Proceedings of the Eighth (1998) International Offshore and Polar Engineering Conference Montreal, Canada, May 24-29, 1998 Copyright 1998 by The International Society of Offshore and Polar Engineers ISBN 1-880653-34-6 (Set); ISBN 1-880653-35-4 (Vol. 1)

Foundation Aspects for the Load-Out of 24,000-Tonne Jack-Up Rig

S, Dasgupta Hyundai Heavy Industries Co, Ltd,

Ulsan, Korea

1.0 ABSTRACT

Massive 24,000 Tonne Jack - up Rig was fabricated, in various stages, at the fabrication yard of Yard number 2. Schematization of the foundation system become very important due to heterogeneous soil characteristics across the fabrication yard and due to progressive build-up of the structure. It become a challenge to the Geotechnical engineer to plan an economic foundation system to take care of the settlement behavior during different stages of fabrication. Foundation system was schematized on four skid - way system. During load-out, the load was transferred in such a manner that the quay wall was capable of sustaining the load with control settlements. The calculated behavior matches very well with the recorded observations of the foundation system. This paper deals with the analysis , design and behavior of the foundation system of the jack - up rig.

2.0 KEY WORDS

Jack-up rig, Skid-way, Concrete blocks, Piles, Quay-wall, Compression strut, Settlement

3.0 INTRODUCTION

Fabrication of the 24,000 Tonne Jack - up rig was planned to be carried out at Yard No.2. The exact location of fabrication was chosen in such a way so as to take the maximum advantage of the existing facilities. It was therefore decided to fabricate the Jack - up rig where previously two mammoth Jackets, each weighing more than 35,000 Tonne were fabricated. Just before the fabrication of the Jack - up rig, various Jackets, weighing between 2,500 and 3,500 Tonne, were fabricated in the same area. The sub - soil in the area was therefore subjected to considerable amount of consolidation and compaction under the heavy loads at different time over the past several years.

4.0 FOUNDATION SCHEME

The schematization of the foundation system was done , keeping in view the future requirements of the foundations with respect to the following stages of progress and operation of the 'Jack - up rig'

1. Supporting system during the fabrication of the 'hull' 2. Supporting system of the three 'Spud - legs' 3.Supporting system during the 'Jacking up and Jacking down' tests

of the rig 4. Supporting system during the 'Load - out' of the Jack - up rig 5. Safety of the existing 'Quay wall' during load -out of the rig 6. Overall stability of the entire foundation system 7. Economizing the foundation by using the existing facilities and

foundations

The Jack - up rig, consists of three numbers of Spud - legs, which will eventually carry the entire weight of the rig, are spaced in a triangular manner of spacing 74.75 m, as shown in fig. - 1. The configuration of the 'Hull' of the Jack - up rig is also shown in fig. - 1. During the fabrication of the rig, the Hull was to be supported initially. The three 'Spud - legs' will have separate foundation system.

5.0 SUBSOIL PARAMETER

Sub - soil parameters at the Fabrication yard generally consists of 'Fill' material at the top varying in thickness between 4.0 meter to 23.40 meters, followed by a deposit of 'Transported soil'. The 'Transported soil' varies in thickness between 9.0 meter to 23.50 meters. Thereafter 'Bed - rock' was encountered having different weathering effect. Fig. - I also shows the detail plan of Bore hole locations in the area. Fig. - 3 shows a typical Bore-log. The salient design soil parameters for the foundation design of the Jack - up rig is shown in Table-I.

The 'Fill' material at the top generally consists of loose to medium dense silty fine Sand ( SM ) followed by silty angular Gravel with fine sand, in saturated medium dense condition. Where the 'Fill' material extends to a greater depth the material consists of medium to dense and very dense Sand ( SM ) and Gravel ( GM ). The 'Transported soil' generally consists of Silty sub - rounded Gravel with fine to coarse sand ( GM ), saturated, medium to very dense in nature. At a greater depth 'Transported soil' consists of silty fine Sand with shell fragments, silty angular Gravel with fine to coarse sand (GM ) dense to very dense in nature.Bedrock consists of highly weathered bedrock of Shale, crumbles to silty sand and rock fragments very dense in nature followed by partly weathered bedroc~ of Shale.

