Experimental study on load transfer characteristics of fully bonded anchors in granite residual soil layer

There are abundant research results on the load transfer characteristics of the grout/ground interface of the ground anchors in the industry, but the problems in the cohesive soil layer are still confused such as interface bond stress concentration, stress peak transfer, critical fixed length and anchoring efficiency, etc. For these purpose, according to the normal construction level, 23 full-length fully bonded anchors are constructed in the granite residual clay within the Shenping Anchor tests, and some anchors are embedded with distributed optical fiber. The results of load tests with new type jack and distributed optical fiber tests show that: (1) The ultimate pullout resistance of fully bonded anchor increases approximately linearly with the length in the whole 18 m fixed length, and the anchoring efficiency gradually decreases over 18 m. (2) The bond stress of the front part of anchor will be transferred to the latter part before the bond strength is reached. The stress will be transferred to the anchor end for a short length and then increase to the bond strength in the nearly whole length, while for a long length, the stress of the front part reaches the bond strength first, then passes back to the end, the latter part approaches or almost reaches the bond strength lastly. (3) The axial distribution curve of grout tensile stress can be divided into four sections such as rapid increase, deceleration increase, slow decrease and return to zero. (4) The composite stiffness of anchor body is mainly reflected on the stiffness of tendon, and the composite modulus of fixed length should not be calculated according to the elastic modulus of grout body.