共和隧道开裂段页岩蠕变本构试验及离散元数值模拟研究

渝湘高速公路共和隧道地质条件十分复杂,隧道施工遇到很大困难,隧道开挖后初期支护多处出现纵向开裂。开裂段围岩为砂质页岩,现场实际监测资料表明,页岩层理、节理发育,易风化,亲水性较强,有水软化倾向并具有一定蠕变性。页岩的这些性质对隧道初期支护效果及隧道长期稳定性具有重要影响。鉴于此,对共和隧道页岩进行蠕变试验,通过系列试验得到不同应力水平下页岩的应变-时间关系曲线,建立与之适应的蠕变模型,并推导出蠕变公式,计算出公式中相应参数值。在此基础上,应用离散元数值计算方法对隧道开裂段施工全过程进行研究,分析了隧道围岩可能的破坏模式以及隧道锚杆支护结构的受力情况等。研究成果为隧道开裂段初期支护结构新方案的设计提供了重要支撑,成功地解决了隧道初期支护纵向开裂的工程难题。

Creep tests on shale of cracking position in Gonghe tunnel and simulating it by DEM

The geological condition of Gonghe tunnel is very complex. There are many difficulties when the tunnel is being constructed. There are many vertical cracks in the primary support after the tunnel is excavated. The surrounding rock of the cracking position is shale, which is easy weathered, more hydrophilic, water-weakening and creeping and has identified beddings and joints. These properties of the shale have an important impact on the primary support and the long-term stability and reliability of the tunnel. So the creep test of shale is carried out. The strain-time relation curves of different stress levels are obtained by series of tests. The creep model is built and the parameters of it are got. Based on these, the constructing process of the Gonghe tunnel’s cracked segment is studied by DEM. The possible broken mode of the surrounding rock and the force situation of the supporting structure in tunnel are analyzed. The research achievements provide important support for the new supporting structure scheme of the cracked segment in the Gonghe tunnel. So this engineering problem is successfully solved.