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7.4.8.5 Block interfacesAt the horizontal block interfaces, the eccentricity of the resultant of the vertical and horizontal actions should be limited such that the concentration of the local effects in the blockwork and any bedding material does not cause failure. Except under accidental actions, the eccentricity should not exceed one‑third of the width of the common interface.The sliding resistance at horizontal joints with no shear keys depends on the type of surface finish on the top and bottom of the blocks. Limiting coefficients of friction between two plain surfaces of precast concrete units lie typically within the range 0.4 to 0.6.7.4.8.6 Hydrostatic upliftFull hydrostatic uplift should be assumed in horizontal joints. Where sealed joints are provided, the possibility of uplift should be taken into account.7.5 Precast reinforced concrete walls7.5.1 GeneralPrecast reinforced concrete walls are used in maritime works, both as quay walls and as bulkhead walls adjacent to suspended deck quays. Plain cantilever walls are not generally used for heights in excess of 8 m, and for greater heights a counterfort wall may be used. Units more than 18 m high have been used (see Figure 21).7.5.2 FoundationThe recommendations given for the foundations for concrete blockwork walls (see 7.4.4) and concrete caissons (see 7.6.3) apply equally to those for precast reinforced concrete walls. For high walls, the tolerance on the level of the top of the rubble foundation should be determined in relation to the design of the joints between units.7.5.3 Precast unitsThe toe of the precast units should be arranged so that it does not project into the berthing area (see 4.1.6.5).Crack widths in the walls of the precast units should be determined for all maximum bending conditions, including during each stage of construction. Crack widths are discussed in 4.4.2.3.Methods of lifting and handling the units should be devised during design. Lifting points should be specified. Generous splays should be provided at internal corners to minimize local cracking. Arrises should be chamfered to minimize mechanical damage.