开挖地下基坑（槽）时，合理确定开挖顺序和分层开挖深度，当接近地下水位时

When excavating an underground foundation pit (trough), reasonably determine the excavation sequence and layered excavation depth. When it is close to the groundwater level, the excavation at the lowest elevation should be completed first to facilitate centralized drainage at this place. After excavation, when digging to within 50cm from the bottom of the trough, a horizontal line 50cm from the bottom of the trough should be marked. From the end of each trough 20cm, small wooden prongs are nailed at the level of the trough side every 2-3m. When the excavation is close to the bottom elevation of the trough, use a ruler or a 50cm standard ruler beforehand, and use a small wooden prong to level the elevation of the trough bottom at any time. Finally, the two ends of the axis (center line) lead the pile to pull the line, check the dimension from the groove edge, determine the groove width standard, repair the groove according to this, finally remove the soil at the bottom of the groove, smooth the pile head and extend the cushion 50mm, Repair the bottom and shovel level.

When excavating underground pits (grooves), the excavation sequence and the depth of stratification should be reasonably determined, and when approaching the water table, the excavation at the lowest elevation should be completed in order to facilitate centralized drainage there. After digging to within 50cm from the bottom of the groove, should mark the horizontal line 50cm from the bottom of the groove, from the end of each groove 20cm every 2-3m in the slot nail horizontal elevation of small wooden birch. When digging to near the bottom height of the groove, use a ruler or in advance to measure the 50cm standard ruler rod, at any time with a small wooden moustice to level the bottom of the groove elevation. Finally by the two ends of the axis (center line) lead pile pull through the line, check the size of the slot edge, determine the slot width standard, according to the dressing groove help, and finally clear the bottom of the groove earth, the pile head grinding and extending the mat layer 50mm, repair bottom leveling.

When excavating underground foundation pit (groove), the excavation sequence and excavation depth shall be reasonably determined. When approaching the groundwater level, the excavation at the lowest elevation shall be completed first to facilitate centralized drainage at this place. After excavation, when the excavation is within 50cm from the bottom of the groove, the horizontal line 50cm from the bottom of the groove shall be marked. The horizontal elevation pegs shall be nailed every 2-3m from 20cm at the end of each groove. When excavation reaches the elevation near the bottom of the groove, measure 50cm standard ruler bar with ruler or in advance, and level the bottom elevation of the groove with pegs at any time. Finally, the pile is drawn through by the axis (center line) at both ends, the dimension from the groove edge is checked, the groove width standard is determined, the groove help is trimmed accordingly, the earthwork at the bottom of the groove is removed, the pile head is ground and the cushion is extended by 50mm, and the bottom is leveled.<br>