Abstract
Considering the deficiency of traditional anchors, we propose a new type of inflatable controlled anchor system in this paper. The working mechanism and its structural composition of newly designed inflatable controlled device are discussed in detail. To investigate the performance and pull-out capacity of this new anchor system, a series of field tests were carried out under different inflation pressure conditions. By comparing these test results with those of traditional grouting anchors, a full-process constitutive model of anchor-soil interface is proposed to depict the pull-out characteristics of the inflatable controlled anchor. The results show that the ultimate bearing capacity of the inflatable controlled anchor is greater than that of the traditional grouting anchor when the inflation pressure is greater than 0.2 MPa and the ultimate bearing capacity of this new anchor improves obviously with the increase of inflation pressure. When the inflation pressure reaches 0.4 MPa, the ultimate bearing capacity of the inflatable controlled anchor is 2.08 times that of the traditional grouting anchor. Through comparison with the experimental curves, the results of model calculation indicate that the proposed anchor-soil interface constitutive equation can describe the pull-out characteristics of the inflatable controlled anchor. The designed controlled anchor has the advantages of no grouting, recyclability, rapid formation of anchoring force, and adjustable anchoring force.
Highlights
Considering the deficiency of traditional anchors, we propose a new type of inflatable controlled anchor system in this paper. e working mechanism and its structural composition of newly designed inflatable controlled device are discussed in detail
For meeting requirements of different geological conditions, working environment, and bearing capacity, a variety of new type anchors were developed successively, such as the splitset anchor, the water swelling anchor, the flexible pressurized grouting anchor, the inflatable anchor, and the inflatable anchor with the end baffle [3]. e split-set anchor, which is forcibly squeezed by external force into the vertical slit steel pipe with a larger diameter than that of drilling hole, achieves the anchoring effect through the fiction produced by mechanical external force between anchor and the hole wall [4, 5]. e main disadvantage of the thin-walled split anchor is that the anchoring force is not easy to control and is greatly influenced by the difference between the pipe diameter and the anchor hole diameter
Based on the field tests of an inflatable controlled anchor system, the following conclusions can be drawn: (1) A new type of inflatable anchor system is designed and developed, which mainly includes four separate parts: squeezing device, expansion device, force transmission device, and control device. e expansion device is enclosed with the squeezing device, which can be dynamically controlled and set. e radial enlargement of expansion device pushes the squeezing device to contact with the hole wall tightly, and the friction resistance generated by the Inflation pressure (MPa)
Summary
Considering the deficiency of traditional anchors, we propose a new type of inflatable controlled anchor system in this paper. e working mechanism and its structural composition of newly designed inflatable controlled device are discussed in detail. To investigate the performance and pull-out capacity of this new anchor system, a series of field tests were carried out under different inflation pressure conditions By comparing these test results with those of traditional grouting anchors, a full-process constitutive model of anchor-soil interface is proposed to depict the pull-out characteristics of the inflatable controlled anchor. For meeting requirements of different geological conditions, working environment, and bearing capacity, a variety of new type anchors were developed successively, such as the splitset anchor, the water swelling anchor, the flexible pressurized grouting anchor, the inflatable anchor, and the inflatable anchor with the end baffle [3]. E main disadvantages of the water swelling anchor include that the recovered anchor has almost no reuse value, the use of double-layer seamless steel pipe has a high requirement on the high costing material and manufacturing technology, and its large internal pressure is not suitable for soft soil. Advances in Civil Engineering anchor is difficult to recycle and reuse after use. e water swelling anchor, which is fabricated into double concave tubular rod, is developed by injecting high-pressure water to expand the thin seamless steel pipe and squeeze the anchor hole wall [6]. e main disadvantages of the water swelling anchor include that the recovered anchor has almost no reuse value, the use of double-layer seamless steel pipe has a high requirement on the high costing material and manufacturing technology, and its large internal pressure is not suitable for soft soil. e flexible pressurized grouting anchor with the similar principle of the water swelling anchor can only be used in rock layers with small deformation or soft rock conditions as its maximum deformation should not exceed 30% [7], so it is not suitable for highly deformed soil layers. e inflatable anchor, first proposed by Professor Tim Newson in 2000, forms an expansion head of rubber membrane and squeezes the soil hole wall by inflation pressure and offers anchoring force [8,9,10]
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