Figure 6-7: Basic wedge in uniform soil for SWM (from Ashour et al. 1988; refer to reference for

76 Similar to the p-y method, this method must be analyzed using computer software. Multiple programs capable of performing SWM are available commercially. The software inputs and design process for the
SWM are similar to those for the p-y method, although the way in which the soil resistance is computed is different from the p-y method. The SWM method is briefly described herein. Additional information regarding the use of SWM can be found in Norris and Abdollaholiaee (1985), Gowda (1991), Ashour et al.
(1996), Ashour et al. (1998), Pilling et al. (2001), Ashour (2002), Ashour et al. (a, Ashour et alb, Ashour and Norris (2003), Ashour et al. (2004), Ashour and Norris (2005), Shamsabadi et al.
(2005), and Ashour and Norris (2006). The method relates soil response and parameters participating in the D response of the wedge to the response and parameters of the one-dimensional case of the beam on elastic foundation pile/shaft system. The soil stress-strain and strength properties, which can be determined from laboratory triaxial testing, are used to relate the horizontal strain in the passive wedge in front of the pile/shaft to the deflection (y) versus depth. The horizontal stress change is related to the nonlinear modulus of subgrade reaction, which is the slope of the p-y curve. The SWM can therefore be used to develop p-y curves for soil (Brown et al. 2010). In this method, the passive wedge is divided into various horizontal slices or sublayers of constant thickness. In each slice, the soil is considered to behave uniformly, to be under plane stress conditions, and to have the same properties, which area function of the slice location. The deflection of the pile/shaft in front of the slice is controlled by equilibrium conditions according to the soil-pile/shaft interaction established. The wedge shape is affected by soil type and properties. The mobilized depth of the passive wedge at anytime is a function of the various soil parameters, stress levels, pile/shaft bending stiffness, and pile/shaft head fixity conditions. In general, the geometry of the passive wedge changes as the load increases while satisfying compatibility between pile/shaft deflections and soil modulus profiles. The strains are assumed to vary linearly over the depth of the passive wedge, as shown in Figure 6-8.

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