Compaction Energy of Common Laboratory Compaction Methods

Compaction energy can be defined as the mechanical energy applied per volume of soil from some mechanical equipment during compaction process. The function of this mechanical energy is to rearrange soil particles, reduce the voids in the soil, increase the soil’s bearing capacity and shear strength and reduce soil permeability. The compaction energy or compactive effort depends on acceleration due to gravity (g), the volume of the mould being used, the height of fall of the rammer, the weight of the rammer, the number of blows and the number of layers receiving each number of blows. The following formula given by (Arcement and Wright, 2001) can be applied to determine the compaction energy.                                    

Where E is the compaction energy, N_B is the number of blows per layer, N_L is the number of layers, W is the weight of the rammer, H is the height of drop and V is the volume of the mould

Table 1: Details of common compaction methods

Applying Equation 1 to Table 1 above, one can determine the compaction energy for the methods. Acceleration due to gravity, g would be a constant value of 9.81 ms^-2

Standard Proctor, E = (2.5 x 25 x 0.3048 x 3 x 9.81)/0.000944= 593, 900 J/m³

Modified Proctor, E = (4.5 x 25 x 0.457 x 5 x 9.81)/0.000944 = 2, 671, 380 J/m³

British Standard Light, E = (2.5 x 27 x 0.3048 x 3 x 9.81)/0.001 = 605, 493 J/m³

British Standard Heavy, E = (4.5 x 27 x 0.457 x 5 x 9.81)/0.001 = 2, 723, 526 J/m³

West African Standard, E = (4.5 x 10 x 0.457 x 5 x 9.81)/0.001 = 1, 008, 713 J/m³

Table 2; Summary of Results