Abstract: Creep between the anchor and the soil is a critical factor in determining the prestress loss of the anchor, directly influencing the long-term stability of the slope. Unlike traditional anchors, the prestress loss calculation for anchors with grout bulb, which serve as pressure-bearing anchors, must account for the coupling effects of soil shear and compression creep. Thus, revealing the unique creep mechanism resulting from the interaction between anchors with grout bulb and the soil holds significant research value. Firstly, shear and compression creep tests on red clay were conducted to obtain clays creep parameters. Secondly, a creep characteristic test for the grout bulb anchor was performed using a self-developed model test system. Finally, a fractional-order creep model for grout bulb anchors, incorporating the coupling effects of soil shear and compression creep, was established based on fractional calculus theory. The results indicate that, compared to traditional grouting anchors, the attenuation creep stage of anchors with grout bulb lasts longer and exhibits a slower attenuation rate. In red clay, compression creep accounts for over 90% of the total creep and increases over time. The anchor with grout bulb creep model, which considers the coupling creep of soil shear and compression, more accurately describes the creep behavior of anchors with grout bulb in soil. This study not only provides a theoretical basis for the design and application of the new type of prestressed anchor with grout bulb but also contributes to the broader understanding of prestressed anchors with grout bulb.

Key words: anchor with grout bulb, shear and compression, creep, red clay, coupled effect