2015 ~ Building Construction

Introduction

The construction site is usually prepared in two steps: first the vegetation is cleared, and then the surface soil layer is removed. These operations can be done either by hand or by machine.in both case, special pieces of equipment such as ropes, cables and chains may be required. You will learn about these first, to be able to make the best and safest use of them.

First remove the vegetation

Then remove surface soil to the out side limits of the site

Ropes, cables, chains block and fittings

Using the equipment

Ropes, cable, chains, pulley block and fittings are normally used for pulling down and clearing heavier trees, brush, etc., for pulling out rocks or other obstructions, and for moving heavy equipment around the site. The important factors are the pulling or traction load and the strength of the different components. The load can be applied either by hand using animal power, or by machine.

Clearing the site

The site should be cleared of all obstructions such as

woody vegetation,where the roots can cause severe cracking in pond structures such as concrete water inlets and outlets.

Tree stumps which, when decaying, can also weaken concrete pond structures by leaving voids in the soil.

Large stones,which may need to be dug out

Ant hills and animal burrows, which should be dug completely; clayey soil should be tramped into the hole created.

Where to clear
Define carefully the exact area to be cleared before you begin. Determine the outer corners of the building area, which should include the entire area to be covered by dikes. You could mark the area using wooden stakes and cord or poles. When this is done, mark out an additional area beyond the dikes to serve as a work space and a walkway around the site.Then you are ready to proceed.

Proceeding with the clearing
The clearing method to be used largely depends on the type of vegetation on the site. In open savannah country, it is a relatively easy task that can be done manually with limited special equipment. In heavier forested area on the country, clearing generally requires either a large work force and/or the use of machines. If an area is too heavily forested, it might be best not to select it as a construction site, unless no other alternative exists.

*There are two basic ways to clear the woody vegetation from a site:

You can cut the trees and then remove the stumps.
You can feel whole trees with their roots attached.

Fell whole trees with roots

Cut trees and then remove stumps

The clearing of the site should be completed by gathering all cut vegetation, stumps, roots and large stones.All these should be removed from the work area. When conditions are dry enough, the clearing can be completed by starting a fire, which should be carefully kept under control.

Gather cut vegetation and burn it

Collect large stones and carry them away

Note. You can often sell the wood cleared from the site or make charcoal and sell it at a good price

The cutting of trees

Tree cutting is a very dangerous job. It requires much skill and experience to avoid accidents. If you have never cut trees before, you should subcontract this specialized work to people known for their practical experience.You should however learn about a few basic point that will help you to plan this clearing operation better.
High stumps are more easily removed than low ones. This is particularly true if you remove the stumps using either a winch or low-powered machinery.Reminder that if the wood is valuable,you will get less money from shorter trees.

High stamps are easier to remove, but give less usable timber

Low stumps are harder to remove, but give more usable timber

Preliminary work

Remove shrubs and undergrowth

Ready to cut

Basic steps for cutting trees

There are two steps when cutting trees

Making the undercut: cut a pie-shaped piece out of the tree on the side facing the direction in which the tree is supposed to fall. The depth of the cut should be one-fifth to one-quarter of the diameter of the tree.
Making the back cut: 3 to 5cm above the base of the undercut and at right angles to the falling direction, cut horizontally nearly all the wood that remains on the back of the tree.

If at the end of the backcut, the tree does not fall by itself, hammer a wedge into the backcut to push the tree over in the desired direction.If pulling or guide cables are to be used, they should be attached before the cutting is started.

Note: felling large trees may be dangerous. For tree with a diameter over 60cm at the stump, special techniques have to be used.

Selecting equipment

Small trees can be chopped with an axe theycan be sawed. A handsaw requires two operators and the use of a wedge in the backcut.

Felling by hand

Chainsaws

The removal of tree stumps

Standard way of removing tree stump from the ground are either to dig them out or to pull them out.small stumps can easily be dug out by hand.Larger stumps may require the use of machine power. Stump pulling is done by placing a rope, cable or chain around the trunk and pulling as follows.

Direct pull by an animal or machine
Winding in of a cable on a winch
A combination of these methods with pulley blocks

2. In the next section ,you will learn about the most appropriate methods.

Dig small stumps by hand

Pull large stumps with animals, machine power or winch using pulley blocks as needed

Digging out tree stumps by hand

To make work easier, dig trenches around the stump in the following sequence, cutting any roots encountered.

1.Dig trench 1

2. Dig trench 2

3.Dig trench 3

Pull the top of the stump as shown. If it fails to be dislodged, dig trench 4 and cut remaining roots.Try again to dislodge the stump.

If you cannot pull it out

Dig trench 4

Then pull again

Note. if the trunk has been cut near the road,you should excavate around the stump.

Lift the stump out of the ground if it is a small stump, put a rope or chain around the foot of the stump. If it is a large stump,first attach a rope or chain around one of the strong stump roots.

Small high stump

Lead the line over a notched pole, a stumping trestle or shearlegs,which you can easily make yourself . while pulling the line with one group of people, have other people push the stump up with crow bars to free it from the ground.

large law stump

Push with crowbar

Removing tree stump with hand winch

A hand winch consists of a metal casing in which a double set of claws grips a steel cable. A hook is secured to the back of the casing.As the handle of the winch is cranked,the claws move horizontally and pull the cable inside the winch casing. Excess cable comes out through the back.The cable is equipped with a hook at its end. There are various models of hand winches available, their traction force varying from 0.5 to 10 tonnes. A very useful one is the more common three-tonne hand winch.

