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Geodetic Monitoring of the Deformation of a 50,000 t Sugar Storage Tank
Founded on 124 Long Bored Piles
P. Savvaidis and I. Ifadis
Laboratory of Geodesy
Dept. of Civil Engineering
Aristotle University of Thessaloniki
Greece
Monitoring of the behavior of large technical structuresMonitoring of the behavior of large technical structures
These deformations may be attributed to several reasons: incomplete investigation of foundation soil properties improper construction of the foundation system insufficient knowledge of the operating conditions earthquakes etc.
These deformations may be attributed to several reasons: incomplete investigation of foundation soil properties improper construction of the foundation system insufficient knowledge of the operating conditions earthquakes etc.
Monitoring of the behavior of large technical structures has been a reality for the last few decades.
Monitoring of the behavior of large technical structures has been a reality for the last few decades.
Deformations that occur may cause severe damages to structures or even loss of life and injury to people.
Deformations that occur may cause severe damages to structures or even loss of life and injury to people.
The continuous monitoring of the behavior of a structure can detect deformations and displacements authenticating study and construction theories and proving the safety of the operation of the technical work.
The continuous monitoring of the behavior of a structure can detect deformations and displacements authenticating study and construction theories and proving the safety of the operation of the technical work.
The 50,000 t Sugar Storage Tank - 1The 50,000 t Sugar Storage Tank - 1
A heavy storage tank for storing 50,000 t of sugar founded on a large group of bored piles.
The tank is located in the installations of the Hellenic Sugar Industry S.A. at Plati, about 50 Km from the City of Thessaloniki.
It is the largest structure of this category in Europe and its construction was completed in 1995 with a cost of more than 2,500,000 USD.
A heavy storage tank for storing 50,000 t of sugar founded on a large group of bored piles.
The tank is located in the installations of the Hellenic Sugar Industry S.A. at Plati, about 50 Km from the City of Thessaloniki.
It is the largest structure of this category in Europe and its construction was completed in 1995 with a cost of more than 2,500,000 USD.
The 50,000 t Sugar Storage Tank - 2The 50,000 t Sugar Storage Tank - 2
The complex consists of a cylindrical shell of a 350 mm thick circular, prestressed concrete wall. The concrete shell has 46 m external diameter, it is 33.36 m high and it is covered by a wooden roof. The superstructure is founded on a 1200 mm thick circular concrete raft, 2.50 m above the ground surface, which is supported by 124 bored piles. The dead weight of the whole structure is approximately 12,000 t.
The complex consists of a cylindrical shell of a 350 mm thick circular, prestressed concrete wall. The concrete shell has 46 m external diameter, it is 33.36 m high and it is covered by a wooden roof. The superstructure is founded on a 1200 mm thick circular concrete raft, 2.50 m above the ground surface, which is supported by 124 bored piles. The dead weight of the whole structure is approximately 12,000 t.
The most important undesirable effects of settlements to avoid in designing tank foundations are:
Overall settlement of the tank.Differential settlement across the diameter, which mayoverstress internal piping connections.Differential settlement along the periphery, which may overstress the superstructure.Differential settlement between the tank and the external connection pipework.
The most important undesirable effects of settlements to avoid in designing tank foundations are:
Overall settlement of the tank.Differential settlement across the diameter, which mayoverstress internal piping connections.Differential settlement along the periphery, which may overstress the superstructure.Differential settlement between the tank and the external connection pipework.
Foundations consideration and design - 1Foundations consideration and design - 1
Storage tanks are relatively flexible structures and they can tolerate greater settlements than other engineering structures. However, there is a limit to
the settlements expected to take without distress.
Storage tanks are relatively flexible structures and they can tolerate greater settlements than other engineering structures. However, there is a limit to
the settlements expected to take without distress.
Foundations consideration and design - 2Foundations consideration and design - 2
Finally, the rotary, cast in place, large bored piles with bentonite slurry were selected as the most efficient pile type.
Finally, the rotary, cast in place, large bored piles with bentonite slurry were selected as the most efficient pile type.
The theoretical mean total settlement of the group of piles was evaluated equal to 12 cm.
