Abstract
This study aims to evaluate the sensing performance of glass fiber‐reinforced polymer (GFRP) rock bolt sensors instrumented with strain gauges for monitoring rockslides. Experimental studies are conducted with four different types of GFRP rock bolt sensors and concrete blocks having central holes and two shear joints. Two GFRP rock bolt sensors are inserted into holes and then fixed in concrete blocks with cement grout and soil, respectively. The other two are coated with heat‐shrink tubes to protect strain gauges and wires, which are then fixed in concrete blocks with cement grout and soil, respectively. Double shear tests are performed to produce shear deformations of GFRP rock bolt sensors, and then strain change with shear displacement is monitored. The results manifest that the variation in strain with shear displacement is more sensitive in the GFRP rock bolt sensor fixed with soil than with cement grout. Also, strain gauge wires in the GFRP rock bolt sensor fixed with cement grout are broken earlier than with soil. Furthermore, it is confirmed that the heat‐shrink tube effectively protects strain gauges and wires, so that GFRP rock bolt sensors coated with heat‐shrink tubes work for a longer time than the uncoated sensors. The present study shows that the GFRP rock bolt sensor can be useful for monitoring rock slope failure.
Highlights
Rock bolts are rock reinforcement systems, which are commonly used to stabilize rock slopes [1, 2]
Double shear tests under static loading were conducted with a universal test system (Model 815, MTS Systems Corporation), which has a load capacity of 4600 kN, to evaluate sensing performance of four different types of glass fiber-reinforced polymer (GFRP) rock bolt sensors as shown in Figure 18. e GFRP rock bolt sensors embedded in concrete blocks were installed in the double shear apparatus as shown in Figures 2 and 18. e double shear test apparatus was placed between the upper and lower grip of the universal test system. e load cell was mounted on the lower grip. e vertical upward load was applied to the double shear apparatus at a constant displacement rate of 0.5 mm/min
As the shear deformation of the GFRP rock bolt sensor increases, the grout is crushed causing a reduction of the bonding strength between the grouted rock bolt and the concrete block. is results in the strain to be more sensitive to the shear displacement. e nonlinear behavior of the strain appears after the displacement of 6 mm. e strain gradually increases as the shear displacement increases from 6 mm to 7 mm in displacement
Summary
Rock bolts are rock reinforcement systems, which are commonly used to stabilize rock slopes [1, 2]. When rock deformations or rock movements occur, shear or tensile load produced by unstable weak rocks is transferred to rock bolts. Li [8, 9] have reported that in situ rock bolts observed in fields were deformed or failed due to shear or tensile load caused by rock movements and deformations. Theoretical and experimental studies to investigate the rock bolt behavior have been performed. Wu et al [6] investigated the influence of roughness on the shear behavior of the rock bolt. Eir mathematical model demonstrated that the joint roughness strongly affects the shear behavior of the rock bolt. Lee and An [10] performed theoretical and experimental studies on the reinforcing effect of the rock bolt
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