Presentation Outlines

1. Introduction

2. Construction practices

3. Field Testing and Numerical Simulation

4. Case Studies Pile foundations have been used as load carrying and load transferring systems for many years

Early days of civilization from the communication, defence or strategic point of view villages and towns were situated near to rivers and lakes.

Strengthen the bearing ground with some form of piling Timber piles were driven in to the ground by hand or holes were dug and filled with and stones

In 1740 Christoffoer pathem invented pile driving equipment which resembled to days pile driving mechanism.

Steel piles have been used since 1800 and concrete piles since about 1900 And then… • The industrial revolution brought about important changes to pile driving system through the invention of steam and diesel driven machines

• More recently, the growing need for housing and construction has forced authorities and development agencies to exploit lands with poor characteristics.

• This has led to the development and improved piles and pile driving systems. Today there are many advanced techniques of pile installation PILE •Piles are structural members that are made of steel, concrete or timber.

•Used to support the structure and transfer the load at desired depth either by end bearing or skin .

•Pile foundations are usually used for large structures and in situations. where the soil at shallow depth is not suitable to resist excessive settlement, resist uplift, etc. Terminology What is Residual ? • Soils that form from rock weathering or accumulation of organic material and remain at the place where they were formed are Residual Soils. • Residual soil profiles generally show a gradual transition from soil to rock, rather than a distinct line of separation of soil and rock. • The degree of disintegration may vary appreciably over the thickness of its stratum. What is a Large diameter pile ? • Pile foundations of diameter greater than 1 m are usually termed “Large Diameter” • Monopiles of 4.0 m and 4.7 m diameter have been used . • Monopiles of 1.6 m and 1.2 m dia have been used in the construction of the Bangalore Metro and other major infrastructure projects. Issues in Large Diameter Piles Foundations in Residual Soils

• Identifying the transition between the sub-strata layers. Sometimes IGM can be mistaken for . • At what depth should the pile be terminated? • How large should the diameter of the pile be? India:1.6m Abroad: Upto 4-4.7 m • Should one socket in IGM or rock? • How deep should the socket should be? • Testing techniques developed, proven for small dia piles only • Predicting Load-Displacement relationships • Know-how on grouting to improve load bearing *Intermediate geometrical(IGM) capacity. Field exploration Design and Construction &Testing of Pile foundation Process Geotechnical analysis of Bored cast-in situ

Load displacement Axial & Lateral curve ultimate capacity Final Geotechnical Recommendations

Final Design/Drwg/Specification

construction Field test Final QA/QC PDA/PIT Non Destructive test

Final acceptance

CURRENT PRACTICES

• IS:2911(Part I/Sec-2)-1979(Reaffirmed 2002) Code of practice for Design & Construction of pile foundations . Part I: Concrete Piles; Section 2: Bored cast-in-situ concrete piles.

• IS:2911(Part 4)-1980 Code of practice for Design & Construction of pile foundations. Part 4: Load tests on pile. Construction Equipment

Small Diameter Pile Foundations Large Diameter Pile foundations

• Generally Large Diameter Piles not used in India till recently; lack of availability of large cutters, buckets and drill rigs. • • Typical Bore log Report • • • • MASWtesting identify bed rock and profilessoil Newgeophysical methods availableareto method investigations of Therelotproblems areof boreholein TypeofBoring: Rotary Drilling GWT:No 150 Diameter:mm Site: AgaraJunction, HSR Layout – eg.

11.2 m 13.8 m

Weathered Rock Silty 1 m

3.2 m Parameters γ =20 c =KN/m 10 c =KN/m 20 γ =14 Ø Ø 35º = Ø 20º = KN/m KN/m 3 2 2 3 ClayBinders with Greyish Greyish Yellow Sand with thePrescence Weathered Rock Description Yellowish Yellowish Grey of of Mica

Legend 20.0 15.0 13.8 9.0 7.5 6.0 5.5 4.5 4.0 1.5 0.0 Depth(m) UDS UDS SPT DS DS DS DS DS DS DS DS -- SPT SPT SPT SPT SPT SPT SPT Sample 80 60 40 26 18 13 ------7 N-Value Single pile under Vertical Axial Load

AIM:

• The purpose of this case study is to simulate the pile- loading test using Numerical simulation, and compare the simulation results with the field pile load test results of Sommer & Hambach (1974) and analytical methods (equations).

