Using Saudi Natural Soils from Jeddah-Makkah Boundaries as Liner

Bed in Sanitary Landfills, Suitability Study

M. AboushooK1

, M. N. Fatani2, H. Abdulrahman

3, A. Fadol and M. Kotob

4

1,2Faculty of Engineering, King Abdulaziz University, KAU, Jeddah, Saudi Arabia

3Faculty of Environmental Designs, KAU, Jeddah, Saudi Arabia

4Faculty of Engineering, KAU, Jeddah, Saudi Arabia

Abstract. Thirteen locations in Jeddah-Makkah boundaries in Saudi Arabia containing clayey soils were

selected, based on previous geological studies, to test the possibility of using natural soils brought from these

sites as liner-bed in solid waste landfills. The main function of the liner-bed layer in solid waste landfills is to

protect underground water aquifer against contamination from infiltrated pollutants. Physical and engineering

properties of soil samples brought from these locations are investigated. The permeability of a liner bed

material should not exceed a limiting value of 1x 10-7

cm/sec while the total shear strength (t) at saturation

state should not be less than 50 kPa at 200 kPa of normal stress (n). Most of the engineering properties are

measured at a fixed initial state of the standard Proctor optimum moisture content (wopt.) and maximum dry

density (dmax.). Most of the soil samples from Makkah-Jeddah area were classified as clayey type soils. Four

out of the thirteen samples met both requirements of permeability limit and shear strength, while a pair of

samples met the permeability limit condition only and another pair met the shear strength requirement only.

The rest of samples did not meet any condition. As a conclusion four samples were found to be suitable as

liner bed material while nine samples were found to be unsuitable.

Keywords: Natural soils, Solid waste, Underground water, contamination, Permeability, Shear strength

1. Introduction

Solid waste management is one of the serious problems with growing potential in developing countries

such as Saudi Arabia. Poor management of solid waste may lead to severe soil and groundwater

contamination resulting in adverse health hazard [1]-[3]. One of the practical solutions, of such a problem, is

achieved by enclosing the solid wastes in a specific location (dump) and using insulated container to prevent

percolation of waist liquids. For economic construction, engineers use insulating soil barrier called "liner

bed" at the base of the solid waste dump. The liner bed material should be impervious to prevent infiltration

of pollutants such as heavy metals and other toxic materials into groundwater aquifer. It should also be

strong enough to resist shear failure that may be caused by the weight of the solid wastes [4]. To build more

economical solid waste dump, the use of local natural materials should be investigated. Natural clayey soils

or modified mixture of such soils with bentonite could be used [5], [6]. For one of these materials to be

suitable as compacted soil bed, it should meet the conditions of permeability and shear strength [6].

According to [7], [8], the permeability of a liner bed material should not exceed a limiting value of 1x 10-7

cm/sec and the total shear strength (

n). The efficiency of this bed depends largely on the hydro-mechanical behavior of the

soil along with its capacities of attenuation and retention of the liquid component of the contaminant [8]. If

suitable earthen material is available on or near the site of construction, a lining of compacted earth is

considered economical and efficient means of controlling percolation. A well- compacted lining of such soil

can be highly impermeable, satisfying the above-mentioned requirements for liner bed material.

Corresponding author. Tel.: +966568365313

E-mail address: profdraboushook@gmail.com.

International Proceedings of Chemical, Biological and Environmental Engineering, Vol. 88 (2015)

DOI: 10.7763/IPCBEE. 2015. V88. 14

81

This paper investigates the suitability of using natural clay soils around the boundaries of two major

cities in Western region of Saudi Arabia as liner bed in solid waste dumps. These cities are, Makah and

Jeddah. The liner bed would be constructed at the bottom of the solid waste landfill at a depth of 25-30 m

below ground level. Soils at Makah and Jeddah locations are considered to be similar in the geological origin

and soil condition. Eight test sites (S1-S8) were chosen within Jeddah region, while five test sites (S9-S13)

were considered for Makah region. The locations of these sites are shown on the geological map of these

regions (Fig. 1). The physical and engineering properties of soils under investigation have been determined

based on ASTM specifications [8]. All engineering properties measurements were conducted through a fixed

initial state of standard Proctor optimum moisture content (wopt.) and maximum dry density (dmax.). However,

the swelling potential and settlement behavior were measured according to the modified Proctor conditions.

