Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities

A.6 P-Y CURVES FOR LIQUEFIED SANDS (ROLLINS ET AL. 2005)

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Soldier Rev B

Figure A Example p-y curve for liquefied sand (after Rollins et al. 2005).

A.6 P-Y CURVES FOR LIQUEFIED SANDS (ROLLINS ET AL. 2005)
Based on experiments, Rollins et al. (2005) developed a concave p-y criterion that increases the stiffness as pile deflection increases, as shown in Figure A, for liquefied sand. The proposed p-y curve is only a function of depth and the unit weight of the sand. The p-y criterion for liquefied sand proposed by Rollins et al., 2005 is given by
𝑝𝑝 = Equation A)
Where: A, B, and C are coefficients defined below p is the soil resistance (in kN/m); y is the lateral deflection of the pile/shaft (in mm and z is the depth (in m. The coefficients are defined as A = 3 (10
-7
) (z + 1)
6.05
; B = 2.80 (z + 1)
0.11
; and C = 2.85 (z + The use of Equation A should generally be limited to conditions comparable to those from which it was derived, specifically for soil resistance p of approximately 85 lb/in. or less, pile deflections of 6 in. or less, depth of 20 ft or less, and sands with initial relative densities of about 50 percent. The equation above was developed from a site where the groundwater was near the ground surface. For cases with different subsurface conditions, the depth (z) maybe selected so as to obtain initial vertical effective stresses that are consistent with those of the study by Rollins et al. (2005), for which the effective unit weight of the sand was approximately 61.8 pcf.

233
Figure A Example p-y curve for liquefied sand (after Rollins et al. 2005).
Note that Equation A is valid only fora pile diameter D = 324 mm (12 in. For other pile diameters, the
p
values should be corrected. The effect of diameter on the p-y curves developed by Rollins et al. (2005) was studied by Weaver et al. (2001) who proposed a modification factor for correcting Equation A as follows Equation A) Where D is the diameter of the pile in meters. The value of p calculated using Equation A is multiplied by P
d
to obtain p-y curves of piles for diameters other than the reference value. However, Equation A may not be appropriate for piles/shafts with diameters significantly smaller than approximately 0.3 minor larger than 1 min ln 𝐷𝐷 + 5.6

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