375

6.0 DETAIL FOUNDATION SCHEME

A brief description of each foundation system are as explained below

6.1 Foundation during thefabrication of the Hull

Entire area where fabrication was carried out was paved with 200 mm thick concrete over compacted existing fill material. Foundation system of the Jack - up rig was planned to be on several small foundations of steel base plate footings of dimensions 1.5 m square. in general. The steel tubular members connected to the footings were supporting the Hull of the Jack - up rig. These small footings, totaling about 200 in numbers, were placed in a regular grid pattern below the hull of the Jack - up rig. Total weight of the Hull was approximately 150 Mn ( 15,000 Tonne). Hence average load carried by each small footing, resting on the concrete pavement are 750 Kn. The safe bearing capacity of each footing, considering the effect of 200 mm thick concrete pavement, was 500 Kpa. Accordingly 200 numbers of footings were planned in a regular grid manner. It is of interest to note that settlement was kept very much within the allowable limit by placing the footings after observing the settlement behavior. The Hull build up its load progressively over a period of one year. Accordingly the number of footings were increased depending upon the 'Weight control report' of the Hull.

6.2 Foundation of the Spud -legs

The Jack - up rig consists of Three Spud legs as shown in Fig. - 1. Various alternative foundation system was planned for the Spud legs. Finally the most economic and practical system adopted for the foundation is as shown in Fig. - I. Each spud leg was having three elevated steel plate which provides the base. The foundation was designed as an isolated footing under each of these elevated steel plate. These foundations were designed to carry the load during testing of the Jack - up rig.

6.3 Foundation system during the Load out of the jack up rig

Due to the mammoth weight of the Jack - up rig, the 'load - out' was planned to be carried out on 'Skid - ways'. On careful planning, it was decided to load out the 24,000 tonne ( 240 Mn ) rig using four skid -ways as shown in Fig. - 1 and Fig. - 2. In order to re - use the facilities available at the fabrication yard, the skid-ways were located at a place where earlier Jackets were fabricated. Two skid - ways were therefore founded on two existing skid - ways of earlier jacket. The balance length of the skid - way were founded partly on piles and partly on existing concrete blocks as shown in Fig. - 2. Remaining two skid - ways was founded on two new foundation system which was again partly on piles and partly on existing concrete blocks. Existing Skid way was founded on 40 meter long, 610 mm Outside diameter steel tubular piles of 16 mm wall thickness. Reinforced Concrete mat foundation consisting of several mats, each of size 6.0 m * 3.0 m * 0.7 m thickness were used beyond the piled foundation. As can be seen from Fig. - 2, the two new skid - ways were founded on 36.7 meter long pile cap, just behind the Quay wall. Balance skid - way, beyond the pile foundation, was supported on R.c. Mat. The extent or length of Skid - way resting on piled foundations was on the basis of overall stability of entire foundation system.

6.4 Quay wall of the fabrication yard

On the basis of detail analysis it was observed that the existing Quay wall was not strong enough to carry the distributed load of Jack up rig

during load out operation. The load shall be applied at the center of the Quay wall as a 'point load', so that it is not subjected to high de-stabilizing moment. For that purpose the 'Skid beam' was planned to be supported between the Quay wall and the Pile cap. The Skid beam will be resting on 'Stubs' so that during the load out of the Rig, the load coming on the Skid beam will be transferred to the Quay wall through the 'Stubs' as point load. 'Link Beam' was placed between the Quay wall and the 'Transporter barge' for load out of the Rig. Link beam was supported on the same 'Stub' as 'Skid beam', thus ensuring the transfer of Rig load as 'concentrated load' at the center of the Quay wall.

6.5 Overall safety of the entire foundation system

Two types of stability analysis were carried out to ensure the overall safety of the entire foundation system.

6.5.1 Stability during fabrication, testing and load out

Simplified Bishop's method of stability analysis were carried out to find the 'global stability' of the 'entire foundation system' during fabrication, testing and load out operation of the rig, Slip circle analysis were carried out in a grid manner. Fig. - 2 shows the critical slip circle with minimum safety factor of 1.937, thus ensuring the overall stability during fabrication, testing and load out. The case considered here was the stability of the foundations due to the de-stabilizing force exerted by the weight of the rig.

