the response of p-y curve of soil-pile characterized … · 2018-12-28 · and practical...

VOL. 13, NO. 23, DECEMBER 2018 ISSN 1819-6608

ARPN Journal of Engineering and Applied Sciences ©2006-2018 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

9041

THE RESPONSE OF P-Y CURVE OF SOIL-PILE CHARACTERIZED

BY THE DESIGN PARAMETERS IN LIQUEFIABLE SAND

Baydaa Hussain Maula1, Hayder Hussein Moula

2, Hussein Yousif Aziz

3 and Qais Mikhael Bahnam

1

1 Institute of Technology, Middle Technical University, Baghdad, Iraq 2Ministry of Higher Education and Scientific Research, Baghdad, Iraq

3College of Engineering, Muthanna University, Samawa, Muthanna, Iraq

E-Mail: [email protected]

ABSTRACT

This paper proposed the establishing procedure and introduced an OpenSessPL for investigating dynamic p-y

curves in liquefying ground based on the simulated shaking table tests for pile-soil-bridge structure were conducted

successfully corresponding to liquefying ground covered with clay layer simulated as a middle circumference of three

layers adopting reinforced concrete single pile-pier exposed by a series of sinusoidal and EI centro earthquake events wave

of different amplitudes and frequencies. A series of numerical simulations based on the established 3D finite element

analysis method was carried out by including earthquake events to investigate the deveplod of p-y curves due to the effect

of design parameters such as; pile stiffness, the internal angle of sand and the depth of pile insertion. The mentioned

parameters beside seismic motion shape, peak acceleration (g) and degree of ground inclination have a certain theoretical

and practical significance for seismic design related to lateral resistance and pile displacement.

Keywords: pile-soil stiffness ratio, depth of Insertion, dynamic pile response, dilation angle.

1. INTRODUCTION

It was a familiar event that pile foundations

Suffered damage by soil liquefaction due to earthquakes

[1, 2]. In fact, most of the footing destruction was

supposed to be connected with the effects occurred to the

ground prompted by liquefaction and / or lateral ground

spreading. This suggests that the effect of soil

displacement should be properly taken into consideration

when determining safely seismic design pile foundations.

An expectation of the dynamic p-y behaviors in liquefiable

soils is difficult, but achievable [3]. There are some

methods, like collecting data from investigational test and

NFEMS, which can be anticipated such manners defined

as the relationship of lateral resistance with relative

displacement between soil and pile, using a large number

of experimental data [4-9].

Figure-1. Sketch diagram of a series of shaking

table tests achieved [9].

A series of shaking table tests under the

successive support of National Natural Foundation of

China since 2002, were performed to understand the basic

mechanisms of SSPSI in Liquefiable ground, including the

cases of single piles and pile groups, low/ elevated cap pile

groups, pile groups, liquefiable / non-liquefiable ground,

different soil profile involved of two ( horizontal /slope)

[2]. Soil layers with the upper layer of thick normally

consolidated silty clay and the lower layer of thick

saturated sand beside experimental test of three horizontal

soil layers with the upper layer of thick normally

consolidated silty clay, with middle layer of deep thick

saturated sand and the lower layer of thick soft clay,

synoptically described in Figure-1.

These works have gotten the excessive value of

finding observation on the pile performance, mostly in the

soil of liquefiable trend, and have shown that the design

parameters have a significant effect on dynamic p-y

behaviour during liquefaction; however, it is indefinite

how the shape and amplitude of the diminution of p-y

curves develop through various design parameters.

Variations in soil lateral resistance during the

generation of p-y curves are required for the safe design of

pile foundations in an area subjected to tremble -induced

lateral spreading.

The main purpose of this research is to obtain

dynamic p-y curves at diverse ranges of shaking induced

liquefaction, as represented by a range of design

parameters. These constructed curves will support

computational modeling of soil-pile interaction. To report

this objective, series of modeled shaking table tests of

pile-supported structures in liquefying ground; are

conducted. In the following section parts, the

experimental-simulation, layout, procedure, and results

discussion are presented.

