Friction angle together with cohesion defines the shear strength parameters of soil. Its definition is derived from the Mohr-Coulomb failure criterion. It can be determined in the laboratory by direct shear test or triaxial tests or from theoretical correlations with density or N SPT number.

The current tool sets the rules to calculate friction angle for granular soils based on N SPT number.

The current tool estimates the deformation modulus or modulus of elasticity of soft rock based on Hoobs (1974) mass factor theoretical equation. It requires as an input the unconfined compressive strength of rock from UCS laboratory tests and RQD values from coring. The equation also requires an estimate of the modulus ratio value, Mr, to account for rock type.

Based on RQD, the equation calculates the mass factor j, to account for rock mass discontinuities, fractures, and weathering and the modulus ratio value, M, to account for rock type.

The current tool is an implementation of Casagrande’s plasticity chart (1948). It is used to classify fine-grained soils using their plasticity characteristics as expressed by the Plasticity Index (IP) and Liquid Limit (LL).

Samples with high plasticity tend to be clay-based materials, samples with low plasticity tend to be silt-based materials, and samples with no plasticity tend to have little or no silt or clay.