Pull-out resistance characteristics and anchorage mechanism of bond ground anchor in granite soil layer

The tendon free length of bond type ground anchor in actual engineering fills with grout and integrated with tendon bond length, and their mechanical properties mechanical characteristics are quite different from theoretical model. 45 test anchors were fabricated according to the engineering conventional method in this paper. The load test and distributed optical fiber test results show that for the bond anchors in the granite residual viscous soil layer: (1)The critical anchoring length exceeds 18m, and the pullout resistance is approximately proportional to the length of the grout body within 18m.(2)The simple post-grouting process commonly adopted in engineering has a limited effect on improving the pullout resistance.(3)The grout in tendon free length generates bonding resistance. When the length is longer and the proportion to the bond length is appropriate, the pullout resistance is significantly higher than that of the fully bond anchor. (4)After the anchor is subjected to a load, it is first directly transferred from the tendon to the interface between the tendon free length and the bond length. Then, it is synchronously transferred in both directions to the bond length in the form of tensile stress and to the tendon free length in the form of compressive stress.The mechanical characteristics are equivalent to a combination of a fully bond anchor and a compression type anchor. (5)The positive strain/stress curve of the grout can be divided into the tensile strain/stress section, the compressive strain/stress section and the orifice section. The strain difference in the strain/stress reduction section reflects the bonding stress characteristics at the grout-ground interface.