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Introduction in the building
- Structure of the building is monolithic reinforced concrete structure The building has 11 storeys and 20 spans All the geometric data of the building is illustrated in the below table.
- Construction and site conditions of the building:
Geological properties: soil grade II with high strength of soil There’s no need to reinforce foundation pit.
The level of water table is by far greater than the level of foundation pit.
Project data
Figure 1 Structural plan of building
Foundation structure
Hm t m cm à Choose t = 45 (cm) b Dimension of foundation are chosen following to the formula below:
Ground
Roof
- 2 layers of traditional terra-cotta floortile (ceramic tile)
Wall
- According to axis: External wall 200 (mm), internal wall 110 (mm).
- Plaster 40% of external wall area ; 50% of internal wall area.
- Paint 40% of external wall area ; 50% of internal wall area.
- Doors ( and windows) take 60% of external wall area ; 10% of internal wall area.
Power, water factor
- 0,32 working hour per 1m 2 of floor.
Construction plan and location of building
Figure 11 Building location on construction plan
CONSTRUCTION SCHEDULE
FOUNDATION CONSTRUCTION
3 Pouring lean concrete of foundations and ground beams.
4 Installing foundation, ground beam and column reinforcement.
5 Installing foundation and ground beam formwork.
6 Pouring foundation and ground beam concrete.
7 Dismantling foundation and ground beam formwork.
18 Pouring lean concrete for 1st floor ground base
19 Installing reinforcement for 1st floor ground base
20 Pouring concrete for 1st floor ground base
2 Construction method and the calculation of work volumn
2.1.1 Selection of soil excavation method
Select the dimensions of ground beam : 45 x 20(cm)
Total depth of the excavation: Hd = 3 × 45 + 10 5 (cm) = 1,45 (m)
Slope factor: m = 1:0,25 (soil grade II)
The figure below shows the dimensions of a typical foundation.
Figure 12 Excavation pit for isolated footing axis A-2
Figure 13 Excavation pit for isolated footing axis B-2
Figure 14 Excavation pit for isolated footing axis C-2
When not considering the excavation for the construction of ground beams, we have a excavation plan of isolated footings as flollow:
According to figure 15, 16 and 17, although soil left after digging foundation pits following to axis A and B, D and E are large with 2.45m length, that after digging foundation pits axis B, C and D are small with 0.6m lenth In addition, soil left after digging foundation pit following to axis 1,2,3,…,21 are also small with 0.3m length Moreover, ground beams are located on the surface of 1 st step of isolated footing.
Excavation method: Mechanical combined with manual method The method is divided into 2 phases:
1 st phase: Excavating pond dig from ground level (-0,9 m) to bottom of lean concrete of ground beam level (-1,9 m)
2 nd phase: Excavating holes for 2 nd level of footing from bottom of concrete of ground beam level (-1,9 m) to bottom of lean concrete of isolated footing level (-2.35 m)
The foundation pits are flattened by labour and roller.
I have excavation plan as blow:
Figure 18 1st phase excavation plan
Figure 19 2nd phase excavation plan
Recalculate the pit excavation dimension: a) 1 st phase: Excavating pond dig from ground level (-0,9 m) to bottom of lean concrete of ground beam level (-1,9 m)
b) 2 nd phase: Excavating holes for 2 nd level of footing from bottom of concrete of ground beam level (-1,45 m) to bottom of lean concrete of isolated footing level (-2.35 m)
Excavating holes for axis A, E: There are 42 pit holes.
Excavating holes for axis B, D: there are 42 pit holes
Excavating holes for axis C: there are 21 pit holes
- Excavation volume by manual method:
2.1.3 The selection of excavator a) Excavator selection
Base on volume of soil excavated, we select Backhoe excavator EO-3322B1 with the following parameters:
Kd = 1: Factor of full-filling bucket
17 1,1 1 ck vt quay ck ck
Productivity of backhoe per shift: N 65,16 8 521,3( m shift 3 / )
Number of shifts for the excavation:
Select one machine with 4 shifts for excavation process
Using a excavator, the working time 1 shift/day and work for 4 days
The machine stands on high to put the bucket under the foundation pit to dig the ground When the bucket is full of soil, turn the bucket from the digging position to the pouring position, and the car is standing next to it. b) Dump truck selection
Assume that distance from site to the material gathering yard about 30km. Velocity of the truck is about 70km/h.
Time for truck to do a cycle: 1 2 30 0,86( ) t 70 h
Number of cycle a truck can do in a shift:
The truck can do 6 cycles in a shift
Select dump truck VEAM VM-551605 with following parameters:
Volume of soil that one truck can do in a shift: V 6 15,6 93,6( m 3 )
Number of trucks needed in a shift:
6 trucks needed for the transportation in 1 shift
Select 6 trucks with 4 shifts for excavation process
Lean concrete is mixed at construction site and then transported to the foundation pit by manner The lean concrete volume is estimated by the following table:
2.3 Isolated footing and gorund beam construction
2.3.1 Calculation of concrete, reinforcement, formwork volume for isolated footings and ground beams
Axis Element Dimension (m) Area per unit (m 2 )
- Number of partitions should ensure the continuousity of production line.
- Difference between the largest and smallest partition should not exceed 25%.
- Volume of concrete in a partition must be poured continuously in a work shift.
- Partition must stop at settlement joint of building.
- Partition must stop at position with low value of internal forces.
Construction site is devided into 4 partitions as shown in the figure below:
2.3.3 Calculation of concrete, reinforcement, formwork for each partition
Table 6 Lean concrete volume of each partiton
Determine the mass difference between the largest subdivision and the smallest subdivision: 33,13 25,99 100% 21,5% 25%
The difference in volume between segments