8 Execution

8.1 Receipt and quality control of materials

8.1.1 All prefabricated facing units or palettes of modular blocks, all batches or rolls of reinforcements shall be identified with unambiguous marks or labels, conforming to the denominations used on the plans. Geosynthetic materials shall conform to EN ISO 10320.

8.1.2 The details of each roll or batch of reinforcement delivered to the site shall be checked against the materials specified and the serial numbers shall be recorded and retained.

8.2 Handling and storage

8.2.1 A suitable storage area of sufficient dimensions shall be prepared to allow the unloading, loading, storage and moving of all reinforcing and facing materials, and accessories delivered to the site, without damage occurring.

8.2.2 Handling and storage of reinforcing and facing materials shall be carried out with care and in accordance with the project specifications. The relevant recommendations of the supplier or manufacturer should be also complied with.

8.2.3 Items having different sizes or physical characteristics should be stacked separately.

8.2.4 Reinforcing and facing products take many different forms. Where the above requirements do not apply to a particular product, further advice may be sought from an approving body, the supplier or the manufacturer.

8.3 Preparation of the site and foundation

8.3.1 General

8.3.1.1 The foundation shall be constructed to the levels and falls in accordance with the requirements of the design.

8.3.1.2 The preparation shall be carried out in accordance with the design and the specific environment of the structure and includes, if required, the construction access for plant and machinery, the excavation required to clear the area and the cleaning, levelling and treatment of the foundation.

8.3.1.3 If the soils encountered during the preparation works do not correspond with the design this shall be reported immediately.

8.3.1.4 Where vertical drains are to be installed beneath any type of reinforced fill structure, from some intermediate fill level, care shall be taken to ensure that the thickness of fill placed is adequate to safely bear the loads imposed by the construction plant. Additionally, installation of vertical drains shall not induce damage in the underlying reinforcement in excess of that already allowed for in the design.

8.3.1.5 Where reinforcement to any type of reinforced fill structure is to be placed over piles then, unless otherwise specified, consideration should be given to chamfering the edges of pile caps and/or covering the pile caps with a layer of fill to prevent damage to the reinforcement.

8.3.2 Earth retaining structures and reinforced slopes

8.3.2.1 Unsuitable materials shall be removed from the area to be occupied by the reinforced fill structure. All elements that might damage the reinforcements shall be removed from the foundation area. Depending on the case all organic matter, vegetation, slide debris and other unstable materials shall be stripped off and the sub-grade compacted before the placing of any fill material. Soft spots should be removed and replaced with well graded and compacted fill.

8.3.2.2 In the case of earth retaining structures with hard facing units a trench excavation, stepped like the foundation platform, should be provided at the foundation level for a levelling pad beneath the facing. This levelling pad is not a structural foundation but temporary works to aid alignment and facilitate the erection of the facing units. It should be formed in-situ of thin, mass, unreinforced concrete.

NOTE Mass concrete may be replaced by gravel under thick facings such as modular blocks, sloping panels or planter boxes. Such levelling pads are not usually required for soft or flexible facing units.

8.3.3 Embankments with reinforcement at the base

8.3.3.1 On vegetated sites, only substantial vegetation such as bushes or trees shall be cut down to be level with the natural ground level. Debris likely to cause puncturing or other mechanical damage to the reinforcement should be removed from the areas prepared to receive the reinforcement. Root systems of felled trees or bushes and vegetation giving ground cover may be left in place. Organic material will decay and consideration should be given to the long term effects of substantial deposits if they are to be left on the site.

8.3.3.2 On sites known to have a desiccated crust care shall be taken not to rupture this crust during site preparation and initial filling unless otherwise specified in the design.

8.3.3.3 Before placement of the reinforcement commences all abrupt changes in ground profile shall be evened out by placement and compaction of a regulating layer of suitable fill. The fill of the regulating layer and any geosynthetic separator between the ground and the fill shall not impair any dissipation of pore water pressure from the foundation soil.

8.4 Drainage

8.4.1 Drainage of earth retaining structures

8.4.1.1 If the foundation of the structure is not free draining, a longitudinal drainage trench, or a porous or open jointed drainage pipe of suitable size, or a geocomposite drain shall be placed at the base of the structure to collect water and bring it to the site drainage system. Any facing shall allow water to pass through to this drain if it is located in front of the facing. The omission of joint filler from the vertical joints in the embedded depth of panel facings can normally allow water to pass through the facing without the need for weep holes.

8.4.1.2 Where water flow is expected from the retained soil drainage trenches or geocomposite drains shall be placed at intervals along the wall.

8.4.1.3 In cases of significant water flows a drainage blanket of sufficient thickness, or a geocomposite, shall be constructed below the reinforced fill wall and discharged beyond the toe. If required this blanket may be continued up along the face of the temporary excavation.

8.4.1.4 Any drainage material shall be designed to avoid loss of reinforced fill or adjacent soil into the drain

8.4.1.5 Special drainage considerations shall apply to partially or temporarily submerged reinforced fill structures

8.4.2 Drainage of reinforced slopes

8.4.2.1 Drainage considerations for reinforced slopes shall follow the procedures detailed in 8.4.1. In addition it may be necessary to ensure that rainfall falling on the face of the slope does not lead to washout.