Soil Classification in Excavation for Measurement and Payment
In accordance with IS-1200 – part-I, all excavated materials are categorized into specific classes, and payment is made according to the rate for that particular class. The classification is not based on whether the material is dry, moist, or wet. Therefore, any earthwork can be assigned to any of the following categories:
a) Ordinary soils
The term “ordinary soils” refers to a variety of soils that can be excavated using simple tools such as spades, pick axes, and shovels. These soils may contain kankar, sand, silt, hard and soft murrum, shingle, gravel, clay, loam, peat, ash, shale, and other similar materials. They do not fall into the categories of “soft and decomposed” or “hard rock,” which are defined separately.
Typically, excavation of ordinary soils is performed manually, but mechanical equipment such as excavators, shovels, and draglines can also be used. The removal of these soils using such machinery is still subject to payment at the same rate as for manual excavation.
In addition to the soils themselves, ordinary soils may also contain embedded rocks and rubble that are no longer than 500 mm in one direction and no more than 300 mm in the other two directions. These materials can be excavated and removed along with the ordinary soils.
b) Soft and Decomposed Rock Soils:
The materials classified as “hard rock” include various types of rock such as rock, boulders, slag, chalk, slate, hard mica schist, and laterite. These materials do not require blasting and can be removed using tools such as picks, hammers, crowbars, wedges, and pneumatic breaking equipment. However, if a contractor chooses to use blasting for their own reasons, this does not make the material qualify as “hard rock.”
The classification of “hard rock” also encompasses excavation work in macadam and tarred roads and pavements. Additionally, this classification includes rock boulders that are longer than 500 mm in one direction but do not exceed 500 mm in any of the other two directions.
c) Hard Rock Soils:
Hard rock refers to any type of rock that occurs in large, continuous masses and cannot be removed without the use of explosives to loosen it. This category includes both hardened varieties of rock with or without veins and secondary minerals that also require blasting. Additionally, boulders of rock that are of a size that cannot be classified under the aforementioned categories are also considered hard rock.
Reinforced cement concrete is also classified as hard rock. However, in this case, the reinforcement must be cut through, but not separated from the concrete itself.