Model Test Research on Bearing Mechanism of Underreamed Ground Anchor in Sand

Gang Guo,Yibing Deng,Aiping Tang,Zhong Liu,Jiqiang Zhang

doi:10.1155/2018/9746438

Abstract

To improve the capacity of ground anchors, scholars and engineers worldwide have developed various types of underreamed anchors with expanded anchor parts. Underreamed anchors have a completely different mechanism from traditional shaft anchors. The expanded section of an underreamed anchor induces an end bearing force to endure the uplift force similar to a reversed pile. Therefore, the total resistance of an underreamed anchor includes friction and end bearing force. To clarify the bearing mechanism of underreamed anchors, a series of model tests were performed using fiber Bragg grating (FBG) sensors and the photogrammetry measuring method. Based on the tests, the distribution and development of the friction and end bearing force of the underreamed anchor model were acquired by the FBG sensors when being pulled out. Moreover, the deformation state of the soil around the anchor model was observed by the digital photogrammetry measuring method. Finally, the interaction mechanism between an underreamed anchor and surrounding sand was obtained, which was identified as the inherent reason for the distribution and development law of the resistance of the underreamed anchor in sand.

Highlights

Geotechnical anchor technology transfers tensile forces from the constructions to the soil or rocks to endure the structural tensions resulting from the soil pressure, water pressure, or buoyancy
Regarding the method of lengthening the anchor section, Barley [1] believed that the anchor force would not increase effectively with the lengthening of the anchor section once the length reached a certain value
Liao [5, 6] in Taiwan described a cone-shaped anchor technology, Massarsch [7] developed the Soilexanchor system, Hobst and Zajic [8] reported the blasting anchor method, Cheng [9] produced a type of deep mixing anchor, Park [10] simulated underreamed anchors by pulse discharge technology, Zhu [11] tested a kind of umbrella-shaped anchor, and Liu [12] reported an anticorrosive underreamed anchor with a capsule

Summary

Introduction

Geotechnical anchor technology transfers tensile forces from the constructions to the soil or rocks to endure the structural tensions resulting from the soil pressure, water pressure, or buoyancy. Based on the above theory, scholars and engineers from various countries developed dozens of methods to improve the anchor force. Regarding the theory of underreamed anchors, increasing the diameter of a part of the anchor section can improve the friction area between the anchor and corresponding soil and convert the shaft anchor mechanism into an end bearing mechanism with friction. Being limited by test methods, the above research results were obtained from simple theoretical derivations or statistical induction without considering the basis of the real interaction mechanism between the anchors and surrounding soil. H mechanism of underreamed anchors and deriving the real interaction relationship between an anchor and surrounding soil lay a foundation for proposing a practical formula for the ultimate capacity of an underreamed anchor. The test results will assist in understanding the bearing mechanism and designing the formula for achieving the ultimate capacity of underreamed anchors practically

Mechanism Analysis of the Resistance of an Underreamed Anchor

Analysis of the Deformation Mechanism of the Soil around the Anchor

Conclusions

Findings

Conflicts of Interest