geotechnical investigation aceh road/bridge reconstruction & rehabilitation patek...

SEMINAR NASIONAL-1 BMPTTSSI - KoNTekS 5 G-125 Universitas Sumatera Utara, Medan - 14 Oktober 2011

GEOTECHNICAL INVESTIGATION ACEH ROAD/BRIDGE RECONSTRUCTION & REHABILITATION

PATEK BRIDGE LOCATION

Samsuardi Batubara

Program Studi Teknik Sipil, Universitas Katolik SantoThomas, SU Email: unika.sipil @yahoo.com

ABSTRAK This paper present the result of geotechnical investigation and engineering assessment for proposed Patek Bridge at Sta.124+035. The papers includes analysis and design of deep foundation based on the soil investigation data. The design will be one of the engineering reference to confirm the pile foundation design of Patek Bridge - Aceh Road Reconstruction Project. The purposes of our investigations were to explore the soil conditions at project area and to provide recommendations in relation to the foundation design.

Key words: geotechnical, drilling, foundation, compression, lateral

INTRODUCTION 1.This report present the result of geotechnical investigation and engineering assessment for proposed Patek Bridge at Sta.124+035.

The reports includes analysis and design of deep foundation based on the soil investigation data. The design will be one of the engineering reference to confirm the pile foundation design of Patek Bridge - Aceh Road Reconstruction Project.

SCOPE AND PURPOSES 2.The purposes of our investigations were to explore the soil conditions at project area and to provide recommendations in relation to the foundation design. The scope of the investigations included:

§ Drilling, performing standard penetration test, taking undisturbed samples and continuous coring. § A laboratory testing program on undisturbed samples to evaluate the engineering characteristics of the

subsurface strata encountered. § Performing engineering analysis to evaluate and to provide site specific geotechnical information required for

design recommendations.

FIELDWORK AND LABORATORY TESTING 3.Fieldwork was carried out from 13 December 2007 until 16 December 2007 and comprised the following:

§ One borehole ( BH-01), Abutment -1 at coordinate 529582.299(N), 772798.293(E) drilled to 18.00m with elevation of existing ground level 0.979 m. Borehole were advance using rotary wash bore methods and testing was carried out at 1.50 m interval. Testing comprised SPT in non cohesive and stiff cohesive soil and UD sampling in soft to firm cohesive soil.

§ All of the testing was carried out under the full time supervision of geotechnical engineer who were responsible for set out, schedulig in – hole testing, logging of recorvered samples and selection of samples for subsequent laboratory testing. Laboratory testing was carried out in our Medan laboratory.

GEOTECHNICAL CONDITION 4.In this part we explain the result of site investigation at Patek Bridge such as Drilling and Standard Penetration Test (SPT).

From drilling data at Patek Bridge we can define the elevation of ground water table is about 0.30 m from the existing of ground level where drilling is done. The ground water condition describes that soil strength is influenced by the water, which should be consider during structure excavation.

Detailed reports for the drilling are provided in appendix A.

The stratifications of soil of borehole report indicates very stiff fine sandy clay for the upper 1.00 m depth underlain by medium dense medium sand mixed shell until 2.00 m depth and underlain by dense clayey sand until 6.00 m

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G-126 SEMINAR NASIONAL-1 BMPTTSSI - KoNTekS 5 Universitas Sumatera Utara, Medan - 14 Oktober 2011

depth.. Medium to coarse sand & shell indicated until 8.00 m depth which is underlain by dense clayey sand until 10.50 and underlain by looses fine sany clay indicated until 15.00 m depth. At 4.50 m depth found dense clayey sand with N-SPT value more than 50 and then until 13.50 m depth N-SPT value descend. The very dense stones and napal depth is begun at 15.00 m with N-SPT value more than 50.

FOUNDATION SYSTEM 5.The following list identifies some of conditions that require pile foundation (Vesic, 977).

1. When one or more upper layers are highly compressible and to weak to support the load transmitted by the superstructure, piles are used to transmit the load to underlying bed rock or stronger soil layer. When bedrock is not encountered at a reasonable depth below the ground surface, piles are used to transmit the structural load to soil gradually. The resistance to the applied structural load is derived mainly from frictional resistance developed by the soil-pile interface.

