Experimental and numerical study for the optimization of bottom of foundation shapes on soft soils

Shallow foundations resting on a deep layer of soft saturated clay are considered a geotechnical challenge. The design engineer is faced with challenges in selecting safe and economic solutions for the foundations of these light weight structures by turning to the shell-shaped foundations to deal with such foundation problems and avoid the use of the costly deep foundations or other soil improvement schemes. This paper introduces different bottom of foundations shapes resting on extended soft clay layer in an effort to minimize the soil stresses and reduce the settlements. Elliptical, trapezoidal and inverted folded footings have been used as an alternative to the conventional flat bottom shallow footings. The purpose of the current study is to reach the optimal shape of the foundations, which achieves reduced stresses, reduced settlements and consequently cost. The geotechnical behavior of different bottom of foundation shapes resting on saturated soft clay is investigated experimentally and numerically. The experimental investigation started with studying a model for the conventional square flat footing shape resting over saturated soft clay. Elliptical, trapezoidal and inverted folded bottom of foundation models are tested and compared with the reference conventional square flat ones. In addition to the experimental study, a numerical analysis is performed using the finite element software ADINA. Verification of the numerical model is conducted first against the experimental results for all the studied cases. The verified numerical model is then extended to cover full-scale footing sizes of conventional and other studied footing cases and shapes. The optimum bottom of foundation shape is the one that gives the lowest soil stresses and consequently the lowest settlements.