Size Columns Settlement For Free

As a first approximation, a general value of the critical column length of 2 and 2.5 times the footing diameter may be considered for ordinary and encased stone columns, respectively.

Stone column ground improvement involves adding vertical columns of stone into the ground to a depth of at least 4m below the ground surface. A layer of compacted gravel can then be put over the top of the columns, ready for the construction of new house foundations.

An optimum area replacement ratio of 30?40% exists for the control of settlement. The settlement performance of a small column group is highly influenced by inter-column and footing interaction effects.

When the columns are installed, the area replacement ratio is defined as the ratio of the cross-sectional area of a column to the tributary area of the column, as shown in Figure 1. Under rigid loading, the stress distribution on the columns and the soil can be simplified as shown in Figure 2.

Priebe?s method is based on the unit cell concept and the columns are considered to be in a plastic state, while the surrounding soil behaves elastically. The solution is given as a settlement improvement factor, n, defined as the ratio of the final settlement with and without columns.

The key parameters relevant to the design of floating stone columns include the area replacement ratio, the friction angle of the column material, the loading intensity, and the post-installation earth pressure.

The area replacement ratio may also be expressed as follows: as = 0.907 (D/S)2 where the constant 0.907 is a function of the pattern used which, in this case, is the commonly employed equilateral triangular pattern. The value of n generally lies between 2.5 and 5 at the ground surface.