2. CORRELATED AND PRECEDING WORK

In previous research papers, authors reported vast

shaking table experiment in 0.2, 0.1 m diameter pile

mailto:[email protected]




9042

driven into composing soil strata of liquefiable sand and

overlying soft clay. Due to the well-instrumented gauges

and sensors to the pile, bending moments imparted on the

pile shaft was measured. The Mathematical expression

represented by double integration, the moment divided by

EI concerning the length of the pile could generate soil

displacement ysoil, while double differentiation of the

bending moment achieved lateral resistance p concerning

the length of the pile.

Numerous studies and experimental researches

have been carried out at centrifuge and 1-g scales to assess

the unique behavior of the soil during liquefaction [2, 10].

Many studies; researchers realized that liquefaction

lowered the hardness and stability of the liquefiable layers.

However, such a depression was noticed. There is an

insufficiency of understanding on the shapes of the p-y

curves generated at liquefaction or during subsequent

events, for example, tests [11-12] adoption a turned S-

shaped p-y curve convex up, rather than convex down

when the surrounding soil is liquefied. Such behavior of p-

y curve designates low adjacent stability at minor to

reasonable ysoil, whereas successively gives hardening at

greater one. Liquefaction sources, deviation in p-y

manners, and the phases leading up to widespread

liquefaction have not been sufficiently examined to

contract with the p-y features.

3. NUMERICAL MODELLING OF SHAKE-TABLE

TEST

3.1 Model design and layouts

The test plan was fixed via a shake-table reported

by [2]. Including a 3D model of the soil-pile system,

shown in Figure-2, was created with OpenSeesPL. The

model dimensions are 2.0 m (long) 1.5 m (transverse) 1.9

m (height) with the same constitutive model of soil (three

layers) and (Rc) pile of 2.52m, 0.62 m part left free above

the examination system (soil-pile), with D= 0.1m as

reported by [1, 2]. The bottom of the soil domain is y m

below the pile tip. The ground surface inclination is 0, 2,

4°. Figures 2 (a) and 2 (b) and Figure 3 show the plane XZ

with an isometric view of the model, with numerical

elements respectively.

The limitation settings are factored in the

evaluating: (1) the base of the soil domain is immovable in

the three directions; (2) the boundary condition for all

planes of the model is Laminar Container and; (3) Plane of

symmetry is fixed in the y-direction and free in Z and X

direction. The base-shaking analysis is used to assess the

pile and soil behavior. Variation motion event is used as

an input motion in the longitudinal (X) direction.

The test program was exposed to a set of El

Centro and sinusoidal earthquake events with a changeable

level of shaking as characteristic ground indication

response, listed in Table-1.

Table-1. Set of seismic events.

Step event Motion Peak

acceleration (g)

A Sinusoidal 0.10g

B El Centro 0.10g

C Sinusoidal 0.20 g

(a) Plane View (b) Isotropic View

Figure-2. FEM of the SP system.

a) EDOF number b) node DOF

Figure-3. Brick element “Solid-fluid coupled 20-8 node”.

3.2 Simulation results

3.2.1 Results and interpretation

Figure-4 shows free-field displacement; pore

water pressure time histories, along with horizontal

ground displacements measured at the surface, 0.4 m, and

1.2 m depth. Generally, the Figure shows that the soil is

less displaced under case A and B.

Soil lateral displacement focuses on the surface

and the top 0.4 m of depth, as a result of liquefaction in

this area. The lowest level of liquefiable sand layer

confirmation minor effects performed comparable to an

inflexible bulk, and it's hard to slip along the base. The

upper part of the sandy soil field deforms

correspondingly.

1 2

3 4

5 6

7 8

9

10

11

12

13

14

15

16

17

18

19

20




9043

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 Soil surface

Dis

. (m

m)

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 0.4 m depth

Dis

. (m

m)

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 1.2 m depth

Dis

. (m

m)

0 2 4 6 8 10 12 14 16

0.0

0.2

0.4

0.6 0.4 m depth

ru

0 2 4 6 8 10 12 14 16

0.0

0.2

0.4

0.6 1.2 m depth

ru

Time (s) a) Case A

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 Soil surface

Dis

. (m

m)

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 0.4 m depth

Acc

. (g

)

0 2 4 6 8 10 12 14 16 18 20 22-0.06

-0.03

0.00

0.03

0.06 1.2 m depth

Dis

. (m

m)

0.0

0.3

0.6

0.9

1.2 1.2 m depth

ru

0 2 4 6 8 10 12 14 16

0.0

0.3

0.6

0.9

1.2 0.4 m depth

ru

Time (s) b) Case B

Figure-4. Times-histories of free-field [2].

