Lecture 8 тсп 1

1.

08
LECTURE 8
Cranes, Calendars,
and Closing the Site
Finishing the earthwork, choosing the right lifting crane, planning the work
calendar, and checking that it was all done right
COURSE
TECHNOLOGY OF CONSTRUCTION
PRODUCTION
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
1

2.

WHAT WE'LL COVER
Four Stops on Today's Site Visit
01
02
03
04
Finishing the Earthwork
Choosing the Lifting Crane
Planning the Work
Calendar
Checking the Work
Wrapping up topsoil removal: the two
site-layout patterns, and how scrapers
and bulldozers strip the ground before
real construction can start.
The geometry behind picking a crane:
how high it must lift, how far it must
reach, and how much weight it must
carry.
Turning a list of operations into a dayby-day schedule — labor costs,
machine-time, and the calendar graph
itself.
The flow method for overlapping workfronts, the critical path, and how
quality is verified once the digging is
done.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
2

3.

SECTION I
Finishing the Earthwork
Last time we rated an excavator's productivity. Before anything else can be built, the
ground itself still needs preparing — starting with the layer of topsoil.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
3

4.

TOPSOIL REMOVAL
Why the Topsoil Has to Come Off First
The fertile top layer of soil on a building site cannot simply be buried or dug
into — it has real value for farming and landscaping later on.
It must be stripped off within the site boundary and carried to stockpiles, so it
can be reused for reclamation once construction is finished.
Regular excavators are usually a poor fit for this job: the layer is normally too
thin for their buckets to fill properly, so scrapers or bulldozers take over
instead.
< 10 cm
Layer this thin usually isn't worth stripping separately
≤1m
Trenches narrower than this at the top skip the step too
Waterlogged
Sites that are too wet are also normally left alone
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
4

5.

TOPSOIL REMOVAL · SCRAPERS
Two Ways to Lay Out the Work
Sequential passes: the scraper works numbered cells one
after another, moving down the site in a simple grid.
Alternating strips: the site is divided into long strips; the
scraper works one full strip, then shifts sideways to the
next.
Which pattern to use depends on the job: the strip method
lets the scraper cut a shallower slice each pass (useful when
the topsoil is thin), while sequential passes are simpler to
plan on an open site.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Figure 1. Left: numbered sequential passes (site limited to under 200 m). Right: alternating strips, widths B and B'
one after another.
5

6.

TOPSOIL REMOVAL · SCRAPERS
How Wide Each Strip Really Is
After the very first pass, every later strip is narrower than the scraper's
bucket — the passes are made to overlap on purpose.
That overlap keeps the cut edges clean and lets the scraper work without
needing a pusher tractor behind it, as long as the slice it's cutting is shallow
enough.
0.3 – 0.5 m
Typical overlap b between adjacent passes
≤ 50%
B' = B − b
B = bucket width
B' = width of the strip actually cut
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Cutting depth allowed without a pusher tractor, as a share of the
scraper's rated maximum depth
b = overlap between passes
6

7.

TOPSOIL REMOVAL · SCRAPERS
How Far the Scraper Must Travel to Fill Up
A scraper's bucket doesn't fill itself instantly — it needs a certain run-up
distance, cutting a thin slice of soil the whole way, before it's full.
That run-up distance depends on how big the bucket is, how thick a slice is
being cut, and how completely the bucket actually packs (soil is looser than it
looks, so it never fills to a perfectly neat 100%).
0.8 – 1.1
Typical fill coefficient on cohesive (clay-like) soils
0.3 – 5 km
Haul distances where a scraper is the economical choice
Ln = (q · kn) / (hc · B')
Beyond about 5 km, hauling soil this way stops paying off — trucks
take over instead.
Ln = fill-up distance q = bucket capacity kn = fill coefficient hc = cut thickness B' = strip width
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
7

8.

TOPSOIL REMOVAL · BULLDOZERS
Stripping Topsoil with a Bulldozer
A bulldozer works its own section of the site — up to 30 m
wide — pushing soil ahead of its blade toward a temporary
stockpile.
The whole site is broken into work sections between 30 and
60 m wide, sized so each stockpile stays as close as possible to
the section it came from.
One bulldozer shuttles back and forth (a “channel” pattern);
two bulldozers working side by side, blades almost touching,
can push a wider, more efficient load.
Figure 2. One bulldozer working a section (top); two bulldozers paired blade-to-blade (middle);
the safe slope for a temporary stockpile (bottom).
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
8

9.

TOPSOIL REMOVAL · BULLDOZERS
How Far Is Too Far to Push It
Short hauls, up to about 50 m, use a simple back-and-forth channel pattern
with a single bulldozer.
Longer hauls, up to about 150 m, call for two bulldozers working together,
with small intermediate soil berms along the way to catch material that
would otherwise scatter.
Once the topsoil is off, the site still needs a preliminary grading pass before
the next stage of work can begin.
≤ 50 m
Single-bulldozer channel-pattern haul
≤ 150 m
Paired-bulldozer haul, using intermediate berms
0.5 – 3%
Soil lost to scatter for every metre the load travels
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
9

10.