6.5.2 Overall stability during pulling of the rig

During load out operation, pulling force to the rig was applied from the transporter barge. The pulling force was estimated as 15 percent of the vertical load. Transporter barge thus exert a horizontal reaction force on the quay wall through the fenders. Safety of the quay wall and other foundation system was therefore verified. On verification, it was observed that concrete blocks of the quay wall will slide against each other, thus becoming unsafe against the applied horizontal force. The quay wall was constructed by placing concrete blocks on each other. A scheme was developed for 'not transferring' this horizontal pulling force to the 'quay wall'.

376

Two tubular members, called 'compression struts', were hinge connected, between the transporter barge' and each of the four 'pile caps'. Total eight numbers of 'compression struts' were provided on four pile caps. This struts, trlsfer the horizontal pulling force, directly to the pile cap and hence to the piles. Stability check were carried out for the piles. Single pile analysis were carried out using P - Y data and equivalent horizontal force, acting on the pile. Analysis revealed that the piles were safe against the pulling force. Detail analysis are not discussed in this paper. It may be observed from Table - 3, that actual maximum friction was 13.58 percent during initial pulling as against 15 percent assumed.

7.0 DETERMINATION OF SOIL FOUNDATION PARAMETER

In order to assess the design soil parameters for the analysis and design of foundations, following investigations were carried out

a) Footing load tests for assessment of sub-grade modulus! soil spring constant

b) Assessment of sub grade modulus! soil spring based on soil properties

7.1 Footing Load Tests

Footing load tests were carried out at four locations for establishing the sub grade modulus I soil spring values. Load tests were carried out on each of the four skid ways. These values were compared with the values obtained from the sub soil shear strength parameters and finally was used for the settlement analysis of the various foundation system. Footing load tests were carried out on 2m*2.5m* 1.2m thick Concrete blocks, each weighing about 140Kn. The test was carried out for a maximum load of 1000 Kn. The results of the tests were quite interesting. The settlement under two test footing shows very little settlement with no change in the slope of the 'load - settlement curve'. This footings were placed where earlier two heavy jackets were fabricated, thus indicating compaction and settlement earlier. Other two footings shows changes in slope of the 'load - settlement' curve.

7.1.1 Assessment of Sub-grade modulus

For the assessment of sub-grade modulus of the actual foundation, consideration was given for the zone of influence of the pressure bulb of each foundations. On careful assessment upper and lower bound values of sub-grade modulus were established. These values ranges between 6.5 Mpa to 12.0 Mpa. The area covered under foundations were wide spread, as can be seen from the bore-logs. The subsoil parameters are variable. Hence settlement of each foundation system were computed using sub-grade parameters depending upon the soil stratification I layering, soil shear strength parameters, degree of compaction, relative density etc.

8.0 ANALYSIS AND DESIGN OF FOUNDATION SYSTEM

Detail analysis were carried out for each of the following foundation system

a) Pile foundation for skid way b) Raft foundation using concrete blocks for Skid way c) Isolated Reinforced concrete Spud-leg foundation d) Quay wall foundation

8.1 Skid - way foundation

Entire structure was loaded out on four skid - ways as shown in Fig.-2. Each skid way was resting partly on pile cap, supported by 610 mm 0.0. * 16 mm thick steel tubular piles. The balance length of skid-ways were resting on Mat foundations prepared by 'existing concrete blocks', each of size 6 m * 3 m * 0.7 m thick. Two concrete blocks were placed one above the other, thus making the foundation thickness as 1.4 m with width of footing as 6 m. On the top of the concrete blocks and pile caps, skid beam and skid shoes were placed. The pile supported foundation of the portion of the skid-ways of row 17 and 25 were resting on existing pile cap. The piled foundation was extended by a 'New pile foundation system'. The new pile cap was 13.6 m long and 5 m wide, except near the quay wall where the width of the pile cap was 6 m for a length of2 m. The 'Stub' of the skid beam and the link beam were directly resting on the first row of three piles. Skid-ways of rows II and 33 were founded on new piles I pile cap of length 36.7 m and width 5 m , except near the quay wall where the width was 6 m for a length of 5.75 m. Estimated pile capacities and pile lengths under different rows, considering subsoil design parameters, were calculated and shown in Table-2. Based on above estimated pile capacities the total number of piles,along with spacing under different skid-ways, were estimated and

