To solve the cavities problem behind the segments and joints of the middle arch in the prefabricated assembly of the arch of the railway tunnel constructed by the mining method, a case study is conducted on the Hujiagou tunnel on the east ring line of the Chongqing railway hub. Then, the tunnel arch grouting technology is introduced in detail. Meanwhile, the construction tests are conducted on the radial grouting of the arch and the grouting of the longitudinal joints to determine the grouting parameters suitable for the arch grouting process of the tunnel arch. The analysis and research of the samples detected by radar reveal that the grouting pressure, mix ratio, and singlehole grouting amount determined according to the grouting tests can fill the cavities at the arches and joints to meet the requirements of nondestructive testing of railway tunnel linings.