In this paper, the physical characterization of all soil samples will be discussed. Then, the engineering

behavior of these natural soils is investigated. The suitability of each of these materials as liner bed is then

determined based on the conditions of permeability and shear strength.

Fig. 1: Location and Geologic map of Jeddah-Makah Quadrangle showing the locations of the investigated clay deposits

(Modified after [9]

).

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

CL-ML

CH

CL

MH or OHMLH or OL

S1

S8

S6

S2

S4

S12

S10

S13

S3

S11

S7

S9

S5

Liquid limit

Plas

tici

ty in

dex

%

Figure 3.8: Location of studied samples on Cassegrand Chart

CL-ML

CH

CL

MH or OHMLH or OL

S1

S8

S6

S2

S4

S12

S10

S13

S3

S11

S7

S9

S5

CL-ML

CH

CL

MH or OHMLH or OL

S1

S8

S6

S2

S4

S12

S10

S13

S3

S11

S7

S9

S5

Fig. 2: Location of soil samples on Cassegrand chart

2. Physical Characterization

82

Physical characterizations are meant to provide a rational basis for verifying the suitability of natural

soils extracted from chosen sites in Jeddah- Makah region to be used in the liner system of waste

management structures. Visual description is summarized in Table 1. Sample photographs given in this table

show that most samples look like natural shale soils which are hard in dry state and tend to swell and soften

in wet state as indicated by the free swell (FS) values in Table 2. The following physical properties are

determined, according to ASTM Standard Specifications [8] to identify the studied soils in point of view

their suitability to be a liner: Moisture content and density; Fines percentage and clay content; Plasticity

characteristics and activities. Field density and moisture content deduced from undisturbed samples and

presented in Table 2, indicate relatively high values of field dry density and low values of moisture content.

That reflects hardness of natural samples. The high maximum dry density of compacted soils also reflects

good strength conditions. The percentages of sand, silt and clay contents are also listed in the Table 2. Most

of the natural samples, except S6, have more than 20 % fines (silt & clay); 10% clay; 7% plasticity index

and 0.3 activities. From the Casegrand chart, the most studied natural soils are classified as silty clay with

high to low plasticity (CL or CH) (Fig. 2). All the physical properties results are summarized in Table 3.

Comparison between standard and modified Proctor compaction of studied soils (Table 2), most of studied

soils have tendency to absorb more compaction energy.

Therefore, most of studied soils are expected to become suitable materials for a bed liner compaction.

That means that the most studied samples are suitable to be liner materials from the point of view of physical

properties according to the specification of liner materials, Table 3. However, the suitability of a soil to be a

clay liner material does not depend only on the physical properties requirement, but the most important are

the engineering behavior requirements which will be investigated in the next section.

Table 1: Visual description of studied soils from Jeddah and Makah

Soil No. Location General Description Sample Photos

S1

Jeddah Bound.

N 22 12 39.5,

E 39 15 04.8

Reddish brown slightly to medium

cemented clayey silty sand.

S2

Jeddah Bound. N 22 11 19.6,

E 039 15 43.6

Reddish brown slightly cemented

clayey silty sand.

S3

Jeddah Bound. N 22 21 40.0,

E 39 19 32.1

Dark reddish brown medium stiff stratified silty clay (shale)

S4

Jeddah Bound.

N 21 59 39.36, E 39 20

04.16 Grey stiff stratified silty clay (shale)

S5

Jeddah Bound.

