Sand and stone columns in soft soil at different relative densities

Abstract

The technique of sand or stone columns is widely used to improve the load carrying capacity and reduce the settlement of soft soils. The technique consists of excavating holes of specific dimensions and arrangement in the soft soil and backfilling them with either stone or sand particles. The efficiency of the technique depends primarily on the type of the backfill material (sand or stone) and gradation as well as the placement relative density. In the present research, holes 50 mm in diameter and 300 mm in length were excavated in a bed of soft soil, 400 mm in thickness, of undrained shear strength between 16-19 kPa. The holes were backfilled with either sand or stone particles at loose and dense states. Each column was loaded gradually through a circular rigid footing 64.6 mm in diameter up to failure with continuous monitoring of the settlement. The outcomes of the model tests revealed that for both floating and end bearing types, the sand columns at low relative density exhibited higher bearing improvement ratios and lower settlement reduction ratios compared to stone columns. On the other hand, a reverse behavior was noticed, when the backfill material was placed at "dense state". The results shed the light on the importance of placement relative density of both backfill materials. The results are thoroughly analyzed in terms of the stress concentration ratio and stiffness ratio.

Shear Strength and Consolidation Behaviour of Kaolin Clay Reinforced with a Granular Column Backfilled with Crushed Waste Glass

“…The column backfill material is commonly selected based on suitability, economy and availability (Baumann and Bauer 1974;Zukri and Nazir 2018). Crushed stone is often preferred due to its high friction angle and stiffness (Al Saudi et al 2016). However, sand could also be used where crushed stone is unavailable (Kadhim et al 2018).…”

“…IS 15284 (2003) broadly suggests that well-graded granular materials ranging from 2 to 75 mm may be used as column backfill. However, almost no specifications are currently available in the published scientific literature on the optimal particle size range (PSR) of column backfill (Al Saudi et al 2016). Siahaan et al (2018) also mentioned that the role of particle size of the column backfill on the geotechnical behaviour of granular columns remains relatively under-researched.…”

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

“…After… completion of… the final… layer, the… top surface… was scraped… and… leveled to… get as near… as a flat… surface. The models…consist of… eight columns… at area… replacement ratio… of (0.196) in… a square pattern the… configuration of… the columns… shown in figure (4). PVC… tube (50 mm… in diameter and 500…mm in… height) was… inserted vertically… to the required… depth (300 mm… from the… top surface) and… the soil was… removed completely… inside the… tube.…”

Studying the Behavior of Expansive Soil Reinforced by Micropiles

“…The outcomes of the experiment revealed that the micro piles will resist deflection of the soil and expand the zone at failure if the micropile depth is long enough relative to the thickness of the footing's failure surface. However, a field study examining the application of micro piles for methods of ground improvement has been done [15][16][17].…”