A. Guess how the paragraphs will continue.

b. What do you think the text is about?

1. Read the text and match the openings above to the paragraphs. Example: 6-a)

a)… First, machines which plane off a thin layer of soil and push it in front of them. Second, machines which plane off a thin layer of soil at the same time picking it up and carrying it where required. Third, machines which dig out soil by some form of a bucket and load it for transportation into separate vehicles. Fourth, machines designed especially for trenching by means of a number of buckets mounted either on a continuous chain or on a wheel.

b)… The crawler-mounted excavator has two other advantages over its rope-operated counterpart: with separate hydraulic motors for each track it is possible to put one track in reverse while the other is driven forward so that the machine can be turned within its own length and the boom can be of the adjustable radius type, so that the reach, digging depth and discharge height can be quickly varied to suit the job.

c)… leveling the machine on sloping ground so that trenches with vertical sides can be cut perpendicular to the direction of the slope. In some models the revolving superstructure of the machine can be moved transversely in special guides so that a trench can be dug parallel and close to a wall or some other obstruction this movement being carried out hydraulically too.

d)… A bulldozer represents by itself an earth-moving machine which carries out its work with the help of a blade mounted on a tractor of either crawler or wheel type.

e)… the employment of a great plant of powerful earth-moving machines, the excavators being the most important of them.

f)… It has a cutting edge that digs. There is a considerable variety of scrapers from small units to huge ones made to accommodate 30 cubic yards of soil and to absorb the power of two tractors while at work.

g)… shovel, drag line, backacter or backhoe, grab or clamshell, crane. Conversion from one type to another is a comparatively easy operation.

h)… Now hydraulically operated excavators are in wide use, especially hydraulic backhoes. In hydraulically operated backhoes hydraulic rams are used instead of ropes and winches to operate the boom and the dipper arm. The hydraulic system makes it possible to pivot the bucket on the dipper arm. This movement provided by an additional ram on the dipper arm gives the operator a means for selecting the proper angle of cutting for the bucket both at the start of the digging stroke and during the stroke to obtain optimum digging performance.

i)… Site preparation and excavation are the most fully mechanized of all the operations in building construction. Most excavating machinery is heavy and slow-moving and must be carried from site to site on special transporters. It is clear that the use of expensive mechanical plant requires careful planning and efficient site organization if full advantage is to be taken of its high rate of production.