3Answer the questions to the text.

a. What will the result in movement be?

b. What is the disturbance of the coal measure strata?

c. What can you say about the extent of workings?

d. How many cases do you know? Name them!

e. Upon depends the distribution of pressure?

4 Fill in the text with the necessary words

Disturbance of the coal measure strata is the combination of the … or … of moving stone. From the first principles of dynamics the force created by the second method is … … created by the first method. In each case the … has to be absorbed by the… and underlying rocks and therefore in the second case they suffer much more …, with more broken roof and sides and floor …or blowing.

The cases may be divided into:

a) Effect of one … in a virgin area.

b) Effect of a … … driven in a virgin area.

c) Effect of a … … driven into a virgin area.

The first problem is roof control, and it depends on a proper understanding of the … and … of the rocks in the working zone.

LESSON 19

1. Read and remember new words.

Temporary supports – тимчасова опора

props and bars – стійки та переклади

chock – кострове кріплення

lid – переклад, балка

neglect - знехтувати

forepoling – забивне кріплення

Permanent supports – постійна опора

2. Read the text and extract the main information. Support (part 2)

Longwall faces are usually supported by two means: a) temporary supports; b) permanent supports.

Temporary supports, that is, props and bars, chocks, all of which can be withdrawn and reset, are used for carrying the weight of stone-inside the pressure arch; therefore the wider the arch the more weight the props and chocks have to carry. Another important duty of the temporary supports is to reduce the amount of roof movement, and so they should be set as soon as the coal has been extracted and as tight as possible. The lid set on the top of a prop gives a rough indication of the load or pressure on it by the amount of crush it undergoes.

Prop set on soft floors requires foot lids to spread the pressure from the roof through as great a surface area as possible and thus prevent or reduce floor movement. Bars are a safeguard against the parallel breaks due to the cutting of the face.

Steel props and chocks are being used to an increasing extent because of the cost of timber. To allow chocks to be set solid and still permit easy with drawal, steel chock releases are used. Steel, however, has one disadvantage, its strength, which is great compared with wood. It will stand up to greater roof pressure and so allow continued working under zones when the pressure arch is too wide and the load too high due to the neglect of permanent supports. This will ultimately cause a .break­down of roof.

Now, it is necessary to discuss road supports. The quality of workmanship in temporary and permanent supports on the face determines the quality of the roads, but the latter must also have good individual supports, such as:

1) Packs on one or both sides of the roads according to the position of the road in the working area;

2) Temporary supports at the ripping face and roof to check movement. The types used are:

Staking props stretchers

Specially bent bars forepoling

Telescopic bars temporary props and bars

Permanent supports. Steel arches or wood or steel props and bars with suitable covering wood or sheeting are used. It is com­mon practice now to build the arches or props on

stilts to allow a certain amount of downward movement to take place. Sometimes the floor too is supported on yielding arches (Fig. 15).

Where stone headings are driven, forepoling and steel arches are popular methods of support (Fig. 16). Coal headings, which are usually in weaker ground and generally mechanized, need attention'to the break line developing at the side

of the heading. It has been found as a general rule that if one side of the coal heading face is kept in advance of the other, a break will develop on the leading side which can be controlled by double legging of the bars at that side of the road. The usual method of support is long bars or channels running across the road with three or more props set for support. When these headings are ripped or brushed they are supported in the usual manner.

The problem of road repair becomes difficult with the increasing rate of mechani­zation, and uncontrolled falls must be avoided if continuity of output is desired. Good work in supporting the face, wastes and roads helps to maintain the roof in a reasonably sound condition, so that it can be got by pick or explosive in controlled amounts. Each ripping must be supported at the face and roof by methods mentioned above to arrest undue movement.

Enlargement usually requires a lot of ground to be taken away before the existing road supports are removed, and in this work it is necessary to commence in solid ground where suitable chocks and bracing girders can be carried with safety, and it is desirable to use a working platform with suitably devised loading traps to reduce the risk of accident or loss of output.

As has already been mentioned, the amount of movement can be reduced by employing the most complete

mechanical, compressed-air or even hydraulic stowing may have to be introduced. method of stowing the goaf. If this measure becomes necessary then solid

The strata composing the earth's crust are, generally speaking, subject to two main natural forces, namely, vertical and lateral compressive forces. Both of these can, normally, be considered as being in equilibrium (that is, in a state of balance).

The general effect of mining is to create a space into which the overlying strata tend to subside and break down. In this way the normal state of equilibrium is disturbed, and there are vertical and lateral movements in the strata, which ultimately transmit themselves to the overlying surface. These movements will continue until the space has been closed and all the forces have been redistributed and equilibrium restored.

3.Write down the sentences with new vocabulary and translate them.

4.What differences are there between permanent and temporary supports

LESSON 20-21

І Прочитай та запам’ятай слова

backhoe ['baekhou] я обратная ло­пата

blast [blo:st] л вибух; v вибухати;

Hasting - підрив; підривні роботи;

block out ['bbk'aut] v наіезати поклад на блоки; нарізати стовпи

clearing ['kliann] л вирівнювання грунту; планіровка грунта

crash [кгдП v подрібнювати; рушити;

earth-mover ['э:0'ти:уэ| - землекопальне обладнання; syn exca­vator

excavator ['eksksvcits] - екскава­тор;

bucket-wheel - роторнийеэкскаватор;

multi-bucket ~ багаточерпаковий екскаватор;

single-bucket - одночерпаковийеэкс­каватор

grab [gneb] л грейфер, ковш, чер­пак; екскаватор;

grabbing- погрузка грейфером;

hoist [haist] - підйомний пристрій(машина); підйомник; лебід­ка; v піднімати;

hoisting- шахт­ний підйом

plough [plau] - струг

power shovel ['раиэ - меха­нічна лопата; екскаватор ти­пу механічної лопати

range [reindj] – коливання у певних межах;

rate [rcit] л норма; швидкість, темп; коефіцієнт; ступінь; сорт; потужність; расход (води)

remote [ri'mout] а віддаленийй; ~ control дистанційне керування

result [n 'zjvlt] v (in) приводити (до); мати своїм результатом; (from) слідувати (из),

safety ['seifti) л безпека; тех­ніка безпеки

slope [stoup] n забой, сплошной забой, очисний забой; v чистити забой, виймати породу, ; syn face;

sloping - очисні роботи;

open sloping – добича відкритим забоєм;

shrinkage sloping - виїмка системою с магазинуванням (руди)

powered roof - ме­ханізоване кріплення;

self-ad­vancing powered roof - пересувне механізоване кріплення