# Study on the Effect of Anchor Cable Prestress Loss on Foundation Stability
## 1 Introduction  
The development and improvement of anchoring technology is very important for the progress of modern engineering technology. Since the application of anchoring support technology, its applicable field has been constantly developing and growing. With the deepening of the theoretical research on anchorage technology, many new technologies and new methods of anchorage technology are emerging, which make the anchorage support technology of foundation pits develop rapidly [1]. Prestressed anchor cable is an active support method to transfer the support stress of the main structure to the deep, stable rock. It has the advantages of convenient construction, low cost, and no space occupied in the pit, and is widely used in various engineering fields [2]. Prestress is the prerequisite for anchor cable to play its role. Due to the limitations of current technology, prestress loss cannot be avoided during the construction or service period of anchor cable. The influence of prestress loss on the stability of the foundation pit and whether the support structure can meet the requirements after prestress loss are worthy of further study. Studies have been conducted on the interface stress distribution characteristics of pressure-concentrated and pressure-dispersed anchor cables. After prestressing is applied to traditional pressure-concentrated anchor cables, the stress is mainly concentrated in the upper part of the anchoring section, resulting in serious stress concentration [3]. The pressure distributed on the anchor cable is compensated before tensioning. Due to the different positions of its anchoring sections, the prestressed load acts on the anchoring sections of each unit, respectively, so that the bond stress is evenly distributed, the stress concentration is avoided, and the bearing capacity of the deep stratum is fully utilized [4]. In view of the reinforcement effect of prestressed anchor cable, [PERSON] [5] points out that in sandy mudstone strata, the axial stress and strain distribution of the anchor cable mortar body attenuates rapidly in the range of medium- and small-tonnage anchor cables, and the attenuation reaches its minimum value at about \(1/2\) the length of the anchor cable. After anchor cable reinforcement, the mechanical properties of rock and soil mass are improved [6], and the distribution density of the anchor rod is basically linear with the strength and elastic modulus of rock mass. Through the anchor cable reinforcement project of the ship lock of the Three Gorges Dam, the engineering effects of non-prestressed anchor cable, bonded prestressed anchor cable, and unbonded prestressed anchor cable are compared and analyzed. The deformation, wave velocity, and elastic modulus changes of rock and soil masses before and after anchor cable reinforcement are analyzed, indicating that unbonded prestressed anchor cable reinforcement technology is feasible [7; 8]. [PERSON] et al. [9] conducted a study on the mechanical characteristics and group anchor effect of prestressed anchor cables. The concepts of the first and second effects of group anchorage in prestressed anchorage on a high rock slope are put forward. It is considered that increasing the length of the anchorage section is not the best way to improve the cable bearing capacity. The cementing material used in foundation pit engineering has a significant influence on the loss of prestress of anchor cable. Anchoring cementing materials can be divided into inorganic anchoring materials and organic anchoring materials [10]. On the basis of conventional cement mortar, many scholars change the properties of cement slurry by adding different substances. Geopolymer and cement mortar were used as grouting materials to conduct anchor rod pulling tests, and it was found that geopolymer mortar could bond better, have high strength, and develop rapidly in early strength. However, adding expansion agent on this basis would slow down the development of early strength of mortar [11].