Main methods for detecting excavation section of tunnel engineering

Direct measurement method, rectangular coordinate method and three-dimensional close-range photography method.

1, direct measurement method, with the internal model as reference, measure the distance from the internal model to the rock wall with a steel ruler.

2. Rectangular coordinate method, using theodolite to measure the horizontal angle and vertical angle of each change point of the excavation section, and using the principle of solid geometry to calculate the vertical and horizontal coordinates of each measuring point.

3. Three-dimensional close-range photography, using phototheodolite to obtain stereo image pairs of various positions in the tunnel.