Effect of Spacing between Stone Columns on the Behavior of Soft Soil

Zeena A Al-Kazzaz,Moataz A Al-Obaydi,M Karkush,D Choudhury,M Fattah

doi:10.1051/e3sconf/202131801006

Abstract

Soil improvement by stone columns is extensively used, especially for the soft ones. This is because of their efficiency and no environmental impact. Several factors affect its efficiency in improving the mechanical properties of the soil, and the most important of these factors are the spacing, length, and diameter of the stone columns. In this study, the finite element method was used to study the impact of the spacing between the stone columns on the amount of settlement and the bearing capacity of the soil. The study comprises three different spaces (s) that were taken in relation to the columns’ diameter (d), which are (s/d= 3, 4, and 5). In addition, three types of the sectional shape of column involved circular, rectangular, and square sections with different lengths of (L/d=2, 4, 6, 8, and 10). The results showed that the spacing between the stone columns is effective when the vertical load is greater than 30 kN/m2, and below this, there is no effect of the spacing. In general, the settlement decreases, and the bearing capacity increases with the decrease in the spacing between the stone columns. The spacing becomes a more pronounced effect with the longer length of the stone columns. All sections of the stone columns with a short length of (L/d=2) showed the same settlement of 271 mm at a distance (s/d=5), which decreases by 7.4, 6.6, and 8.9% at a distance (s/d=3) for the circular, rectangular and square sections respectively. In the case of long columns (L/d=10), the settlement at (s/d=3) improves by about 27.5% which drop to about 18% at (s/d=5). A slight improvement in the soil's bearing capacity is associated with decreases in the spacing between the stone columns. The improvements in the bearing of soil treated with short columns (L/d=2) are 6.0, 6.5, and 4.7% for circular, rectangular, and square sections, respectively, when changing the distance from (s/d=5) to (s/d=3). Whereas they become greater when increasing the columns’ length to (L/d=10) to be 7.9, 9.2, and 6.4%.

Highlights

Stone Columns method is an efficient, low-cost, and environmentally friendly technique used to enhance the properties of soft cohesive and non-cohesive soils
From the results of the laboratory tests on a rigid footing underneath by a soft soil treated with floating stone columns, Black et al [5] concluded that the maximum settlement takes place at an area replacement ratio of 30%
It can be seen that the rate of improvement in settlement owing to the spacing ratio (s/d) increases with increasing the length of the columns

Summary

Introduction

Stone Columns method is an efficient, low-cost, and environmentally friendly technique used to enhance the properties of soft cohesive and non-cohesive soils. El-Garhy et al [7] found experimentally improving the settlement and bearing capacity functional to the area replacement ratio of the soft soil treated with floating granular stone columns. The bearing capacity of the stone columns group increased with decreased spacing between columns, i.e., increased the area replacement ratio. Bonab et al [13] showed that the bearing capacity of the soft soil increased with increasing the diameter of stone columns and area replacement ratio. From their experimental results, Bouziane et al [14] concluded that the spacing between stone columns arrangement in square or triangular scheme control the performance of the soil-stone columns system. The columns’spacing effect on some engineering properties of the soft soil was numerically studied using PLAXIS-2D code in the case of rectangular and square sections in addition to a circular section

Analysis Procedures

Results and Discussion

Conclusions