Transcript SITE PREPARATION

SITE PREPARATION
• A plan should be produced showing
all areas for excavation, tipping and
filling before commencing earth
moving.
• The quantities of excavated material
and required fill should be shown
on this plan, so as to facilitate the
most economic movement of soil.
When large quantities of soil have
to be moved, a 'mass haul' diagram
should be prepared (Fig 2.1).
• Such a diagram shows the distances
and direction of haul and gradients
calculated to balance the cut and
fill.
Fig 2.1 Mass Haul Diagram
(Source : Fig 2.1 Holmes, R.(1995), Introduction To
Civil Engineering Construction, University of the West
of England, Bristol)
• If the excavated material is likely
to be particularly variable some
indication should be given of its
method of disposal, i.e. whether
to haul to spoil heap rather than
fill areas.
• Construction methods for smaller
sites, eg basements, deep pits,
trenches etc, will depend to a
great extent on the following
factors:
– Type of soil or rock
– Quantity of material to be moved
– Presence of water
– Depth of dig
– Working space available
– Whether excavated material can be
left on site.
• As a general rule, for large pits
and basements, where space will
allow, the excavation should be
achieved by 'battering' the sides
of the dig. This allows a clear
working area, free from
obstruction or shoring (Fig 1.2).
Figure 2.2 Excavate with battered sides
(Source : Fig 2.2 Holmes, R.(1995), Introduction To
Civil Engineering Construction, University of the
West of England, Bristol)
Setting out for
earthmoving plant
Figure 2.3: Setting out for cuttings
(Source : Fig 2.3 Holmes, R.(1995), Introduction To Civil Engineering
Construction, University of the West of England, Bristol)
• In Fig above, the batter stake shows the
depth of cut (C = 2.6 m) and its distance
from the centre line 12 m. On the edge
of the stake the slope (11 in 2) is marked
as a fraction, and on the back face of the
stakes the distance along the centre line
from the first station. After reducing the
levels a series of final level pegs are
positioned at the shoulder and centre
line. This procedure can be used for
almost any form of mass excavation.
Retaining Walls
Stake out/remove sod
- Begin by staking out the wall. For curved sections, use a
garden hose to lay out the wall line. Dig a trench along this
line. The width of the trench should be twice the depth
(front to back) of the block used. If block is 8 inches deep,
make trench 16 inches wide. When using one, two or three
courses of block, make the trench deep enough to bury half
of the first course plus 2 inches of compacted base material.
When using four or five courses of block, make the trench
deep enough to bury the full first course plus 2 inches of
base material. When using six or more courses of block, bury
the full first course plus 4 inches of base material.
2. Add base material
• Remove loose soil and firmly compact
the soil in the bottom of the trench with
the tamper. Then place base material in
the bottom of the trench. Base material
can be paver base or an equivalent to ¾inch minus (with fines) aggregate. Use
the appropriate amount of base
material for the number of courses you
are building.
3. Level and compact base
• Add a 2-inch layer of base material,
rake out and firmly compact with
tamper. Level the surface from front
to back and side to side. Check with a
carpenter’s level, checking level every
few feet. The more level the base
material, the easier it is to level the
block. Add another 2 inches of base if
needed for the height of the wall (see
Step 1).
4. Lay and level block
• Use a hammer and chisel to remove
the rear lips from all blocks used for
the base course. Use string to align
the back edges of the first course.
Position the wall units side by side
on the prepared base so that front
edges touch. Level block in both
directions. Check individual units as
installed and check units with each
other as you install wall. Begin next
course by laying a block with the
rear lip down and pulling it forward
until the lip is securely in contact
with the units below. Assemble
additional courses by placing units
in a staggered relationship to the
course beneath (running bond).
5. Backfill wall
• Fill behind each course with
drainage aggregate (such as ¾inch free draining) that extends 6
inches behind the wall. Compact
aggregate with tamper. Organic
soil or clay-type soil is not
recommended for backfill
material.
6. Cut block
• To make all blocks fit, you may need to
cut wall blocks. Use a circular saw with a
masonry blade to cut blocks and caps
from the top. Read and understand the
operating manual before using a saw.
90° Corner:
• For some products, you will need to use
a circular saw with a masonry blade. Cut
a 45-degree angle on two blocks. Cut
from the front corner to the back of the
block. Glue pieces together with
construction adhesive so two block
faces form the finished outside corner.
7. Mark and cut caps
• For capping curves, trim caps to follow the
wall radius. Place a cap at the beginning of
the curve. Skip a space and place the next
cap in the third position. Rest a cap on the
top of the original two, aligning its face
with the face of the wall. Mark the bottom
of the cap along the edges. Use a circular
saw with a masonry blade to cut the
marked cap. Place the cap. On a 90-degree
corner wall, the caps need to be saw-cut to
achieve a 45-degree mitered corner. At the
end of the wall, cut the cap so the
manufactured edge is exposed and the cut
edge is against the next cap.
8. Glue caps
• Use an exterior concrete
construction adhesive to secure
the caps.
• There are two main types of
retaining; wall the gravity retaining
wall and the cantilever retaining
wall. The former is mainly used for
the support of solids such as soil,
fuel, chemical and waste materials.
