Study on Cause Analysis and Treatment Measures of Lining Cracking and Ballast Bed Freezing at Tunnel Portal in Seasonally-Frozen Regions

The purpose of this study is taking the ZEST tunnel of Xilin hot-Ulanhot Railway in Inner Mongolia province of China as an example to investigate the cause and treatment measures of lining cracking and ballast bed freezing at tunnel portal in seasonally-frozen regions. Field investigation method was used to investigate the characteristics of lining cracking and ballast bed freezing in winter. The results show that the longitudinal cracks in the side wall are symmetrical and located in the middle of the wall. The longitudinal cracks have obvious seasonal characteristics, which mainly occur in winter, and the width of cracking was alternatively varied and broadened year by year, of which the process proved to be irreversible. The number of cracks and the width and length of the cracks all have the trend of further development in the last year. Numerical calculation method was used to study the internal force change law of the lining structure of the ZEST tunnel under seasonal frost heaving force. The results show that the lining cracking is mainly caused by the frost heaving force load. Based on the above analysis results, the treatment measures for the frost heave cracking, ballast bed freezing and the leakage of water leakage during the spring thawing period are proposed, the remediation measure proposed is quite effective and the problems such as cracking, ballast bed freezing and water leaking of tunnel lining are completely solved.