Annex F

(informative)

Timber sheet piles and walings

F.1 General

The terminology for timber and imperfections in sawn timber are given in EN 844-1:1995, EN 844-3:1995, EN 844-7:1997 and EN 844-9:1997 as.

Timber for sheet piles and walings in permanent sheet pile wall structures is normally of high durability.

Tropical hardwood normally meets this requirement without any preservation. However coniferous species when used in waterfront structures, need to be impregnated by a preservation fluid pressed into the wood under vacuum conditions.

EN 335-1:1992 and EN 335-2:1992 provide a general decision-making procedure for arriving at the hazard class and the associated biological agents in order to determine the preservation treatment.

Cutting, boring and similar operations should preferably be carried out in the factory before the timber is impregnated. When impregnated timber is subsequently cut, bored or similarly re-shaped, it is necessary to treat the affected area with special protecting liquid.

F.2 Delivery of timber sheet piles and walings

Orders for timber sheet piles, walings and timber anchoring plates, normally cover the following aspects :

  • wood species (strength requirements);
  • the nominal values of thickness and length;
  • the shape and dimensions of the tongue and groove joints;
  • the shape and size of the splice joint in the waling;
  • the shape and size of the bevelling at the toe of the sheet piles if required (see figure F.3);
  • the nominal dimensions of the special sheet piles as for example corner piles;
  • the type and method of applying the preservative treatment. Normally these aspects are checked at delivery to the site.

F.3 Quality requirements

Table F.1 gives quality requirements for sheet piles and walings of sawn softwood and hardwood. The main testing criteria are for:

  • imperfections;
  • dimensional tolerances;
  • straightness in the longitudinal and tranverse direction.

F.4 Transport and storage

Normally timber sheet piles and walings are delivered in packages. These packages are stored on a flat surface not in contact with the ground. Tropical harwood sheet piles and walings are stapled one on the other This prevents loss of moisture, warping, twisting and cracking. Because of the durability treatment pinewood is stacked with spacers between the individual elements. It is recommended to leave the staples intact as long as possible and to protect them from direct sun radiation by covering with a sheet.

To avoid mixing, packages of treated timber sheet piles, walings and other timber parts stored on the construction site are labelled according to :

  • timber which will be underground;
  • timber which will be applied in fresh water under fully submerged condition;
  • timber which will be applied in salt and brackish water.

F.5 Tolerances

Criteria for the maximum distortions (warp, cup and twist) are given in table F.1.

The maximum allowed variations from the nominal dimensions are presented in table F.2.

F.6 Joints

Normally timber sheet piles are jointed by tongue and groove type interlocks of a trapezoidal shape. However a rectangular shape is also used.

Table F.3 gives recommendations regarding shape and dimensions of the tongue. The dimensions of the tongue determine the size of the groove as shown in figure F.1.

Shape and dimensions of tongue and groove interlocks of timber sheet piles

Legend

  • A Tongue and groove with trapezoidal shape
  • B Tongue and groove with rectangular shape
Figure F.1 – Shape and dimensions of tongue and groove interlocks of timber sheet piles

F.7 Corner sheet piles

Corner sheet piles generally have a square cross section with grooves to connect the adjacent sheet piles (see figure F.2).

Example of a timber corner pile with grooves
Figure F.2 – Example of a timber corner pile with grooves

F.8 Execution

Normally timber sheet piles are only used in retaining structures with a limited retained height. Typical uses are :

  • vertical or nearly vertical embankments along canals and ditches;
  • small quays in yachting harbours and similar.

Driving is usually carried out with light driving equipment. If a free falling mass is used the height of the drop should not exceed 2,5 m.

When a vibrator is used, panels of several piles are driven as units.

In order to keep the sheet piling in the correct position, a guide frame is used.

Low pressure water jetting is often used to assist driving work in sand layers.

In order to ascertain a proper tongue and groove connection, the sheet piles are often bevelled at the "free"side of the toe as shown in figure F.3.

Bevelling at the toe and driving direction

Legend

  • a driving direction
  • b bevel width
  • c ground pressure
Figure F.3 – Bevelling at the toe and driving direction
Table F.1 – Delivery conditions for sheet piles and walings of sawn softwood and hardwood and for the execution of timber sheet pile walls
Imperfections soft wood hardwood
worm holes no probability of extension * *
probability of extension *  
compression cracks * *
heartwood * *
bark pockets * *
knots in sheet piles and walings hard knots fixed * *
loose *
soft knots *
knots disturbing the fitting *
percentage of knots, max. *
diameter max.   *
  *
cracks fissures *  
face shakes * *
end shakes * *
clefts * *
heart shakes *  
sapwood *  
fungous affects   *  
  * *
  *  
Wane (see figure F.4) sheet piles 1)    
walings two edges : max 0,3x width, resp. thickness of timber not acceptable
mechanical damages loose or broken fibers acc. to depth into the wood < 0,1 x thickness of the wood constricted parts resulting from steel bands acc. provided that the fibers are not damaged.
warping of sheet piles 2) max. bow per metre (see figure F.4) 4 mm 3 mm
max. spring per metre (see figure F.4) 2 mm max. 1/3 of the length of the tongue
max. cup over 100 mm width (see figure F.4) 2 mm no requirement
max. twist per metre (see figure F.4) 2 mm not acceptable
warping of walings 2) max. bow per metre (see figure F.4) 4 mm at the retaining side: 1 mm; at the other side: 4 mm
max. spring per metre (see figure F.4)  
max. cup over 100 mm width (see figure F.4) 2 mm no requirement
Max. twist per metre (see figure F.4) 4 mm not acceptable

* To be stated by the design

1) A small wane is acceptable over a length of max. 250 mm from the bottom end of the timber sheet pile, provided that it does not harm a proper fitting of the tongue and groove connection

2) Deformations over the full length of the timber sheet pile or the waling

Legend

  • a wane
  • b width of the waling
  • h height of the waling
(1) bow
(3) cup		 (2) spring
(4) twist
Figure F.4 – Definitions of various distorsions
Table F.2 – Maximum allowable difference of the actual dimensions with respect to the nominal values in mm
  Sheet piles Walings
individual average ≤ 105 1 > 105 1
length ±100 ≥ 0 + 50
–25		 + 50
–25
width     ±2 + 2
–3
thickness ±2 ±0,5 ±2 ±2

1) Thickness of the waling perpendicular to the sheet pile wall
Table F.3 – Dimensions of tongues in sheet piles
  Length of tongue (mm)
soft wood length of sheet pile of tropical hardwood (m)
thicknessof thesheet pile(mm) thicknessof thetongue(mm) < 3,5 3,6 to 4,5 4,6 to 5,5 5,6 to 6,5 6,6 to 7,5 7,6 to 8,5
30
40
50
60
70
80
90
100
110
120		 10
13
16
19
23
26
29
33
36
39		 11
13
17
18
22
24
24
24
24
24		 11
 
 
 
 
 
 
 
 
 		 13
13
 
 
 
 
 
 
 
 		 15
15
15
 
 
 
 
 
 
 		 -
 
18
18
18
 
 
 
 
 		 -
-
22
22
22
 
 
 
 
 		 -
-
-
24
24
24
24
24
24
24

EN 12063-1999 Execution of special geotechnical work – Sheet-pile walls