Cause investigation and verification of lining cracking of bifurcation tunnel at Huizhou Pumped Storage Power Station

[Display omitted] •Cause investigation and verification of lining cracking of tunnel is studied.•Field survey and exclusive method are used to investigate cracking causes.•Comparative analysis is utilized to verify if the conjecture is reasonable.•Tensile-strain-concentrated zones are in good agreement with fractured status.•Deficiency in concrete thickness is the main factor inducing lining cracking. A wide range of cracking happens in concrete lining at the crown of the lower adit and high-pressure bifurcation in the water-filled test of bifurcation tunnel at Huizhou Pumped Storage Power Station. Then a field investigation is undertaken to explore the main reason of such prominent lining cracking. Through investigating several possible inducing factors, it is found that mass defects exist in the concrete lining in constructing bifurcation tunnel, and insufficient thickness of concrete lining is probably the main factor causing lining cracks. In order to verify if this conclusion is reasonable, comparative analysis through numerical simulation is utilized to assess the influence of different concrete thicknesses on tunnel stability for the lower adit and high-pressure bifurcation. And then the fracturing process of concrete lining with the increase of internal water pressure during the water-filled test is simulated. The results reveal that the displacements and tensile strains in the lining crown are significantly bigger than other parts of tunnel, with deficiency in concrete thickness considered. It is also concluded that whether the cavities exist or not in the crown, rather than the cavity thickness, is the main factor influencing the values and distributions of the tensile strains and displacements for tunnel lining. Besides, the distribution of tensile-strain-concentrated zones is approximately in good agreement with the in-situ fractured status of concrete lining. Finally, a conclusion can be drawn that deficiency in concrete thickness in the crown is the primary triggering factor for lining cracking.