2. When subjected to horizontal forces. Pile foundations resist by bending, while still supporting the vertical load transmitted by the superstructure. This type of situation is generally encountered in the design and construction of tall structures that are subjected to high wind or earthquake forces.

3. In many cases, expansive and collapsible soil may present at the site of a proposed structure. These soils may extend to a great depth below the ground surface. Expansive soils swell and shrink as their moisture content increases and decreases, and pressure of the swelling can be considerable.

4. The foundations of some structures, such as transmission towers, offshore platforms, and basement mats below the water table, are subjected to uplifting forces. Piles are sometimes used for these foundations to resist the uplifting force.

5. Bridge abutments and piers are usually constructed over pile foundations to avoid the lost of bearing capacity that a shallow foundation might suffer because of soil erosion at the ground surface.

The axial compression capacity of driven pile can be calculated by semi empirical method or load transfer method. In this case we apply the load transfer method to calculate the ultimate axial compression test for driven pile with square 40 x40 cm and diameter 60 cm.

Prediction of pile capacity by Standard Penetration Test (SPT) Prediction of the Bearing Capacity of Piles Based Exclusively on N Values of the SPT by Meyerhoff 1976”.

pANCQ p ..= where 40³C used 40 (1)

DLC .4=

sss AfQ .=

'204.0 xNf s = or (2)

5'.ASNQ s = (3)

LDA s ..p=

nNN

N 10'+

= (4)

spu QQQ += (5)

FSQ uQ a = (6)

Where ; Qp = ultimate of end bearing capacity N = value of SPT Ap = area piler D = Diameter piler Qs = Ultimate of friction capacity As = Area of perimeter L = Depth of piles Qu = Ultimate bearing capacity

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Qa = allowable bearing capacity C = Soil coefficient K = Soil coefficient Fs = Skin fractional stress N’ = Average N SPT FS = Safety factors = 2.5 With C = soil coefficient: Soil Type C (t/m2) Clay 12 Clayey Silt 20 Sandy clay 25 Sand 40

Allowable axial compression capacity of pile based SPT Value can be seen in Table 1 and 2.

Table 1. Allowable axial compression capacity of pile square 40x40 cm based SPT Value BH-01

Square 40x40 cm

Depth (m) N N' AS (SQ=0.4)

Ap (SQ=0.4)

Qp (ton)

Qs (ton)

Qu (ton)

Qa (ton)

0 0 0.00 0 0 0 0 0 0 1.5 22 22.00 2.40 0.16 140.80 10.56 151.36 60.54 3.0 12 17.00 4.80 0.16 76.80 16.32 93.12 37.25 4.5 50 28.00 7.20 0.16 320.00 40.32 360.32 144.13 6.0 31 28.75 9.60 0.16 198.40 55.20 253.60 101.44 7.5 35 30.00 12.00 0.16 224.00 72.00 296.00 118.40 9.0 7 26.17 14.40 0.16 44.80 75.36 120.16 48.06

10.5 6 23.29 16.80 0.16 38.40 78.24 116.64 46.66 12.0 11 21.75 19.20 0.16 70.40 83.52 153.92 61.57 13.5 19 21.44 21.60 0.16 121.60 92.64 214.24 85.70 15.0 60 25.30 24.00 0.16 384.00 121.44 505.44 202.18 16.5 60 28.45 26.40 0.16 384.00 150.24 534.24 213.70 18.0 60 31.08 28.80 0.16 384.00 179.04 563.04 225.22

Table 2. Allowable axial compression capacity of pile D = 60 cm based SPT Value BH-01

D=0.6m

Depth (m) N N' AS (d=0.60)

Ap (D=0.60)

Qp (ton)

Qs (ton)

Qu (ton)

Qa (ton)

0 0 0.00 0 0 0 0 0 0 1.5 22 22.00 2.83 0.2826 248.69 12.43 261.12 104.45 3.0 12 17.00 5.65 0.2826 135.65 19.22 154.86 61.95 4.5 50 28.00 8.48 0.2826 565.20 47.48 612.68 245.07 6.0 31 28.75 11.30 0.2826 350.42 65.00 415.42 166.17 7.5 35 30.00 14.13 0.2826 395.64 84.78 480.42 192.17 9.0 7 26.17 16.96 0.2826 79.13 88.74 167.86 67.15

