The bearing capacity of a circular footing on gypseous soil before and after improvement

الملخص EN

Bearing capacity of soil is an important factor in designing circular footing.

It is directly related to foundation dimensions and consequently its performance.

The calculations for obtaining the bearing capacity of a soil needs many varying parameters, for example soil type, depth of foundation, unit weight of soil, etc.

In this work, the comparison between the values of bearing capacity of circular footing on gypseous soil before and after improvement determined by two different methods, the first method using compacted cement dust (Case1).

The improvement were performed by making trench under the footing filled with compacted cement dust (at its optimum moisture content) at three depths [(Depth of trench, D =Width of trench, B =2 * the radius of footing R); (D=2B=4R) ; (D=3B=6R)], the trench had the same footing Dimensions, The second method is reinforcing gypseous soil with biaxial geogrids (Case2) have been shown to be an effective method for improving the ultimate bearing capacity of granular soils.

The ultimate bearing capacity of footing is estimated in terms vertical load and the generated settlement curves by using PLAXIS 2D Professional v.8.2.

The computer program uses a finite element technique to solve the two dimensional problems of soil improvement.

The improvement ratio in bearing capacity (BCR) was calculated by comparing the ultimate bearing capacity value when testing gypseous soil alone with its value of gypseous soil improvement.

The ultimate bearing capacity obtained from the using compacted cement dust tests has been analyzed and compared with the value developed by reinforcing soil.

From the results, it was found that the compacted cement dust in case1 has BCR at D=2R larger than BCR values occurred from single–layer reinforced soil but multi-layer reinforced soil N=2 and 3, indicated more larger than case1 improvement with dust cement.

The optimum geometry of the geogrid layes is [N=3; depth of the first layer, u=0.3; distance between geogrid layers S=0.3; and width of geogrid layer b=4], which it gives ultimate bearing capacity more than when used compaction layers of cement dust with depth, [D=4R or D=6R].