Comparison between Sand Columns and Sand Columns Stabilized with Lime or Cement with Stone Columns Embedded in Soft Soil

Abstract

Sand and stone columns are used to improve bearing capacity of soft clayey soils… because of their stiffness which is higher than the soil was replaced, the compacted columns… produce shearing resistances which provide vertical support… for overlying structures… or embankments. Also the sand… and stone columns… accelerate the settlement… in the native surrounding soil… and improve the load settlement… characteristics… of foundation. The technique… consists of excavating… holes of specific… dimensions and arrangement… in the soft soil… and backfilling… them with either… sand or… stone particles.The present work investigates the behavior of soft soil reinforced with group of stone columns, sand columns and sand columns stabilized with lime or cement. The percentage of lime and cement used in this research, were determined previously in papers of single sand column stabilized with lime and cement, 11% by weight lime and 9% by weight cement. The model tests were carried out on a soil with undrained shear strength ranging between 16-18 kPa. The models consist of eight… columns at area replacement ratio of (0.196) in square pattern, the holes 50 mm in… diameter and 300 mm… in length were excavated… in a bed… of soft soil. The holes… were backfilled… with stone, sand and sand… stabilized with lime or cement particles. Each group… of columns was loaded… gradually through… a rectangular… rigid footing, its dimensions… 400×200 mm with 50 mm thickness, up to failure… with continuous… monitoring of the settlement. The test… results are analyzed… in terms… of bearing improvement… ratio… and settlement reduction… ratio for all… columns… and in terms… of the stress… concentration… ratio and… stiffness ratio.The results show that the improvement in bearing capacity was about 70% and 62% for sand columns stabilized by lime and cement respectively, and the improvement in bearing capacity was about 42% and 34% for sand columns stabilized by lime and cement compared with stone columns respectively.

Numerical Study of Stress Distribution in Soft Clay Treated with Stone Column

“…Then, for the sand column, it was 1.5, and n for the sand +11 % lime was 2. The stiffnesses of both types of columns improved by 1.7 to 5.5 and 6.5 percent, respectively [10]. The unit cell or plane strain model can calculate n for a stone column to account for this.…”