* Before I going to my field test results, here excellent field pile load tests results conducted by Sommer & Hambach(1974) by using load cells at the pile base to measure the loads directly at pile base Field pile load test results of Sommer & Hambach (1974).

• The reaction beam was supported by 16 anchors (Fig). • The loading system consists of 2hydraulic jacks working against a reaction beam. • The loads were applied in increments and maintained constant till the settlement rate was negligible. • The pile diameter of 1.3m & length of 9.5m • Load cells were installed at the pile base to measure the loads carried directly by pile base. • The upper 4.5m consist of silt followed over consolidated clay to great depths. • The ground water table is about 3.5m below the ground Layout of 16anchors in load test surface. Fig: Schematic of load test Field Vertical pile load test data Sommer & Hambach (1974-Germany).

Load (kN)

0 500 1000 1500 2000 2500 3000 3500 0 Ultimate Load capacity

5

10 Method Load(kN)

Single abscissa 2000 15 Total Load [kN]

20 12 mm Diameter 2250 Settlement (mm) Settlement 25 Double abscissa 2750

30 10% Diameter -----

35

• This test is for a large diameter pile (diameter = 1300 mm), (Length = 9.5m) • Has been carried out properly: • Linear and non-linear portions clearly visible • Test carried out to failure (12mm) • Methods to determine Ultimate Load shown in the table can be used effectively Numerical Simulations

 Axi Symmetry geometry model.

 The element mesh - 15-node element.

 Geometry : 2D: 4m x 14.5m

 Pile radius:0.65m ; Length: 9.5m .

 5 noded beam-column element. 3 DoF per node.

 Ground water table is located at 3.5m.

 Stage-wise loading done, upto 3250kN. SOIL PROPERTIES AND PILE DETAILS Sommer & Hambach (1974).

Parameter Symbol Silt OCR Clay Concrete pile Unit

Material Model Mohr-Coulomb Hardening-Soil Linear Elastic [-]

Behaviour Type Drained Drained Non-porous [-]

Dry Weight gunsat 19 20 25 [kN/m³]

Young’s Modulus Eref 10E+3 10E+3 30E+6 [kN/m²]

Poisson’s Ratio n 0.3 0.2 0.2 [-]

Cohesion cref 5 21 - [kN/m²]

Friction Angle j 27.5 21 - [°]

 Linear Elastic: Stress & strain are linearly proportional. No failure, tensile stresses allowed.  MC: Linear elastic until yield and further perfectly plastic. The model involves five parameters namely E,ν,φ,c,ψ. Loading and unloading modulus are the same.  HS: More versatile. MC strength parameters. Different loading and unloading modulus Medium Fine

Around 500 elements Around 250 elements • •

Around 1000elements The “Medium” meshis used ofallin following the simulations The “Medium” meshcurve is closest to the field the data. tests

Very Fine

Settlement (mm) 40 35 30 25 20 15 10 5 0 0 Mesh Mesh size 250 500 750 1000 Medium Very fine Fine Total Load [kN] 1250 Load (kN) 1500 1750 2000 2250 Sommer & Hambach (1974). HambachSommer& 2500 2750 . 3000 3250 3500 Evaluating End Bearing & Skin Friction from Numerical simulation

Load (kN) 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 0

Total Load [kN] 5 Skin Friction [kN] Base Load [kN] 10 Total Load with Plaxis Base Load Plaxis 15 Skin Friction Plaxis

20 Sommer & Hambach (1974).

25 Settlement (mm) Settlement

30

35

40 Method Skin friction End bearing Total Load (kN) (kN) ( kN) IS code 3674 1646 5320 Meyerhoff’s 1940 8840 10780 PLAXIS 2D 2183 1067 3250 ANALYTICAL METHODS Various approaches to determine Ultimate Load Bearing capacity Method 1: IS:2911(Part I/Sec 1) code Method 2: Meyerhoff’s Method • Based on parameters(Lab Testing) • Based on Standard Penetration Test (Field Testing)

