Excavation problems during construction usually emerge due to unfavorable groundwater conditions, inclement weather conditions, and slope instability. Proper control of groundwater is critical in the excavation process as it can make other issues such as slope instability less severe. One can always anticipate excavation problems and try to avoid them by setting a good plan and considering suitable construction practices.
How to Avoid Excavation Problems Through Good Construction Practices
- Stop the excavation process when seepage of water into the excavated area surpasses the capacity of the dewatering system. Apply corrective measures to control the problem.
- However, if the increase of water seepage is due to temporary factors such as heavy rain, then the issue would disappear in a short time and needs no further measures apart from halting excavation for a while.
- Sometimes, groundwater seepage is low, but excessive hydrostatic pressure beneath the relatively impervious soil layer creates uplift pressure and causes foundation instability.
- Carefully observe the excavation work and look for signs of uplift pressures such as the upliftment of the ground surface, lateral movement, development of soft wet areas, piping of materials from the slope, or uncontrolled seepage flow.
- Record quantity of disposed water from excavated area accurately to monitor any increase of water flow into the excavated area.
- Surface water is another source of a problem that may come up during the excavation process. Provide proper surface drainage such as a ditch to divert surface runoff; otherwise, the excavated area suddenly gets filled with water and causes construction delay.
- Maintain the surface drainage to keep the excavated area in good condition till the end of the backfilling process. Additionally, install snow fences around the excavation area at strategic locations to protect the excavation area from drifting snow.
- If the excavation requires shoring and bracing, install shoring and bracing before allowing excavation cut. Lateral pressure of moved soil after excavation is larger than the lateral pressure of unmoved soil.
- Provide sufficient distance between the excavation edge and location of operating heavy machinery and stockpiling to avoid endangering the stability of the excavated area.
- Prevent excessive erosion of slopes of excavation. Cover the slopes of excavation with polyethylene sheeting, straw, silt fences during heavy rain to prevent erosion.
- Classify excavated material into various classes of backfill and stockpile them accordingly. Add water to the backfill material to achieve optimum moisture content for compaction. Protect backfill material to avoid the entrance of water.
FAQs on prevention of excavation problems through good practices
The main sources of excavation problems are ground water, adverse weather condition, and slope stability.
The signs of uplift pressure are uplift of the ground surface, lateral movement, development of soft wet areas, piping of materials from the slope, and uncontrolled seepage flow.
Cover the slopes of excavation with polyethylene sheeting, straw, silt fences during heavy rain to prevent erosion.