Study On Standardization Of Double Side Heading Method

Tunnel portals section always has the characteristics of broken rock, poor stability and highly construction risk. Large span tunnel excavation usually used the double side heading method to control rock deformation and to make the excavation stable and safe. Double side heading method was first used by Germany, who has successfully applied this in urban subway construction. In recent years, Double side heading method has been widely used in the construction of large span underground engineering such as roads, railways, urban subway tunnel in our country, and a great deal of experience has been accumulated. In spite of this, there are still many security accidents happened in the shallow tunnel portal construction, such as the collapse, dropping block, bolt Invalid, concrete cracking, steel arch distortion and so on. The occurrence of these accidents, on one hand is for the weakness of construction management and safety measures, on the other hand is for the unstandardization of double side heading method.Take the tunnel size and rock condition of real construction as example, with the help of large scale geotechnical engineering software FLAC3D, this paper will make a research on the standardization of the curvature radius, side wall size and mid tunnel size under the study of rock deformation, shaping zone, stress of temporary support. We take curvature radius into four conditions as R=11.6m?520?R=5.76m?1060?R=5.46m?1040 and R=+? ?1800,take side wall size into three conditions as L=1/3B?L=1/4B ? L=1/5B,take mid tunnel size into four conditions as h1=1/2H(two steps)?h1=1/3H(two steps)?h1=3/5H(Corresponding to the maximum fracture surface, two steps)?h1=h2=1/3H (three steps).According to the analysis above, we determine the most reasonable parameters. In the end, the paper proposed standardized construction scheme for double side heading method.