Hand winches

To remove a tree stump with a hand winch proceed as follows:

Use a robost standing tree or stump, a rock or a heavy vehicle not too far away from the stump to be removed. The distance between the two should not be longer than the length of the winch cable.
Tie a sling (a steel cable with two thimbles) around the base of the standing tree or other object which will be used as an anchor.With a vehicle, attach the hook or cable directly to the towbar or chassis fixing point .
Attach the hand winch to this sling, using the hook at the back of the casing

Wrap sling around tree

Other ways to attach a winch

To a vehicle

To a staked log

To an anchored steel plate

Tie either a sling or a chain around the stump to be removed

it is best to use a chain long enough to be wrapped around the stump and from at its end an angle smaller than 60⁰
^{If the diameter of the stump is too large to do this, it is preferable to use a cable sling}
^{To avoid the sling or the chain slipping off the stump, cut a groove around it into which the sling or chain will fit.}

Attach winch to sling

Note: If the stump is too far from a possible anchor, enlarge the sling around the anchor with a chain or a cable and connect the latter to the winch hook.

*Using the winch cable as a choker around the stump will damage it and greatly reduce its strength .Never do it

Attach the hook of the winch cable to this sling or chain.
Dig around all or part of the stump so that the bigger roots can be cut.
Slowly start cranking the winch with its handle, checking that all line and their fittings are in order.

*Using a winch can be dangerous.check that each piece of equipment used is strong enough to withstand the traction farce applied by the winch. Check regularly for wear and tear. Keep people away from lines under tension.

Using the monkey winch

Another simple, reliable and heavy-duty winch is the monkey winch. It can be very effectively used in the same way as the hand winch.

Increasing pulling force

You can easily improve your pulling efficiency for stump removal in the following way

Apply a lifting action to the stump by using a notched pole, shearlegs or a stumping trestle and attaching the line to one of the strong roots
Apply tipping action to the stump by making a notch in its top surface and attaching the chain as shown.
Use pulley block to increase the strength of your winch. Remember that this also increases the loading of the equipment such as sling, shackles and pulley block, which should be strong enough to withstand the extra loading .

Using pulley block to increase the pull

Using the winch with one pulley block

To double the strength of the winch, you can use one pulley block, and one (or better two) anchor(s) as follows.

Attach the winch to its anchor
Run the winch cable in the block over the pulley and run it back to the anchor.
Attach the winch cable to this anchor
Using a cable or a chain attach the hook of the pulley block to the stump to be removed
Dig a trench around the stump and cut all major roots that can be reached close to the stump
Crank the winch carefully

Example

If you are using a small one-tonne winch, you can now pull the stump out with a two -tonne traction force as follows.

traction on winch cable = 1 tonne
Traction on single anchor = 1+1=2
Traction on stump = 2 tonne

if a second anchor is available, you may use it to attach the end winch cable , this will reduce the traction force by half on each of the two anchors, as shown below.

Use one pulley block

Using the winch with two pulley block

To treble the strength of the winch,you can use two pulley blocks and two anchors,as follow.

Attach the winch to anchor 1
Run the winch cable in the first pulley block and run it back toward the second block .
Run the winch cable in this second pulley block, run it back toward the first block and attach the cable to it
Attach the second block to strong anchor 2.
Attach the first block to the stump.
Crack the winch carefully, checking anchor 2 especially.

Example

If you are using a small one-tonne winch, you can now pull the stump out with a three-tonne traction force as follows.

Traction on winch cable = 1 tone
traction on anchor 1 = tonne
traction on anchor 2 = 2 tonnes
Traction on stump = 3 tonnes

Using two pulley blocks

When clearing a site with many trees, you should progress systematically from the centre of the site to its margins, so that

the trees can serve as an anchor for each other
all trees can be pulled out

For large sites, it is also useful to clear several access areas through which trees can be moved out of the site.

Removing stumps with a bulldozer

Crawler tractor with dozer blade

If a tractor equipped with a front-mounted dozer-blade is available, it can considerably speed up the removal of stump. This is particularly important for a forested site. For best efficiency, proceed as follows.

01. Raise the dozer blade and place it against the trunk part of the stump.

02. As you push against the stump,raise the blade further to apply a lifting action to the stump, it will also increase the grip of the tractor on the ground.

03. Tilt the trunk forward until the roots in front of the tractor are slightly out of the ground.

04.Back the tractor and lower the blade

01. Insert the blade under the roots.

05. Push while lifting with the blade to break the stump out of the ground.

Uprooting whole trees

A common method of removing smaller trees and their roots from a construction site is to uproot whole trees. This can be relatively easy because of the greater leverage obtained when pushing or pulling a tree at a point high up its trunk.But to be safe. this method should be used only if.

There is a adequate space.
The tree is not rotten, cracked or split.

Using a hand winch to uproot a whole tree

The pulling angle with the horizontal should not exceed 30o , if space is restricted or a grater angle of pull is required, use a pulley block to change the pulling direction.

Uprooting a whole tree using a winch

If you only have a hand winch or a monkey winch to work with, you can proceed as follows.

Position the winch at a distance at least twice the height of the tree and as close as possible to a robust tree that can be used as the anchor.
Attach the back of the winch to a sling/chain tied around the base this anchor tree.
Climb up the tree to be uprooted and attached the winch cable high up the tree trunk to a sling/chain tied around it.
Dig a trench around the base of the tree to reduce the resistance of the stump against pulling.
Place a log against the base of the tree facing the winch to assist in the extraction of a maximum amount of roots and aid in removal of the soil.
Crank the winch carefully

*You can also use two anchor trees for example to change the direction in which the uprooted trees will fall.

*Always attach the cable to the tree to be pulled as high as possible and the sling to the anchor tree as low as possible

Using one anchor tree