On the Laboratory Testings to Characterize the Smear Zone

Rudi Iskandar

, A. Perwira Mulia Tarigan

, Roesyanto

Teaching Staff at the Civil Engineering Post Graduate Study Program, Faculty of Civil Engineering, Universitas

Sumatera Utara

Teaching Staff at the Civil Engineering Post Graduate Study Program, Faculty of Civil Engineering, Universitas

Sumatera Utara

Teaching Staff at the Civil Engineering Post Graduate Study Program, Faculty of Civil Engineering, Universitas

Sumatera Utara

Keywords: Smear Zone, Extent Ratio, Permeability Ratio, Laboratory Testing, PVD Instalation, Consolidation.

Abstract: Due its effect on the effectiveness of the PVD performance, the existence of the smear zone is a matter of

considerable interest. The objective of this paper is to review the laboratory testing of the previous studies

concerning the smear zone. Two main parameters are the focus in this study in order to characterize it, ie the

extent ratio and the permeability ratio. Differences in the laboratory set-up lead to the ranges of the values of

the two main parameters and difficulty to compare their values. It is suggested that a standarized laboratory

testing be established to obtain a more accurate and consistent laboratory results.

1 INTRODUCTION

The main parameters proposed for characterizing the

smear zone are the extent ratio and the permeability

ratio. The extent ratio s or s’ is the ratio of the radius

of the smear zone r

to the radius of the drain r

or to

radius of mandrel rm. The permeability ratio κ is the

ratio of the horizontal permeability k

at the

undisturbed location to that at the disturbed site k

The value of these ratio are important in soil

improvement planning using PVD and preloading. If

the s' and κ are not planned well, they will result in

the incorrect rate and duration of consolidation and

thus disrupt the schedule of infrastructure to be

built.One method that can be used to measure s' and

κ is by conducting laboratory testing. This method

most likely cost less and need shorter time then the

method using trial embankment in the field.

Although comprehensive set-up of equipment in

the laboratory has not been established, many

researchers have used the laboratory testing to obtain

the s' and κ (Bergado et al., 1991;Indraratna, and

Redana, 1998; Sharma and Xiao, 2000; Indraratna

and Rujikiatkamjorn, 2004; Sathananthan and

Indraratna, 2006; Fang and Yin, 2006; Shin et al.,

2009; Saowapakpiboon et al., 2010; Tran-Nguyen

and Edil, 2011; Ghandeharioon, et al., 2012; Chai et

al., 2013; Rujikiatkamjorn et al., 2014; Indraratna et

al., 2015; Joseph et al., 2015; Pajouh et al., 2015;

Sengul et al., 2016; Choudhary et al., 2016). Those

whose results are compared in this study can be seen

in column 2 in Table 1. There is no agreement on the

value of s’ and κ resulting from laboratory testing.

Therefore, it is important to review set-up laboratory

testing that has been used in studying the

characteristics of the smear zone and to comprehend

the main causes of why the values vary.

2 THE MAIN POINTS OF

LABORATORY WORKS

2.1 Laboratory Set-up of Equipment

The laboratory set-up used to determine the s' and κ

values involved at least 6 factors presented in Figure

1. Figure 2 shows an example of a large-scale

consolidation apparatus utilized by Indraratna and

Redana (1998).

Iskandar, R., Tarigan, A. and Roesyanto, .

On the Laboratory Testings to Characterize the Smear Zone.

