Driven Pile Sand TZ (Mosher) [Mosher, 1984]

[Mosher, 1984] developed load-transfer criteria for axially loaded piles in sand from instrumented pile tests at the US Army Waterways Experiment Station and proposed a hyperbolic side-resistance curve defined by the ultimate unit side resistance and an initial modulus:

$$\tag{1} t = \frac{z}{\frac{1}{K_t}+\frac{z}{t_u}}$$

where,

$t$ = unit side resistance (skin friction) $z$ = vertical displacement of the pile $t_u$ = ultimate (nominal) unit side resistance $K_t$ = initial modulus of side resistance

Initial estimates of $K_t$ by relative density:

Description	$ϕ$ (°)	$K_t$ (lb/ft²/in)
Loose	28–31	6000–10000
Medium dense	32–34	10000–14000
Dense	35–38	14000–18000

$t_u$ is entered directly as the ultimate shear stress of the layer; where it is not known, Figure 76 of [Mosher, 1984] relates it to relative depth and friction angle.

The WES report is on the DTIC server but could not be retrieved at the time of writing, so the model is implemented as it is reported in the secondary literature. It will be checked against [Mosher, 1984] once the report is obtained.

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[Mosher, 1984] Mosher, R. L. (1984). Load Transfer Criteria for Numerical Analysis of Axially Loaded Piles in Sand. Part 1: Load-Transfer Criteria. Technical Report K-84-1, U.S. Army Engineer Waterways Experiment Station, Vicksburg. (Report not on file.)