Steel tube is used to simulate rock mass in laboratory impact tests of rock bolts. The steel tube must be equivalent to the borehole in the rock mass in radial stiffness in order to obtain valid test results. The stiffness of the steel tube is directly associated with the thickness of the steel tube. The importance of the tube thickness has not been paid enough attention in the laboratory tests of rock bolts at present. This technical note derives a formula for calculating the required thickness of the steel tube used for laboratory tests of rock bolts. It also provides a formula for calculating the stiffness of the steel tube under plane stress which is the realistic loading condition of rock bolts in the field. The analysis reveals that the grout in the tube hole does not play a role in the calculation of the thickness of the steel tube. The required thickness of the steel tube is solely dependent on the Young's moduli and Poisson's ratios of the tube steel and the rock mass to be simulated.

钢管用于模拟岩石锚杆实验室冲击试验中的岩体。钢管的径向刚度必须与岩体中的钻孔相当，才能获得有效的试验结果。钢管的刚度与钢管的厚度直接相关。目前在锚杆的室内试验中，管壁厚度的重要性还没有引起足够的重视。本技术说明推导出用于岩栓实验室试验的钢管所需厚度的计算公式。它还提供了计算钢管在平面应力下的刚度的公式，该应力是现场岩石锚杆的实际加载条件。分析表明，管孔内的灌浆对钢管厚度的计算没有影响。