Fatigue behaviour of steel connections in potash mine shafts

当矿体位于地下深处时，需要竖井来开采矿石。大型升降机（“箕斗”）用于将矿石运送到地面，并在地面和矿站之间运输设备和人员。箕斗由电缆吊起，并通过沿垂直钢导轨移动的滚轮组件在竖井中上下导向，垂直钢导轨由连接到竖井壁的钢结构（“钮扣组”）按规则间隔进行横向支撑。最近设计的矿井的箕斗重达65吨，并将以超过65公里/小时的速度沿着竖井行驶。即使是导轨的轻微错位也会导致箕斗从一侧弹跳到另一侧，并对支撑钢结构施加反复的水平撞击力。因此，钢结构，特别是螺栓连接，必须设计成能够抵抗反复的撞击力，而不会在竖井50年的设计寿命内失效。提出的研究解决了与此问题相关的两个重要设计问题。首先，有必要根据螺栓连接的配置和螺栓连接技术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。为了实现这一目标，将在实验室对全尺寸螺栓连接进行实验测试，并辅以计算机建模。其次，必须确定撞击力的大小。这将被研究使用复杂的计算机模型来计算力的因素，如导轨不对准，跳过速度，和钢结构的刚度的变化。该项目将使设计人员能够最大限度地减少钢材的数量和制造时间，同时确保矿井钢结构的足够安全水平。它有可能在施工阶段为矿业公司节省大量成本，并为设计工程师提供设计安全矿井结构所需的信心。预计研究结果还将影响与螺栓连接承受重复载荷的阻力相关的钢设计标准。

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.