Builder's Engineer

In general, shallow pads and strips are the economic foundation for most structures where ground conditions allow this solution.

The suitability of shallow strips and pads should be one of the first considerations for the engineer and their use tends to form the  normal  foundation criteria against which the extra over cost of abnormal foundations tends to be judged.

This does not mean however, that strips and pads should be used wherever possible since as they become deeper or more heavily reinforced the alternatives of vibrocompaction and/or piles becomes competitive.

However, at shallow depth, they are the economic alternative.

1 Trench fill   A brief description of trench fill strips is given previously. The design of such strips is relatively simple, and it is true to say that there is more design involved in making the decision to

2 Trench fill design decisions   A typical trench fill foundation is shown in Fig. 11.7 where (a) indicates a typical section, (b) shows the typical design forces, and (c) illustrates the possible externally applied ground...

3 Sizing of the design   In the case of mass concrete trench fill the foundations can be sized using the assumptions that dispersion of load through the strip can be assumed to be at an angle of 45°. In the case...

4 Design Example 1: Trench fill strip footing   The internal load-bearing wall for a four-storey office block is to be supported on a strip foundation. Borehole investigations produced the consistent soil profiles shown in Fig. 11.13. Soil...

5 Design Example 2: Deep mass concrete pad base   A steel-framed building is to be built on a site adjoining previously, where variable fill extends down to the level of the bedrock. A heavily loaded stanchion, carrying axial load only, is to be supported on a...

6 Unreinforced concrete strips   The unreinforced strip footing requires slightly better ground conditions than trench fill to maintain trench stability during construction of the masonry over it. The adoption of a thin...