• Geomechanics and Engineering
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• v.7 no.2
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• pp.165-181
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• 2014

In the past decade, different types of underreamed ground anchors have been developed for substructures requiring uplift resistance. This article introduces a new type of umbrella-shaped anchor. The uplift behavior of this ground anchor in clay is studied through a series of laboratory and field uplift tests. The test results show that the umbrella-shaped anchor has higher uplift capacity than conventional anchors. The failure mode of the umbrella-shaped anchor in a large embedment depth can be characterized by an arc failure surface and the dimension of the plastic zone depends on the anchor diameter. The anchor diameter and embedment depth have significant influence on the uplift behavior. A finite element model is established to simulate the pullout of the ground anchor. A parametric study using this model is conducted to study the effects of the elastic modulus, cohesion, and friction angle of soils on the load-displacement relationship of the ground anchor. It is found that the larger the elastic modulus and the shear strength parameters, the higher the uplift capacity of the ground anchor. It is suggested that in engineering design, the soil with stiffer modulus and higher shear strength should be selected as the bearing stratum of this type of anchor.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.113-118
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• 2017

Numerical analysis was carried out using a finite element analysis program to analyze the behavior characteristics of enlarged cylinder type anchor. It was found that the ultimate resistance of enlarged cylinder type anchor increases with the enlargement angle from numerical analysis for various enlargement angle cases. In the case of $30-60^{\circ}$ of enlargement angle, the deformation and stress distribution characteristics in anchor are similar regardless of enlargement angle. However, when the same tensile force is applied, there is a difference in the degree of frictional resistance because of difference of displacement of top of grouting zone. Also, it was found that the maximum compressive force and tensile force were generated at the cone of the upper portion of the grouting zone, and tensile fracture of the upper grouting portion is likely to occur.