Liquefaction Mitigation of Silty Sands in Utah Using Stone Columns with Wick Drains

Abstract

This paper presents a case history in which pre-fabricated vertical (wick) drains were used in connection with stone column treatment for a 4 m thick layer of liquefiable silty and to sandy silt. Despite the high fines content, which ranged from 31 to 88%, the average (N 1 ) 60-cs increased from an average of 17 before treatment to 33 after treatment, an increase of 94%. This increased penetration resistance is similar to that observed at the Salmon Lake Dam where similar soils were encountered and wick drains were also used. The stone column treatment in the silty sand/sandy silt layer with a replacement ratio of 27% was about as effective as stone column treatment in cleaner sand (less than 15% fines) with a replacement ratio between 10 and 15%.