Experimental Study On Bearing Performance And Theoretical Models Of Large Diameter GFRP Anti-floating Anchor

The Glass Fiber Reinforced Polymer(GFRP)anchor is a new composite reinforcement bolt developed from non-metallic anchors.It is immersed in a matrix material(such as epoxy resin)by glass fiber filaments,and is pultrusion prepared under high temperature and high pressure.It has the advantages of light weight,high tensile strength,low cost,good corrosion resistance and strong anti-electromagnetic interference capability.Compared with the traditional twisted steel anchor,the GFRP anti-floating anchor can meet the tensile requirement of the bottom plate(the tensile strength can reach up to 1800 MPa),which better solves the structural durability degradation caused by the corrosion of the steel bar.In addition,the GFRP anti-floating anchor is not easy to decompose,which can avoid pollution to the underground soil layer,and is a new environmentally-friendly civil construction material.Due to the short application period of GFRP anti-floating anchor in actual underground anti-floating engineering,in order to further improve its anchoring theory and provide theoretical basis for engineering,the main research work and achievements are as follows:1.Based on the destructive pull-out test of GFRP anti-floating anchors and steel anti-floating anchors of a weathered granite site,the displacement of the rod and anchor solid during the uplifting process of the floating anchor is measured.The bearing performance of anti-floating anchors with different materials and different anchor lengths and the difference of relative slip between robs and anchor solid are explored.The constitutive models of rock anti-floating anchors are optimized by comparing different load-displacement constitutive models.(1)In the middle weathered granite,the GFRP anti-floating anchors under the same anchoring length are 13%?14% more than the anti-floating anchors of the steel bars,and the GFRP anti-floating anchors are more likely to cause the rod body to be pulled out and destroyed,which indicates that the anchoring system still has residual bearing.It is proved that it is feasible to use the GFRP anti-floating anchors instead of the steel anti-floating anchors.(2)Due to the large difference in the elastic modulus of the two anti-floating anchor materials,the load-displacement curves of the anti-floating anchor rods and the anchor solid have obvious inflection points,while the GFRP anti-floating anchor rod and anchor load-displacement curve increase approximately linearly.(3)The GFRP anti-floating anchor with an anchor length of 6.5 m has a larger slip relative to the anchor solid than the GFRP anti-floating anchor with an anchor length of 4.5 m,indicating that increasing the length of the GFRP anti-floating anchor can effectively increase its rod slip length.However,the increase of the anchorage length has no significant effect on the failure mode of the steel anchor.(4)The hyperbolic function and the power function Qs curve model are inferior to the experimental measured values.The exponential function and the finger-power function Qs curve model have higher prediction accuracy for the failure load of the test anchor,and the overall trend of the curve is more consistent.2.According to the anchoring characteristics of anti-floating anchors,the large-diameter(28 mm)GFRP anti-floating anchors are pulled by the test device with anchoring and pulling at both ends.Based on this,the influence of different external anchorage anchorage lengths and new stress-distributed anchors on the bond-bonding performance between large-diameter GFRP anti-floating anchors and concrete is explored.After comparing the different bond-slip constitutive models,the hyperbolic function model with modified material correction coefficient is proposed to predict the bond-slip deformation between GFRP anti-floating anchor and concrete with larger diameter(>25 mm diameter).(1)The anchorage efficiency of the GFRP anti-floating anchors anchored by the new stress-distributed anchors is 7%?11% higher than that of the bare anchors.The average bond strength is 7.9%?24.4% higher than that of the bare-strand GFRP anchors.(2)In terms of calculation model,the BEP model,CMR model and Gao Danying model calculated the specimen-slip curve and the measured value deviation greatly.The bond-slip curve calculated by the Zheng Yuzhou model has a high degree of agreement with the measured curve,but there are still some deviations.(3)According to the material characteristics of the large-diameter GFRP anti-floating anchor,the hyperbolic function-slip-slip model corrected by the material correction coefficient is in good agreement with the measured curve.The applicability of the model to the prediction of the bond-slip curve between large-diameter GFRP anchors and concrete is verified by different experimental examples.3.According to the pull-out test of four GFRP anti-floating anchors under long-term stress,the creep behavior of GFRP anti-floating anchors is explored.Under the 40% load of the failure load,the GFRP anti-floating anchor will not creep.The creep constitutive equation of the test anchor was calculated by the standard linear solid model,and the long-term time damage variable and long-term uplift capacity of the four tested GFRP anti-floating anchors were solved according to the damage mechanics,and the calculation was carried out in actual engineering.And after calculation,it is proposed that 40% of the bearing capacity should be reserved as the reserve bearing capacity in the actual project.