Treatment of soil swelling using geogrid reinforced columns

Raid R. Al-Omari (*), Mohammed Y. Fattah (**) & Haifaa A. Ali (***)
(*) Professor, Civil Engineering Department, College of Engineering, Al-Nahrain University, Baghdad, Iraq.
(**) Professor, Building and Construction Engineering Department, University of Technology, Baghdad, Iraq. Corresponding author e-mail: myf_1968@yahoo.com
(***) Lecturer, Civil Engineering Department, College of Engineering, University of Baghdad, Iraq.

In this paper, a method of treatment of swelling of expansive soil is presented. The method is simply based on the embedment of a geogrid (or a geomesh) in the soil. The geogrid is extended continuously inside the volume of soil where the swell is required to be controlled and orientated in the direction of swell. Soils with different swelling potentials are employed; bentonite "which is mainly composed of montmorillonite" base-Na and bentonite base-Ca in addition to kaolinite mixed with bentonite. To investigate the swell, swell-partial shrinkage and other phenomena for untreated soils in comparison with their counterparts treated soils, small scale tests were carried out in ASTM CBR (California Bearing-Ratio) mould. Each soil sample was compacted at dry side of the compaction curve using static compaction test. Swelling and consolidation tests were carried out on each sample. Geogrid columns of different diameters; 20, 30 and 50 mm were inserted through the swelling soil and filled either with the same clay or with sand. A considerable effect of geogrid was observed on the restriction of swelling in the soil. The dependence of swell on reinforcement stiffness substantiates the anticipation that soil-reinforcement bond would be so strong that the clay cannot expand unless the reinforcement is extended. Swell increases with the column diameter. The gradual increase in the diameter of geogrid reinforced column provides the cylinder with the largest surface area that supports the increase of the interlocking interface with the soil. Using sand as a fill material in the geogrid reinforced columns is more effective than using the same treated soil since sand is more permeable and less compressible than clays.

swelling soil, treatment, geogrid, sand columns.