Investigation & Supervision Of Remedial Ground Works

Site Investigation and Supervision of Remedial Ground Works

Remedial ground works is the process of taking an area of land and making it suitable for its intended re-development. Therefore, the term remediation covers many activities and solutions for land development projects. Although typically remediation occurs for chemical contamination of soils, groundwater and hazardous gases, this page will discuss ground improvement techniques. For chemical contamination and remediation consult the page Phase III Remediation.

Ground improvement is defined as “controlled alteration of the state, nature, or mass behaviour of ground materials to achieve an intended satisfactory response to existing or projected environmental and engineering actions”.

The common purpose of ground improvement is:

• Improve soil permeability to increase drainage capacity
• Improve the shear strength of the fill and soil to increase the bearing capacity of the ground for foundation and/or slope stability
• Increase the density of the fill mass and/or subsoil to prevent liquefaction
• Increase bearing capacity of the soil to prevent excessive settlement of the ground in areas of loading due to buildings, road, or other structures.

The benefits of ground improvement are that it can be completed before and after construction on the site. It can often be more efficient and cost effective to improve the in-situ ground than have it removed and replaced with high quality but expensive fill. Additionally post construction the flexibility and feasibility of ground improvement means specific areas of the site can be targeted if they do not meet the necessary remediation standards.

There are various ground improvement techniques with advantages and disadvantages varying depending on site suitability, some common examples are.

• Soil mixing- in-situ admixtures of like, cement or fly ash
• Grouting
• Soil compaction techniques such as vibration
• Preloading or surcharging the ground with or without vertical drainage

Soil mixing improves soft clays and other weak soils with a high moisture content. The soils are mechanically mixed with a dry or wet cementitious binder to create a silcrete. This process increases the bearing capacity and decrease settlement within the soils.

Grouting involves the injection fluids into the soil or rock formation to decrease the permeability and increase the bearing capacity and shear strength by binding the soil and rock together.

Soil Compaction increase the soil density and decreases air volume while maintaining water content. This technique increases bearing capacity, shear strength and decreases settlement and heave. This technique is often used in construction to produce suitably level base by compacting the existing soil or fill.

Preloading or surcharging the ground involves add material to cause dead load to the ground before construction that is similar in weight to the final load or excess respectively. This process induces primary and secondary settlement of the soil before construction takes place. Afterward the load or surcharge is removed, and construction can commence following validation assessments.

GES also works in areas of previous coal mining, and designs Pile Platform, and retaining walls, more information on these topics can be found on the pages, ‘Phase III Remediation’, ‘Pile Platform Design’ and ‘Slope stability and Retaining Wall Design’.

The design and management of remediation and ground improvement techniques are handled by our geotechnical team.

We have the capability to:

• support the remediation strategy through the planning process,
• agreeing key targets,
• providing a range of on-site management services, from a simple watching brief to full time site attendance for the more complicated or location sensitive remedial works,
• monitoring procedure and protocols,
• information management,
• attendance at project meetings, and
• validation of the remediation process upon completion, including gas protection systems.

Not only do we have the technical ability to support and manage remediation projects, but we also have the commercial awareness to understand cost is also a factor in remediating a site and whatever remediation strategy is adopted must also be commercially viable within the remit of the development project.