Study on deterioration, cracking mechanism and treatment measures of plain concrete lining with cold joints in high-speed railroad tunnel

Cracks in lining will lead to derivative diseases even seriously threaten the safety of high-speed trains. Construction-induced defects and external environmental changes are the main causes of lining cracks. From a typical high-speed railroad tunnel with a large number of lining cracks in China, construction cold joints are the main cause of its lining cracks. Based on the current research, both microscopic model and macroscopic model of concrete with cold joints were established to verify the applicability of the macroscopic model to simulate concrete elements with cold joints. Besides, finite element models with single and multiple cold joints were con-structed to analyze the bearing performance and cracking mechanism of lining with cold joints. Finally, measures were proposed for the lining cracks caused by the expansion of cold joints. The results showed that: Using macroscopic model to simulate concrete elements with cold joints is reasonable. The tension area with cold joints has the most obvious deterioration, which is consistent with the cracking characteristics of field lining. Therefore, it is necessary to detect the cold joint defects in tensile area and where the pouring intervals exceed the initial setting time. The cracking of lining with single cold joints can be divided into two patterns, the back-side tension misalignment model and the inner-side tension misalignment model. While the cracking model with multiple cold joints can be regarded as a combination of single cold joint cracking models. The stress distribution and performance deterioration of lining with multiple cold joints is more complicated than that of single cold joints, more researches can be carried out by the method of this study.