402.1. General 1. Grouting for ground stabilisation shall mean injecting grout for
the safe progress of the Works, the elimination or mitigation of settlement and the reduction of groundwater inflows into the Works. Cementitious grout with suitable additives will be used, followed where necessary with chemical grouts as the nature of the ground to be treated and the purpose of the grouting dictates.
2. Grouting shall be carried out only by contractors employing staff and operatives skilled in the work and notified in advance to the Engineer. They shall produce evidence of satisfactory performance on projects where the purpose of the work and extent was comparable.
3. The Contractor shall carry out such trials, additional tests and ground investigation as he deems necessary to formulate his proposals.
4. The Contractor shall take precautions to minimise hydro- fracture stress levels within the ground imposed by grouting which might cause damage to structures and/or heave. Where significant stress changes are likely to be imposed, the Con- tractor shall employ systems to monitor and protect sensitive structures.
5. The Contractor shall take precautions to avoid injected grout entering sewers, drains, granular drainage blankets or other underground structures.
6. The performance of any grouting system shall be monitored by the Contractor in accordance with the Contract, and inter- pretation of the results agreed with the Engineer.
402.2. Contractor’s proposals
1. The Contractor shall agree with the Engineer details of the proposed grouting scheme including:
(a) where grouting design is the responsibility of the Contrac- tor, information and case records to support the grouting proposed in respect of its ability to penetrate the strata and its ground enhancement effect
(b) where grouting design is the responsibility of the Contrac- tor, specific criteria to measure the adequacy, sufficiency or completeness of the ground treatment
(c) details of the treatment zone and grout injection patterns with respect to the Works and adjacent structures
(d ) details of plant proposed
(e) method statement and programme including arrangements for storage of materials, mixing grout, Quality Control of grout, recording grouting pressures and grout take and tests to prove the efficacy of the grout in the ground,
health aspects associated with the materials and grout proposed at all stages of the process and during excavation of treated ground, and means of protecting persons from any adverse effects
( f ) an assessment of the environmental impact of the materials and methods proposed
(g) an occupational health risk assessment, including methods of risk reduction on all aspects of the grouting operation. 2. Where the grouting contractor is responsible for the design of the grouting, he shall automatically record grouting pressures and flows and produce ongoing assessments of the grout performance in relation to the objectives of the design.
402.3. Drilling 1. Any drilling to be undertaken for the grouting works shall be
carried out in such manner as to minimise ground disturbance and soil loss. Where drilling or treatment techniques employing air or foam/air are proposed, the issues of escape of air into the ground and disturbance of previously grouted ground shall be agreed with the Engineer.
2. Drill tubes left in the ground after final use shall be flushed out and filled with an approved cementitious grout. Each tube shall be cut off at least 1 m below ground level and the area restored.
402.4. Plant Plant shall be brought to site and maintained in good working
order. Batching and mixing plant shall be provided with gauges and equipment which will control accurately the proportions of materials within the required limits and ensure proper mixing and injection of the grout. Gauges shall be checked at the start of each shift. Spares for plant and spare gauges shall be held at site. Current calibration certificates shall be available on site for all electronic measurement equipment.
402.5. Disposal of waste
1. The Contractor shall dispose of leakage and wash-out water from injection points and risers in a safe way and shall not allow them to contaminate the site or watercourses or property elsewhere. The Contractor shall take preventative measures to avoid leakage and shall take measures to stop up leakages should they occur. He shall submit his proposals to the Engineer for his consent.
2. The Contractor shall adopt proper safety precautions to avoid health hazards to all persons, dependent on the nature of the grouts in use.
402.6. Records The Contractor shall keep full and detailed records as are appro-
priate to the type of treatment being carried out, including direction and full depth of injection pipe, quantities of materials used, time, location and volume of grout injected, volume of grout to waste by leakage and other reasons, pressure of injection (measured as close to the injection point as possible), both for initial injections and re-injections. Copies of such records shall be given on a daily basis to the Engineer. Continuous automated monitoring of grout pressures and flows shall be made and presented electronically along with summary records. Records of tests carried out on the treated ground shall also be given to the Engineer.