A method for predicting the water-flowing fractured zone height based on an improved key stratum theory

In the process of using the original key stratum theory to predict the height of a water-flowing fractured zone(WFZ),the influence of rock strata outside the calculation range on the rock strata within the calculation range as well as the fact that the shape of the overburden deformation area will change with the excavation length are ignored.In this paper,an improved key stratum theory(IKS theory)was proposed by fixing these two shortcomings.Then,a WFZ height prediction method based on IKS theory was established and applied.First,the range of overburden involved in the analysis was determined according to the tensile stress distribution range above the goaf.Second,the key stratum in the overburden involved in the analysis was identified through IKS theory.Finally,the tendency of the WFZ to develop upward was determined by judging whether or not the identified key stratum will break.The proposed method was applied and verified in a mining case study,and the reasons for the differences in the development patterns between the WFZs in coalfields in Northwest and East China were also fully explained by this method.

新型铝合金花环齿槽节点的抗剪性能试验研究

单层铝合金网壳具有自重轻、耐腐蚀、外形优美等诸多优点,近年来被广泛应用于大跨空间结构。由于板式节点构造简单且安装方便,已成为单层铝合金网壳最常用的节点形式之一。但由于该节点仅通过盖板与铝合金梁的翼缘连接,而与腹板并不连接,导致其抗剪承载力及面内轴向刚度严重不足,容易发生失稳破坏,不能满足大跨度铝合金网壳对节点性能的需求。为此在现有节点的基础上,提出一种新型花环齿槽组合节点。为探究新型铝合金花环齿槽节点的抗剪性能和破坏形态,对新型节点和传统板式节点进行了抗剪试验,获得了两种节点在面外荷载下的失效模式和荷载-位移曲线,并分析了新型花环齿槽节点的抗剪性能。运用ABAQUS软件对新型节点的加载全过程进行数值模拟分析,并验证了有限元模型的可靠性。结果表明,板式节点的破坏模式主要表现为盖板的拉剪破坏,铝合金梁并未发生明显的弯曲破坏;新型节点的破坏模式主要表现为铝合金梁的弯曲破坏,盖板发生翘曲以及花环齿槽体撕裂,这主要是由于新型节点中的花环齿槽体有效分担并传递了很大一部分剪力。花环齿槽体改变了传统板式节点的传力方式和破坏形态,将铝合金梁腹板连接成一体,更加有效地分担并传递了剪力,减轻了盖板的剪力负担,提高了节点的抗剪性能,从而改变了板式节点脆性破坏的缺点,使其具有良好的延性和耗能能力。由于新型节点的中心区域设置了花环齿槽体,因此相对于传统板式节点,新型节点的抗剪承载力提高了47.4%,抗剪刚度提高了103.9%,具有良好的工程应用前景。对新型节点的有限元分析结果表明,有限元解析得到的荷载-位移曲线的线性段吻合较好,与实测位移的误差在5%以内,抗剪承载力误差仅为0.14%,验证了有限元模拟结果的可靠性。当新型节点承受极限荷载时,上、下盖板与杆件相接的部位应力较大,而上盖板大部分区域都进入了塑性,下盖板仅小部分区域进入塑性,螺栓孔处以及花环齿与槽体的交接处均出现应力集中现象。