are shown in Fig. -2. The extent and length of pile cap I pile foundation was governed by the 'Overall stability' of the entire foundation system as was explained earlier. Pile Driveability analysis were carried out using 'wave equation analysis' utilizing 'GRL WEAP' software package. Kobe K - 45 diesel hammer was used for driving the piles to the design penetrations with pile tip resting on rock strata. Exact driven lengths of the piles were within + I - 5 m of the design penetration. The factor of safety of the piles varies between 1.65 to 1.98 with respect to estimated capacity. Load on each skid - way was calculated as 2.0 Mn I m. Considering 10 percent more load for design consideration, the skid - way was designed for 2.2 Mn I m of loading. Thus foundation was designed for 0.37 Mpa of load. However the existing double layer concrete blocks were safe for 3.0 Mn I m ofload.

8.2 Assessment of Bearing capacity of Concrete block Mat foundation of Skid - way

Total fabrication and load out area of the jack-up rig was covered by sixteen bore holes, as shown in Fig. - I. Bearing capacity of Mat foundation was assessed based on worst bore hole data. For assessment purpose of bearing capacity, soil parameters up to a depth of 12.5 m was considered. Safe bearing capacity of 6 m wide foundation resting directly on so.il was estimated as 0.45 Mpa with a safety factor of 2.0. Settlement was however calculated at different location using actual available soil parameter and will be discussed later in this paper.

8.3 Spud - leg foundation

Each spud - leg was resting on three isolated footing. Spud - leg foundation was designed to carry the total load of the jack - up rig. During jack up and jack down test of the rig, the foundation system has to be safe enough to carry the entire load. Also during jack up condition, the Hull of the rig was at a height of around 10m above the ground level. However the foundation system was checked and designed for an elevated hull at 100 m above ground level, with wind speed of 125 Kmph. Considering equal load distribution on three legs, the load on each leg becomes 240 I 3 = 80 Mn. 20 percent more loads were considered due to uncertainties of load distribution etc .. Thus spud leg isolated foundations was designed for a vertical load of96 Mn. Each spud - leg was having three elevated steel base plates. After studying several alternatives, Isolated foundations were provided under each of the three base plates. Thus each isolated footing carried a vertical load of 96 I 3 = 32 Mn. Additionally foundation also carried a load due to horizontal wind force during the jack up condition. Based on above load, foundation size of isolated footing works out as 8.5 m * 8.0 m * 2.0 m thick. The depth of foundation was 2.0 m below the existing ground level. Bearing capacity of the foundation was assessed based on the worst bore hole soil shear strength parameter. The minimum safe ( Safety factor = 2.0 ) bearing capacity of the above foundation works out as 0.60 Mpa. Maximum foundation pressure estimated during jack up (test) condition of the rig at 100 m above the ground level was 0.52 Mpa thus ensuring the safety of the isolated foundation. Settlement was however assessed based on bore hole data and soil parameter at the actual location.

8.4 Quay wall foundation

Existing Quay wall was constructed using concrete blocks as shown in Fig. - 2. Maximum load on quay wall due to'reaction' of 'skid beam'

377

and 'link beam' was 17.2 Mn. This load was planned to be taken directly by the quay wall as concentrated load at the center of the quay wall. Considering load dispersion of IH in 2V, the load at the base of the quay wall was 0.375 Mpa. Safe allowable bearing capacity estimated from the subsoil parameter was varying between 1.15 Mpa to 1.5 Mpa. Settlement at different location of the quay wall was estimated considering actual soil parameter of the location.

9.0 LOAD - OUT PROCEDURE

Load-out of the jack-up rig was carried out in two stages

Stage-I Pre-load out Stage-II Final load out

Load out was carried out using 'Active shoe system'. Two shoes were used in each of the skid ways. Each shoe of skid ways in rows II, 17 and 25 was supported by 16 numbers of2.5 Mn capacity jack having a stroke of 200 mm. Thus under each shoe, 16 jacks were used with total capacity of 40.0 Mn. Under skid way 33, each of the two shoe was supported by 12 jacks of 2.5 Mn capacity and stroke of 200 mm. Thus total 120 numbers of jacks with total capacity of 300 Mn were used during the load out of the jack up rig. Total estimated pulling force required during load out was 0.15 * 240 = 36 Mn. Hence 'pulling system' utilized, comprised of 8 numbers of 5.6 Mn jacks, thus giving a total pulling force of 44.8 Mn. During load out operation, actual pulling force required at different stage is shown in Table - 3. 'Teflon' was applied on the skid way to reduce the friction during pulling. Pre load-out was carried out prior to actual load out. The jack-up rig during the pre load out stage was brought very near to the quay wall, with skid shoes resting on the pile cap. Final load out was undertaken after 12days of pre load out.

