Development of PSS-bolt with high load and large deformation capacities

Abstract

As mining migrates to deep levels, engineering disasters such as excessive deformation, rockburst and massive roof collapse occur frequently. It is important to develop rockbolts that have high load and large deformation capacities, which translates into high energy-absorption capacity, for ground support. This paper presents a piston self-swelling bolt (abbreviated as PSS-bolt) that utilizes steel stretching and frictional sliding to maximize the bolt’s energy absorption capacity. The structure design and working mechanism of the PSS-bolt are introduced. The influence of rod strength, piston length and tube shape on the load–displacement curves of the PSS-bolt was investigated. Laboratory and field static pull-out tests were carried out to optimize the piston length of the PSS-bolt. The test results show that when the piston length is 1350 mm, the load varies between 180 and 210 kN, the displacement can reach 500 mm, and the energy absorption capacity is 95 kJ. In addition, the bolt can reach 71.4% and 100% of its ultimate strength 12 h and 24 h after installation, respectively. The PSS-bolt presented in this paper has high force and large deformation capacities, which can provide a large energy capacity for ground support in high stress and large deformation conditions.