## 4 Concluding Remarks  
The foundation settlements, contact pressure of the soil, and the coefficient of the subgrade reaction were investigated for square raft foundations located at the surface of clayey and sandy ground under a uniform vertical load. The Mohr-Coulomb model was used to model the soils, with the strength parameter corresponding to various shear wave velocities of the soil (\(V_{s}\leq 180\) m/s). The findings are summarized as follows:  
1. For the raft foundation models simulated in this study, the rigidity of the foundation \(K_{r}\) was calculated following the Egyptian code. The values of \(K_{r}\) were in the range of 0.005-0.1, indicating that the foundations were semi-rigid. The maximum foundation settlements were found at the center of the foundation models. The foundation settlements decreased with increases in soil stiffness. 2. The contact pressure distribution was significantly affected by the rigidity factor of the foundation and the soil stiffness. For the rafts with \(L=16\) m in clay, the contact pressure was relatively consistent. For the raft with \(L\geq 26\) m in very soft clay, the contact pressure was found to be low at the center and high at the edges. As the clays became stiffer, a higher contact pressure was then noted at the center. For the foundation with \(L=16\) m in sandy soil, the contact pressure was independent of soil stiffness and was low at the center. For the foundation with \(L\geq 26\) m in sandy soil, high contact pressure was observed at the center. This pattern was more prominent in soil with higher soil stiffness. Owing to the discontinuity of the structure geometry, sudden changes in contact pressures near to the edges were observed in all cases; however, it was negligible for high soil stiffness. 3. Unlike the distributions of contact pressure, the distributions of coefficients of subgrade reactions of the soils under the raft were found to be more consistent. They will be generally lower at the center and become higher at the edge. For the smallest rafts in clay, the coefficients of subgrade reaction would be slightly varied under the foundation. 4. The coefficient of subgrade reactions \(k_{s}\) is suggested by mathematic function. The value of \(k_{s}\) can be determined by multiplying the reference value \(k_{sc}\) at the center of the foundation with a 2D polynomial function. For raft foundations in sand, the functions are only dependent on foundation dimensions. For raft foundations in clay, the functions are dependent on both soil stiffness and foundation dimension. 5. With the presumed design loads, the coefficient of subgrade reaction \(k_{sc}\) at the center of foundations was found to be 1186-1768 kN/m/m\({}^{2}\), 2201-3983 kN/m/m\({}^{2}\), and 7456-8078 kN/m/m\({}^{2}\) for Clay 1, Clay 2, and Clay 3, respectively. Similarly, for Sand 1, Sand 2, and Sand 3, the value of \(k_{sc}\) was found to be 4948-5281 kN/m/m\({}^{2}\), 7808-8793 kN/m/m\({}^{2}\), and 11,262-13,075 kN/m/m\({}^{2}\), respectively. It is noted that the value of \(k_{sc}\) will be affected by foundation dimensions. 6. It should be noted that the actual stiffness of sand in the field could be much higher than the values obtained in this study. Much higher values of \(k_{sc}\) for sand should be expected in actual applications. In spite of the possible influence of \(k_{sc}\), the suggested functions are applicable to sand because the influence of soil stiffness was found to be trivial to the proposed functions in sand.