Building foundation structure
For any type of structure, the foundation has to be constructed below the ground surface. Foundation in order to rest on a hard surface, the base level of the foundation is to be excavated. For this purpose, the trenches are dug by hand tools such as pick-axe, chisel, hammer etc. in case of foundations having single wall buildings. In case of large project work of the foundation of the building structure, the trenches are dug by mechanical diggers. During the process of excavation, there is a chance of collapse of the sides and in order to prevent this temporary timbering support to the excavated trenches is given to uphold the sides of the excavation. Thus it also protects the labors working in the trench. The type of timbering support and its erection for trenches depends upon type and characteristics of rock or soil.
Face Line Method: In this method center line is not taken into account. In load bearing structure, each face of the foundation trench is measured from the edge of plot and fixed by wooden pegs. In case framed structure, each face of the column footing is measured from the edge of plot boundary and then it is being marked on the ground.
Timbering and strutting: It is the method of giving the temporary support to the sides of the trench, when the depth of the trench is large or when the sub-soil is loose or soft.
Explain earthwork for embankment: For all large embankments, before the starting of actual work, the center line should be marked by pegs at suitable intervals, properly laid out curves, at the top and bottom edges of the excavation. The site must be cleared of all trees, grass and any other obstructions if any, to receive the new excavated earth. All loose surface or soft soil should be removed. In case of embankments for a dam, sand or gravel is mixed with clay. From a stability point of view, the embankment must be non-slippery and water tight.
Line Method: In this method, in case of load bearing structure before the commencement of the excavation of trenches for the foundation, foundation plan is first prepared. The plan is fully dimensioned at all breaks and openings.
The center line of the wall, which is perpendicular to the long wall is marked by setting up a right angle. A right angle is set up by forming triangles with sides 3, 4 and 5 units long. This can also be done with the help of theodolite.