DOI: 10.5220/0010084502730279

In Proceedings of the International Conference of Science, Technology, Engineering, Environmental and Ramiﬁcation Researches (ICOSTEERR 2018) - Research in Industry 4.0, pages

273-279

ISBN: 978-989-758-449-7

273

Figure 1. Set Up Testing Equipment at Laboratory



Figure 2. Large-Scale Consolidation Apparatus (Indraratna and Redana 1998 )



Laboratory Set-Up

Dimension

and Tank

Shape

Type of

Soil

Sample



Sample

Prepa-

ration



Preconsolidation

and

Consolidation

Stresses

Mandrel

Dimension

and Instala-

tion Speed



Method of

Determination

of s’ and κ

values



s’ and κ values

ICOSTEERR 2018 - International Conference of Science, Technology, Engineering, Environmental and Ramiﬁcation Researches

274



Figure 3. Sample Preparation And Determination Phases of Smear Zone Characteristics in Laboratory



2.2 Determination of Smear Zone

Characteristics in Laboratory

Testing normally starts from the sample preparation

stage. The sample preparation and the ensuing

determination stage of the smear zone characteristics

are presented in Figure 3. Columns 11 - 14 in Table 1

show the results of the 17 previous laboratory studies

on the characteristics of the smear zone composed

mainly of soft soils.



3 LABORATORY RESULTS

Bergado et al.(1991) concluded using PVD smear

effect is an important factor in evaluating the rate of

consolidation. Indraratna and Redana (1998)

conclude, there is significant decrease of k

towards

SD, where k'

is relatively unchanged. Where k'

soil permeability coefficient in the vertical direction

zone. Sharma and Xiao (2000) showed that there are

two remedial smear zone, parts located close to PVD

and reconsolidated zone that are located between the

remoulded zone and the intact zone. Fang and Yin

(2006) showed that the buckling effect on PVD will

increase the influence of well resistance and decrease

rate of consolidation. Indraratna and Rujikiatkamjorn

(2004) and Saowapakpiboon et al. (2010) combines

PVD, preloading and vacuum, proposing s' without

and using vacuum the same value.

Tran-Nguyen and Edil (2011) reported there were

two identifiable zones around PVD in the soil mass

after PVD installation. Ghandeharioon, et al (2012)

may present a variety of excess pore pressures at

different locations during PVD installation and

mandrel withdrawal. Pajouh et al. (2015) found a

slight increase in the decrease after excess pore

pressures dissipated in each of the loading stages that

may be associated with the creep phenomenon.

Sengul, et al. (2016) indicates that there are three soil

zones adjacent to PVD namely smear zone, transition

zone and undisturb zone. Choudhary et al. (2016)

evaluates the characteristics of the smear zone based

on changes in the hydraulic gradient derived from

excess pore water pressure data measured in the radial

direction.

Rujikiatkamjorn et al. (2014) stated that the soil

will significantly lose its structure after the

installation of PVD, especially in locations close to

PVD. Indraratna et al. (2015) reported the degree of

disturbance in soil in the field can be higher when the

installed PVD is longer, and the disturbance in the

soil is greater towards PVD.With reference to the

results of previous studies it is found that the extent

ratio s’ values vary between 2.0 - 6.3, and

permeability ratio κ values from 1.03 - 3.13. The

minimum values of s’=2.0, the maximum=6.0, and

the average=4.0. The range of the s’ values can be

classified as follows, low:1<s’<2, moderate: 2≤ s’

<4, and high : 4≤ s’<7. Then the value of s' laboratory

test results are mostly in the moderate to high. The

minimum values of κ = 1.03, maximum=3.13, and the

averaged= 2.0. The range of κ values can be

classified as follow, low:1< κ<4, moderate: 4≤ κ <7,

and high 7≤ κ<12. Then the value κ laboratory test

results are in the low range.

On the other hand, the range of κ value appears to

be limited within the low values.

