Infinite slope safety factor

Calculates soil unit weight as sample weight divided by sample volume.

Calculates simple vertical soil stress from unit weight and depth.

Calculates q_ult = c*Nc + q*Nq + 0.5*gamma*B*Ngamma from manually supplied factors and multipliers.

Calculates vertical stress σ_z below a point load P at radial distance r and depth z.

Calculates approximate T_v from U: for U <= 0.60 it uses (pi/4)*U^2, for larger U it uses -0.933*log10(1-U)-0.085.

Calculates T_v = c_v*t/H_dr^2 and inverse modes for time, c_v, and drainage path.