The theoretical mean total settlement of the group of piles was evaluated equal to 12 cm.
A group of 124 piles was designed and constructed. Each pile has a diameter of 1.20 m and it is 37.17 m long.
A group of 124 piles was designed and constructed. Each pile has a diameter of 1.20 m and it is 37.17 m long.
A survey of similar structuresA survey of similar structures
A heavy storage tank capable of storing 15,000 t of liquid ammonia located at the industrial area of the city of Thessaloniki near the seaside. It is founded on a circular concrete raft, which is supported by 112 bored piles. Deformation measurements for vertical displacements.
A heavy storage tank capable of storing 15,000 t of liquid ammonia located at the industrial area of the city of Thessaloniki near the seaside. It is founded on a circular concrete raft, which is supported by 112 bored piles. Deformation measurements for vertical displacements.
A heavy storage tank capable of storing 40,000 t of sugar at Forlipopoli, Italy. The circular concrete raft is founded on 396 piles.
Deformation measurements for both horizontal and vertical displacements.
A heavy storage tank capable of storing 40,000 t of sugar at Forlipopoli, Italy. The circular concrete raft is founded on 396 piles.
Deformation measurements for both horizontal and vertical displacements.
1985-today1985-today
1994-19961994-1996
Measurement of deformation - 1Measurement of deformation - 1
Measurement of deformation - 2Loading history
Measurement of deformation - 2Loading history
The deformations of the tank were observed after the completion of its construction during the first loading with sugar. The tank was gradually
filled with 10,000 t of sugar. Then the sugar was removed, the tank remained empty for about five months and, finally, it was again filled
with sugar to the maximum load of 50,000 t.
The deformations of the tank were observed after the completion of its construction during the first loading with sugar. The tank was gradually
filled with 10,000 t of sugar. Then the sugar was removed, the tank remained empty for about five months and, finally, it was again filled
with sugar to the maximum load of 50,000 t.
0100002000030000400005000060000
0 100 200 300 400 500
Days from start
Su
gar
Lo
ad
[to
ns]
Measurement epochs:
6
Measurement epochs:
6
In order to monitor the horizontal deformation, of the cylindrical shell concrete wall:
Two lines of control points, each of 12 cone-shaped targets, were installed on the wall of the tank from bottom to top, at the diameter NW-SE, the lower 6 at distance of 3 m from each other and the rest at distance of 6 m.
In order to monitor the horizontal deformation, of the cylindrical shell concrete wall:
Two lines of control points, each of 12 cone-shaped targets, were installed on the wall of the tank from bottom to top, at the diameter NW-SE, the lower 6 at distance of 3 m from each other and the rest at distance of 6 m.
Measurement of horizontal deformation - 1Measurement of horizontal deformation - 1
A control network consisting of a number of reference points (pillars) was established around the tank.
The network was remeasured with GPS receivers at each epoch.
The coordinates of the targets on the wall were computed due to the measurement of intersections from the points of the control network.
A control network consisting of a number of reference points (pillars) was established around the tank.
The network was remeasured with GPS receivers at each epoch.
The coordinates of the targets on the wall were computed due to the measurement of intersections from the points of the control network.
Measurement of horizontal deformation - 2Measurement of horizontal deformation - 2
Measurement of horizontal deformation - 3Measurement of horizontal deformation - 3
A free network adjustment of the complete network (both reference and control points included) was done for each epoch. A similarity transformation was used to obtain a common reference system between the coordinates of the points of the specific epoch and the coordinates of the points of the zero measurement. The horizontal displacement of each control point was computed as the difference between the zero measurement coordinates and the corresponding transformed last epoch coordinates.
A free network adjustment of the complete network (both reference and control points included) was done for each epoch. A similarity transformation was used to obtain a common reference system between the coordinates of the points of the specific epoch and the coordinates of the points of the zero measurement. The horizontal displacement of each control point was computed as the difference between the zero measurement coordinates and the corresponding transformed last epoch coordinates.
Measurement of vertical deformation - 1 Measurement of vertical deformation - 1
The benchmarks can be divided into three groups: P1, P2, P3, and P4 located on the central piles P5, P6, P7, P8, P9, and P10 located on piles at an intermediate periphery P11, P12, P13, P14, P15, and P16 located on piles at the external periphery of the slab.