10.5 6 23.29 19.78 0.2826 67.82 92.13 159.95 63.98 12.0 11 21.75 22.61 0.2826 124.34 98.34 222.69 89.08 13.5 19 21.44 25.43 0.2826 214.78 109.08 323.86 129.54 15.0 60 25.30 28.26 0.2826 678.24 143.00 821.24 328.49 16.5 60 28.45 31.09 0.2826 678.24 176.91 855.15 342.06 18.0 60 31.08 33.91 0.2826 678.24 210.82 889.06 355.62

Negative skin friction on piles Due to the site fill over the existing soft soil at the plan site, we recommended to include the negative skin friction in calculating the allowable compressive bearing capacity.

The unit negative skin friction is calculated as suggested by Bjerrum (1965) using the following equations :

For cohesive soil : 020.0 pf s = (7)

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For cohesionless soil : )43tan(...

21

0 fpkf ss = (8)

Where : fs = unit negative skin friction p0 = effective overburder pressure ks = coefficient of lateral earth pressure

= internal friction angle of cohesionless The ultimate negative skin friction then to be calculated by using the following equation :

sNN fLDP ...p= (9) Where : PN = ultimate negative skin friction on pile D = diameter of pile LN = length of pile to neutral point fs = unit negative skin friction

Laterally loaded piles Analysis of the lateral capacity of piles in cohesionless soils based Broms Method (1964).

The laterally loaded piles is calculated as suggested by Broms for long pile using the following equations :

5/25/3 ).(93.0

E InHy

ho = (10)

Where : yo : deflection H : lateral load nh : relative density E : modulus of elasticity I : moment of inertia The values of the coefficient of modulus variation nh can be seen in Table 3.

Table 3. Factors for calculating coefficient of modulus variation (nh) for cohesionless soil

Relative density Loose Medium dense Dense nh for dry or moist soil (Terzaghi) (kN/m3) 2425 7275 19400 nh for submerged soil (Terzaghi) (kN/m3) 1386 4850 11779 nh for submerged soil (Reese et al) (kN/m3) 5300 16300 34000

CONCLUSION/ RECOMMENDATION 6.From the geotechnical investigation and analysis we can conclude:

1. The ground water level at site is about 0.30 m from the ground surface. This information is important during structure excavation and for calculation the effective overburden stress of soil.

2. At 4.50 m depth is found very dense clayey sand and N-SPT value more than 50. At this level continuing driving might be damage to the pile cap, so when this level will be considered as bearing strata then the capacity of lateral and lift up shall be considered.

3. Soil stratification at 18.00 m depth is fine sandy clay, medium sand mixed shell, clayey sand, medium to coarse sand mixed shell, clayey sand, fine sandy clay and stones. The very dense stones and napal layer start at depth 15.00 m with N-SPT value more than 50. When necessary and deal with the condition of the contract, in order to reach the driving pile until 16.00 m depth, pre-boring should be considered to penetrate at the 4.50 m depth.

REFERENCE: Annual Book of ASTM Standard 1989 Volume 04.08 Bowles,J.E.,” Engineering Properties of Soil and Their Measurements”, Mc Graw Hill Book Company. Das, B.M.,” Principle of Geotechnical Engineering”PWS Publishing Company, Boston Das, B.M.,” Principle of Foundation Engineering”, Thomson, Books Hunt, R.E.,” Geotechnical Engineering Techniques and Practice”, Mc Graw Hill Book Company. M.J. Tomlinson “ Pile Design and Construction Practice”A Viewpoint Publication

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APPENDIX A BOREHOLE & SPT REPORT

Bridge NameBore LocationStationCoordinateElevationDate

0.00-0.5 : Fine Sandy clay-1.0 : Darkly brown-1.5 : Very stiff-2.0 : Low 7 10 12 22-2.5 : Medium-3.0 : 0.00 - 1.00 m-3.5 : Medium sand mixed shells 3 4 8 12-4.0 : Redly yellow-4.5 : Medium dense-5.0 : Non plastic 16 30 20 50-5.5 : Medium-6.0 : 1.00 - 2.00 m-6.5 : Clayey sand 10 14 17 31-7.0 : Grey-7.5 : Dense-8.0 : Non plastic 14 16 19 35-8.5 : Medium-9.0 : 2.00 - 6.00 m-9.5 : Medium to Coarse sand & shells 3 3 4 7

