8 Terms Related To Earthwork – Cutting & Filling, Benching, Witness, Turfing, Borrow pit, Lead and Lift, Spoil bank3rd April 2019
8 Terms Related To Earthwork
There are 8 major terms which related to earthwork such as Cutting & Filling, Benching, Witness, Turfing, Borrow pit, Lead & Lift, Spoil bank, etc. are described below
1. Cutting And Filling
The process of cutting and removing earth from its original position, transporting and dumping the same as a fill or in the form of a spoil bank is known as an earthwork in cutting or excavation.
When the formation level of a road is to be kept lower than the natural ground level, the road is run in cutting.
The process of cutting and removing earth from borrow pits, transporting and placing it as a fill in the form of an embankment is known as an earthwork in embankment or filling.
When the formation level of a road is to be kept higher than the natural ground level, the road is run in filling.
2. Angle of Repose
The natural slope which a soil mass will take during its settlement is called the angle of repose. It depends upon mainly the water content and the type of soil.
The art of cutting side slopes in steps is called benching. When the embankment is constructed on hillside slopes, it is necessary to bench the surface of the hill slope to add stability to the slope. These benches should have a gentle fall towards the hillsides. Thus benching reduces the probability of sides of slopes.
The small portion of earth left undug in borrow pit to measure the quantity of excavation which is known as Mutam or dead man or witness.
5. Lead and Lift
The horizontal distance through which the excavated earth from a borrow pit is carried to the place of the embankment is known as lead.
The vertical height through which the excavated earth from a borrow pit is to be lifted is known as lift.
Turfing is done on side slopes and on shoulders of a rural road to prevent soil erosion. It also reduces the dust nuisance and gives a pleasing appearance of the roadside. Turfing is generally done in the rainy season.
For turfing, good quality grass is cut with at least 5 cm the earth and it is then placed on the dressed side slopes and shoulders of the embankment. After laying turfs, it is gently compressed with wooden flat rammer after applying water so that it adheres to the soil of embankment.
7. Borrow pit
The pits dug along the alignment of a road for using their material in the construction of the road embankment are known as borrow pits. These pits are dug just outside the permanent land width. Borrow pits should be dug at least 5 m away from the toe of an embankment.
These are dug to a uniform depth which is limited to 1.5 m. These pits should never be made continuous. Ridges not less than 8m in width should be left at an interval not exceeding 300 m.
8. Spoil Bank
The banks constructed from surplus excavated earth on the side cutting parallel to the road alignment are known as spoil banks. The height of spoil banks should be nearly 1.5 m. They should be constructed at a distance of 3 m from the top edge of cutting.