Free P-Y Curve Generator — Matlock, Reese, API Sand & More
Generate p-y curves online for Matlock soft clay, Reese stiff clay, Reese and API sand, and weak rock — plotted and tabulated, free, no login.
How to use it
- 1
Pick the p-y model
Choose from Matlock soft clay, Welch & Reese stiff clay (above water), Reese-Cox-Koop stiff clay (below water), Reese sand, API sand, or Reese weak rock.
- 2
Set the state
Enter the depth below ground, pile width, and effective unit weight; choose static or cyclic loading.
- 3
Enter the model parameters
Each model asks only for its own inputs — undrained strength and ε₅₀ for clays, φ and k for sands, qᵤ, RQD and Eᵢᵣ for weak rock.
- 4
Read the curve
The tool evaluates the exact published formulation and returns the plotted curve, a point table, method ID, and the ultimate resistance pᵤ.
Why generate a single p-y curve?
A p-y curve is the nonlinear relationship between lateral soil resistance p (force per unit length of pile) and lateral deflection y at one depth. A full analysis builds one at every node, but looking at a single curve is how engineers actually develop judgment: it shows how stiff the soil is at working deflections, where it plateaus, and how sensitive the response is to each parameter. It's also the fastest way to hand-check what a program is doing internally — if the curve at 3 m doesn't match the published formulation, neither will the pile response.
The models, exactly as published
This tool evaluates the same implementations PileCalc's solver uses, validated against LPILE and RSPile: Matlock (1970) soft clay, Welch & Reese (1972) and Reese, Cox & Koop (1975) stiff clay, Reese (1974) and API / O'Neill & Murchison sand, and Reese (1997) weak rock. Each model page walks through the equations, parameters and a worked example. Supply the effective unit weight (total above the water table, buoyant below) — the tool computes the vertical effective stress at your depth from it.
Common questions
Go deeper
Need layered soils, reports, or saved projects?
The full app runs the same reviewed engine with broader declared input domains, method metadata, layered profiles, reports, and saved versions.
Open the full app