An Improvement of Bearing Capacity of Soft Soil and Reducing Excess Porewater Pressure Using Several Patterns of Floating Stone Columns

Floating Stone Columns in Thick Soft Soil

  • Mahdi Karkush Professor
  • Anwar Jabbar M.Sc. University of Baghdad


One of the common geotechnical problems is the construction on the soft soil and improvement to meet the design requirements. A stone column is one of the well-known techniques used to improve the geotechnical properties of soft soils. Sometimes thick layers of soft soil imposed the designer to use floating stone columns for improvement, in this case, the designer will be lost the end bearing of the stone column. In this study, the effects of several patterns of floating stone columns distribution under footing on the bearing capacity of soil and distribution of porewater pressure are investigated. The soft soil used in this study has a very low undrained shear strength (cu) of 5.5 kPa and improved by several patterns of stone columns (single, linear, triangular, square, and quadrilateral). The stone column has a length of 180 mm and a diameter of 30 mm. The material of the stone column is poorly graded sand has a high angle of internal friction (48.5°) at a relative density of 65%. The results indicated a significant increase in the ultimate bearing capacity of soft soil when treated with stone columns in spite of the small ratio of area replacement and reducing the excess porewater pressure and settlement. Also, the ultimate carrying capacity of soil calculated from experimental work is compared with some of the proposed equations in the previous studies to evaluate the validity of using such equations.

Author Biography

Anwar Jabbar, M.Sc. University of Baghdad

Master of gotechnical Engineering

Civil Engineering