Anchoring mechanism and application of hydraulic expansion bolts used in soft rock roadway floor heave control

Comparing with the resin bolt, the hydraulic expansion bolt has different anchoring mechanism and application advantage. According to the working mechanism of the hydraulic expansion bolt, its anchoring force is expressed in four forms including support anchoring force, tension anchoring force, expansion anchoring force and tangent anchoring force, and their values can be obtained on the basis of each calculation formula. Among them, the expansion anchoring force, which is the unique anchoring force of the hydraulic expansion bolt, can provide confining pressure to increase the strength of rock. Aiming at solving the problem of stability control in the soft rock roadway in Jinbaotun Coal Mine which has a double layer of 40 U-type sheds and cannot provide enough resistance support to control floor heave, the study reveals the mechanism of floor heave in the soft rock roadway, and designs the reasonable support parameters of the hydraulic expansion bolts. The observed results of floor convergence indicate that the hydraulic expansion bolts can prevent the development and flow of the plastic zone in the floor rock to control floor heave. Research results enrich the control technology in the soft rock roadway.

Anchorage Performance and Interfacial Mechanics Transfer Characteristics of a Composite Anchor Bolt with Different Surface Shape

To solve the deficiency of steel anchor blot in corrosion resistance and flaw of GFRP anchor bolt in fracture resistance, our research group develops a new composite anchor bolt made of steel strands wrapped up with compound fiber resin. To improve the cohesion performance of the composite anchor bolt, pull-out tests of different composite anchor bolts with different groove intervals and depths were made and analyzed. The results show that the pulling resistance of the composite anchor bolt increases with the increase of groove interval and depth, but groove interval and depth have optimal value. Based on elastic mechanics, the cohesion between anchor bolts and anchor bodies and its distribution characteristics caused by axial tension are analyzed and cohesion formula is obtained. By contrast, the experimental result is consistent with the theoretical analysis. Therefore, the surficial change of anchor colts could influence the performance of the composite anchor bolt. The cohesion force and anchorage performance can be improved by changing the surface of anchor bolts. Research results show that the new composite anchor bolt is high-performance material in the civil engineering.

Bond Mechanical Properties of Glass Fiber Reinforced Polymer Anti-Floating Anchor in Concrete Baseplate

Combined with fiber Bragg grating(FBG)sensing technology,four glass fiber reinforced polymer(GFRP)anti-floating anchors and four steel anti-floating anchors were tested for on-site destructive failure to investigate the anchoring performance and the bonding characteristics between GFRP anti-floating anchor and concrete floor.The test results show that bending GFRP anchor will be broken at the common boundary between vertical anchorage section and bending section during the pullout process,and the spring-back load provided by the rupture contributes to a decrease of bearing capacity and an inflection point on the load-slip curve.The loaddisplacement curve of the straight anchor GFRP anti-floating anchor is smoother and has better predictability than the same type of steel anchor.Additionally,different forms of GFRP anti-floating bolt have different bondslip constitutive relations.By introducing the sliding-slip correction factor of bending bolt,constitutive models describing the rising-section of sliding-slip relation of bending and straight-anchored GFRP anti-floating bolt are established respectively.The model can fit the test results rightly.