软岩隧道EPP混凝土受力特征及卸压效果分析

Stress Characteristics and Pressure Relief Effect Analysis of EPP Concrete in Soft Rock Tunnel

研究目的:软岩隧道在运营期间由于围岩蠕变导致隧道衬砌发生大变形及开裂,严重影响运营安全。在前期试验取得的EPP(聚丙烯)泡沫混凝土力学参数的基础上,开展软岩隧道EPP泡沫混凝土缓冲层受力特征及卸压效果分析,提出一种抵抗隧道围岩蠕变、减小衬砌变形的方法,为类似隧道工程设计提供参考。研究结论:(1)EPP泡沫混凝土作为软岩隧道缓冲层对衬砌受压有良好的改善效果;(2)以EPP泡沫颗粒含量为64%的混凝土作为缓冲层且厚度为0.8 m时,衬砌受到的压应力最小,衬砌处于全断面受压状态,且极限承载能力最高;(3)缓冲层的让压量是决定其卸压效果的直接原因,缓冲层EPP泡沫含量越高,厚度越大,让压量就越大,卸压效果最好;(4)EPP泡沫混凝土应用于土木工程领域铁路和公路工程方向软岩隧道初期支护与二衬之间缓冲层结构中,其应用前景广阔,为进一步改善EPP泡沫混凝土卸压性能及提升工程实用性,需对材料配合比及压缩特性开展优化研究。

Research purposes:During the operation of soft rock tunnel,the creep of surrounding rock leads to large deformation and cracking of tunnel lining,which seriously affects the operation safety.Based on the mechanical parameters of EPP(polypropylene)foam concrete obtained in the previous test,the stress characteristics and pressure relief effect of EPP foam concrete buffer layer in soft rock tunnel are analyzed,and a method to resist the creep of tunnel surrounding rock and reduce the deformation of lining is proposed,which provides a reference for similar tunnel engineering design.Research conclusions:(1)EPP foam concrete,as a buffer layer of soft rock tunnel,has a good effect on improving the pressure of lining.(2)When the concrete with 64%EPP foam particles is used as the buffer layer and the thickness is 0.8 m,the compressive stress of the lining is the smallest,the lining is in the full section compression state,and the ultimate bearing capacity is the highest.(3)The yielding deformation of the buffer layer is the direct reason that determines its pressure relief effect.The higher the content and thickness of EPP foam in the buffer layer,the greater the yielding deformation,and the best pressure relief effect.(4)EPP foam concrete is applied to the buffer layer structure between the initial support and the secondary lining of soft rock tunnel in the direction of railway and highway engineering in the field of civil engineering.Its application prospect is broad.In order to further improve the pressure relief performance of EPP foam concrete and enhance the engineering practicability,it is necessary to carry out optimization research on the material mix ratio and compression characteristics.