Schmertmann method The Schmertmann method () calculates settlement from layer stiffness data or cone tip bearing resistances, q c obtained from a Cone Penetration Test (CPT). The method proposed a simplified triangular strain distribution and calculates the settlement accordingly. A time factor can also be included to account for time dependent (creep) effects. The equation for settlement is: Where C 1 = the correction to account for strain relief from excavated soil, σ cd' = effective overburden pressure at bottom of the footing Δ P = the net applied footing pressure (equation) C t = correction for time-dependent creep, t = time (years) E si = one-dimensional elastic modulus of soil layer i Δ z i = thickness of soil layer I zi = the influence factor at the centre of soil layer i as described below. Influence factors The influence factor, I z is based on an approximation of strain distributions below the footing. There are two possible formulations for I z; the original 1970 approximation and the improved 1978 approximation. 1970 formulation This is described in Schmertmann (1970).
The strain influence factor I z increases linearly from zero at the bottom of the footing to a maximum of 0.6 at a depth of ½ B below the footing where B is the footing width. The strain influence factor then decreases linearly to zero at a depth of 2 B below the footing bottom. This distribution is shown below. Strain influence factors from Schmertmann () 1978 formulation This is described in Schmertmann et al (1978).
With this method, the peak value for I z is calculated by Where σ op' is the effective overburden pressure at the depth of I zp. The depth of I zp depends on the shape of the load. For an axisymmetric load (a circle or a square), I zp occurs at a depth of B/2. For the plane strain case (length of the load is >10x the width), the I zp occurs at a depth of B. The values for I z (shown in the figure below) are calculated as follows: Axisymmetric: I z varies linearly from 0.1 at the bottom of the footing to I zp at a depth of B/2. The strain influence factor then decreases to zero at a depth of 2 B.
This application calculates settlement of a footing placed on a cohesionless material (sand) using the Schmertmann method (Schmertmann, 1970, Schmertmann et al, 1978). Ace Utilities Activation Code there. Fleet Command Windows Vista.
Plane strain: I z varies linearly from 0.2 at the bottom of the footing to I zp at a depth of B. The strain influence factor then decreases to zero at a depth of 4 B. In the Schmertmann calculator, I z is calculated using the axisymmetric equations for circle and square loads. For rectangular loads in which the length is greater than ten times the width, the plane strain approach is used. For rectangular loads in which the length is less than ten times the width, a linear interpolation between the axisymmetric and plane strain case is performed, dependent on the length to width ratio. Strain influence factors from Schmertmann et al. Dilwale Dulhania Le Jayenge Blu Ray Video Songs. Stiffness conversion The elastic modulus E s can be estimated from the results of a Cone Penetration test: E s = 2.0 q c (1970 formulation) E s = 2.5 q c (1978 formulation, axisymmetric footing) E s = 3.5 q c (1978 formulation, plane strain footing) where q c is the cone tip bearing resistance.