Method for excavating rock pillars in huge-span cavern and pre-support system of method

The invention provides a method for excavating rock pillars in a huge-span cavern and a pre-support system of the method. The method comprises the following steps that S1, excavation partitions are arranged, and the positions of the middle rock pillars and side rock bodies are determined; S2, a pre-support cavern group is constructed above the middle rock pillars, wherein the pre-support cavern group comprises a plurality of advanced pilot tunnels arranged in the same direction as the cavern and a plurality of connecting channels for communicating the adjacent advanced pilot tunnels; S3, the side rock bodies are excavated, and a side rock body primary support is constructed; and S4, in the advance pilot tunnels, longitudinal foundation beams are constructed along the full length of the advance pilot tunnels, in the connecting channels, transverse foundation beams are constructed along the full length of the connecting channels, and the longitudinal foundation beams and the transverse foundation beams are rigi