Fatigue behaviour of steel connections in potash mine shafts

当矿物矿体位于地下深处时，需要垂直矿井来接近矿石。 大型升降机（“箕斗”）用于将矿石运输到地面，并在地面和采矿站水平之间运输设备和人员。 箕斗由缆绳提升，并通过滚轮组件沿竖井上下引导，滚轮组件沿沿着垂直钢导轨行进，垂直钢导轨由连接到竖井壁的钢结构（“浮式卸料装置”）以规则间隔横向支撑。 最近设计的矿山箕斗重达65吨，并将以超过65 km/h的速度沿竖井沿着。 即使是轻微的导向偏差也会导致翻斗从一侧反弹到另一侧，并在支撑钢结构上施加重复的水平砰击力。 因此，钢结构，特别是螺栓连接，必须设计成能够抵抗反复的砰击力，而不会在轴的50年设计寿命内失效。 拟议的研究解决了两个重要的设计问题，这个问题。 首先，有必要根据螺栓连接的配置和螺栓连接技术的类型确定螺栓连接的最佳设计，以便它们能够承受大量的重复载荷而不会失效，同时不会过度设计。 为实现这一目标，将在实验室对全尺寸螺栓连接进行实验测试，并辅之以计算机建模。 其次，必须确定砰击力的大小。 这将使用复杂的计算机模型进行研究，以计算力的因素，如引导错位，跳跃速度，钢结构的刚度变化。 该项目将使设计师能够最大限度地减少钢材数量和制造时间，同时确保矿井中钢结构的足够安全水平。 它有可能在施工阶段为采矿公司节省大量成本，并为设计工程师提供设计安全矿井结构所需的信心。 预计结果也会影响与反复荷载下螺栓连接的抗力相关的钢结构设计标准。

When mineral ore bodies are located deep underground, vertical mineshafts are required to access the ore. Large elevators ("skips") are used to transport the ore to the surface, and to transport equipment and personnel between the surface and mine station levels. Skips are hoisted by cables and guided up and down the shaft by means of roller assemblies that travel along vertical steel guides, which are supported laterally at regularly spaced intervals by steel structures ("bunton sets") that are connected to the shaft walls. Skips for recently designed mines weigh as much as 65 tonne, and will travel along the shafts at speeds exceeding 65 km/h. Even a slight misalignment of the guide will cause the skips to bounce from side to side and exert repeated horizontal slamming forces on the supporting steelwork. The steelwork, particularly the bolted connections, must therefore be designed to resist repeated slamming forces without failing for the 50 year design life of the shaft. The proposed research addresses two important design issues related to this problem. First, it is necessary to identify an optimal design for the bolted connections in terms of their configuration and type of bolting technology so that they can withstand a very large number of repeated loads without failing, while not being over-designed. Experimental tests, supplemented by computer modelling, will be conducted on full-scale bolted connections in the laboratory to achieve this objective. Second, the magnitude of the slamming forces must be determined. This will be investigated using sophisticated computer models to calculate the forces as factors such as guide misalignment, skip speed, and stiffness of the steelwork change. This project will allow designers to minimize the quantity of steel and fabrication time, while ensuring adequate levels of safety for the steelwork in mine shafts. It has the potential to provide significant cost savings to mining companies during the construction phase, and provide design engineers with the confidence they require to design safe mine shaft structures. Results are also expected to influence steel design standards related to the resistance of bolted connections subjected to repetitious loading.