Engineering Projects

Raft Foundation Design General Considerations A mat supported on strong bedrock transmits the load in a relatively small area near columns. The pressure distribution on raft foundation will be as shown Fig. 1(a). If the mat rests on stiff or compact soils, the mat distributes the load to the subsoil in larger areas as shown in Fig. 1(b). If the mat rests on weak soil the pressure distribution on the mat tends to be uniform as shown in Fig. 1(c). In raft foundation design, the stresses developed underneath the mat…

The settlement is not a problem for raft on sands as allowable bearing capacity is computed on the basis of settlement criteria. However, settlement is of great concern when a raft rests on a deposit of normally consolidated clay. The net foundation pressure for computing settlement is taken as:    ———– (1) The pressure in the Eq. (1) shall not cause settlement in excess of permissible value. If settlement exceeds the permissible limits, the foundation pressure should be reduced either by increasing the area under the structures or by increasing…

What is Bearing Capacity of Mat Foundation? Cohesionless Soil – In cohesionless soil a mat foundation does not fail in shear. For example, the bearing capacity of a raft foundation having a width of 6 m, and founded to a depth of 3 m in a sand deposit having relative density corresponding to SPT N-value of 10 is about 700 kN/m2 which is extremely high. In such case, the foundation may experience excessive settlement or even fail before attaining a bearing pressure of the order cited above. This means that the…

A mat foundation is a thick reinforced concrete slab supporting arrangements of columns or walls in a row or rows and transmitting the loads to the soil. It is used to support storage tanks, industrial equipment, silos, chimneys, and various tower structures. A mat foundation is used when the subsoil is weak and column loads are so heavy that the conventional spread footings cover more than 50 % of the building area. It is common to use mat foundation or deep basements to transfer the column loads to the underlying…