Batter boards, or slope rails as they are sometimes called, are used to control the construction of the side slopes of a cutting or embankment and . Consider . If the stake adjacent to the slope stake is set 0.5 m away, then, for a grade of 1 vertical to 2 horizontal, the level of point X will be 0.25 m higher than the ground level at A. From X, a batter board is fixed at a gradient of 1 in 2 (50%),
using a 1 in 2 template and a spirit level. Stakes X and Y are usually no more than 1 m apart. Information such as chainage, slope and depth of cut are marked on the batter board. In the case of an embankment , a boning rod is used in the control of the slope. Assuming that a boning rod 1 m high is to be used, then as the near stake is, say, 0.5 m from the slope stake, point x1 will be 0.25 m lower than the ground level at A, and hence point x will be 0.75 m above the ground level of A. The batter board is then fixed from x in a similar manner to that already described. The formation and sub-base, which usually have setting-out tolerances in the region of ±25 mm, can be located with sufficient accuracy using profiles and travellers.
Figure shows the use of triple profiles for controlling camber, whilst different lengths of traveller will control the thickness required. Laying of the base course (60 mm) and wearing course (40 mm) calls for much smaller tolerances, and profiles are not sufficiently accurate; the following approach may be used. Pins or pegs are established at right angles to the centre-line at about 0.5 m beyond the kerb face . The pins or pegs are accurately levelled from the nearest TBM and a coloured tape placed.
Controlling camber with triple profiles
Pins used to control setting out of base and wearing courses
around them at 100 mm above finished road level; this will be at the same level as the top of the kerb. A cord stretched between the pins will give kerb level, and with a tape the distances to the top of the sub-base, top of the base course and top of the wearing course can be accurately fixed (or dipped). The distance to the kerb face can also be carefully measured in from the pin in order to establish the kerb line. This line is sometimes defined with further pins and the level of the kerb top marked on.