the behaviour of multi-pressurized soil nails. Ten soil nails were constructed in weathered soil and then, subjected to pull-out loads. The test results showed that the ultimate pull-out resistances of soil nails constructed with high pressure were about 42~142% larger than those obtained from conventional soil nails. The deduced interface shear strength at the ground-grout interface was 71 kPa for conventional soil nails, while higher shear strength of 95~166 kPa was obtained for pressurized nails. The diameter of grouted borehole increased by about 12~27% compared to ordinary soil nails under low pressure. Also, the predicted value by the cavity expansion theory is in good agreement with the measured expanded radius of grout under injection pressure by field pull-out tests.