Installation of

PVD/SD

Consolidation

Stress

Determination

s’ and κ values

Mixing the soil with

water until saturated

Putting it into a

consolidometer

Extracting

trapped air

Pre-consolidated

compression

Sample

Preparation:

On the Laboratory Testings to Characterize the Smear Zone

275

Table 1: Summary results of previous laboratory testings to characterize the smear zone

Table 2: Summary results of previous laboratory testings to characterize the smear zone (continued)

Tank Basic Soil Properties Sample Preparation Stress Speed of Determination

No. Researchers Dimension PVD Mandrel Installation Smear

(kPa) mm mm mm/s Zone r

k

12 3 4 5 6789101112

13 14

10 Ghandeharioon

h =900 mm

Reconstituted Lucustrin

Sample is mixed with water until w = 1.1

Po=20 100 x 4 - - Small 2.65 5.8 kh/kv= kh/kv=

et al. (2012) d =650 mm LL = 55 %, PL =27 %, e =1.46 x LL , placed in cell consolidometer ΔP=50 sampels 1.2-1.6 1.6-1.8

h/d =1.38 layer by layer, and compacted.

11 Chai et al. h =700 mm Reconstituted Soft Bangkok Clay Samples are placed in cell consolido- Po=50 50 x 3.5 81.9x18.2 - Back- 2,0 - 3.0 -

et al.(2013) d =450 mm w =113%,LL =104%,PL =45%, meter layer by layer. ΔP=100 recta- Calcula-

h/d =1.56

=2.66,



=14.7 kN/m

ngular tion

12 Rujikiatkamjorn h =561 mm Undisturb Bulli Clay The soil around the sample is dug andPo=20w=50 55x5 - Small 3.7 5.5 1.33-2.85 1.11-1.33

et al.(2014) d =345 mm w =41%, LL = 50%, PL =25%, cut from base, wrapped to ΔP=200 recta- sampels

h/d =1.60 Gs



=18.5 kN/m

prevent loss of w, stored in a humidity- ngular

controlled room, and placed into cell

consolidometer.

13 Indraratna et al h =25,4 mm Undisturb Ballina Clay Samples for Oedometer testing - 100x3 120x60 - Oedometer 6.3 - 2.7 -

(2015) d =63,5 mm w =94,7%,LL =98%,PL =32%, are collected from around the PVD ΔP=200 recta- test

h/d =0.40 Gs =2.58,e =2.44,γ=16.5 kN/m3 installed in the field. A series ngular

oedometer testing is performed.

14 Joseph et al. (2015) h =600 mm Reconstituted Cochin Marine Clay Sample is placed into the tank Po=5 SD. diam.50 hammer Small 5.0-6.0 - 1.3-1.4 -

d =600 mm w =112%,LL= 156%, consolidometer, with w = LL layer by ΔP=120 diam.46 circular w=2.6 kg sampels

h/d =1.00

PL =34%,G

=2.62 layer. h=30 cm

15 Pajouh et al.(2015)

h =200 mm

Reconstituted Kaolinite, bentonite

Samples are mixed with water to w =(1.4-1.8)

Po=20 SD. diam.25 - Directly 3.0xr

-4.0-

d =250 mm w =120%,LL =67-87%,PL =27-34% LL , placed into Rowe cell, and given stress ΔP=200 diam.22 circular at cell

h/d =0,80 PI =40-43% cell =110 kPa,back pressure = 100 kPa Rowe

for saturation.

16 Sengul et al. (2016) h =530 mm Reconstituted HRK,LL =51%, Samples with w equal to the Po=25 130x18 120x15 2-5 Directly 3.3 7.3 2.0 1.21

w = 350 mm

PL =26%,IP =25%,G

=2.60 field are placed on the box, ΔP=hydraulic recta- at SZM

t = 130mm Reconstituted CID,LL =51%, placed in SZM instrument coating, Head= ngular instrument 2.3-2.4 5.2-5.8 2.86-3.13 1.75

PL =30%,,IP =21%,Gs =2.76 and compressed with vibrator. 50

17 Choudhary et al. h =450 mm Reconstituted Balina Clay Clay is taken 2 m below ground surface, Po=20 100x4 115x10 - Directly 2.5 - 1.3 -

