复合垫层钢棚洞抵抗落石冲击性能研究

工程上常用砂土垫层来缓冲棚洞结构的落石冲击力，但砂土的自重很大，增加了静载作用下结构的内力。由于EPS泡沫材料密度轻、缓冲性能好，本文考虑在砂土垫层中用EPS材料替换部分砂土形成复合垫层，减小落石对棚洞结构的冲击力。基于室外大尺度模型实验，建立了落石冲击作用下EPS复合垫层钢棚洞结构的数值计算模型。不同落石高度下，实验方法获得的测点处的应力时程曲线和数值结果吻合较好，说明了本文建立的数值模型的可靠性。在此基础上利用该数值模型研究了复合垫层对落石冲击的缓冲效果。结果表明：在垫层总厚度不变的前提下，复合垫层的缓冲性能优于砂垫层。EPS厚度越大，棚洞结构受到的冲击力越小，主梁的应力、挠度均减小。但是EPS材料的最大压缩量以及承受的压应力随着EPS厚度增加而增加，这不利于EPS继续承受冲击力。因此，在确保钢棚洞安全的基础上，需要考虑使用EPS材料的经济性，选择最优的EPS厚度。

Numerical study on impact resistance of steel shed gallery with composite cushion

Sand cushions are commonly used in engineering to buffer the rockfall impact of the shed structure. however, the sand has a large self-weight, which increased the internal forces of the structure under static load. Due to low density and good cushioning performance of EPS foam, a composite cushion was formed by replacing some sand soil with EPS material in the sand cushion. Thus, the goal to reduce impact force of rockfall to shed gallery was achieved. Based on prototype experiments, a numerical model was established to simulate steel shed impacted by rockfall. The results of tests and simulation were in good agreement under different rockfall height, indicting the numerical model is reliable. Then the cushioning effect of composite cushion was studied. The results show that the cushioning performance of composite cushion is better than that of sand cushion when the total cushion thickness is constant. Increased with the thickness of EPS material, the shed structure bears smaller impact force, and the stress, the deflection of beams are reduced. However, the maximum compression and compressive stress of EPS material are higher with thicker EPS cushion, which is adverse for EPS material to bear impact force later. Therefore, on the basis of ensuring the safety of the steel shed gallery, it is necessary to consider the economy of EPS material and select the suitable EPS thickness.