花石沟炭质片岩隧道弱爆破与机械联合开挖法

在十白高速花石沟隧道的施工过程中,遇到了大面积的炭质片岩,其强度低、风化快、易吸湿、变形大,采用普通隧道爆破技术和开挖施工工艺时,超挖现象普遍,支护变形严重。本文应用FLAC3D软件进行炭质片岩隧道拱顶沉降数值模拟,得出其流变变形规律,为支护设计和施工工艺优化提供了依据。根据花石沟隧道的实际情况,提出了弱爆破与机械联合开挖方法,其主要技术措施包括:下台阶分区作业;小进尺,快初支;预留吸水软化层;减弱爆破设计;缩短二衬间隔。工程实践证明,该方法有效控制了炭质片岩隧道施工中的超挖现象和支护变形。

Weak blasting combined with machine excavation for construction of Huashigou Tunnel with carbonaceous schist

A large area of carbonaceous schist was met with in the construction of Huashigou Tunnel on Shiyan-Baihe Expressway. Carbonaceous schist has the properties of low strength,rapid weathering,high hygroscopicity and large deformation. The common construction technology of tunnel blasting and excavation would cause the overbreaking of the tunnel and serious deformation of the supports. This paper uses FLAC3D software to simulate the vault subsidence of carbonaceous schist tunnel and obtains its rheological deformation law, which provides a basis for the supporting design and the optimization of construction technology. According to the actual situation of Huashigou Tunnel, it puts forward a method of weak blasting combined with machine excavation. The main technical measures are as follows:partition constructing in the lower section of the tunnel; small digging length, rapid preliminary supporting; reserved water-absorbing softened layer; weak blasting; shortening the time interval of the secondary concrete lining. The construction practice proves that the proposed method can effectively control the overbreaking of tunnel with carbonaceous schist and the deformation of supports.