Qu = Ap (0.5Dγ Nγ) + Ap (PD Nq) +∑ Ki PD1 tanδ Asi Qu = (40NAp) / 3+ (N As) / 5

Where,

Qu is the Ultimate Bearing Capacity Ki is the Coefficient of Earth Pressure Ap is the Cross Section Area of Pile PD1 is the Effective Overburden of corresponding layer D is the Stem Diameter of Pile δ is the Angle of Wall Friction γ is the Unit Weight of the Soil Asi is the Surface Area of the corresponding layer N is the Average SPT in the region of the shaft Nγ and Nq are Bearing Capacity Factors PD is the Effective Pile Diameter: 1.3 m ; Pile Length: 9.5m

Method Skin friction End bearing Total Load FIELD ULTIMATE LOAD= 2000 TO 2750 KN (kN) (kN) ( kN) IS code 3674 1646 5320

Meyhorff’s 1940 8840 10780 *In small diameter piles these methods are quite suitable , but not in large diameter Bangalore Metro Project

• Foundations for urban flyover bridge structures are generally built on deep foundations using cast-in-situ piles.

• The metro rail project of Bengaluru has employed precast post- tensioned prestressed concrete girders of spans 25 m to 30 m which are supported on massive cast-in-situ piers supported on large pile caps combining nine piles of 1 to1.6 meter diameter, each cast at site over a depth 15m to 30m resting on rocky strata.

Pile Dia 1.2 m 1. Metro(Jayanagar)-Group of piles (4) 2. Metro (M.G )-Monopiles Dia 1.2 m Dia 1.6 m

3.Flyover(Kalyan nagar )-Group of piles (5) 4. Flyover (HSR Layout)-Group of piles (4) Dia 1.2 m Dia 1.0 m

FEW PILE LOAD TESTS WHERE I WAS INVOLVED Field Tests: Routine Vertical Load Test

•Test load is applied on the pile by jacking against a reaction frame which is either loaded with • Hydraulic jack to apply load on pile head. For more accurate measurement of load, a load cell or proving ring may be used • Displacement of the pile head is measured by dial gauges ( 3 or 4 nos.) • Load is applied in suitable increments and settlement observed • Each load should be maintained for 2 hours or till the rate of settlement becomes 0.2 mm/hour, whichever is earlier. Load (kN)

0 2000 4000 6000 8000 10000 0

0.5

1

1.5

2 Settlement Settlement (mm)

2.5

3 • This test is for a large diameter pile (diameter = 1000 mm) Site : Kalyan Nagar • Has not been carried out properly: • Non-linear portion incomplete • Test carried out neither to 12mm settlement nor to meet 10%-of diameter regulation. • The 10% of diameter method to determine Ultimate Bearing Capacity cannot be used. • The double abscissa method would be more accurate if larger loads were used. • 10% of dia is 100mm. Achieving such settlements may be impractical and unnecessary. • Guideless needs to be modified as they were made for smaller dia piles. • Current codes need to be modified or testing till 12mm should be deemed sufficient. Numerical Simulation

 Axi Symmetry geometry model.  The element mesh - 15-node element.  Geometry : 2D: 5m x 20m  Pile radius:0.5m ; Length: 15m .  5 noded beam-column element. 3 DoF per node.

 No Ground water table is located.  Stage-wise loading done , upto 8250kN. Comparison of Field test & Numerical simulation

LOAD (kN) Site 3 :Kalyan nagar 0 3000 6000 9000 12000 0

0.5 Field curve 1 Observation PLAXIS 2D CURVE Analytical method(Iscode) is 1.5 BASE LOAD BY PLAXIS reasonably matching with skin 2 friction obtained from Numerical 2.5 simulation. 3  It is also noticed that field curve

Settlement (mm) Settlement 3.5 has shown a different shape starting

4 from 2mm settlement, which may

4.5 be attributed to field test problems.  Out-dated methods used to 5 record data, time consuming, labour intensive, costly. – Quality Ultimate load capacity of pile by different methods issues Method Skin friction End bearing (kN) Total Load  So, we need to suggest some (kN) ( kN) alternative techniques which are more reliable – With proper IS code 5700 4620 10320 instrumentation . Meyerhof’s 2830 7540 10740

