The invention discloses a silent refuse soil 
discharge drill bit used for cast-in-place bored 
pile construction of a rotary drilling rig. The silent refuse soil 
discharge drill bit comprises a 
drill tube, a square-head upper plate 
assembly, a left and right drill board, a refuse soil 
discharge plate, a plurality of 
dowel bars and a pressure plate, wherein the square-head upper plate 
assembly is fixed to the top end of the drill tube, the left and right drill board is fixed to the bottom end of the drill tube, the refuse soil discharge plate and the multiple 
dowel bars are arranged in the drilltube, and the pressure plate is located right above the square-head upper plate 
assembly and is of a circular ring-shaped structure; the top ends of the multiple 
dowel bars all pass through an upperplate of the square-head upper plate assembly and are fixedly connected with the pressure plate; and the bottom ends of the multiple dowel bars are fixedly connected with the refuse soil discharge plate. According to the silent refuse soil discharge 
drill bit, the pressure plate and the refuse soil discharge plate are fixedly connected through the dowel bars; when the 
drill bit is lifted out of abore, a circular disk on a drill stem presses down the pressure plate to push the dowel bars to push the refuse soil discharge plate, and thereby, refuse soil in the drill tube is rapidly pushed out of the drill tube; the 
drill bit can be used for different soil 
layers, has small 
noise and a wide application range; and in addition, the drill bit has the advantages that construction is convenient,the operation 
habit of a drilling rig does not need to be changed, the construction efficiency is high, cost is saved, and the economic benefit is improved.