Prefabricated drainage cavity top arch structure of drainage gallery

The prefabricated drainage cavity top arch structure of the drainage gallery comprises a plurality of sections of top arch structures arranged at the top of the drainage gallery, and the top arch structures are sequentially arranged in the length direction of the drainage gallery and connected with one another; drainage cavities and reserved drainage holes communicated with the drainage cavities are formed in the top arch structures, the reserved drainage holes are vertically formed above the drainage ditches of the drainage gallery, and the drainage cavities of the adjacent top arch structures are communicated. According to the method, the drainage hole of the dam body of the dam can be rapidly positioned on the drainage gallery, the drainage hole can be communicated with the drainage ditch of the drainage gallery without accurate positioning by complex control means, and smooth drainage of seepage water of the drainage hole of the dam is guaranteed; and the structure can also be used as a permanent structur