3.2.2 Liquefaction characteristics of the ground

The noticeable movements in the soil skeleton,

that yield liquefaction "are as follows: Seismic influences

mainly shear waves, passing through saturated granular

layers, distort the granular structure, and cause loosely

packed groups of particles collapse. Disruptions to the

particulate structure generated by these collapses cause

transfer of load grain-of grain contacts in the pore water"

[13]

Test phenomena are shown in Figure-4 (b). The

following phenomena summarized as the most significant

moment of the OpenSess PL due to shaking that was

present at the boundary between sand and clay layers;

ground displacement, were almost the same peak, only

slightly larger than the calculated value of the surface in

the case B value. By comparing the event A and event B,

the seismic response, well demonstrates that the case B

shaking test analysis show liquefaction represented by ru

≥1 for the same time of shaking and Peak acceleration (g), the explanation of this fact is due to the motion shape

which plays an enormous role in prone liquefaction.

3.3 The progress of p-y curves

As cited previously, the strategic objective of this

paper was the p-y curves at the achievement levels of pore

water pressure ≤ 1.0. To generate these curves, design

parameters will be involved explaining the behavior of

these curves.

3.3.1 Initial pile-soil stiffness ratio Figures 5,6 shows the pile stiffness vs. peak

bending moment on the single pile, along with the

stiffness value increases, the peak moment changes with a

variation similar to that as the depth increases, the peak

moment first increased and then decreased. Meanwhile, as

the depth increases, the pile stiffness value changes caused

by peak bending moment on the pile getting smaller and

smaller. Differences in soil boundary show the peak

moment has increased trend; the peak moment is

consistent and linear change, which these three are

stiffness values, the slope of the linear variation is almost

the same, especially when the depth reaches a certain

value.




9044

The simulation result of Figure-6 coordinates that

the flexibility of the pile; displacement of the pile head

and the displacement along the pile in the lateral load

direction were more significant. The pile displacement

was not profound to its connected stiffness, which may be

correlated to the inelasticity of the pile.

-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

E=1e010 kPa

E=5e005 kPa

E=5e006 kPa

E=1e008 kPa

Bending moment (kN.m)

2° sloping ground

Dep

th (

m)

Figure-5. Bending moment vs. Pile length for different EI.

-0.5 0.0 0.5 1.0 1.5-1.5

-1.0

-0.5

0.0

0.5

1.0

Dis. (mm)

2° sloping ground

E=1e010 kPa

E=1e008 kPa

E=5e006 kPa

E=5e005 kPa

Dep

th (

m)

Figure-6. Impact of stiffness of the pile in Event B.

Consistent to Figure-6, it is remarkable to note

that the pile displacement is very unaffected with pile

stiffness. That is, the high stiffness pile experienced about

the same total movement as the low stiffness pile;

however, the final bending moments, as shown in Figure-

5, are vastly different. Here, the low stiffness pile

produced the highest bending moment.

The results from Figure-7 specified that the

stiffness of the pile had some effect on the p-y curve of the

single pile in the inclined shallow soil.

Model results of the inclined soil-pile system (2°)

were shown in Figure-7. The results showed the p-y curve

of the laterally loaded single pile was not sensitive to the

material modules, the p of soil "would be developed

deeper, so the transform point of the resistance moved

down, and the lateral resistance below soil increased,

which was beneficial to enhancing the lateral bearing of

the pile" [15].




9045

-0.04 -0.02 0.00 0.02 0.04 0.06-6

-4

-2

0

2

4

6

8

E=1e010 kPa

p (

kN

/m)

-0.02 -0.01 0.00 0.01 0.02-2

-1

0

1

2

3

E=1e008 kPa

p (

kN

/m)

-0.0030 -0.0015 0.0000 0.0015 0.0030 0.0045-1

0

1

2

y (mm)

E=5e 006 kPa

p (

kN

/m)

-0.003 -0.002 -0.001 0.000 0.001 0.002 0.003-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

E=5e 005 kPa

y (mm)

p (

kN

/m)

Figure-7. Effect of the stiffness of the single pile on the p-y curves of the pile at depth 0.5 m in Event A.

