[Rabigh]Geotechnical Evaluation

Ruwais Refinery Expansion PKG-2 ProjectRuwais Refinery Expansion PKG-2 ProjectRuwais Refinery Expansion PKG-2 ProjectRuwais Refinery Expansion PKG-2 Project

Global Leader

Soil Investigation Report Soil Investigation Report ReviewReview

Rabigh ProjectRabigh Project

2011.06


Global LeaderContentContent

1. Subsurface Condition

2. Seismic Evaluation

3. Shallow Foundation

4. Deep Foundation

5. Others


Global Leader1. Subsurface Condition1. Subsurface Condition

• In general, the project site subsoil consists of Medium Dense to Very Dense silty Sand with occasional gravel & sandy clay layer.

• At BH 722, 740, 870, loose sand layer was identified, but these boring holes do not located within our package area.

• N=5 soft Clay was identified in BH-708 (CP3) at depth between 12m and 13.5m.

• Although there exist no SPT data from surface to 1.5m bgs, it appears that this layer mainly consists of dense to very dense gravel & sand aggregates fill placed recently.

Area Package Code Relative Boring Hole #

1 RP2, CP1 723, 724, 729, 730, 741, 750, 757, 758, 764, 765, 768, 770, 761, 772

2 CP2, CP3, CP4703, 704, 705, 706, 714, 715, 716, 717, 725, 731, 732, 733, 734, 738, 739, 742, 743, 745, 746, 752, 753, 754, 755, 759, 762, 766

3 CP3, CP5 707, 708, 709, 710, 711, 718, 721, 727, 735, 736, 737

Relative Boring Holes (Per SI Report)



RP2 CP1

CP2

CP3

CP4



CP5

CP5

CP3


Global Leader2. Seismic Parameter2. Seismic Parameter

• The Rabigh Area is seismically inactive zone (UBC Zone =1)

• The Geotechnical Investigation report adopted seismic data from Saudi Aramco Design Standard ASES-A-112 (2008).

• In general, seismic parameters(PGA,Ss,S1)) from IBC is smaller then UBC, and Aramco Standard follows IBC procedure.

• Given that PGA is 0.04~0.08g and the subsurface is mainly consists of medium dense sand, the liquefaction potential would be low at the project site.

• IBC Return Period = 2 % exceedance in 50 years = 2,500 years

Seismic Zone Map (UBC)



ASES-A-112 (2006)

• Should be noted that SI report used 2008 ASES-A-112 data.

• 2008 seismic parameters are slightly higher than those from 2006

(Report Ss = 18.8, S1=6.7, Sg=4, Site Class D)

• In general, Sg=0.4S1=7.5, but Sg=4 in report

• Seismic parameters in Soil Report need to be confirmed.



Design Seismic Parameter

Mapped Spectral Response AccelerationSoil Condition Adjusted Spectral Response

AccelerationDesign Spectral Response Acceleration (5%

Damping)

Ss S1 Sms Sm1 Sds Sd1

0.188g 0.067g 0.3g 0.16g 0.2g 0.11g



Design Response Spectrum





0

0.1

0.2

0.3

0.4

0.01 0.1 1 10T (Second)

Sa

(g)

UBCCode,Zone 1,Class C

IBCCode,Class C


Global Leader3. Shallow Foundation3. Shallow Foundation

• Appears that the existing subsurface is relatively good condition and would be suitable for the shallow foundation.

• SI investigation report presents allowable bearing pressure for varying embedment depth and footing size.

• SI report estimated net allowable bearing pressure using a representative borings within each area.





PGA = Settlement was estimated up to 5 years after construction

• SI report estimated net allowable bearing pressure using a representative borings within each area.

• However, it appears that the worst boring hole was selected as a representative boring hole in SI Report.

• Consequently, the allowable bearing pressure presented in the SI report would be a conservative value.

• If the design bearing pressure is exceeds the net allowable bearing pressures presented in the report or additional bearing pressure is required, the allowable bearing pressures be re-calculated using corresponding boring holes.

Boring # Average N Boring # Average N

744 32

723 23

717 40

725 30

714 30

752 36

711 31

748 39Area 3 38 710 27

Area 2 43

725

714

30

30

Area 1 41 723 23

Used Boring # in SI Report AllowableBearing Capacity Calc

Lowest Average NBore Hole #Location

Average Nof All Boring Hole

within area

Selection of Representative Boring



• The allowable bearing capacity presented in SI Report checked using a Modified Schmertmann method with respect to the settlement.

• The results shows that method and procedure for allowable bearing capacity calculation in SI reoprt appears correct.

SI Report Allowable Bearing Capacity Calculation Check

Bearing Pressure(kPa)

Settlement(mm)

CP1, RP2 1 BH 744 225 225 24.6

BH 714 180 180 24.9

BH 717 215 215 24.2

* Embedment Depth : 2m, Size 3m by 3m

CP2~4 2

Net Allowable Bearing Pressure(kPa)

SI Report

Calculation Check

Location

Package AreaUsed

BoringLog


Global Leader4. Deep Foundation4. Deep Foundation

• The allowable pile capacity presented in SI report is calculated using BH #807 up to 13mbgs and profiles from BH#207 and #209 were utilized depth between 13m and 30m.

• Most of boring logs presented in the report conducted up to depth of 13m, and BH#207 and #209 is not included in the report.

• Given that BH#807 is located far away from the our project location and the soil condition is relatively loose, if the deep pile foundation applied within our project site, the pile capacity would be higher than the values presented in the report.

BH-807

Project Site


Global Leader5. Others5. Others

• Water table is located approximately 2.5m ~ 6m below the existing surface.

• In case the ground water level remains above the excavation bottom, an appropriate temporary dewatering system should be implemented.





























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[Rabigh]Geotechnical Evaluation