Factor of Safety Against Bearing Failure of Cellular Cofferdam Embedded in Clay

Given Information:
Height of cell above the top of the stratum (H) = 15 m
Unit cohesion (c) = 60 kN/m²
Unit weight of cell fill (γ) = 18 kN/m²

Introduction:
A cellular cofferdam is a temporary structure used in construction projects to create a dry working environment in areas that are below the water table. It consists of a series of interconnected cells filled with granular material or concrete. The cofferdam is embedded in the ground to provide stability and prevent water from entering the excavation area.

Factor of Safety Against Bearing Failure:
The factor of safety against bearing failure can be determined by considering the equilibrium of forces acting on the cofferdam. The bearing capacity of the clay stratum needs to be assessed to determine the stability of the cofferdam.

Calculation:
The bearing capacity of the clay can be determined using the Terzaghi's bearing capacity equation:

qult = cNc + γDNq + 0.5γBNγ

Where,
qult = Ultimate bearing capacity of the clay
c = Cohesion of the clay
Nc = Bearing capacity factor for cohesion (depends on the internal friction angle of the soil)
γ = Unit weight of the soil
D = Depth of the cell below the top of the clay stratum
Nq = Bearing capacity factor for surcharge (depends on the internal friction angle of the soil)
B = Width of the cell

Since the cofferdam is embedded in clay, the cohesion (c) and unit weight (γ) of the clay are given. However, the values of Nc and Nq are not provided in the given information. Therefore, in order to calculate the factor of safety, we need to determine the values of Nc and Nq based on the internal friction angle of the clay stratum.

Conclusion:
Without the values of bearing capacity factors (Nc and Nq) and the width of the cell (B), it is not possible to calculate the factor of safety against bearing failure of the cellular cofferdam embedded in clay. The given information is insufficient to perform the calculations.