-10.0 : Grey-10.5 : Dense-11.0 : Non plastic 4 3 3 6-11.5 : Low-12.0 : 6.00 - 8.00 m-12.5 : Clayey sand 3 5 6 11-13.0 : Grey-13.5 : Dense-14.0 : Non plastic 7 8 11 19-14.5 : Medium-15.0 : 8.00 - 10.50 m-15.5 : Fine sandy clay 60/2 >60-16.0 : Yellowish grey-16.5 : Looses-17.0 : Medium 60/12 >60-17.5 : Medium-18.0 : 10.50 - 15.00 m-18.5 : Stones & napal 60/12 >60-19.0 : Grey-19.5 : Very dense-20.0 : Non plastic-20.5 : Low-21.0 : 15.00 - 18.00 m-21.5-22.0-22.5-23.0-23.5-24.0-24.5-25.0-25.5-26.0-26.5-27.0-27.5-28.0-28.5-29.0-29.5-30.0

Sandy Clay - Consistency N-Value N-Values Density

Medium Sand - Very Soft - 0-1 0-4 -Very Loose Description - R 20%Clayey Fine Sand - Soft - 2-4 5-10 -Loose Very Poor - <25

Medium to Coarse Sand Medium Soft - 5-8 11-24 -Medium Poor - 25-50Clay - Stiff - 9-15 Dense Fair - 51-75

Stones/Rock/Coral - Very Stiff - 16-30 25-50 -Dense Good - 76-90

Hard- 31-60 >50 -Very Excellent - >90

Very Hard - >60 Dense

ACEH ROAD/BRIDGE RECONSTRUCTION AND REHABILITATION PROJECT

BORE LOG Standard Penetration Test (SPT)

No. of Blows

45 cm SPTN Value

: PATEK: Abutment - 1: 124 + 035: 529582.299 (N) 772798.293 (E): 0.979 M

GRANULAR SOIL*) ROCK QUALITY

DESIGNATION (ROD) *)COHESIVE SOIL*)

=

PlasticityMoist. ContentDepthDescriptionColour

=

Disturbed Sample (DS)

PlasticityMoist. Content

Type

of

Test

Dep

th(m

)

=

Undisturbed Sample (US)

LEGENDS SYMBOLS AND RANGE OF VALUE

Sym

bol

Description of Layer

Standard Penetration Test

(SPT)

ColourConsistency

: December 13 - 16, 2007Ground Water Level : -0.30 M

Legend :

ColourConsistencyPlasticityMoist. ContentDepthDescription

- Ground Water Level (GWL)

*) reference from handbook of Joseph E. Bowles, Foundation Analysis and Design; fourth edition. Page 141

DescriptionColourConsistencyPlasticityMoist. ContentDepthDescription

Consistency

DepthDescriptionColourConsistencyPlasticityMoist. ContentDepthDescriptionColourConsistencyPlasticityMoist. ContentDepthDescriptionColourConsistencyPlasticityMoist. ContentDepthEND OF BORING

=================

0 10 20 30 40 50 600.0

-0.5

-1.0

-1.5

-2.0

-2.5

-3.0

-3.5

-4.0

-4.5

-5.0

-5.5

-6.0

-6.5

-7.0

-7.5

-8.0

-8.5

-9.0

-9.5

-10.0

-10.5

-11.0

-11.5

-12.0

-12.5

-13.0

-13.5

-14.0

-14.5

-15.0

-15.5

-16.0

-16.5

-17.0

-17.5

-18.0

-18.5

-19.0

-19.5

-20.0

-20.5

-21.0

-21.5

-22.0

-22.5

-23.0

-23.5

-24.0

-24.5

-25.0

-25.5

-26.0

-26.5

-27.0

-27.5

-28.0

-28.5

-29.0

-29.5

-30.0

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