Abstract: The occurrence of the prestress loss of anchor cable is more commonly encountered in foundation pit due to the influences of the excavation and strength of the stratum. Field tests were carried out in a practical project to analyze the effects of the tension load, tension locking mode, length of unbonded segment and cyclic loading on the prestress loss of anchor cable. The occurrence mechanism of the prestressed loss of the anchor cable was discussed. The results show that the debonding slip between the anchored solid and the surrounding stratum is an important reason for the prestress loss. A greater anchor force will induce more substantial loss of the prestress. As for the dispersed anchor cables, single tension locking is beneficial for minimizing the prestress loss. The length of the unbonded segment has an effect on the stiffness of the anchor head:a shorter length of the unbonded segment will result in more substantial loss of the prestress. Furthermore, it is found that the plastic deformation of the anchorage will be further locked under more times of cyclic loadings, which as a result reduces the loss of the prestress. The relevant rules and conclusions can provide useful references for the design and construction of the foundation pit anchorage cable.

Key words: foundation pit, prestressed anchor cable, prestress loss, field test, debonding slip