(2016) d =650 mm w =94%, LL = 98%, mixed with distilled water ΔP=Additional recta- at cell

h/d =0.69 PL =32%, Gs =2.6 with w = 1.4 LL , placed into cell end ngular Consoli-

consolidometer and given a light vibration. load dation

h = high r = radius Po = Pra-consolidatiion stress (+v) = With PVD + vacuum preloading

d = diameter

HRK = Hydrite R Kaolinite

ΔP = Consolidation stress

= Permeability of soil at transition zone

w = wide

CID = Craney Island Dredgings

i = Gradient hydraulic

= Equivalent radius of transition zone

t = thickness SZM = Smear Zone Model (l),(s)=Mandrel long and short axis SD = Sand Drain

Extent Ratio Permebility RatioDimension

Tank Basic Soil Properties Sample Preparation Stress Dimension Mandrel Speed of Determination

No. Researchers Dimension PVD Installation Smear

(kPa) mm mm mm/s Zone r

k

1 2 3 4 5 6 7 8 9 10 11 12

13 14

1 Bergado et al. h =920 mm Reconstituted Soft Bangkok Clay Samples are placed in cell consolidation Po=10.2 40x6 60x60 - Small 2.0 - 1.5-2.0 -

(1991) d =455 mm



=14.7 kN/m

, Cc =0.80, layer by layer. Sand of 5 cm thick is given ΔP=47.8 recta- sampels

h/d =2.02 Cs =0.13,e =2.3 on the surface. ngular

2 Indraratna and

h =950 mm

Reconstituted Allivial Clay, Sydnay Samples are mixed with water, placed in Po=20 SD diam.50 - Small 4.0-5.0 - kh/kv= -

Redana (1998) d =450 mm w =40%,LL =70%,PL =30%, a consolidometer cell and compacted ΔP=200 diam.46 circular sampels 1.15

h/d =2.11

=2.6,γ=17.0 kN/m

layer by layer.Surface is given sand 5 cm.

3 Sharma and

h =400 mm

Reconstituted Kaolinit

Kaolinite is mixed water up to w = 2 x LL ,

Po=100 SD diam.50 5.0 Small 4.0xr

-1.30 -

Xiao (2000) d =1.000 m

w =65%, LL =70%,PL =40%, put into consolidation tank and be ΔP=1,102 diam.50 circular sampels

h/d =0.40 e=1.4,Gs=2.61 vacuumed for stress at 90 kPa for

several days.

4 Indraratna and

h =950 mm

Reconstituted Allivial Clay, Moruya Samples are mixed with water up to w Po=20 100x3 125 x 25 - Small 3.0xr

- kh/kv= -

Rujikiatkamjorn.

d =450 mm w =45%,LL = 42%, PL=17%,

slightly larger than LL, placed in a coating, ΔP=30+50 recta- sampels 3.0xr

(+v) - 1.17-1.20 -

(2004)

h/d =2.11

=2.6,γ=17.0 kN/m

compacted using consolidometer cell. ngular

5 Sathananthan and h =1040 mm Reconstituted Allivial Clay, Moruya Clay is mixed with water, kept on Po=20 100x3 125 x 25 8.3 Small 2.5 - 1.34 -

Indraratna (2006) d =650 mm w =45%, LL = 42 %, PL =17%, container for several days, placed ΔP=200 recta- sampels

h/d =1.60 Gs =2.6,



=17.0 kN/m3 in coating consolidometer cell ngular

(150 mm/Layer), and compacted.

6 Feng and h =450 mm Reconstituted Hongkong Marine Clay is mixed with water and stored in Po=20 50x5 60x13 - Direct 2.0 - 2.00 -

