Construction Site Preparation
The Construction Site Preparation site should be surveyed before
The centre line of one of the longest walls should be marked by stretching the string between two wooden pegs driven at two ends. The centre lines of walls are set out with reference to the above line made in the plan. The pegs should be ﬁxed at about 1 metre outside the limits of excavation. The top of all pegs should be in horizontal level irrespective of the level of the ground. All lines at right angles should be ﬁxed by” using 3:4:5 method.
The setting out and checking right angles can also be done by using wooden square. For large and important works, instruments like dumpy level/theodolite may be used. The measurement should be made only by using steel. The accuracy of right angles should be checked by measuring the two diagonals from opposite corners which should be equal to each other. If there is any difference, either in the sides or diagonals, the errors are to be neutralised by adjusting the position of the strings of the pegs.
Small wire nails should be driven at the exact string points on the pegs. On either side of the centre line, the foundation trench lines are marked with a pick-axe. Once lines are marked, the pegs and the strings may be removed.Instead of driving the pegs on the ground, masonry pillars can be built about 1 metre away from the outer edges of excavation with a width of about 300 mm. wider than the foundation trenches. After hacking the lines, the strings stretched on the central points are pressed by a mason’s trowel after applying some cement mortar on the top of the pillars.
Thus the centre line of walls and the outer line of foundation trenches are ﬁxed permanently for cross reference during construction work.The first peg has to be driven on the South-West corner of the plot and the other one on the South-East corner with reference to the ﬁrst peg; The third side should be at North-West. The fourth side should be at North East.The excavation will be conducted over the entire foundation and the work should be done in layers.
The details have not been explained in this book and the sizes and the arrangements of timber to be used depend upon the nature of soil and depth of cutting.Sometimes, the underground water level will be high, and the underground water is met within the foundation trenches.The water should be drained before laying the foundation. A simple method will be by providing drains by the side oftrenches and providing a shallow sump well at one end of the lowest point to collect water from them which can be drawn out by means of pumps or buckets. in some cases, water has to be pumped out and various kinds of pumps are available in the market.
The common tools used for excavation works are
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