N 21 59 35.44, E 39 20 09.57

Reddish brown medium stiff stratified

silty clay (shale)

S6

Jeddah Bound.

N 21 52 27.7, E 39 25 13.5 Yellowish brown slightly cemented

silty sand, traces of clay

S7

Jeddah Bound.

N 22 15 00.3,

E 39 13 29.1

Reddish brown medium cemented clayey silty sand

S8

Jeddah Bound.

N 22 13 33.51, E 39 13 49.24

Grey stratified medium stiff sandy

silty clay (shale)

S9

Makkah Bound.

N 21 49 34.08, E 39 28

11.01

Dark reddish brown slightly to medium cemented clayey silty sand

S10

Makkah Bound. N 21 41 05.0,

E 39 45 02.0

Very dark brown highly cemented

silty sand, traces of clay ( volcanic Tuff)

83

S11

Makkah Bound. N 21 50 48.2,

E 39 44 44.2

Friable pieces of grey stratified silty

sandy clay (friable shale)

S12

Makkah Bound.

N 21 46 02.90, E 39 40

36.27

Grey stratified medium to stiff sandy silty clay (shale)

S13

Makkah Bound. N 21 26 03.47, E 39 37

37.20

Light brown medium to stiff silty clay (shale)

Table 2: Basic physical properties of natural soil samples*

PP.

Basic Physical Properties

S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13

Fie

ld m % 3.4 4.1 8.5 9.5 7.7 3.1 8.4 13.4 6.7 5.3 8.1 3.9 4.1

d kN/m3 16.6 17.3 15.4 14.0 16.2 16.0 16.4 14.5 16.6 16.5 16.8 16.4 16.7

% Sand 55.0 35.0 7.7 0.4 2.0 85.0 49.0 47.0 39.0 71.0 39.0 40.0 1.4

%Silt 25.0 40.0 51.3 52.6 60.0 5.0 25.0 15.0 32.0 21.0 10.5 32.0 51.6

%clay 20.0 25.0 41.0 47.0 38.0 10.0 26.0 38.0 29.0 8.0 50.5 28.0 47.0

LL % 29.2 37.1 62.5 69.1 61.8 8.0 37.8 57.6 39.0 28.2 70.1 43.3 28.8

PL % 20.7 18.9 37.8 34.9 43.3 6.0 20.8 31.9 17.9 19.2 25.4 19.7 14.4

SL 17.5 16.1 29.6 24.6 29.5 0.0 16.2 25.5 14.6 15.8 17.7 11.2 8.2

PI 8.5 18.2 24.7 34.2 18.5 2.0 17.0 25.7 21.1 9.0 44.7 23.6 14.4

Activity 0.4 0.7 0.6 0.7 0.5 0.1 0.7 0.7 0.7 1.1 0.9 0.8 0.3

FS % 37.5 50.7 68.6 70.8 39.5 7.5 76.5 66.7 33.3 37.5 87.5 60.0 16.7

Sta

nd

ard

w opt. 17.0 16.2 24.0 19.0 27.0 15.7 15.8 22.0 14.8 15.4 17.8 14.5 12.0

d max

kN/m3 17.8 17.3 14.7 15.0 15.3 18.5 17.6 14.4 18.8 18.5 17.6 17.8 18.2

Mo

dif

ied

w opt. 13.5 14.5 19.0 16.0 20.0 13.7 12.5 18.2 13.5 14.0 14.5 12.5 10.6

d max

kN/m3 19.1 19.0 16.2 15.3 17.1 18.9 18.2 16.4 19.3 19.2 18.1 19.2 19.4

*All values are deduced from measurements on three identical samples

Table 3: Physical properties specification requirement for liner material

Properties General requirements

% Fines (passing the No. 200 sieve- silt & clay size) -30%

% Clay (0.002 mm) fraction -15%

% Gravel size Particles( 4.36 mm)

Not contain any particles larger than (25 to 50 mm) < 5-10%

Plasticity index

Soils that have PI greater than about 30% are undesirable: Difficult to work with

in the field - Form hard clods when dry- Are too sticky when wet.