Yin (2006) d =300 mm Clay, w =85,6 %, LL = 51.1 %, container for several days, placed in ΔP=80 recta- at cell

h/d =1.50 PL =26.1 %, Gs =2.58. coating consolidometer cells (150 mm/ ngular consoli-

layer) and compacted. dation

7 Shin et al. (2009) h =1000 mm Reconstituted Busan Clay The test sample passed the sieve No.40. Po=50 85x6.4 100x50 20.0 Direct 4.0-4.2 (l) - - -

d =700 mm w =56 %, LL = 46.4 % is mixed with water up to w = 2 x LL . ΔP=200 recta- at cell 3.3-3.4 (s) - - -

h/d =1.43 PL =24.1 %, Gs =2.64 The trapped air is removed by vacuum ngular consoli-

during mixing. dation

8 Saowapakpiboon h =500 mm Reconstituted Soft Bangkok Clay The sample is taken into 3-4 m from - 100 x 3.5 - - Back- 2.0 - 2.70 -

et al. (2010) d =305 mm w =113%,LL = 102%,PL =40%, the ground surface and placed in the cell ΔP=100 Calcula- 2.0 (+v) 2.50

h/d =1.64

=2.66,



=14.7 kN/m

. consolidometer coating. tion

9 Tran-Nguyen h =530 mm Reconstituted HRK, LL =49 %, Sample with w equal to the Po=25 100 x 3.2 15x120 1.0-2.5 Directly 3.0 (HRK) - 1.03 -

and Edil (2011) w = 350 mm PL =24 %, Gs =2.59. field is placed on the box. ΔP=Gradien. recta- at SZM -

t = 130mm Reconstituted CID LL =49 %, Placed in SZM instrument coating, hydraulic ngular instrument 4.2 (CID) - 1,25

PL =20-25 %,Gs =2.71 compressed with vibrator. i=20-30

Extent Ratio Permebility Ratio

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4 DISCUSSION

4.1 Shape and Ratio of H/Diameter of

Tank

Tank soil in the laboratory is typically cylindrical and

box. Researchers variously designed dimensions of

consolidometer tank cylinder. In column 3 of Table 1,

the diameter of the tank (d) varies from 300 mm-700

mm, the height (h) varies from 400 mm-1,000 mm,

and the h/d ratio varies from 0.4 to 2.11. There is no

agreement whether the ratio h/d>1, h/d =1 or h/d <1.

Generally the tank used has a ratio h/d > 1. However

Joseph et al. (2015) used the ratio h/d=1, while

Sharma and Xiao (2000), Indraratna et al. (2015), and

Choudhary et al. (2016), used a h/d ratio of <1. The

tank-shaped box was made by Tran-Nguyen and Edil

(2011), and further developed by Sengul et al. (2016).

4.2 Basic Soil Properties Tested

Soil stiffness depends on basic properties of the soils.

According to Sengul et al. (2015), and Sathananthan

and Indraratna (2015) the r

and

ratios depend

on the soil stiffness. For a more stiff soil the ratio is

larger than for a less stiff soil. When compared to the

soil characteristics data in column 4 of Table 1, the

sample water content w values vary between 40%-

112%, liquid limit LL between 42% -102%, plastic

limit PL between 17%-34%, specific gravity G

between 2.56-2.76 and unit weight γ between 14.7

kN/m

-18,5 kN/m

. The inheritance properties of the

soil tested resulted in differences in stiffness, the r

and

ratios generated.

4.3 Preparation of Soil Sample

The sample preparation data can be seen in column 5

of Table 1 of. In the disturbed sample, w when mixing

varies from the natural w in the field up to 2 times the

LL of soil. Saturation time varies from a few days to 6

months. The technique of removing the air trapped in

the soil during mixing also varies. Some use the

technique of compressing, vibrating, or vacuum. The

similar conditions occur in undisturb samples. Large

and intact samples were taken from the field for

testing on consolidometer cells with small samples

taken for oedometer testing. Different preparation of

soil samples resulted in different s' and κ ratios being

generated.

4.4 Pre-consolidated Stress P

This Stress represents the amount of existing stress

acting on the soil. Refering to column 6 of Table 1 the

magnitude varies from 5 kPa-1,100 kPa. This

difference results in the difference in s' and κ values

generated.

4.5 Consolidation Stress ΔP

Refering to column 6 of Table 1 the consolidation

stress varies from 80 kPa-1,102 kPa. Sengul, et al.

