8.9 Walings and struts
8.9.1 Walings and struts shall be constructed and installed to comply with 7.3.1.
8.9.2 Gaps which occur between the sheet piles and waling shall be filled to ensure uniform load distribution to the waling.
NOTE Fillings between sheet pile and waling may be plates or wedges of steel, wood or plastic. Bags filled with concrete or cement mortar may also be used (see figure 12).
- a sheet pile
- b waling
- c strut
- d support bracket
- e bag filled with concrete
8.10 Excavation, filling, drainage and de-watering
8.10.1 Excavation, filling, draining and de-watering shall be carried out with appropriate care and shall be in accordance with the design specifications.
NOTE In the case of excavation by dredging, the tolerances in the levels can be rather large. The dredging accuracy depends on the following :
- type of dredger;
- type of soil;
- water depth and wave characteristics.
Dewatering prior to sheet pile driving introduces higher effective stresses in the soil which may adversely affect the subsequent installation.
8.10.2 The excavation and filling shall not cause damage to the parts of the sheet pile wall structure already installed.
8.11 Extraction of sheet piles
8.11.1 When extracting sheet piles the following shall be considered :
- vertical and horizontal deformations in the surrounding ground;
- the possibility of short cutting different groundwater regimes.
NOTE In particular, cohesive soils can adhere to the pile sides thereby creating voids in the ground when the piles are extracted.
In loose sands and silts, vibrations and voids may cause ground displacements which can cause damage to nearby buildings and installations. Such ground displacements and possible links between groundwater regimes can be avoided by injecting the voids with cement-grout or similar, simultaneously with pulling.
8.11.2 Where sheet piles are close to sensitive structures, chemical plants, sensitive infra-structural services, underground railways etc., the extraction shall be carried out with particular care.
8.11.3 The handling and transport of sheet piles to be re-used, shall be in accordance with the requirements of 8.3.
8.12 Rock dowels and anchor bolts
Examples of rock dowels and anchor bolts are shown in figure 13.
8.12.1 When the application of rock dowels is necessary, a suitable tube shall be properly attached to the piles to ensure the correct positioning of the dowel in the rock.
8.12.2 The bottom 0,5 m of the installation tube should be protected or strengthened to avoid deformations.
8.12.3 The installation tube for the rock dowel shall end 50 mm above the toe of the sheet pile.
8.12.4 The tube shall be closed at the bottom end by a plug, normally of concrete.
8.12.5 The dowel shall be anchored to the rock by grouting the hole.
8.12.6 To verify that rock dowels will meet the requirement of the design, the gap between the toe of the sheet pile and the rock level shall be determined with an accuracy of 40 mm.
8.12.7 If rock excavation is carried out close to the toe of the sheet piles, the toe shall be secured in accordance with the design or by other measures, such as inclined anchor bolts as shown in figure 13.
- a rock dowel
- b inclined rock bolt in case of rock excavation in front of the sheet pile wall
- c bed-rock
- d sheet pile
- e reinforced concrete beam
- f cleaned surface
- g level of sheet pile toe
- h excavation contour in the rock
- i tube placed where the distance from the sheet pile to the rock is expected to be the smallest
- j spare tube
- k concrete plug to be put in before installation
When soft clay overlies bedrock, the openings between the toe of the sheet piles and the rock shall be sealed in accordance with the design requirements.