Optical fiber strain measurements and numerical modeling of load tests on grouted anchors.
This paper reports on the behavior of a grouted anchor instrumented with a fiber optic strain sensor in the grout body along the entire anchor length. During load tests up to the estimated pull-out capacity, the strain measurements indicate that a delamination occurs in the tendon bond length between the steel tendons and the grout body. The upper delaminated part of the grout body is under compression, whereas the lower bonded part of the grout body is under tension. This delamination gradually progresses as the anchor load increases. Furthermore, a significant part of the load is transferred from the anchor to the soil in the tendon free length. The anchor behavior is further modeled with a one-dimensional finite element model that includes the steel tendons and the grout body, where an interface damage model is used to account for possible delamination of the interface. The numerical model confirms that the observed compressive and tensile strains in the grout can be related to a delamination of the steel strands in the tendon bond length. The experiment and numerical modeling demonstrate how optical fiber measurements in the grout body can be used, in operational conditions, to assess the anchor behavior, the mobilization of the soil resistance, and the estimation of the remaining anchor capacity.