Some Computer Programs

The source codes for some of the computer programs written by Hodge for his own purposes, are available here in Fortran for anyone who wishes to reproduce them in their own favourite language of more recent vintage.

Soil Permeability or Hydraulic Conductivity


This program goes about estimating hydraulic conductivity from input value for soil-structure void ratio, particle size distribution, hydraulic gradient, and water temperature. It determines for itself the fluid (in this case, water) viscosity from the temperature given.

It uses the J.S. Kozeny (1931) inspired technique whereby an equivalent pipe diameter can be assigned to this soil aggregation. He realized, quite brilliantly, that this could be justified by equating the Fluid Mechanics parameter, hydraulic radius, to the Soil Mechanics ratio of pore volume to surface area of all the grains. Once in the pipe analogy mode it is a simple matter to determine conductivity from a combination of the Darcy–Weisback formula and the Colebrook equations for surface roughness (e/D = 0.05 adopted herein). Flows ranging from laminar to turbulent are assigned based on Reynolds Number, and where transient conditions are sometimes found to be appropriate for coarse sands.

Interpretation of Cone Penteration Test data


This program takes the standard output of piezo-electric cones and then uses the generally sanctioned relationships published by others, including UBC, to calculate soil parameters. What is perhaps unique about this program is the way it computes effective vertical pressure: in fine soils it uses moisture content of nearby sampling, and for granular soils it uses relative densities computed from tip resistance, to find void ratio. Then assuming G=2.65 it finds unit weights. If the tip was above the water table it assumes S=25%. It also prints out the thickness of strata by accumulating adjacent slices of the same soil–type.

Falling Sphere velocity-distance Relationship


This program computes the velocity and vertical position of a solid spherical object at any time following its release from a stationary position beneath the water surface. It requires input for sphere diameter, specific gravity of solid, and water temperature. It is a simple but tedious incrementation of the spheres fall under gravity while being retarded by hydraulic drag forces. The time intervals must be very small to achieve accuracy. Once the steady state condition of Terminal Velocity is achieved, the program stops.

Hydraulic Gradient during Soil-Water relative movements


This is the program Hodge used to compute the "Crowding-factor" [K] and the excess hydraulic gradient to be attributed to relative movement between water and a multi-sized aggregation of solid spheres. For a more detailed explanation of what is involved it is best to read the GN articles.