10.0 SETTLEMENT ANALYSIS

Settlement analysis was carried out for the following foundation system a) Spud-leg foundation during the 'Jacking up' and Jacking down'

tests b) Skid way foundations resting on pile cap c) Skid way foundation resting on Mat made of double layer

concrete blocks d) Quay wall

Settlement and behavior of every foundations were recorded and comparisons were made between the calculated and recorded settlement and will be shown in subsequent paragraph of this paper.

10.1 Settlement analysis of Spud leg foundations

Settlements were calculated at center, comer and edge of each of the 9 isolated spud leg foundations and are shown in Table - 4

Settlement of Spud-leg foundations, calculated, depends on the followings

a) sub-grade modulus at different locations of the footings b) area of influence at center, comer and edge c) load intensity etc.

Although the load carried by each spud legs were more or less same, but load under each isolated footings under each spud leg was different.Recorded settlements during Jacking up and Jacking down

tests after 21 days are as shown in Table - 5. Values of 'estimated settlements' and 'observed settlements' recorded during tests, were compared. It may be observed that the estimated settlement matches very well with the recorded settlement.

During 'jacking up' and 'jacking down' tests, the "hull' of the jack up rig was elevated by 10m above the skid way foundation level. It was kept in that position for about 14 days and then 'jacked down' and kept about 500 mm above skid way foundation for another 7 days.

10.2 Settlement Analysis of skid - way foundations resting on pile cap

It may be observed from Fig. -2 , that part of the skid way foundation was resting partly on pile - pile cap foundation system near the quay wall. Lengths of the piles were variable. Maximum skid way load was 2.2 Mn per m run. Hence load on two piles at extreme end of the skid way, away from the quay wall, were 2.85 Mn and 3.47 Mn. The loads on the piles were within the safe allowable capacity of the piles. Assessment of settlements of piles hence pile cap were carried out based on the following parameters

a) Elastic settlement of the pile b) Settlement of pile i_ soil system

10.2.1 Elastic settlement of piles

Point of fixity of pile, obtained from the "single pile analysis', was 14.0 m. Stiffness of pile obtained was 442.0 Mn 1m. Elastic settlement of pile varies between 6.3 mm and 7.7 mm.

10.2.2 Settlement of pile - soil system

Axial skin friction versus pile axial deflection ( T - Z ) data and End bearing versus axial deflection ( Q - Z ) data was developed based on pile - soil data. On the basis of loads exerted on the piles, both deflections were worked out from the T - Z and Q - Z data. From the pile capacity data developed' from pile - soil parameters it was observed that the 'skin friction' was fully mobilized and end bearing was partly mobilized which resulted in a pile displacement varying between 1.53 mm to 6.1 mm.

Hence total pile head settlement under the skid way load varies between 9.0 mm to 14.0 mm.

10.2.3 Observed pile cap settlement

During load out of the Jack up rig, settlements were recorded at regular intervals along the entire leFigth of the skid way. Recorded I observed settlements of skid ways resting on pile - pile cap foundation system varied between IO mm to 19 mm., thus showing very close resemblance with the 'calculated settlement' figures.

10.3 Settlement analysis of Skid way footing resting directly on soil

10.3.1 Settlement analysis of skid way

Part of the 'skid - way' foundation beyond the pile cap was resting on 'concrete mat foundations' made of available 'concrete blocks'. Two blocks were placed one above the other and placed one after the other with width of mat foundation as 6.0 m. It was discussed earlier that jack up rig was supported on each skid -way using two 'skid - shoes' each of length 2*6.0 m = 12.0 m.

