Why Loging Bridges Need?
When a plantations company starting the bussines, they preparing the land before plant any tree on it. Block system now commonly used as separating line and have many benefit. This line ussualy formed as access road.
Access road in thousands hectares have so many point crossing the water line. In the begining we use loging bridges as temporary construction. The construction using residual wood from land clearing, so this construction have no material cost. Loging bridges as temporary construction should be replaced by permanent construction like concrete bridges, box culvert or steel bridges before aged 5 years. After 5 years wood conditions would be very weak. The life design of loging bridges match with palm tree that starting to harvest in 3 years. It means that the bridges will handling more load frequently.
There are two main part of the bridges :
1) Bridge Foundations
Foundations for loging bridges also using wood. There are two common type of log foundations :
a. Pig Head Foundations
Log formations by set wood in 3 side, front river and 2 side as high as road level. This type of foundations will be strong enough to hold the soil pressure from behind tthe structure, also can reduce the water stream from collapsing the bridge.
b. Wood Pile Foundations
In this type of foundations bridge deck put on some wood pile.
2. Bridge deck
Bridge deck using log put and arranged in horizontal positions together. Soil layer used as finishing touch to binding the log and provide smooth surfaces for truck passes the bridges.
The constructions need excavators. Time to complete this work depend on the length of bridges and depth of the river. One week is a fair average time. You can estimate cost by calculate HM of heavy equipment.