Overexcavation refers to the part of the actual excavated section outside the reference line based on the designed excavation contour line. Here are several common explanations:
1. Overexcavation in mining: In mining operations, overbreak refers to the situation where the actual volume of rock excavated exceeds the designed or expected excavation boundary during the excavation process. This may be due to the inaccuracy of drilling and blasting techniques, or intentionally done to ensure the stability of the working face. Overexcavation can lead to resource waste and additional costs, as it means extracting more rocks than ores.
2. Overexcavation of tunnels and underground engineering: In tunnel construction and other underground engineering projects, oversize or overbreak refers to the actual excavation size of tunnels or caverns being greater than the design size. This may be due to limitations in construction technology, such as insufficient drilling accuracy and improper blasting control. Overexcavation may lead to structural instability, increase support costs, and may require additional repair work.
3. Overexcavation under complex geological conditions: In some complex geological conditions, in order to ensure construction safety and structural stability, the construction party may intentionally carry out a certain degree of overexcavation. This can provide more space for subsequent support and lining work to cope with unforeseeable geological changes.
4. Overexcavation in construction: In above ground construction, over excavation may refer to digging deeper than the design depth during the foundation excavation process. This situation is usually caused by measurement errors, construction errors, or measures taken to solve foundation problems.
How to handle the over excavation part?
In basic construction, if over excavation occurs, corresponding measures may need to be taken, such as sand piles, cement fly ash piles, dynamic compaction method, replacement method, preloading method, etc., to ensure the bearing capacity and stability of the foundation.
In construction projects such as site excavation or tunnel excavation, there may be three situations: over excavation, under excavation, and exact excavation height. Over excavation requires backfilling of the site, while under excavation requires continued excavation, both of which result in wastage of manpower, material resources, and financial resources. In order to better control costs and schedule, construction workers usually set up temporary leveling elevations based on the site conditions, and promptly inform excavator drivers or laborers of the required excavation thickness according to the elevations.