(1) Before trench excavation, backfilling and preloading shall be carried out for the designed pipe top elevation which is insufficient from the original ground and the original foundation is loose, and then excavation construction can be carried out, so as to prevent the pipeline interface from being damaged and the pipeline from being displaced during road gene filling and rolling construction.
If there are underground pipelines, the location, depth, direction, pipes and joints of various underground pipelines should be verified before construction, and then artificial exposure should be taken in advance. Pipeline trench is excavated by 1 m3 backhoe excavator, with manual cooperation. According to the principle of deep before shallow, a certain number of piles should be reserved through earthwork filling and excavation calculation, but the distance between the piles and the edge of the groove should be greater than 2.0 meters. When the soil quality is poor, it is forbidden to pile soil near the pipe trench. The excavator digs to the place 20cm away from the bottom of the trough, and adopts manual digging, bottom cleaning and slope repairing.
According to the buried depth of the pipeline, the trench excavation face is implemented in two situations:
1) When the trench excavation depth is less than 3m, slope excavation is adopted, and the slope coefficient is 1: 0.5.
2) When the trench excavation depth is more than 3m, the two-stage slope excavation method is adopted, and the slope coefficient is 1: 0.5, and support is adopted if necessary.
3) When soft soil and miscellaneous fill are encountered, the miscellaneous fill should be removed by soil replacement cushion method, and the soft soil should be replaced by graded pond slag.
4) Trench drainage: Open ditches of 20cm* 15cm are set on both sides of the trench, which are pumped out by mud pumps, introduced into the sump and discharged outside. The sump is set at the lowest elevation of each well section.
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