378

Structural load dispersion of 45 degree was considered for assessment of 'effective size' of skid foundation. Effective zone of influence of 2 times the width, that is 12 m below the base of mat was considered, for estimation of settlements of tlie skid way mat foundations. Actual available Soil data along the length of each skid way was considered for assessment of settlement. Based on different sub grade modulus values at different locations, estimated settlement curve was developed and presented in Fig. - 4. It may be observed from the curves that the estimated settlements along the four skid ways varies between 22 mm to 141 mm. From the nature of the sub soil it may be observed that the soil is predominantly sandy in nature. Thus settlement will be somewhat immediate in nature. Due to presence of silts and some thin intrusions of clay seams, the long term settlements will continue but the magnitude was estimated to be very small. Moreover load - out operation was somewhat continuos and immediate in nature with respect to settlement. Thus the . immediate settlement' was expected to be of interest for the load out purpose.

10.3.2 Recorded settlement

Settlement recorded along the length of four skid ways varies between 30 mm to 136 mm. The jack up rig load was released entirely on the four skid ways from the legs and was allowed to be in the same position for four days before pre load out operation. The settlement was recorded along the four skid ways at every 6.0 m distance throughout the load out operation and also during the 'load transfer' stage and during four days of jack up 'resting' on the skid ways. Table - 6 shows the settlement recorded along the length of four skid ways. The recorded settlement generally matches well with the estimated settlements which enables the pre load out operation to be quite successful.

10.4 Settlement analysis of Quay wall during load out

Settlement analysis of quay wall was carried out based on sub soil parameters below the quay wall foundations. Estimated settlement along the quay wall varies between 75 mm to 120 mm. This quay wall . was earlier subjected to various loads during the load out operations of various other jackets with different loads. Thus it has undergone considerable amount of settlements earlier. Thus the expected settlement was estimated to vary between 25 mm to 40 mm, about one third of the calculated settlement. Moreover stroke of the jack was 200 mm which therefore can take care of larger settlement variations.

10.5 Special consideration

To take care of variable settlements between each foundation systems like concrete mat foundations, pile - pile cap foundations, quay wall foundations and finally the 'transporter barge', top of foundations were constructed at different levels. Since estimated settlements of pile cap was much less than concrete mat foundations, so top of pile cap was constructed 75 mm below the concrete mat foundations, to take care of 'immediate settlement' of the mat foundations. This enables less differential settlements between the two foundation system. The 'skid shoe' was fabricated to have a shape like 'sledge' or 'ski' for smooth transfer between two foundation systems. Also the 'skid beam' between pile cap and quay wall was made to overhang I cantilevered about 500 mm beyond the 'stub' constructed on the pile cap, to take care of flexibility during transfer of skid shoes from pile cap to quay wall.

11.0 CONCLUSIONS

Load out of the massive Jack up rig is a difficult and complicated operation. Careful schematization of the foundation system to take care of the loads of the rig at different stages of fabrication is of extreme importance for the individual safety of each foundation and overal safety of the entire foundation system. Assessment of subsoil parameter is of paramount importance in estimating the foundation behaviour. Simplified approach using basic principles of soil mechanics and foundation engineering were used for the estimation of bearing capacity, settlement and stability. Recorded observations matches very well with the calculated behavior, thus establishing the applicability of simplified approach.

12.0 ACKNOWLEDGEMENTS

The Author is grateful to the management of Hyundai Heavy Industries Co. Ltd.Jor the encouragement given for the preparation of this paper. Author expresses his deep sense of regards to his colleagues for the valuable information and technical details provided during the preparation of this paper.

13.0 REFERENCES

API RP 2A - WSD, 20th Edition, July1, 1993, Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms -Working Stress Design.

BOWLES, J.E., Foundation analysis and design, McGraw - Hill Book Co.

McCLELLAND, B and REIFEL, M.D., Planning and design of fixed offshore platforms, Van Nostrand Reinhold Company, New-York

POULOS, H.G., Proceedings, 1st International Conference on Numerical Methods in Offshore Piling, Institute of Civil Engineers, London

TOMLINSON, MJ., Pile design and construction practice, E and FN SPON, An Imprint of Chapman and Hall

WINTERKORN, H.F. and FANG, H.Y., Foundation engineering handbook, Van Nostrand Publishing Company, 1975

379

Origin Soil SPT Qu

Classification N Mpa

Fill SM 12 - 30 1.0

Transpo- SM 8 0.5

Rted Soil GM(Med) 15 1.0 GM(Den) 30 3.0

Weather- SM 50 3.0

Ed Rock SM 100 7.5

Soft Rock - -

20.0

Hard Rock - - 100.0

ROWS PILE SIZE, MM

11 610 * 16 thk.

