Ground Stabilisation Safety: Jet Grouting and Soil Nailing RAMS

Table of Contents

• Ground Stabilisation: An Overview
• Jet Grouting: Specific Risks and Controls
• Soil Nailing: Specific Risks and Controls
• Chemical Grouting Controls
• Monitoring and Instrumentation
• RAMS Requirements for Ground Stabilisation
• Frequently Asked Questions
• Next Steps

Ground Stabilisation: An Overview

Ground stabilisation encompasses a range of specialist geotechnical techniques used to improve the load-bearing capacity, reduce the permeability, or increase the stability of the ground. On UK construction projects, common applications include strengthening ground ahead of underpinning, stabilising slopes and embankments, providing temporary retention during deep excavations, and treating contaminated ground in situ.

These are specialist activities that require specific RAMS tailored to the technique being used, the ground conditions encountered, and the proximity of existing structures. Generic RAMS that do not reflect the actual technique will not satisfy a principal contractor reviewer. This guide covers the three most common ground stabilisation techniques encountered on UK sites: jet grouting, soil nailing, and chemical grouting.

For guidance on underpinning — a closely related activity — see our underpinning RAMS guide.

Jet Grouting: Specific Risks and Controls

Jet grouting uses ultra-high-pressure water or grout jets (pressures up to 400-600 bar) to cut and mix the in-situ soil with a cementitious grout, creating a soil-cement column. The extreme pressures involved create specific risks:

• High-pressure line failure — Jet grouting operates at pressures that can be instantly fatal if a line fails. All high-pressure equipment must be certificated and inspected by a competent person before use. Operatives must not stand in line with high-pressure connections during operations.
• Grout spoil ejection — Spoil from the jet grouting process can be ejected at the surface under pressure. Spoil collection and management arrangements must be in place. Exclusion zones must prevent persons from entering the area around the spoil ejection point during jetting.
• Ground heave — Jet grouting can cause heave in adjacent ground, particularly in cohesive soils. Monitoring points must be established on adjacent structures and services before work begins, with trigger levels that will stop work if heave exceeds acceptable limits.
• Underground service damage — High-pressure jetting adjacent to buried services can damage them. A comprehensive service search and any required service diversions must be completed before jet grouting commences.
• Grout environmental contamination — Excess grout and grout-contaminated groundwater must be managed to prevent entry to surface water drains or watercourses. An environmental management plan is required for most jet grouting contracts.

Soil Nailing: Specific Risks and Controls

Soil nailing involves drilling and grouting steel reinforcing bars into the soil to create a composite reinforced earth mass. It is widely used for slope stabilisation and temporary or permanent earth retention. Key risks include:

• Slope and face instability during installation — The face of the excavation or slope is exposed during nail installation. Face stability must be assessed by the geotechnical engineer, and the installation sequence must ensure that the face is not overexposed at any stage.
• Drill rig toppling — Drilling rigs used for soil nail installation must be positioned and secured to prevent toppling, particularly on sloped ground. Ground bearing capacity must be assessed.
• Underground service strikes — Soil nails are typically installed at a relatively shallow angle (10-20° below horizontal) and at depths that may bring them into proximity with buried services. Service searches and GPR scanning are required.
• Grout injection pressure — While lower than jet grouting pressures, grouting pressures for soil nails can still cause localised ground heave or service damage if not controlled. Monitoring of grout takes and pressures during installation is required.
• Manual handling of nail lengths — Soil nail bars are heavy and awkward. Safe handling procedures and mechanical assistance for long nails must be specified.

Chemical Grouting Controls

Chemical grouting (including permeation grouting with sodium silicate or polyurethane resins) is used to strengthen and waterproof granular soils by injecting chemical solutions that react in-situ. Health and safety considerations include:

• COSHH assessment for grout chemicals — Chemical grouts are hazardous substances. A COSHH assessment for each grout product must be completed, referencing the manufacturer's Safety Data Sheet (SDS). Sodium silicate is corrosive; polyurethane resins generate heat during curing. Appropriate PPE (chemical-resistant gloves, goggles, face shields) and ventilation must be specified.
• Ground contamination risks — Chemical grouts can migrate beyond the target zone and affect groundwater quality. An Environment Agency permit may be required. The grout design should minimise uncontrolled migration.
• Confined space entry for access tunnels — Where chemical grouting is carried out from within tunnels or shafts, confined space procedures apply.

Monitoring and Instrumentation

All ground stabilisation works must include a monitoring and instrumentation plan referenced in the RAMS. Minimum monitoring requirements typically include:

• Settlement monitoring points on adjacent structures (surveyed before work begins and at regular intervals during work)
• Crack monitoring on adjacent structures using tell-tales
• Inclinometers for lateral movement monitoring where slopes or retaining walls are involved
• Piezometers for groundwater level monitoring where dewatering or grout injection is involved
• Documented trigger levels (amber alert and red stop-work) for each monitoring parameter
• A clear escalation procedure if trigger levels are reached

RAMS Requirements for Ground Stabilisation

Your RAMS for ground stabilisation must be specific to the technique being used. At minimum, all ground stabilisation RAMS must include:

• Reference to the geotechnical design by the geotechnical engineer
• Equipment specifications and inspection/certification requirements
• Exclusion zones during operation
• Underground service protection measures
• Ground heave and settlement monitoring plan
• COSHH assessments for all chemicals and grouts
• Environmental management measures (grout containment, waste management)
• Emergency stop procedures and trigger levels
• Competency requirements for supervisors and plant operators

Generate a compliant RAMS for underpinning and ground stabilisation using the RAMS AI ground stabilisation template.

Frequently Asked Questions

Do jet grouting contractors need Environment Agency permits?

Potentially yes. If jet grouting is carried out in or adjacent to a Source Protection Zone, near a watercourse, or where grout could contaminate groundwater, an Environmental Permit from the Environment Agency may be required. This should be discussed with the project's environmental consultant and the EA at the pre-construction stage. Your RAMS should document the outcome of this assessment and confirm whether a permit is required.

What qualifications are required for ground stabilisation supervisors?

Supervisors overseeing specialist ground stabilisation works should hold SMSTS or equivalent site management qualification. For jet grouting specifically, the technique is sufficiently specialised that a contractor's own internally certified competency scheme may be more relevant than standard CSCS cards — but this does not remove the need for a formally qualified site supervisor. Always check the principal contractor's competency requirements before mobilising.

How do I handle unexpected obstructions during soil nailing?

Your RAMS should include a procedure for encountering unexpected obstructions (boulders, old foundations, buried services). The procedure typically involves: stop drilling, mark the obstruction position, inform the principal contractor and geotechnical engineer, carry out a service check if the obstruction may be a utility, and obtain the engineer's instruction before proceeding. Do not attempt to continue drilling past an unidentified obstruction.

Next Steps

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Ground stabilisation RAMS require specialist geotechnical knowledge. RAMS AI provides comprehensive templates for underpinning and ground stabilisation that can be tailored to your specific technique, site conditions, and monitoring requirements.