Tunnel excavation supporting trolley and construction method and operation method thereof

The invention discloses a tunnel excavation supporting trolley and a construction method and an operation method thereof, wherein the tunnel excavation supporting trolley is characterized in that a trolley assembly is detachably connected with a lifting main bridge, and a hydraulic lifting system is used for controlling lifting of an approach bridge and the lifting main bridge so that a separated lifting trestle can be switched between a construction mode and a traveling mode; when the separated lifting trestle is in the construction mode, the approach bridge is lifted, walking wheels touch the ground, the lifting main bridge is lifted and separated from the trolley assembly, and the trolley assembly moves on the ground of a tunnel to conduct construction on the tunnel; and when the separated lifting trestle is in the traveling mode, the approach bridge is lowered to the ground of the tunnel, the walking wheels are lifted, the lifting main bridge is lowered to be fixed to the trolley assembly, and the trolley