-10%

Activity > 0.3

Dry Density > 15 kN/m3

3. Engineering Behavior

This section reports the experimental studies that were undertaken to determine the engineering

characteristics of the soil samples S1-S13 extracted from Jeddah-Makah region. Experimental tests reported

here include the direct shear test, unconfined compression test, consolidation test, swelling potential test and

permeability test. All the tests have been executed according to [7], [10].

84

3.1 Engineering Characteristics

Many previous researchers were only interested in the engineering properties at optimum moisture

content, wopt [11], [12]. However, in this research project, the engineering properties have been determined at

saturation moisture content (wsat) as well as at optimum moisture content, wopt. That is because the shear

strength at wopt.is important to the stability of liner material for a short period during and after construction

whereas, the shear strength at wsat is very important to the stability of liner material for a longer period after

installation. The saturation condition is always controlling the design due to the relative weakness

accompanying the presence of water. The investigated engineering properties are as follows:

Shear strength parameters (c &Φ) at (woptand wsat).

Total shear strength () at (wopt and wsat) within 200 kPa as normal stress

Unconfined compressive strength at (wopt and wsat)

Total settlement at saturation condition within 200 kPa. as normal stress which is corresponding to a

total solid waste depth of about 25 m.

Swelling potential at 7 kPa as normal stress of compacted soils (wopt)

Hydraulic conductivity (permeability) of compacted soils (wopt) until saturation state.

3.2 Results and Analysis of Engineering Properties

In this paper, the engineering properties for all samples (S1-S13) collected from Jeddah-Makah region,

were tested at optimum moisture content and maximum dry density. Table 4 summarizes the results of the

measured engineering properties of these soil samples. Studying the results displayed in the above table, the

following points may be made:

In this paper, the shear strength value at a normal stress of 200 kPa (corresponding to the weight of

about 25 m of compacted landfill) has been interested . Hence, one shear stress value at a surcharge

pressure of 200 kPa is used for comparison.

For all soil samples except S9 and S12, the shear strength for a soil sample compacted at wsat is much

lower than that for a sample compacted at wopt. This may be attributed to the soil structure

arrangement in the compaction process.

The shear strength values for soil samples (S1-S13), collected from Jeddah-Makah region,

compacted at wopt, ranged between 38 kPa to 187 kPa, whereas the shear strength values for soils

compacted at wsat ranged between 21 and 115 kPa.

Unconfined compressive strength of soils compacted at wopt. ranged between 185 and 386 kPa

whereas for soils compacted at wsat ranged between 40 & 151 kPa.

The shear box testing condition, where all sides are confined represents the field condition more

closely than in unconfined testing condition, where only top and bottom are confined.

Percentage of settlement has been measured under a normal stress of 200 kPa to give an idea about

the expected percentage of total settlement after the complete depth of landfill over the liner bed is

placed. The settlement percentage ranged between 0.3% and 4.7%.

Swelling potential has been measured, according to specifications, under a very light load intensity

of 7 kPa, to investigate the swelling behavior of liner bed soil during construction. The swelling

potential ranged between 0.1% and 7.5%.

Measured permeability values ranged between 1.22x10-5

cm/sec and 6x10-10

cm/sec. which means

that the tested soils are considered to be of very low permeability to virtually impermeable soils.

It can be generally concluded from the obtained results of engineering properties that some of the tested

soils are meeting the required specification for use as linear materials, while others are not meeting these

specifications. Soils meeting the specification can be used without treatment, while soils not satisfying the

requirements could be treated by various ways to render them suitable for use as liner material. However, the

engineering properties specifications requirements for liner bed materials are shown in Table 5. In other way,

according to a study made by Mc-Cartrey et al. [8] on Geosynthetic clay liner, the deduced shear strength of

bentonite before and after saturation at a total normal stress of 200 kPa were about 100 and 50 kPa

respectively. Therefore, the limit values for shear strength of liner material before and after saturation could

be taken as ( > 100 kPa at wopt and >50 kPa at wsat).