3.3.2. Depth of insertion effect

Considering previous lectures and research [16]

the lateral response with increasing depth interval was

investigated as shown in Figure-8. Response at showllar

depth liquefies earlier, as related the response at the deeper

area. This behavior matches [16-17]. However, the lateral

resistance decreases with increasing depth for horizontal

(0°) (2°) and (4°) sloping ground.




9046

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8-60

-30

0

30

60

2D = 0.4m depth

3D = 0.6m depth

p (

kN

/m)

y (mm)

-1.0 -0.5 0.0 0.5 1.0-15

-10

-5

0

5

10

15

y (mm)

4D = 0.8 m depth

5D = 1.0 m depth

p (

kN

/m)

(a) Horizontal grounds (0°)

-0.4 0.0 0.4 0.8 1.2 1.6-40

-20

0

20

40

60

80

100

2D = 0.4m depth

3D = 0.6m depth

p (

kN

/m)

y (mm)

-0.4 0.0 0.4 0.8 1.2 1.6-15

-10

-5

0

5

10

15

y (mm)

4D = 0.8 m depth

5D = 1.0 m depth

p(k

N/m

)

(b) 2° sloping ground

0.0 0.4 0.8 1.2 1.6 2.0 2.4-40

0

40

80

120

2D = 0.4 m depth

3D = 0.6 m depth

p (

kN

/m)

y (mm)

0.0 0.4 0.8 1.2 1.6 2.0 2.4-15

-10

-5

0

5

10

15

y (mm)

4D = 0.8 m depth

5D = 1.0 m depth

p (

kN

/m)

(c) 4° sloping ground

Figure-8. Lateral response with depth concerning pile diameter in Event C.

The p-y curves for 4° sloping ground shown in

Figure-8(c) describe different types of response. For

example, the first curve at a depth of 0.4 m below the

ground surface displays greater resistance than the curves

immediately below it. The four curves from (0.4 to 1.0 m)

depth show the same manner. The two ground cases (0°)

and (2°) curves from (0.8 and 1.0 m) depth match with

each other. It’s produced greater lateral displacement,

consistent with the two cases.

The large displacement levels are more noticeable

in shallow depth than in deeper one. The reason for this

happening is due to "As the shaking continues, the

effective resistance of the soils has been reduced due to

gapping and inherent strength degradation (the latter of

which is exhibited in the curves by the lower-than-static

peak strengths for a given displacement)" [18].

3.3.3 Effect of difference between the (peaks - critical

state) friction angles

Investigation to variations of the dilation angle

was examine considering [17] definition and procedures.

In this simulation, the critical state friction angle considers

equal to 26°, while the peak friction angle is tested to vary

between 28-40°. Figure 9 illustrates the dynamic response

p-y curves at depth 0.5 m. The dynamic curves show

strain-softening behaviour. For soil with low dilation angle

(2-6°), show more lateral displacement response compared

to the higher dilation angle (8-14°) through shaking

duration.




9047

-0.03 0.00 0.03 0.06-4

-2

0

2

4

6

y.(mm)

2°sloping ground

28°

30°

32°

p (

kN

/m)

-0.03 -0.02 -0.01 0.00 0.01 0.02 0.03-4

-3

-2

-1

0

1

2

3

4

5

y.(mm)

2°sloping ground

35°

38°

40°

p(k

N/m

)

Figure-9. Dynamic pile response with changing dilation angle (at depth 0.5m) in Event B.

4. CONCLUSIONS AND SUMMARY

a) Design Parameter analysis shows that under the

conditions of liquefaction with the increasing pile

stiffness the peak (y) & (p) are reduced. Even the

peak pile bending moment will be decreased; internal

friction angle for sand layer decrease lateral

displacement. With the depth decreases, the peak

displacement of the pile increases.

b) The p-y curves and the relative displacement (y) are

not strongly dependent on the groundwater table, but

the relative displacement (y) is strongly dependent on

the ground surface slope and pile length

c) Construction of p-y curves for inclined pile and for

pile groups (horizontal & inclined) are highly

recommended to capture the response. Effect of

ground motion parameters on p-y need to be

investigated as well.

REFERENCES

[1] Maula B.H., Ling X.Z., Liang T. & Xu P.J. 2011. 3D

FEM numerical simulation of seismic pile-support

bridge structure reaction in liquefying ground.

Research Journal of Applied Sciences, Engineering,

and Technology. 3(4): 344-355.

