Trial pits are commonly used to investigate shallow ground conditions to develop an understanding of the profile of soils within the ground. They can be particularly useful where buried structures, variable conditions or contamination is suspected or needs further investigation. They are also used to assess permeability of materials for soakaway testing to BRE 365.
They can be excavated by hand (to shallow depths) or using a backhoe excavator, generally to a depth of up to 3.50m -5.00m.
Trial pits (or trenches) can be more cost-effective than boreholes but they cannot reach the same depth and boreholes are more applicable for certain geotechnical testing. Trial pits can also be excavated relatively quickly. However, they can cause significant surface disturbance and it can be difficult to properly backfill excavations when the pit is no longer needed.