Definition of Fines and Liquefaction Resistance of Maoluo River Sand Tzou-Shin Ueng Chia-Wen Sun and Chieh-Wen Chen National Taiwan University

INFLUENCE OF FINES ON LIQUEFACTION RESISTANCE Youd, et al. (2001) (N1)60cs = a + b (N1)60 FC ≤ 5%, a = 0, b = 1.0 5% < FC < 35%, FC ≥ 35%, a = 5.0, b = 1.2 FC ↑ Liquefaction Resistance (CRR) ↑

DEFINITION OF FINES Fines Content FC = Percent of soil with grain size, D < No. 200 sieve (0.075 mm)

ALTERATIVE DEFINITIONS OF FINES Clay size, D < 5 mm (Chinese Criteria) FC = Percent of soil with grain size, D < No. 400 sieve Any difference or better? (0.038 mm)

MAOLUO RIVER SILTY SAND Specific gravity 2.68 In situ rd 1400 kg/m3 D50 0.078 mm Cu 43 Maximum rd 1717 kg/m3 Minimum rd 1290 kg/m3 LL 23 PI NP FC (< 0.075 mm) 48 % USCS SM

PROPERTIES OF DIFFERENT GRAIN SIZE RANGES Gs LL PI USCS > #200 sieve (> 0.074 mm) 2.67 ─ SP < #200 sieve (< 0.074 mm) 2.69 36 8 ML > #400 sieve (> 0.038 mm) 2.68 29 SM < #400 sieve (< 0.038 mm) 2.70 38 15 CL Mineral Compositions (%) Grain size Rock fragments Quartz Feldspar Mica Illite Chlorite Kaolinite > #200 24 68 5 3 < #200 > #400 87 7 ≤ #400 41 28 25

CYCLIC TRIAXIAL TESTS Dry density, rd = 1400 kg/m3 Fines contents Defined as D < #200 sieve: 0%, 20%, 48%*, 65%, 100% Defined as D < #400 sieve: 0%, 10%, 20%, 30%, 37%*, 100% * in situ soil Confining press, s’c = 78 kPa Frequency = 1 Hz

LIQUEFACTION RESISTANCES Fines defined as D < #200 sieve

EFFECT OF FINES CONTENT ON LIQUEFACTION RESISTANCE

INDEX DENSITIES FOR DIFFERENT FINES CONTENTS

SOIL STRAIN AND STRESS RESPONSES Fines defined as D < #200 sieve

LIQUEFACTION RESISTANCES Fines defined as D < #400 sieve

SOIL STRAIN AND STRESS RESPONSES Fines defined as D < #400 sieve

COMPARISON OF EFFECT OF FINES CONTENTS

EQUIVALENT FINES CONTENTS Fines Definition Fines Contents (%) D < #400 sieve 10 20 30 37 100 D < #200 sieve 17.5 25.7 34 42.2 48

EQUIVALENT FINES CONTENTS Fines Definition Fines Contents (%) D < #200 sieve 20 48 65 100 D < #400 sieve 15.4 37 50 77 Equivalent D < #400 sieve

CONCLUDING REMARKS Soils with particle size between 0.038 mm and 0.075 mm is essential a very fine sand. The effect of FC on the liquefaction resistance is more prominent for fines defined as D < 0.038 mm than those with fines defined as D > 0.075 mm. Corrections solely based on FC without considering the properties of fines cannot truly reflect the influence of fines on liquefaction resistance. No clear benefit yet to change the present definition of fines, i.e., D < 0.075 mm.