What Does Trial Hole Mean In Construction?
What Does Trial Hole Mean In Construction?
A trial pit (also known as a test pit) is an excavation of ground in order to study or sample the composition and structure of the subsurface. It is typically dug during a site investigation, soil survey, or geotechnical drilling project.
Trial pits are usually between 1 and 4 metres deep and are dug either by hand or using a mechanical digger. They can be used to investigate shallow ground conditions to develop an understanding of the profile of soils within the ground, as well as to take samples for further testing.
In addition, trial pits can be used to determine the suitability of foundations for extension works and utilities, such as water drainage. The advantages of trial pits include that they indicate vertical and lateral variations in the subsoil strata and are relatively cost-effective compared to boreholes.
To obtain a comprehensive view of the sub-surface geology, it is important to carefully choose the location of a trial pit. Typically, at least three locations spaced between 10-30 meters apart are selected, depending on the specific site and project conditions.
In order to conduct a thorough investigation, boreholes, probes, and trial pits are commonly used.
Trial pits are excavated in soils that are stable enough to support themselves for the duration of the investigation. In cases where the soil is loose, shoring may be required.
However, there are limits to the depth that can be excavated in trial pits and the area of ground that is disturbed is also quite large.
In certain environmentally sensitive areas, trial pits may not be permitted. Nonetheless, the advantages of using trial pits include the ability to identify both vertical and horizontal variations in the subsoil strata.
What Is The Purpose Of A Trial Hole?
A trial hole is an essential part of construction projects, as it enables engineers to gain an insight into the soil and subsoil conditions at a site before committing to building works. It is used for purposes such as foundation, utilities, buried services and soil testing.
Through excavating and inspecting a trial hole, engineers are able to determine the type and depth of ground layers; assess plumbing, cabling routes and other subsurface features; identify potential problems such as weak soils and high groundwater levels; plan accurately for the installation of new structures or extensions; and check the disposal suitability of spoil heaps from adjacent pits.
Therefore, it is clear that trial holes are invaluable when making important construction choices before any works begin.
Trial Hole Excavation Procedure
Deciding to dig a trial pit should be in consultation with a structural engineer and should not be attempted by someone without the necessary qualification.
A method statement for trial pits is needed before undertaking the project, which defines the purpose of the hole and what needs to be established; these works may disrupt the surface significantly and are hard to fill after completion, yet they remain popular for many construction purposes due to their relatively few limitations and inability to reach the same depths as boreholes.
Advantages Of Trial Hole
Trial pits offer several benefits for construction projects, such as minimizing damage, cost-effectiveness, increased safety, and determining the appropriate construction materials.
Firstly, trial pits can minimize the risk of damaging buried obstructions, such as cables, by enabling construction teams to identify and avoid them. This prevents costly and time-consuming cable strikes, which can be detrimental to any construction project.
Secondly, trial pits are a cost-effective and practical way to investigate a site. Unlike other methods such as sonic drilling and window sampling, trial pits do not require heavy machinery, which limits transport and fuel costs. Additionally, trial pits can typically be completed within a day, saving both time and money.
Thirdly, trial pits can increase the safety of a project by providing information on soil samples and conducting soakaway tests. This information can alert construction teams to any contamination issues or other risks that need further investigation before work begins. Identifying such risks beforehand can prevent potential hazards to the workforce.
Lastly, trial pits can help determine the appropriate construction materials needed for a project. For instance, when building an extension, trial pits can help check the strength of the existing foundations to ensure they can support the additional structure.
It also enables construction teams to estimate project timelines and budgets based on the required materials. The depth of the foundations, for example, can significantly impact both the timeline and quality of materials needed for the project.
In conclusion, trial pits are a valuable tool for any construction project as they offer several benefits, including minimizing damage, cost-effectiveness, increased safety, and determining the appropriate construction materials.
What Is The Average Depth Of The Trial Holes?
The average depth of a trial hole is anywhere from one metre to 4 metres deep. This is an important job that needs to be performed by experienced professionals as the benefits of trial pits are clear, being a cost-effective way of getting the information needed and usually dug by hand, often within a day for quick results.
If you reach a depth of 1.2 metres then structural measures must be taken to prevent collapse and protect people who have to enter the pits.