SECTION II
Sizing the Sling and Lift Height
Once the ground is ready, the foundation pieces have to be lifted into place. Picking
the right crane starts with the rigging.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
10

11.

CHOOSING A CRANE
Wheels, Tracks, or a Tower?
Foundation blocks and slabs are normally set in place by mobile cranes (truckmounted or self-propelled boom cranes) or by tower cranes.
Where the ground can bear the load, a mobile crane on wheels or tracks is
preferred — it's faster to bring on site and reposition.
Pieces can either be laid out in advance around the site, ready to pick up, or lifted
straight off the delivery truck when space is tight.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Rule of thumb
For lowering pieces deep into an
excavation, always double-check the
crane's capacity to reach down, not just
up — it's easy to overlook.
11

12.

THE RIGGING
How Tall Does the Rigging Need to Be?
For column foundations, a four-legged sling (four cables running from one
hook down to the four corners of the load) is the usual choice.
The steeper those cables hang, the taller the rigging needs to be above the
load — and that height has to be figured out before the crane is picked.
60° ≤ 2Ψ ≤ 120°
2Ψ = the angle between opposite sling cables at the top hook — kept in this range for a
stable, controllable lift.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Figure 3. The sling forms a four-sided pyramid over the load: hs is
the rigging height, 2Ψ the angle at the top, A/B/E the load's own
dimensions.
12

13.

THE RIGGING
Two Numbers That Follow from the Angle
hs ≥ E / (2·tanΨ)
hs = minimum rigging height, E = the load's diagonal footprint dimension
lc = hs / cosΨ
≤5m
Recommended distance from the load hook up to the crane's own hook —
keeps the whole rig manageable
Why it matters
A wider load (bigger E) or a shallower angle both push the required
rigging height up. Get this wrong and the crane's overall lift-height
budget — covered next — runs out fast.
lc = the length of each sling cable itself
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
13

14.

LIFT HEIGHT
Three Heights Stacked on Top of Each Other
Hp ≥ hz + hb + hs
hz
hb
hs
Height of the piece being installed
Safe clearance while the load is moving through the air
Rigging height, from the earlier slide
Hp = the crane's required lift height, measured from the ground up to the hook
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
14

15.

LIFT HEIGHT
Clearing Whatever Is in the Way
That “safe clearance” height isn't arbitrary — it's set by the tallest obstacle
the load has to clear while it's being swung into position: scaffolding, other
equipment, a stack of materials.
≥1m
Recommended clearance margin hz for mobile boom cranes
hb ≥ hpr + hz
hpr = height of the tallest obstacle in the crane's work zone
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
0.5 m
Standard landing height once the crane sets the piece down
15

16.

SECTION III
Positioning the Crane: Reach and
Capacity
Height alone isn't enough — the crane also has to reach the pit from a safe distance,
without tipping, while still carrying the load.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
16

17.

WORKING REACH
One Crane Stance, Several Foundations
The most efficient setup is a single crane position that can reach two or even
four foundation pits without moving — as long as nothing blocks the view and
the crane still has enough capacity at that distance.
The minimum reach needed works out to half the building's column spacing, or
the diagonal distance to the farthest pit corner, whichever the layout calls for.
Working near an unshored excavation is only allowed outside the zone where
the slope could actually give way, with a safety berm width set by standard
construction safety rules.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Figure 4. One crane stance reaching two pits: S and W mark the pit centers, L the
minimum reach, 1 and n the building's column lines.
17

18.

WORKING REACH
Building In a Safety Margin
When a crane sets up and lifts straight “off its wheels” without outriggers planted, it needs a bit of extra reach beyond the bare minimum —
insurance against tipping while aiming the load.
Lp ≥ L + (1 to 1.5 m)
Lp = the crane's required working reach
L = the minimum reach the layout calls for
That small margin is what keeps a crane from tipping forward the instant it's asked to aim precisely at the very edge of its rated reach.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
18

19.

WORKING REACH
When the Excavated Soil Gets in the Way
Piles of excavated soil left next to a trench can crowd out the crane: its
counterweight swings wide, and the turntable needs at least a 1 m gap from
the slope of the pile.
The fix is simple — shift the crane's stance sideways a little, so it clears the
stockpile while still reaching both neighboring pits from one position.
lb = (D − rk + hk·m) · cosα
lb = clearance from the turntable to the slope crest, rk = counterweight radius
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Figure 5. Working next to two stockpiled pits: cross-section (top) and the shifted
crane stances 1a/2a that clear them (bottom).
19

20.

