Improvement of fine-grained and cohesive soils 181
medium 2.25 m vibro compaction grid area resulted in 18.3 mm settlement
at design bearing pressure of 280 kPa which also was found inadequate.
Consequently, vibro replacement with 85 cm diameter stone columns set out
in an equilateral triangular grid of 1.60 m was chosen as foundation method.
The load test result was used to predict the settlement performance of the
tanks. Table 4.13 shows the results of the two load tests performed on vibro
compaction and on vibro replacement stone columns before the foundation
works commenced together with two further load tests carried out as quality
assurance during the vibro replacement works. At design load of 280 kPa, all
three load tests on stone columns show settlements of between 6 and 9 mm,
whilst the load test on vibro compaction settled at 18 mm.
Based on the load tests, total maximum settlements for the centers and
below the shell of the tanks were predicted with 26 and 20 mm, 23 and
18 mm, and 22 and 17 mm for the 20, 15, and 10 m diameter tanks, values
which yet were to be verified during water testing of the tanks.
Figure 4.42 shows the tank farm in summer 2015 when the hydrostatic
tests were performed on these storage tanks according to API 650 resulting
Table 4.13 Results of zone load tests in mm on 3 × 3 m test foundations
at 280 kPa design bearing pressure
Phase
Test
Settlement (mm)
Precontract
On vibro compaction with
2.25 m grid
18.3
Precontract
On 4 nos. stone column
9.3
Postcontract
On 4 nos. stone column
5.8
Postcontract
On 4 nos. stone column
6.7
Figure 4.42 Tank farm in summer 2015. (Courtesy of Keller Group plc, London, UK.)
medium 2.25 m vibro compaction grid area resulted in 18.3 mm settlement
at design bearing pressure of 280 kPa which also was found inadequate.
Consequently, vibro replacement with 85 cm diameter stone columns set out
in an equilateral triangular grid of 1.60 m was chosen as foundation method.
The load test result was used to predict the settlement performance of the
tanks. Table 4.13 shows the results of the two load tests performed on vibro
compaction and on vibro replacement stone columns before the foundation
works commenced together with two further load tests carried out as quality
assurance during the vibro replacement works. At design load of 280 kPa, all
three load tests on stone columns show settlements of between 6 and 9 mm,
whilst the load test on vibro compaction settled at 18 mm.
Based on the load tests, total maximum settlements for the centers and
below the shell of the tanks were predicted with 26 and 20 mm, 23 and
18 mm, and 22 and 17 mm for the 20, 15, and 10 m diameter tanks, values
which yet were to be verified during water testing of the tanks.
Figure 4.42 shows the tank farm in summer 2015 when the hydrostatic
tests were performed on these storage tanks according to API 650 resulting
Table 4.13 Results of zone load tests in mm on 3 × 3 m test foundations
at 280 kPa design bearing pressure
Phase
Test
Settlement (mm)
Precontract
On vibro compaction with
2.25 m grid
18.3
Precontract
On 4 nos. stone column
9.3
Postcontract
On 4 nos. stone column
5.8
Postcontract
On 4 nos. stone column
6.7
Figure 4.42 Tank farm in summer 2015. (Courtesy of Keller Group plc, London, UK.)