An equation for the forces acting on a pile at equilibrium: P = pA + tS + Sn sin ϕ, where P is the load, A is the area of the pile point, p is the force per unit area on the point, S is the embedded surface of the pile, t is the force per unit area parallel to S, n is the force per unit area normal to S, and ϕ is the taper angle of the pile.