10 Use the words below to complete the sentences: types of foundation Part II

Pad foundations are isolated foundations that 1) _____ concrete column or free-standing brick piers. A square concrete pad foundation distributes the load evenly over the ground.

If the pad is constructed of mass concrete, then the 2) _____ must equal the projection from the side of the column (Fig. 8.6).

Figure 8.6 Pad Foundation	Figure 8.7 Stepped Foundation

Stepped foundations are built on 3) _____ sites (Fig. 8.7). This reduces the expense of constructing a foundation that is the same level around the perimeter of the building. A foundation at the higher end of the slope would be 4) _____ deep.

To overcome this, the foundations should be stepped at 5) _____ levels. The higher-level foundation should 6) _____ over and meet with the lower one for a distance not less than its thickness. This should never be less than 300 mm.

The change in level should not be more than the thickness of the strip foundation. It should be measured in multiples of 75 mm, which is the height of a 7) _____ course.

If soil conditions are poor near the surface, then piled foundations should be used. Trial holes will usually indicate the depth of suitable load-bearing soil. Since this may be as deep as 2 or 3 metres below ground, it would be quite expensive to construct 8) _____ foundations. To overcome this problem two types of piled foundation can be used to strengthen the soil:

1. bored or replacement piles, which are concrete 9) _____ poured into holes in the ground at measured intervals;

2. driven or 10) _____piles, which are tree trunks that are hammered into soft ground at spaced intervals.

extent, displacement, different, conventional, support, sloping, thickness, cores, brick, extremely

11 Fill in the gaps in the following passage with a suitable preposition given below: types of foundation Part III

Short-bored piled foundations are used 1)_____ small houses and lightweight framed buildings constructed 2) _____ soils that expand and contract 3) _____ changes in the moisture content. These soil types include clay and black cotton.

The type of foundation shown in Fig. 8.8 can be constructed quite quickly and avoid the need to dig deep trenches. Short-bored piles are more effective and cheaper than conventional foundations if the soil responds easily to the changes 4) _____ the atmosphere.

Figure 8.8 Short-bored Pile Foundation	Figure 8.9 Timber Displacement Piles

These foundations are not suitable 5) _____ use on rock, flint or sites with many tree roots because the holes must be straight and consistent in diameter.

The holes are dug 6) _____ hands with an auger and then concrete is poured 7) _____ them to form a column in the ground when it hardens. The concrete columns in the holes in the ground are the piles.

The measurements in Table 8.1 are typical dimensions for short-bored piles.

Table 8.1 Measurements for Short-bored Piles

Components	Measurements (mm)
Depth of the hole for the piles	2500-3000
Pile diameter	250-360
Pile spacing	1200
Beam width for 225 mm wall	300
Beam depth for 225 mm wall	150-200
Reinforcement diameter	15 mm with 6 mm stirrups

Fig. 8.9 represents timber displacement piles for lightweight buildings. For this foundation straight tree trunks should be used and treated with preservative and sharpened 8) _____ the ends to drive them 9) _____ the ground. It is better to use an auger to remove some 10) _____ the pile-driving process is started.

at before by for(x2) in(x2) into on with