PLAXIS 2D 6608 1642 8250 Load (kN) Field Pile load test 0 2000 4000 6000 8000 10000 12000 14000 0

0.5

1

1.5

2

2.5

3 Settlement Settlement (mm)

3.5

4 • This test is for a large diameter pile (diameter = 1200 mm) Site : Jayanagar • Has not been carried out properly: • linear portion is present – non linear is not present. • Test carried out neither to 12mm settlement nor to meet 10%-of diameter regulation. • The 10% of diameter method to determine Ultimate Bearing Capacity cannot be used. • The double abscissa method would be more accurate if larger loads were used. • 10% of dia is 120mm. Achieving such settlements may be impractical and unnecessary. • Regulation needs to be studied as they were made for smaller dia piles. • Current codes need to be modified or testing till 12mm should be deemed sufficient. Comparison of Field test & Numerical simulation LOAD kN

0 2000 4000 6000 8000 10000 12000 14000 0

0.5 FIELD CURVE

1 TOTAL LOAD WITH PLAXIS CURVE

1.5 BASE LOAD BY PLAXIS

2 SKIN FRICTION BY PLAXIS

2.5 SETTLEMENT (mm) SETTLEMENT 3

3.5

4 Ultimate load capacity of pile by different methods Method Skin friction End bearing Total Load (kN) (kN) ( kN)

IS code 4700 9700 14400 Meyerhof’s 2830 7540 10740 PLAXIS 2D 1543 10572 12115 Because of many problems in static field pile load tests, Dynamic load tests are becoming more common now a days What is Dynamic pile load test ?

•Dynamic of piles is a fast and effective method of assessing foundation bearing capacity that requires instrumenting a with accelerometers and strain transducers and analyzing data collected by these sensors. Why Dynamic pile load test required ? •In addition to bearing capacity, gives information on resistance distribution (shaft resistance and end bearing) and evaluates the shape and integrity of the foundation element. Load Testing

Dynamic Load Testing

PDA/CAPWAP

Comparison of Dynamic load test with Numerical simulation PILE DYNAMIC TESTING

STRAIN GAUGE & HAMMER & CRANE ACCELEROMETER Pile Dynamic Analyzer (PDA) : Procedure ( ASTM D4945)

• When hammer strikes the top of a pile, compression wave travels down the pile. • The impact induces force F and particle

velocity v (particle displacement *angular frequency). •The force is computed by the product of the measured strain signal and pile c/s area and modulus. •The velocity is computed by integrating the measured acceleration •Force/velocity time histories is captured by PDA. RESULTS OBTAINED WITH DYNAMIC LOAD TESTS CORRELATE WITH THE RESULTS OF STATIC LOAD TEST

Load (kN)

0.00 200.00 400.00 600.00 800.00 1,000.00 1,200.00 0.00

PLAXIS 2D

Static Load Test 2.00 Base load by PLAXIS 2D

Skin friction by PLAXIS 2D

4.00

6.00 Settlement (mm) Settlement

8.00

10.00 Proposed Process To Achieve a Good Pile Capacity in Rock • Good Quality Soil Investigation Each Pile Cap n – Aim at Good Core Recovery in Rock & Keep Core box at Pile Loaction • Prepare Core Log & Select Samples for UCS & Point Load Tests • Have a Geologist at Site for better identification & Classification of Rock • Design Rock Socket (by consultant)& Specify Termination Criteria • Consult Equipment Manufacturer for Right Equipment & Tools and Guideline Method • Procure Quality Accessories & Tools • Client- Consultant- Contractor to Have a Team Approach • Adopt Concrete Coring, Contact Coring, Sonic Logging, PIT, Etc. for Proof of Quality & Integrity Dr. Naveen BP Ph.D. (IISc) Associate Professor & Head, Department of Civil Engineering Amity University Haryana Haryana-122413 Mobile No:+91-9916232349 Email: [email protected] [email protected] Web: https://sites.google.com/site/bpnaveen864/home