The latter may be used for both
solids and liquids. Reservoir walls
are often constructed in a cantilever
form. In some cases the wall may be
designed to support dead loads in
addition to the normal lateral loads,
but essentially these walls are
designed to resist lateral movement.
• Both types of retaining wall must be
designed to resist the following
factors:
Figure 2.4 Possible Failures in Retaining Wall
(Source : Fig 2.4 Holmes, R.(1995), Introduction To Civil
Engineering Construction, University of the West of
England, Bristol)
• These possible factors of failure are shown
diagrammatically in Fig 7.4. Gravity
retaining walls depend on their dead
weight for strength and stability. They are
limited in height to approximately 3 metres
if inclined, or 2 metres if the wall is vertical.
Over these heights the thickness of wall, to
comply with the safe height/thickness ratio,
would make the construction
uneconomical. They are designed so that
the width of wall is sufficient to distribute
the resultant loads of the wall and the
earth pressure to the soil below the base of
the wall without under settlement.
• High tensile stresses at the back of the wall
can be offset by designing the width of the
wall so that the resultant force is kept
within the middle third of the base. A
suitable width of base can be taken as
between one quarter and one-half of the
wall height. The width at the top of the wall
can be taken as one-seventh of the wall
height.
Cantilever Retaining Wall
• Cantilever walls are used for
retaining walls up to 7 metres in
height without counterforts, and
if counterforted can be designed
for greater heights without being
excessively thick. The wall shape
may vary to suit the loading and
the material to be supported.
• The walling material is normally
reinforced concrete, although
pre-stressed concrete may be
used for liquid-retaining
structures.
Figure 2.4: Cantilever Retaining
Wall
(Source : Fig 2.5 Holmes, R.(1995),
Introduction To Civil Engineering
Construction, University of the
West of England, Bristol)
Other forms and types of retaining
wall can be used, such as:
•
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Diaphragm walls
Steel sheet piling
Concrete crib walls
Contiguous piling
Anchored walls
Figure 2.5 Concrete Crib Wall
Figure 2.6 Anchored walls
Turfing
• The idea of turfing is to stabilize
the slope. Turfing can help to
prevent a landslide on rainy days.
There are two types of turfing the
first is sport turfing. Grass will be
planted at every 150mm-300mm
each. The second type is close
turfing. Grass will be planted
closely.
Figure 2.7: Turfing
(Source : Fig 2.6 and fig.2.7
Hafidzah, A.(1995), Binaan
Bangunan,Nota Panduan
Politeknik Malaysia
Setting Out
• Purpose : to build up the
proposed building at the exact
place/spot and also as a guide for
excavation and building
construction.
• It will be fixed at least 1m from
the building line to avoid any
damage due the trench
excavation works.
• Wall thickness and base trench
will be marked clearly on the
setting out by using nail or saw
cutting edge or painted.
Procedure of Setting Out
1. Usually one of the building corners
will be set up as a bench mark by
the planner.
2. Then set up any of the building
corner and mark the spot with ‘A’.
3. . Measure the length of A to B and
mark the spot with ‘B’.
4. The corner at ‘B’ can be exact by
using the ‘elbow’ or 3:4:5 ratio.
5. Then continue the process to set up
the ‘C’ and ‘D’ points.
6. After completing all the ABCD
point, check the diagonal to
establish whather the building is
square.
Bonning Rod
• Bonning rod is made up of 2
wooden sticks in T shape, measuring
100mm X 30mm. The length of the
rod is standard, based on the depth
of excavation.
• Usage of Bonning Rod:a. to control/monitor the quantities of
excavated soil.
b. to monitor the excavate slope.
c. to monitor /checked the level of any
excavation surfaces.
• Bonning rod must be used in
conjunction with straight reel in
order to determine the slope of
any excavation works. Straight rail
is a wooden stick joinned to 2
wooden stump horizontally. The
size is 150mm X 50mm.Stump
height are based on the depth of
excavation work.
Process
• Straight reel will be fixed at every
+30.00mm along the excavation lane.
The top of the rods must be levelled
using water level.
• The bonning rod will be set up at the
length of excavation based and the
top of the right reel.
• Threads line will be fixed on the top of
the sight rails. This is to determine
that the thread line is paralled to the
excavation lane.
• Any section of the excavation area can
be examined using the bonning rod,
by making sure that the bonning rod
levelled the top of the rail on sight.
Rubber Hose
• A transparent rubber hose filled
with water is a useful tool to use
as this will give a the some level
for different places at the
construction site. A transparent
rubber hose anables water level
to be seen clearly.
Process
• Fill the rubber hose with water and
mark ‘A’ at one end. (reference level)
then put the second end to the place
to be levelled as and mark ‘B’. Move
the hose up and down till the water
level at that end is stable. Make sure
the, water level at ‘A’ is fixed. Now
point B is levelled with point ‘A’.
Water Level
• Usage of this tools is to test and
determine the vertical and
horizontal surfaces. Tools are
made of wood and steel.
• For the flat horizontal on vertical
surface, the bubble in this water
level will be centered/ in the
middle.