# Study on the Effect of Anchor Cable Prestress Loss on Foundation Stability
## 1 Introduction
Polypropylene fiber is often used to improve the properties of cementing materials. With the increase of polypropylene fiber content, the flexural strength and tensile strength of the consolidated body increase [12]. Adding polypropylene fiber can significantly increase impact resistance while ensuring compressive strength [13; 14]. There is an exponential relationship between the cementation strength of anchor solid, reinforcement and rock mass and the unconfined compressive strength of grouting materials [15]. The addition of fiber materials improves the deformation coordination of cement grout [16], effectively improves the bonding force between the grout consolidated body and the rock mass [17], improves the shear stress distribution in the anchoring section of the anchor rod, and enhances the crack resistance and toughness of the grouting material [18]. These findings provide references for the design and material selection of foundation pit anchoring engineering. Under the influence of many factors, such as the collapse of the clip and the deformation of the waist beam, the prestressing will produce a large loss. In order to ensure the safety of the foundation pit, a large number of scholars have carried out research on the prestressing loss of the anchor cable. Rock and soil mass will creep when subjected to cable load for a long time, which is the key factor causing the prestress loss of the cable [19]. [PERSON] et al. [20] and [PERSON] et al. [21] studied the prestress transfer mode of anchor cables. He [22] proposed a modified layer-summation method based on the nonlinear elastic-plastic constitutive model, which can calculate the creep variable of rock and soil mass under the anchor and then calculate the prestress loss. When the jack is unloaded, the large shrinkage of the clip with the steel strand will also lead to prestress loss. Through the testing of multiple anchorage devices, when the shrinkage of the anchor plug is too large, the over-tension method should be used to compensate for the prestress loss [23]. Considering that the deformation of rock mass on the slope is consistent with the shrinkage deformation of the anchor cable, a generalized Kelvin body is connected to the elastomer to consider the stress relaxation of the anchor cable, and the \"H-2K\" model is obtained [24]. The general development trend of prestressing anchor cable is revealed. Loss characteristics can also be studied by studying the evolution law of prestress and working state. [PERSON] et al. [25] found that magnetic flux can reflect the change in prestress of reinforcement. [PERSON] et al. [26] found that the prestress curve showed a trend of negative exponential decay with time and eventually became stable. [PERSON] (2017) established a numerical calculation model of a single anchor cable to explore the long-term prestress loss of the anchor cable, and its accuracy was verified by subsequent model experiment results ([PERSON], 2017). Prestressing is an effective means to ensure the safety and control the deformation of the foundation pit. Although scholars have studied and explored the causes of prestressed loss of anchor cable, the research mainly focuses on post-construction prestressed loss, and there are few studies on prestressed loss and control measures in the construction stage. Therefore, it is necessary to carry out relevant studies to reveal the influence of prestressed loss of anchor cable on the stability of the foundation pit.