(2016) concluded the decrease of k

and k

smear and transition zone is affected by the increased

of the consolidation stress. Sharma and Xiao (2000),

and Sathananthan and Indraratna (2006) concluded

that κ decreases with the increasing pressure of

consolidation on the ground. Indraratna and Redana

(1998) concluded that smear effects are limited within

short to medium term consolidation. The difference in

consolidation stress causes the variation in s' and κ

ratios.

4.6 Use of Reconstituted Soil Samples

Tran-Nguyen and Edil (2011) who used reconstituted

samples reported that the extent and permeability

ratios measured in their laboratory study were at the

lower limit reported in the literature. This is due to the

fact that soils were very disturbed and had no

structure, thus less susceptible to disturbance. The

laboratory testing using undisturbed soil samples was

done by Rujikiatkamjorn et al. (2014) who found that

permeability reductions were almost twice as much as

those using disturbed soil. On the other hand Bo et al.

(2003) suggested that the smear zone could become

larger in undisturbed soils due to the destruction of the

soil structure. Nevertheless the condition of the soil in

the field is typically intact, leading to the higher

values of s’ and κ ratios. Tests that use reconstituted

and undistub samples are indicated in column 4 of

Table 1.

4.7 Mandrel Shape and Dimensions

The PVD installation in the laboratory is performed

using a mined mandrel of unequal shape and size as

presented in column 8 of Table 1 of. Sathananthan and

Indraratna (2015) said the s’ ratio depends on the

dimensions of mandrel used. Tran-Nguyen and Edil

(2011) suggested the size and shape of mandrel is an

important factor affecting s'. Shin et al. (2009)

denoted a non-spherical shape of the smear zone but

the ellip with a greater range on the longer mandrel

On the Laboratory Testings to Characterize the Smear Zone

277

side compared to the short side. These differences in

mandrel shape and dimensions cause the resulting s'

and κ values to be different.

4.8 Speed of PVD Installation

Due to the absence of a standardized speed, the

researchers used varied between 0.5 mm/s-20 mm/s as

presented in column 9 of Table 1. Sathananthan and

Indraratna (2006) said the s’ ratio value depends on

the installation speed. If the installation speed is

faster, the disturbance on the ground will increase and

thus the permeability ratio κ will increase. The

existence of the speed difference affect the value of s'

and κ generated.

4.9 Determination Method of Smear

Zone Characteristics

There are three ways to determine the characteristics

of smear zone in the laboratory use of small diameter

samples, back calculation and direct measurements in

large-diameter consolidation cells. Using small

diameter samples was performed by sampling small

diameters of large diameter consolidation cells for

oedometer testing. The determination of value is done

using Terzaghi 1-D consolidation theory. With the

measured distance of sampling to PVD and k value,

the changes of k value to PVD distance can be

detected and the smear zone characteristics can be

determined. The method of back calculation of

laboratory testing data to determine the value of

consolidation coefficient in horizontal direction c

based on the Asaoka method [1978] and Hansbo

[1987] is done by adjusting the time-settlement curve,

then obtaining s' and κ. Measuring directly in SZM

(Smear Zone Model) intruments, cell Rowe and

consolidation cells was also performed by

researchers. The methods of determination of smear

zone characteristics are presented in column 10 of

Table 1.

5 CONCLUSIONS

There are no standards established to be used as

references in laborary testing. The resulting smear

zone parameter values are various due partly to

different set up of laboratory equipment. With

reference to the results of the previous studies it is

found that the extent ratio s’ values varies between 2.0

- 6.3 and the permeability ratio κ values from 1.03 -

3.13.

ACKNOWLEDGEMENTS

The authors gratefuly acknowledge the financial

assistance from the University of Sumatera Utara

(Research Contracts Fiscal Year 2018, Number:

2590/UN5.1.R/ PPM / 2017 dated March 16, 2018).

The contribution from Nurhayani Simamora in typing

and formating the paper is appreciated.

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