LIFTING CAPACITY
How Much Weight the Crane Must Actually Carry
Q ≥ Qe + Qg
Qe = weight of the piece being installed
Qg = weight of the rigging hardware itself
Q ≥ 1.05 · Qe
Round up, always
Lift height Hp, reach Lp, and capacity Q should all be
rounded up — to the next tenth — rather than down.
A crane is picked to match, or exceed, these three rounded
numbers, using the manufacturer's own capacity charts for
the specific machine.
Undershoot any one of the three, and the crane simply
cannot do the lift safely at that position.
A shortcut version: a four-legged sling rarely weighs more than 5% of the load, so this
alone is often close enough.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
20

21.

SECTION IV
Planning the Work Calendar
With the ground prepared and the crane chosen, the next question is scheduling:
what happens when, and how long should it take.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
21

22.

CALENDAR PLANNING
Two Levels of Detail
Calendar planning covers every document that turns a list of work volumes and technical decisions into an actual sequence and timetable
for construction.
How detailed that timetable gets depends entirely on what it's for.
The Big Picture
The Detailed Plan
Early-stage schedules that set overall timelines and costs, and lock in the
main technical decisions — usually put together by the investor or client
A contractor's own work-production plan: it includes the day-by-day
schedule for construction work, a site layout plan, and technological maps
side.
for each type of work.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
22

23.

CALENDAR PLANNING
What a Calendar Graph Is Built From
A calendar graph is a planning document that lays out the duration, order, and hand-offs between construction operations — plus how resources
(labor, machines, materials) are spread out over time.
Unlike the big-picture plan, it works operation by operation, counting the actual number of working days each one needs.
1
2
3
The operations table
The graphical chart
Resource nomograms
Every individual operation, who performs it, and the order
and timing of the work.
The same information laid out visually on a time-scale — the
calendar graph itself.
Charts showing how evenly labor, equipment, and materials
are used across the schedule.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
23

24.

CALENDAR PLANNING
A Typical Early-Stage Work Sequence
Before scheduling can start, the physical volume of every operation has to be worked out and entered into a table. For the earliest stage of a
project, the recommended sequence usually looks like this:
1
2
3
4
5
Strip topsoil
Grade the site
Excavate & haul
Set foundations
Backfill & compact
Remove the fertile top layer, as
covered in Section I.
A preliminary leveling pass across
the whole area.
Dig the soil, loading it onto
transport or working it into a spoil
pile.
Install the foundation pieces, after
cleaning the pit floor.
Fill back in layer by layer,
compacting as it goes.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
24

25.

LABOR & MACHINE TIME
Turning Work Volume into Worker-Days
Once the construction machines are chosen for each operation, the labor and
machine-time each one needs still has to be calculated — using standard timenorm reference tables built for exactly this purpose.
The starting assumption is simple: one working day equals an 8-hour shift.
Worked by hand or by machine?
Worker labor cost depends on whether the operation
is done by hand or with machinery. Machine-operator
cost depends on the crew: some machines run solo,
others need a supporting crew of laborers alongside
them.
Q = (Hvr · V) / 8
Q = labor cost in worker-days
reference table's own units
Hvr = standard time norm, worker-hours per unit
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
V = work volume, in the
25

26.

LABOR & MACHINE TIME
What a Planning Table Keeps Track Of
Once every operation's labor cost is worked out, it's collected into one reference table — not filled in with invented numbers here, but this is the structure it
follows:
Operation
Volume
+ unit
Time norm
(worker-hrs)
Labor cost
(worker-days)
Machine
crew
Machineshifts
e.g. “backfill,
compacted”
per the
reference
table's units
workers /
machinists
workers /
machinists /
total
min. crew
per unit
computed
from volume
Different kinds of work use differently shaped versions of this table, but every one of them records the minimum crew needed — which is exactly what's used later to
staff each work brigade.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
26

27.

LABOR & MACHINE TIME
Converting Worker-Days into Machine-Shifts
For mechanized operations, the same labor-cost figure translates directly into a count of machine-shifts — how many shifts a piece of
equipment needs to run to get the job done.
Msm = Q / N
Msm = machine-shifts required
Q = labor cost, worker-days
N = number of workers
This is the number that ultimately tells the scheduler how many days a bulldozer, excavator, or crane needs to be booked on site.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
27

28.

SECTION V
The Calendar Graph and the Flow
Method
Turning all these numbers into an actual day-by-day picture — and organizing
overlapping work so nobody stands around waiting.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
28

29.

THE CALENDAR GRAPH
Building the Graph from a Source-Data Table
A calendar graph is assembled from a source-data table listing every performer's work — again, shown here as structure only, with no invented figures:
Operation
Volume
Labor
cost (days)
Machineshifts
Machines
used
Workers
per day
Duration
(days)
Calendar
position
That table lists work by performer, not by work-type — since one crew or machine often does more than one kind of operation.
Plotted on a time scale, it becomes a matrix: each performer's bar runs horizontally, and the calendar days run down the side, tied to real dates.
This makes it possible to build resource nomograms too — checking that workers, power, water, and site facilities are all used at a steady, sensible rate over
time.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
29

30.