4. Phase Diagram

85

The “Phase Diagram” is constructed to show if a soil sample satisfies both, one or none of the two

requirements of liner-bed material specifications. In this diagram two limit lines are constructed. The first

limit is for permeability coefficient (k) which must be less than 1*10-7

cm/sec (according to liner

specifications, Table 5). The second limit is for shear strength at saturation (

than 50 kPa8. In The "Phase Diagram" (Fig. 3), the soil sample is represented by a point; the co-ordinates of

this point are the permeability coefficient and shear strength values. The two limit lines divide the phase

diagram into four quadrants, the first represents an area where both requirements are satisfied, the second

represents an area where permeability requirement only is satisfied, the third represents an area where none

of the requirements is satisfied, the fourth represents an area where shear strength requirement only is

satisfied. All soil samples are represented in one Figure showing the overall situation of these soils from a

point of view of suitability as liner-bed material.

Table 4: Engineering properties of studied soil

Eng. PP S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13

w opt. stand. % 17.0 16.2 24.0 19.0 27.0 15.7 15.8 22.0 14.8 15.4 17.8 14.5 12.0

d max kN/m3 17.8 17.3 14.7 15.0 15.3 18.5 17.6 14.4 18.8 18.5 17.6 17.8 18.2

UCS (wopt. )

kPa 353 336 386 295 206 315 240 334 245 244 203 320 311

UC (wSat.) kpa 51.0 57.0 62.0 76.0 43.0 45.0 40.0 151.0 59.0 50.0 62.0 106.0 72.0

C (wopt.)kPa 63.0 20.0 13.0 138.0 101.0 12.0 21.0 127.0 8.0 148.0 90.0 24.0 44.0

Φ° (wopt. ) 11.0 18.0 26.0 6.0 12.0 12.0 8.0 11.0 10.0 11.0 13.0 4.0 18.0

kPa 101.9 85.0 110.6 159.0 143.5 54.5 49.1 165.9 43.3 186.9 136.2 38.0 109.0

C (wsat.)kPa 24.0 3.0 10.0 23.0 11.0 20.0 19.0 24.0 89.0 23.0 24.0 65.0 24.0

Φ° (wsapt. ) 8.0 11.0 6.0 6.0 3.0 4.0 5.0 10.0 5.0 10.0 9.0 14.0 5.0

(wsat.)

kPa 52.1 41.9 31.0 44.0 21.5 34.0 36.5 59.3 106.5 58.3 55.7 114.9 41.5

swelling

potential % 0.1 0.43 3.3 7.3 1.58 1.73 0.66 1.32 0.75 2.43 7.25 6.65 2.35

Settlement % -2.13 -2.49 -3.12 -0.30 -1.65 -4.10 -1.53 -4.70 -1.48 -1.48 -4.50 -3.44 -1.61

Permeability

k x 10-5

cm/sec

1.22E-

05

7.44E-

06

7.21E-

06

7.20E-

07

1.14E-

04

6.70E-

07

5.00E-

08

1.00E-

07

1.00E-

07

1.33E-

06

6.00E-

10

9.00E-

08

1.00E-

07

Table 5: Engineering characteristics specification requirement for a liner material[13],[14],[15]

