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

Figure 8-1: Corrected blow count versus residual undrained shear strength (Brown et al. 2010)

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Soldier Rev B

8.3.3 Time-History Analysis

Figure 8-1: Corrected blow count versus residual undrained shear strength (Brown et al. 2010).
Liquefaction may also result in settlement, where the liquefied layer will generally consolidate as pore water pressure dissipates (settlement may also occur due to soil loss from sand boils to the ground surface) If liquefaction occurs below the neutral plane, the axial compression load in the pile will increase along with additional pile settlement. The pile foundation must be structurally capable of supporting the increased drag force. A check should also be performed to ensure any additional settlement is within the structure’s performance criterial. Settlement magnitude can be estimated using procedures in Kavazanjian et al. (2011). Liquefaction can also cause lateral deformations due to lateral spreading or lateral flow as discussed in
Kavazanjian et al. (2011). If there is potential for sliding, lateral spreading or lateral flow, foundations should be designed to accommodate the associated lateral loads. P-y curves can be adjusted to evaluate the bending moments and deformations. Reese’s soft clay p-y curve with low residual shear strength and high values in the liquefiable layer is often used to evaluate the maximum bending moment (Hannigan et al. 2016). Hannigan et al. (2016) also recommends using p-multiplier values of 0.05 in loose sand and
0.30 in dense sand to model foundation p-y response in fully liquefied granular layers.

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8.3.3
Time-History Analysis
For bridges classified as Seismic Zone 4, or for bridges that are geometrically complex or close to an active fault, a time-history structural analysis of the bridge is required by AASHTO (Brown et al. 2010). This analysis involves development of a site-specific time history that is used in structural modeling and analyses as discussed in Kavazanjian et al. (2011). This type of analysis is complex and must be performed by a specialist.

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