土木工程毕设 论文翻译.doc

BUILDING CONSTRUCTION Unit-1 Foundations The definition and functions of foundation have been given in chapter 6. In this chapter broad guidelines for fixing the dimensions of foundation are given and different types of foundations are explained. 1.1 DIMENSIONS OF FOUNDATION Guidelines for minimum dimensions are given below: (a) Depth of Foundation: For all types of foundations minimum depth required is calculated using Rankine’s Formula Where p = safe bearing capacity of soil w = unit weight of soil = angle of repose of soil. However in any case it is not less than 0.9 m. Finding safe bearing of the soil is an expert’s job and it is found after conducting tests in field or in Laboratories. However general values for common soils are listed in Table 7.1. (b) Width of Foundation: Width of wall foundations or size of column footing is determined by first calculating the expected load and then dividing that with SBC. Thus, Width of wall foundation Area of column footing= 1.2 CONVENTIONAL SPREAD FOOTINGS This type of foundations are commonly used for walls and masonry columns. These foundations are built after opening the trenches to required depth. Such footings are economical up to a maximum depth of 3 m. As these foundations are suitable depth, they are grouped under shallow foundations. Figure 7.1 shows a conventional spread footing for a wall and Fig. 7.2 shows it for a masonry column. Before building these footing trenches are opened to required depth and the soil is rammed well. Then a plain concrete of mix 1 : 4 : 8 is provided. Its thickness varies from 150 to 200 mm. Over this bed, stone masonry footing is built. It is built in courses each course projecting 50 to 75 mm from the top course and height of each course being 150 to 200 mm. In case of wall footing the projections are only one direction while in case of columns, they are in both directions. The projection of bed concrete from the lowest course of foundat