THE CALENDAR GRAPH
What the Finished Graph Looks Like
A simplified, illustrative example — the day numbers and durations here are for teaching purposes only, not real project dates:
1
2
3
Task A (2d)
4
5
6
Task B
(1d)
7
8
9
10
11
12
13
Task C (7d)
14
15
16
17
18
Task D (3d)
“Day 1, Day 2 …” runs along the top; each colored bar below is one operation, positioned to show where it starts and how many days it runs.
Reading the bars
A short bar (Task B, just 1 day) can slot into a gap between two longer ones. A long bar (Task C, 7 days) is the kind of operation likely to end up on the critical path —
covered next.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
30

31.

SCHEDULING FORMULAS
Duration for Hand-Worked Operations
Tdn = ΣQ / N
Tdn = duration in working days
ΣQ = total labor cost, in worker-days, added up across the
operation
Given how many workers are on the crew, how many days will it take?
N = number of workers on the crew
N = ΣQ / Tdn
Given how many days are available, how large should the crew be?
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
31

32.

SCHEDULING FORMULAS
Duration for Machine-Driven Operations
Tdn = ΣMsm / (n·m)
ΣMsm = total machine-shifts, added up across the operation
n = number of machines working
m = shifts scheduled per day
Given how many machines are working, and how many shifts a day, how many
days will it take?
n = ΣMsm / (Tdn·m)
Given a target number of days, how many machines are needed?
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
32

33.

THE FLOW METHOD
Splitting the Work into Overlapping Fronts
The flow method breaks one big job into separate work-types, and splits the overall work area into smaller sections (“fronts”) so different crews can
work at the same time, staggered like a relay.
Job A
Job B
Job C
Front I
T(A,I)
T(B,I)
T(C,I)
Front II
T(A,II)
T(B,II)
T(C,II)
Front III
T(A,III)
T(B,III)
T(C,III)
Each cell holds the time one job takes on one front — the raw
input for building a schedule where crews hand off cleanly
between fronts.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
Figure 6. Keeping crews continuously busy: Job A (top row), Job B (middle), Job C (bottom) each move through
Fronts I, II, III in a staggered chain.
33

34.

THE FLOW METHOD
The Other Way to Sequence It — and the Critical Path
Three ways to organize it
Figure 7. Keeping every front continuously occupied instead: crews may sit idle between jobs, but no front is ever
left empty.
Keep the crews continuously busy
Finish one particular front as fast as possible
Finish the whole job in the shortest total time
The critical path
The single longest chain of work, start to finish — it sets the
shortest possible time the whole project can take.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
34

35.

SECTION VI
Quality Control: Checking the
Work
Every operation on the calendar graph eventually gets inspected — earthwork is no
exception.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
35

36.

QUALITY CONTROL
Three Checks, Three Different Moments
1
2
3
Input Control
Operational Control
Acceptance Control
Checking the soil, materials, and documentation
before work starts — mostly by reviewing test
reports, certificates, and delivery paperwork; extra
testing only when something looks off.
Checking the work while it's happening, or right
after — mostly by measurement, visual inspection,
or a simple technical walk-through.
The final sign-off once a facility, or a stage of
hidden work, is complete — the formal decision on
whether it's fit to use or to build on top of.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
36

37.

QUALITY CONTROL
The Work Nobody Can See Later
Once backfill covers them, some parts of the job can never be inspected again — so “hidden work” gets special attention before it disappears
from view:
Artificial bases placed under foundations, including the floor of the excavation itself
Fill placed as a bearing base, and sand or gravel cushions
Any natural soil layer left to carry load beneath a structure
Backfill compacted in layers, checked as each layer goes down
If work stops for a while…
> 1 month
A break in the work longer than this calls for formal
steps to protect the site — and to re-check it before
work resumes
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
37

38.

WRAPPING UP
From Bare Ground to a Booked Schedule
Topsoil comes off first — by scraper on long, gentle slices, or by bulldozer on shorter, section-by-section pushes.
A crane is chosen on three numbers at once: lift height, working reach, and capacity — all rounded up, never down.
A calendar graph turns work volumes into worker-days, machine-shifts, and finally an actual day-by-day timetable.
The flow method lets separate crews overlap on different work-fronts; the longest chain of work sets the critical path.
Quality control never stops — and hidden work gets checked before it's covered up for good.
Next time: the ground is ready and the crane is booked — it's time to start building upward.
TECHNOLOGY OF CONSTRUCTION PRODUCTION · LECTURE 8
38