A study on the reinforcement effect of IPE Arc Support Technique (IAST): a case study of Sabzkuh tunnel

This paper presents a case study of the instability mechanism، re-qualification and reinforcement method adopted to pass through a collapsed zone of a sabzkuh water conveyance tunnel in southwest Iran. The instability problems were encountered during tunnel excavation due to the failure to recognize the fact that alteration in stress field and resulting deformation could cause dilation and increase in the permeability of sand and gravel layers، local fault gouge zones، landslide surface and in turn significant reduction in shear strength and collapse in tunnel. IPE Arch Support Technique (IAST) is for the first time used for T1 part of Sabzkuh tunnel design in order to reinforce the ground around tunnel and to crossing zone falling. However، since the design and construction work with IAST have been done on the basis of only the practical experience of engineers، it needs to analyze quantitatively the reinforcement effect of IAST. In this study، Finite Element Method was applied for analysis of the quantitative reinforcement effect with deformation modulus of ground، IPE length and size. As a result، the settlement increases as length increases and decreases with the increase of the deformation modulus of ground and IPE size.