Mechanical excavation method for large-section municipal hard rock tunnel

The invention relates to the technical field of tunnel excavation, in particular to a large-section municipal hard rock tunnel mechanical excavation method which specifically comprises the following steps: S1, a first section with a 180-degree fan-shaped angle, a second section and a third section which are sequentially expanded, a fourth section with a rectangular lower step, and a fifth section; s2, first fracture surface breaking is carried out, and second fracture surface breaking is carried out after excavation and deslagging of the first fracture surface are completed; trimming the third section; and breaking according to the fourth section and the fifth section from top to bottom in a layering manner. The method has the advantages that the equipment cost is low, and the application range is wide; 2, the excavation precision is high, and the overexcavation amount is small; 3, the construction process has small disturbance on the surrounding environment and buildings; 4, the excavation efficiency is high