LiquefactionSI - Table 1: Factors affecting cyclic mobility...

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Table 1: Factors affecting cyclic mobility or soil liquefaction characteristics and penetration resistance (After Seed, 1979) Factor Effect on stress ratio required to cause cyclic mobility or liquefaction Effect on penetration resistance Increased relative density Increases stress ratio for cyclic mobility or liquefaction Increases penetration resistance Increased stability of structure Increases stress ratio for cyclic mobility or liquefaction Increases penetration resistance Increase in time under pressure Increases stress ratio for cyclic mobility or liquefaction Probably increases penetration resistance Increase in K 0 Increases stress ratio for cyclic mobility or liquefaction Increases penetration resistance Prior seismic strains Increases stress ratio for cyclic mobility or liquefaction Probably increases penetration resistance Table 2: Recommended SPT procedure for use in liquefaction correlations (Seed et al., 1984) Borehole 4 to 5-inch diameter rotary borehole with bentonite drilling mud for borehole stability Drill Bit Upward deflection of drilling mud (tricone of baffled drag bit) Sampler Outer Diameter = 2.00 inches Inner Diameter = 1.38 inches – Constant (i.e. no room for liners in barrel) Drill Rods A or AW for depths less than 50 feet N or NW for greater depths Energy Delivered to Sampler 2520 in.-lbs. (60 % of theoretical maximum) Blowcount Rate 30 to 40 blows per minute Penetration Resistance Count Measures over range of 6-8 inches of penetration into the ground
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Table 3: Summary of the correction factors for SPT measurements (After 1997 NCEER Workshop) Factor Term Equipment Variable Correction Overburden Pressure C N - (P a / σ′ v ) 0.5 C N 2 Energy Ratio C E Safety Hammer Donut Hammer 0.60-1.17 0.45-1.00 Borehole Diameter C B 65-115 mm 150 mm 200 mm 1.00 1.05 1.15
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LiquefactionSI - Table 1: Factors affecting cyclic mobility...

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