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正确评估管棚加固围岩的抗爆性能,对坑道口部防护设计十分重要。基于相似模拟理论,用不同配比的水泥土替代自然岩体和注浆岩体,用塑料管替代钢管,模拟管棚超前支护坑道口部在爆炸荷载作用下的抗爆性能。制作了口部相似模型3件,模型长×宽×高为2 m×2.2 m×2 m,在顶部直接爆炸,分别模拟无管棚、1层管棚和3层管棚下,坑道口部动力响应和破坏特征。试验表明:管棚超前支护能有效加固坑道围岩,整体性增强,受力分布合理;随着管棚层数增加,口部破坏明显减弱,拱顶破坏范围从1.55 m减小到0.45 m、主裂缝最大宽度由25 mm减小到3 mm、网状裂缝最大宽度由24 mm减小到0.3 mm、裂缝条数由14条减少到3条、模型顶部爆坑体积由0.12 m3减小到0.05 m3。管棚超前支护能有效地将爆炸荷载的破坏作用控制在管棚加固层之外,抗打击能力明显增强。
Proper assessment of the anti-explosion performance of the reinforcement of surrounding rock by pipe shed is very important for the protection design of the tunnel mouth. Based on the similar simulation theory, natural rock mass and grouted rock mass were replaced by different proportions of cement soil, and plastic pipe was used to replace steel pipe to simulate the antiknock performance of tunnel mouth under the explosion load. Three similar models of mouth were made. The model was 2 m × 2.2 m × 2 m in length, width and height, and exploded directly at the top of the model. They were simulated without tube shed, 1-layer pipe shed and 3-layer pipe shed, Response and destruction of features. The experiment shows that the advanced support of the pipe roof can effectively reinforce the surrounding rock of the tunnel and enhance the integrity of the tunnel. The stress distribution is reasonable. With the increase of the number of pipe sheds, the damage of the mouth is obviously weakened, and the failure range of the dome decreases from 1.55 m to 0.45 m , The maximum width of the main cracks reduced from 25 mm to 3 mm, the maximum width of the mesh cracks reduced from 24 mm to 0.3 mm, the number of cracks reduced from 14 to 3, and the volume of the blasting at the top of the model decreased from 0.12 m3 to 0.05 m3. The advanced support of pipe shed can effectively control the destructive effect of explosion load beyond the reinforcement layer of pipe shed, and the anti-strike capability is obviously enhanced.