17 610 * 16 thk.

25 610 * 16 thk.

33 610 * 16 thk. Safety factor of 1.5 was adopted

ITEM ROW 11

Dead weight of Jack up rig, Mn 60

Pulling arm from C.G of Jack up rig, M (-) 22.4

Initial Pulling force(OHrs) Mn 8

Subsequent Pulling Force(6 Hrs) Mn 4

Subsequent Pulling Force(20Hr ) Mn 4

TABLE-I.

SUB-SOIL DESIGN PARAMETER

Es K(30) ** Mpa Mn/m3 Degrees

10 - 35 80.0 31 - 35

8,0 33.3 28

18.0 75.0 33

36.0 150.0 40

40.0 165.5 40

80.0 335.5 45

- 500.0 50

- - -

** For 300 mm diameter plate

TABLE-2

ESTIMATED PILE CAP AClTY

kef) for kef) B=lm (Mn/m3) B=5m (Mn/m3)

10-40 3 - 28

75.0 50..0

150.0 95.0

LENGTH,M ESTIMATED SAFE LOAD TEST SAFE

CAPACITY, MN

30m to 34 m

34 m to 40 m

34 m to 40 m

36 m to 46 m

TABLE-3

PULLING FORCE

ROW ROW ROW

17 25 33

64 64 48

(-) 8.05 8.75 33.05

8 8 8

4 4 4

4 4 4

380

4.0 to 4.5

4.5 to 5.05

4.5 to 5.05

4.6 to 5.7

TOTAL

PULLING

FORCE

Mn

32

16

16

CAPACITY, MN

6.25

TOTAL TOTAL

PULLING FRICTION

MOMENT PERCENT

Mn-m

90.8 13.58 %

45.4 6.7%

45.4 6.7%

TABLE-4

SETTLEMENT OF SPUD-LEG FOUNDA TIONS

Location Foundation Depth of Soil Spring Soil Spring Estimated Estimated

Size, m Foundation, Constant, k I Constant, k2 Settlement dl, mm Settlement d2,

M Mn/m3 Mn/m3 mm

Center 8.5* 8.0*2.0 2.0 2.75 4.63 215 85

Comer 8.5*8.0*2.0 2.0 6.7 11.3 88 52

Edge 8.5*8.0*2.0 2.0 4.48 7.62 131 77

Center 8.5* 8.0*2.0 2.0 5.5 11.1 86.0 36.0

Comer 8.5* 8.0*2.0 2.0 13.2 27.0 35 15

Edge 8.5*8.0*2.0 2.0 8.9 18.1 53 26

TABLE-S

RECORDED SETTLEMENT OF SPUD LEG ISOLA TED FOUNDATIONS

Position of Recording Settlement In Leg - I, mm Settlement in Leg - 2, mm Settlement in Leg - 3, mm

A Inner Footing 145 ( 131 ) 197(215 ) 98 ( 88 )

B Clockwise from A 140 172 88

C Anticlockwise from A 125 118 70 ,

Values within brackets are estimated settlements.

TABLE-6 RECORDED SETTLEMENT OF SKID WAYS

STATION NUMBERS * SETTLEMENTS OF SKID WAYS, mm Row - II Row-17 Row-25 Row - 33

1 49 38 41 31 2 96 74 68 39 3 117 96 79 26 4 136 84 78 5 5 124 73 80 13 6 96 70 83 32 7 50 49 63 26 8 13 17 21 II 9 3 I -2 10 I -10 II -8 12 -2

* DIstance between each recordmg statIOns were 6.0 m.

381

'11r

lJl 0 0 0 0

L~ o o o o

30000

Vl I

-..J

to I I

12000 44000

HULL CONFIGURATION OF JACK UP RIG

50000

LEGEND ~ BORE HOLE(S) o OLD BORE HOLE(BH) ~ FOOTING LOAD TESTS(P) _ "TYP. SPUD-LEG FOUNDATION

(8.5*8.0M*2.0M)

FIG-1 SOIL TEST LOCATIONS

382

@ @

--.

:z 0

~ 0 :z ::> ~ ~

Pages 384-391 are blank.

384

-- ---- ------------------

Pages 384-391 are blank.

391