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Derivation of parallel three-hole of small spacing Tunnel in shallow nonbias case, surrounding rock pressure formula in sequence of first side hole after middle hole excavation, drawn the corresponding computational model For the study of parallel three holes of small clear space tunnel surrounding rock pressure in the case of size and distribution in a shallow nonbias, and impact of the law by earth covering thickness change, conducted a comparative calculation When the tunnel clear distance is certain, on the whole, three holes tunnel outside vertical pressure and lateral pressure with depth increases increasing, and approximately linear growth By contrast, drawn parallel to the three-hole and small spacing tunnel excavation, three holes to force state has deteriorated compared with norms calculated in single hole excavation, the calculation specification requires only symmetric stress state is chosen not safe conclusion The most representative works of our country tunneling engineering tunnel surrounding rock pressure calculation is rock pressure single hole tunneling calculations The actual engineering practice, parallel three holes and large section of small clear space tunnel gradually use, its "multi-cavern effect" obviously, but no suitable surrounding rock pressure calculation In addition, cavern excavation sequence between the value of the load great influence, If confined cavern final state, obvious un-reasonable To this end, the theoretical calculation method to explore parallel three holes and large section of small clear space tunnel. Load Calculation Mode For convenience of calculation to simplify calculation model basic hypothesis and simplified as follows [1, 2] (1) Calculation analysis process, it is assumed as a single continuous medium surrounding rock; horizontal ground and are shallow tunnel; between three holes equally spaced and horizontal direction parallel arrangement According to above work wan can take the middle hole medial axis for the sector, taking half for analysis (2) Consider the interaction of adjacent tunnel construction, construction order is sided holes(left and right hole) excavation first(Simultaneously or successively excavation),then middle hole excavation When the excavation sided holes, without considering the interaction between the two holes, Within two lateral tunnel surrounding rock pressure calculation formula is consistent with the specification in the case of a single hole in the tunnel; when excavation middle hole, Surrounding the outer edge of the sided hole pressure remains unchanged, On the interaction region (medialand vault) the force correction (3) Due to the small neighborhood tunnel clear distance D is generally small, Calculate the left hole and the middle hole rock pile within fracture plane intersection point to two side hole distance 1 D , 2 D , 1 D can be D/2 approximately International Conference on Mechanics and Civil Engineering (ICMCE 2014) © 2014. The authors Published by Atlantis Press 700

The Surrounding Rock Pressure Research of Tunnel Group with Large Section and Three-hole of Small Neighborhood