Abstract
Bolts are widely employed as an effective ground reinforcement element to secure the underground workplaces. Due to their inherent accessibility, low cost, and easy implementation, rebar bolts are the most popular and commonly used reinforcement in ground support systems. However, it is expensive to obtain failure stage data from in situ pullout tests to study the ultimate bearing capacity of rebar bolts. In this paper, several function models that are commonly used for predicting the ultimate bearing capacity of bolts are presented. Based on these models, a general function model is constructed to replicate the relationship between the load and displacement of a rebar bolt in a pullout test. In addition, the value ranges of relevant parameters in the function model are also assessed. By analysing the general function model, an improved exponential and power function model, which is essential to bolt design, is presented to simulate the load‐displacement curve and predict the ultimate bearing capacities of bolts. Comparisons between the improved exponential and power function model and other regular models show that the former has a higher calculation accuracy and good stability. Moreover, a comparison of the predicted ultimate bearing capacity and the test results indicates the reliability of the improved exponential and power function model. The improved exponential and power function model can provide theoretical guidance for the design of rebar bolts applied in reinforcement engineering.
Highlights
In civil and mining engineering, bolts are widely used to stabilize underground excavation operations owing to their high load-bearing capacity and low cost [1]
As the depth involved in rock mass engineering increases, the surrounding rock is subjected to more complicated geostresses [2, 3]. e damage and failure of the bolts, such as through prestress loss, plate failure, and bolt shank rupture, have become substantial problems in deep underground engineering applications
Numerous studies have investigated the mechanical behaviors of rock-grout and grout-bolt interfaces [7]
Summary
In civil and mining engineering, bolts are widely used to stabilize underground excavation operations owing to their high load-bearing capacity and low cost [1]. Based on the anchor pullout mechanism, the ultimate bearing capacity of a bolt is mainly composed of the bond stress of the grout and the friction force of the rock-bolt interface (Figure 1). Long [22] proposed hyperbolic and exponential models to simulate the P–S curve of a pullout test and predict the ultimate bearing capacity of a bolt. E anchoring strata studied in this paper are gravel sand viscous soil, middle coarse sand mixed clay, and granite residual soil In this case, it is a fully grouted bolt and the bolt can resist the upward displacement of the buildings on it. E ultimate bearing capacity of the bolt is predicted by an optimized function model with limited measured data from pullout tests.
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