Experimental Study On Drawing Bearing Capacity Of Bonded Anchor

Anchoring technology has been widely used in slopes,foundation pits,mines,tunnels,underground engineering and other projects.The anchoring technology can improve the strength and stability of the rock,ensure the construction safety,and have significant social and economic benefits.Anchorage may occur multiple failure modes under pulling load.For the ultimate pull-out force of anchors,many theoretical researches and experimental verifications have been carried out at home and abroad,and a series of achievements have been made,but there is no uniform at present.Therefore,it is necessary to choose a simple,accurate and practical method to calculate the ultimate pull-out resistance of anchorage.For the factors affecting the ultimate pullout resistance of anchors,most scholars believe that confining pressure,buried depth of the anchor,properties of cemented materials,admixtures,etc.are the main influencing factors.However,the effect of the aperture ratio(drilling diameter/anchor diameter)on the ultimate pull-out resistance of anchorage has not attracted the attention of scholars.Therefore,it is necessary to experimentally explore the effect of the aperture ratio on the ultimate pull-out force of the anchorage.Based on the above,the influence of aperture ratio and buried depth of the anchor on the ultimate pull-out resistance of the anchorage with anchormortar interface failure is studied by the experimental method.The main work and contents of this paper are as follows:(1)The complete loading device and the chiseling machine for the anchorage drawing test are manufactured.To simulate the construction process of anti-floating anchors in engineering,this paper designs the procedure of anchorage pull-out test.(2)The pull-out tests of three groups of anchor specimens with different aperture ratio,different mortar strengths and different bolt types are carried out to explore the failure mode of anchorages under different conditions.The conditions required for the anchor-mortar interface failure of the anchor specimen in this test are obtained,which laid the foundation for the subsequent test.(3)Using plain steel bars as anchor,the pull-out tests of three groups of anchor specimens with different aperture ratios,different depths of the anchor and different chiseling conditions are carried out to investigate the effect of aperture ratio and buried depth of the anchor on the ultimate pull-out resistance of anchorage with steel-mortar interface failure.The experimental results show that when the plain steel bar is used as the anchor,the ultimate pull-out force of anchorage decreases with the increase of the aperture ratio.(4)Using the rebar as anchor,five groups of anchor specimens with different aperture ratios are carried out to investigate the effect of aperture ratio on the ultimate pull-out resistance of anchorage with steel-mortar interface failure.The test results show that when the rebar is used as anchor,the ultimate pull-out force of the anchor increases first and then decreases with the increase of the aperture ratio.When the aperture ratio is 5,the anchorage has the maximum pull-out bearing capacity.(5)The theoretical analysis of the ultimate bearing capacity of anchors is carried out.The accuracy of the theory is verified by comparing the experimental values with the theoretical values.