STEPS OF ROAD BENCHING

      Since year 2000 , new road construction technology methods have been   adopted in Kenya  for example benching.  
Benching is a method applied whenever one intend to extend the carriage width  of road section covered by gravel.
It involve digging on both edge of carriage   to a depth equal to depth of the existing  gravel which in  kenya standard road  of  cross section 5.4 meters is 15 centimeters .The bench should be flat and length atleast equal to width of roller used for compaction.
Steps involved  are:

1.Setting Out:-This involve setting both the horizontal and vertical alignment of the road.This  is accomplished to getting centerline  of the road.From which the half carriage distance is obtained, the inslope and the length of the ditch.
2.Benching:The length of carriage to be extended is established and measured from the existing gravel.
3:Bench excavation:The bench equal  to extended width of carriage is excavate to a level equal to size of existing gravel.
4:Bench compaction:The bench is   then compacted to obtain the required moisture content of the soil.
5:Shuttering:The edge of carriage is covered with shutter of  (6  by  1 ).Gravel is then filled in between shutters and existing gravel edge
6:Gravel compaction:Gravel is compacted to a final depth of 120mm