Properties General requirements

Hydraulic conductivity (permeability) <1x10-7 cm/sec

Angle of internal friction at optimum moisture content- Wopt. > 20°

Cohesion at saturation moisture content- Wopt. > 2.5 kPa

Unconfined compressive strength at Wopt. >200 kPa

Total Settlement < 4%

Liner Thickness

installed in (15-cm) lifts > (75-100) cm

Minimal shrinkage potential to minimize desiccation and cracking

86

All studied Soil samples (S1-S13) collected from Jeddah-Makah region, are represented in Fig. 3. It can

be clearly seen from this Figure that four soil samples (S8, S9, S11and S12) were located inside the first

quadrant which means that these soils are suitable as liner-bed material. Soils (S7 and S13) were located in

the second quadrant which means that these soils are not suitable as liner-bed material from point of view of

shear strength limit. Soils (S2, S3, S4, S5 and S6) were located in the third quadrant which means that these

soils are not suitable as liner-bed material from point of view of the two limits. Soils (S1and S10) were

located inside the fourth quadrant which means that these soils are not suitable as liner material from point of

view of permeability.

1E-11

1E-10

1E-09

1E-08

1E-07

1E-06

1E-05

0.0001

0.001

0 25 50 75 100 125 150

Perm

eabi

lity

cm

/se

c

Shear Strength at saturation kPa

S11

S6S4

S3S5

S7 S13

S10

S8 S12

S2

S9

S1

Acceptable PermeabilityAcceptable Shear Wsat

Non- Acceptable PermeabilityAcceptable Shear Wsat

Acceptable PermeabilityAcceptable Shear Wsat

Acceptable PermeabilityNon-Acceptable Shear Wsat

Limit of Pemeability

Lim

it of

She

ar S

tren

gth

Acc

epta

ble

Non

-Acc

epta

ble

AcceptableNon-Acceptable

Fig. 3: Phase diagram of acceptable soilss arround Jeddah - Makah according to liner specifications

5. Conclusions

From the obtained results of physical and engineering properties of studied soils, (S1-S13) collected

from Jeddah-Makah region, the following conclusions could be noted:

The basic physical properties including fines content, clay content, plasticity index and their activity

are the most important physical properties controlling the engineering behavior of clay soils that may

be used as a liner-bed material.

Shear strength at wopt tends to increase with all basic physical properties, whereas it tends to decrease

for wsat situation. This may be due to the lubrication effect of saturated clay particles.

The shear strength at wopt is important mainly during the construction of liner bed and for a relatively

short time afterwards, whereas the shear strength at wsat is most important for a long time after the full

depth of solid and liquid waste in the landfill is attained and the liner bed will probably become

saturated due to leechate precipitation.

The permeability which is most important for liner material specification tends to decrease with all the

basic physical properties. That is because the clay and fines with their activities are most important

factors affecting the connection between pores of clay soils which has a direct effect on the

permeability.

For most of soils coming from Jeddah and Makah boundaries, permeability tends to decrease and

shear strength at wopt tends to increase with the increase of fines and clay contents, plasticity index and

activity. That is in favor of using these soils as liner bed material. However, for some soils, shear

strength at wsat tend to decrease with physical properties which is in contradiction of liner bed

specification at saturation state.

All soil samples are represented in one "Phase Diagram" showing the overall situation of these soils

from a point of view of suitability as liner-bed material. This diagram is a useful tool when attempts

are made to improve the performance of non-suitable soil by mixing it with a percentage of a suitable

one to produce a new suitable soil mixture. The choice of the suitable soil depends on the violated

requirement. For example if permeability is violated then the suitable soil to be chosen should have a

very low permeability coefficient so that when added to the non-suitable soil, the mixture would attain

the required permeability requirement.

87

6. Acknowledgements

The authors wish to express their sincere gratitude and utmost appreciation to King Abdulaziz City for

Science and Technology (KACST) for supporting this research project under great number "AT 30-32". The

investigators wish to acknowledge University Vice Presidency as well as Vice Presidency for Graduate

Studies and Scientific Research and the Deanship of Scientific Research of King Abdulaziz University for

their academic and material support for this study. The Faculty of Engineering and Earth Sciences, King

Abdulaziz University supplied logistics of fieldwork and allowed the research team to use the civil

engineering department equipment and facilities. Their generous support is gratefully acknowledged.

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88