Forepoling method used in tunneling of weak cemented soft rock roadway

The invention discloses a forepoling method used in the tunneling of a weak cemented soft rock roadway. Firstly, before tunneling the roadway, drilling a hole on the top outline of the cross section of the roadway, wherein an upward angle of 3-5 degrees is formed between the hole and the horizontal; inserting a steel pipe or a steel tube in the hole with the end exposed outside the hole; erecting an arced shed to support the exposed end; secondly, under the protection of temporary forepoling, tunneling the roadway in a normal construction method; stopping tunneling when the drilling footage reaches 2.0m and carrying out the next temporary forepoling according to the first step; thirdly, continuing tunneling under the protection of temporary forepoling, and stopping tunneling when the allowance of the steel pipe in the hole is less than 0.5m; conducting permanent timbering to the roadway in the normal timbering manner until a cycle is finished; and fourthly, conducting the next cycle until the tunneling of the weak cemented soft rock roadway is completed. The forepoling method solves the problems that the weak cemented soft rocks are easy to collapse in the tunneling process and that the cross section of the roadway is hard to shape.