可缩性U型钢支架承载性能足尺试验研究

Full-scale experimental study on bearing capacity of retractable U-steel support

支架的工作阻力是评价可缩性U型钢支架优劣的重要指标,在工作过程中,支架所受载荷分布情况和搭接位置的卡缆连接件性能直接影响支架承载性能的发挥。通过设计室内足尺模型试验,对支架承载性能进行测试,揭示可缩性支架工作阻力变化规律,讨论载荷分布情况和卡缆类型对支架工作阻力的影响。研究结果表明:1)在相同载荷作用下,支架分别装配双槽夹板式卡缆(A型卡缆)与四螺栓双槽夹板式面卡缆(B型卡缆)时的拱腰收敛量相差较大,差值最大可达105.6 mm,而支架拱顶沉降量受卡缆类型的影响不大,差值小于等于6.16 mm;2)支架拱顶沉降量与侧顶压力比κ呈负相关,拱腰收敛量与κ呈正相关;3)在保证相同螺栓预紧力的前提下,装配双槽夹板式卡缆(A型卡缆)的支架始缩阻力和最大滑移阻力均比装配四螺栓双槽夹板式面卡缆(B型卡缆)时的高,而滑移次数的变化规律则恰好相反,说明前者对支架承载性能的提升作用大于后者的提升作用;4)在强侧压(κ=3)作用下,支架的始缩阻力和最大滑移阻力明显比强顶压(κ=1/3)作用下的大,且强侧压下装配A型和B型卡缆的支架最大滑移阻力相较于始缩阻力分别提高了30%和24%,强顶压下装配A型和B型卡缆的支架最大滑移阻力相较于始缩阻力分别降低了12%和22%,说明支架对于强侧压受力状态的适用性更好;5)在同等条件下,相较于对称载荷作用,支架在偏载作用下具有更低的始缩阻力和最大滑移阻力,表明偏载受力状态会影响支架工作性能的正常发挥。

The working resistance is an important index to evaluate the quality of the retractable U-shaped steel support, and the load distribution of the support during the working process and mechanical property of the clamp at the overlap position directly affect the exertion of the support’s bearing capability. Through the design of the indoor full-scale model test, the load-bearing performance of the support was tested, the changing law of the working resistance of the retractable support was revealed, and the influence of load distribution and clamps types on the working resistance of the support was discussed. The results are as follows. 1) Under the same load, there exists great difference in the waist convergence of the support when it is assembled with double-slot splint clamps(type A) and four-bolt double-slot splint clamps(type B), respectively, and the maximum difference can reach 105.6 mm, while the clamps types has little effect on the vault settlement of the support, and the difference is within 6.16 mm. 2) The vault settlement of the support is negatively correlated with the ratio κ between lateral pressure and top pressure, and the waist convergence is positively correlated with the ratio κ. 3) On the premise of ensuring the same bolt pre-tightening force, the initial shrinkage resistance and the maximum sliding resistance of the support with double-slot splint clamps are higher than those of the support with the four-bolt double-slot splint clamps, while the number of slippage has just the opposite law, which indicates that the former is better than the latter in improving bearing capability of the support. 4) The initial shrinkage resistance and the maximum sliding resistance of the support under the effect of strong lateral pressure(κ =3) are significantly higher than that of the support under the effect of strong top pressure(κ =1/3), and the maximum sliding resistance of the support with type A and B splint clamps at strong lateral pressure is increased by 30% and 24% respectively when compared with the initial shrinkage resistance, while the maximum sliding resistance of the former support with type A and B splint clamps at strong top pressure is reduced by 12% and 22% respectively, indicating that support has better applicability to the strong lateral pressure state. 5) Under the same conditions, compared to the symmetrical load,the support has lower initial shrinkage resistance and the maximum sliding resistance under the eccentric load,which indicates that the eccentric load has unfavorable effect on the capacity of the support.