[2] Maula B.H., Xian Zhang L. & Liang T. 2011. Study

on dynamic behavior for pile-soil-bridge structure

seismic interaction in liquefying ground under strong

earthquake. Journal of Emerging Trends in

Engineering and Applied Sciences. 2(2): 239-244.

[3] Maula B.H. 2016. Behavior of seismic soil-pile

foundation in liquefying sloping ground controlled by

mechanical aspect. Journal of Emerging Trends in

Engineering and Applied Sciences. 7(1): 45-55.

[4] Elgamal A, Lu J. and Yang Z. 2006. OpenSeesPL

Three-Dimensional Lateral Pile-Ground Interaction

Version 1.00 User Manual, Report SSRP-06/04,

Department of Structural Engineering, University of

California San Diego, La Jolla, U.S.A.

[5] Elgamal Ahmed, et al. 2006. Liquefaction induced

lateral on the piles. In: Proceedings of the Fourth

Interational conference on earthquake engineering.

Taipei, Taiwan.

[6] Jinchi Lu, Zhaohui Yang, and Ahmed Elgamal. 2010.

OpenSeesPL 3D Lateral Pile-Ground Interaction,

Version 0.6 User Manual, University of California,

San Diego, Department of Structural Engineering.

[7] Ling X.Z., Wang C. and Wang C. 2005. Scale

modelling method of shaking table test of dynamic

interaction of pile-soil-bridge structure in ground of

soil liquefaction. Chinese Journal of Rock Mechanics

and Engineering. 23(3): 450-456 (in Chinese).

[8] Xian Zhang, L. I. N. G., et al. 2004. Large-scale

shaking table model test of dynamic soil-pile-bridge

structure interaction in ground of liquefaction. China

Civil Engineering Journal. 37.11: 67-72.‏

[9] Liang Tang, Pengju Xu, Ling Xian Zhang, Gao Xia.

2008. Shaking Table Test and Numerical Simulation

for seismic soil-pile-bridge structure interaction in

liquefiable ground. The 14th World Conference on

Earthquake Engineering, Beijing, October.

[10] Tao Bo, NaI Lei, Wu Faquan. 2005. Distributive law

of forces between the anti-sliding pile and the

surrounding soil mass. Journal of Jilin University:

Earth Science Edition. 35(2): 201-206.

[11] Xiong, Feng, et al. 2008. Seasonal Freezing Effects

on the Lateral Behavior of Steel Pipe Piles.‏ The 14th

World Conference on Earthquake Engineering,

Beijing, October.

[12] Maula, Baydaa Hussain; Liang, ang; Gazal, Ali

Mahommed. 2014. Decomposition of Dynamic py




9048

Curves Considering Liquefaction during Earthquakes.

Research Journal of Applied Sciences, Engineering

and Technology. 7.24: 5163-5171.‏

[13] Samuel Tadesse. 2000. Behaviour of saturated sand

under different triaxial loading and liquefaction

(Doctoral dissertation. Norwegian University of

Science and Technology).‏

[14] Hussain Maula, Baydaa. 2013. Dynamic response and

simplified analysis method for bridge pile foundations

in the liquefiable sloping ground (Doctoral

dissertation, Harbin: Harbin Institute of Technology).‏

[15] Zhao-Ran, Xiao; Junlin, Wang. 2007. DEM in 3D

Simulation of Influencing Factors of Deformation

Properties and py Curves of a Laterally Loaded Pile.

In: International Conference on Computational

Science. Springer Berlin Heidelberg. pp. 1214-1222.‏

[16] Varun, Dominic Assimaki. 2011. A nonlinear

microelement for dynamic soil-structure interaction

analyses of pile foundations in liquefiable soils.

January, 10-13 5th International Conference on

Earthquake Geotechnical Engineering.

[17] Varun A. 2010. Non-Linear Dynamic Microelement

for Soil Structure Interaction Analyses in Liquefiable

Soils, PhD Dissertation, in: Civil and Environmental

Engineering, Georgia Institute of Technology,

Atlanta.

[18] Gerber Travis M.; Rollins, Kyle M. 2008. Cyclic PY

curves for a pile in cohesive soil. In: Geotechnical

Earthquake Engineering and Soil Dynamics IV. pp. 1-

‏.10

the response of p-y curve of soil-pile characterized … · 2018-12-28 · and practical...

Documents