The benchmarks can be divided into three groups: P1, P2, P3, and P4 located on the central piles P5, P6, P7, P8, P9, and P10 located on piles at an intermediate periphery P11, P12, P13, P14, P15, and P16 located on piles at the external periphery of the slab.
In order to monitor the vertical deformation,16 benchmarks were installed on the upper free part of
certain piles.
In order to monitor the vertical deformation,16 benchmarks were installed on the upper free part of
certain piles.
Measurement of vertical deformation - 2 Measurement of vertical deformation - 2
High precision geodetic levelling
High precision geodetic levelling
Measurement of vertical deformation - 3 Vertical movements of piles during the first loading of the tank with
sugar
Measurement of vertical deformation - 3 Vertical movements of piles during the first loading of the tank with
sugar
660680700720740760780800
0 37 93 190 353 408
Days from start
Ele
va
tio
n [
mm
]
P1
P2
P3
P4
650
700
750
800
850
0 37 93 190 353 408
Days from start
Ele
vati
on
[m
m]
P5
P6
P7
P8
P9
P10
680700720740760780800820
0 37 93 190 353 408
Days from start
Ele
vati
on
[m
m]
P11
P12
P13
P14
P15
P16
P1, P2, P3, and P4P1, P2, P3, and P4
P5, P6, P7, P8, P9 and P10P5, P6, P7, P8, P9 and P10
P11, P12, P13, P14, P15 and P16P11, P12, P13, P14, P15 and P16
The vertical displacements of pile benchmarks generally
follow the loading and unloading of the tank
The vertical displacements of pile benchmarks generally
follow the loading and unloading of the tank
Measurement of vertical deformation - 4 Measurement of vertical deformation - 4
Slab deformation under maximum load during the first loading of the tank with sugar (curved lines are lines of equal vertical displacement, in mm)
Slab deformation under maximum load during the first loading of the tank with sugar (curved lines are lines of equal vertical displacement, in mm)
The maximum settlements of the slab occurred at central piles P1, P2, P3, and P4 with a mean value of approximately 63.5 mm. The settlements observed were smaller with increasing distance from the center of the circular slab.
The maximum settlements of the slab occurred at central piles P1, P2, P3, and P4 with a mean value of approximately 63.5 mm. The settlements observed were smaller with increasing distance from the center of the circular slab.
Conclusions – 1Comparison to the behaviour of similar structures
Conclusions – 1Comparison to the behaviour of similar structures
The model of vertical deformation of the sugar tank at Plati was very similar to the behavior observed in the other two tank structures mentioned above (the ammonia storage tank in Thessaloniki and the sugar storage tank in Forlipopoli).
The model of vertical deformation of the sugar tank at Plati was very similar to the behavior observed in the other two tank structures mentioned above (the ammonia storage tank in Thessaloniki and the sugar storage tank in Forlipopoli).
ThessalonikiPlati
During the first loading of the tank with 10,000 t of sugar, the mean value of the observed settlement was equal to the 25% of the predicted mean final settlement.
After sugar removal the mean remaining settlement was 9% of the final predicted value.
The differential settlements between the center of the foundation slab and the peripheral points were fractions of the overall slab settlement, quite close to the ratio estimated in the computations.
During the loading test with the maximum load of 50,000 t, the mean observed settlement seems to be approximately the 50% of the expected final settlements.
The observed horizontal displacements of the tank wall were insignificant, proving the effectiveness of the design and construction method used.
During the first loading of the tank with 10,000 t of sugar, the mean value of the observed settlement was equal to the 25% of the predicted mean final settlement.
After sugar removal the mean remaining settlement was 9% of the final predicted value.
The differential settlements between the center of the foundation slab and the peripheral points were fractions of the overall slab settlement, quite close to the ratio estimated in the computations.
During the loading test with the maximum load of 50,000 t, the mean observed settlement seems to be approximately the 50% of the expected final settlements.
The observed horizontal displacements of the tank wall were insignificant, proving the effectiveness of the design and construction method used.
Conclusions – 2Conclusions – 2
