ife journal of science...ife journal of science aims and scope ife j our nal of science (ijs) aims...

IFE JOURNAL

OF SCIENCE

A Journal of the Faculty of ScienceObafemi Awolowo University, Ile-Ife, Nigeria

ISSN 0794-4896

Volume 13 Number 1 JUNE 2011

Ife Journal of Science

Aims and Scope

Ife Journal of Science (IJS) aims to publish articles resulting from original research in the broad areas of chemical, biological, mathematical and physical sciences. This extends naturally into frontiers that include the applied areas of Biochemistry and Geology as well as Microbiology and such allied fields as Biotechnology, Genetics, Food Chemistry, Agriculture, Medical and Pharmaceutical Sciences. Shorter-length manuscripts may be accepted as Research notes. Review articles on research topics and books are also welcome.

Editor-in-Chief (Biological Sciences): Prof. J. O. Faluyi

Editor-in-Chief (Physical Sciences): Prof. M. O. Olorunfemi

Associate Editors

Dr. A. O. Shittu - Microbiology Prof. T. O. Obilade - Mathematics Prof. G. A. O. Arawomo - Zoology Prof. J. O. Ajayi - Geology Prof. A. P. Akinola - Mathematics Prof. H. C. Illoh - Botany Prof. F. O. I. Asubiojo - Chemistry Prof. H. B. Olaniyi - Physics Prof. A. A. Okunade - Physics Prof. O. O. Oyedapo - Biochemishy Dr. A. I. Odiwe - Botany Prof. S. B. Ojo - Geophysics Prof. S. O. Asaolu - Zoology Prof. J. O. Nwachukwu - Geology Prof. O. O. Jegede - Physics Dr. A. O. Ogunfowokan - ChemistryDr. B. O. Omafuvbe - Microbiology Prof. G. A. Oshinkolu - CERDDr. F. K. Agboola - Biochemishy Dr. C. C. Adeyemi - Natural History Museum

International Advisory Committee Prof. Dr. Thomas Foken, Bayreuth, Germany Prof. J. O. Nriagu, Michigan, USA. Prof. Dr. Stefan Wohnlich, Germany. Prof. Kwabena Oduro, Legon, Ghana. Prof. O. O. Kassim, Washington DC, USA. Prof. J. O. Olowolafe, Delaware, USA. Dr. Walter Kpikpi, Tamale, Ghana. Prof. Adrian Raftery, Seattle, USA. Prof. J. A. Lockwood, Laramie, USA. Prof. L. G. Ross, Stirling, UK. Prof. Bjorn Malmgren, Goteborg, Sweden. Prof. Reuben H. Simoyi, Portland, USA. Prof. Dr. Gunther Matheis, Berlin, Germany Prof. Tetsumaru Itaya, Japan

Two issues of the journal will be published yearly (June and December).

Submission of manuscripts: All manuscripts should be submitted to either of the Editors-in-chief, Ife Journal of Science: Prof. J. O. Faluyi, Department of Botany, or Prof. M. O. Olorunfemi, Department of Geology, ObafemiAwolowo University, Ile-Ife, Nigeria.E-mail: [email protected] (Tel.: +234-803-7250857)

[email protected] (Tel.: +234-803-7192169)

INTRODUCTIONPavement failures are very common features on Nigeria in roads after few years of performance and often before attaining the design age. These roads are continuously reconstructed or rehabilitated without any effort made to identify factor(s) responsible for their perpetual failure. Pavement failures can either be functional (surface pavement failure) or structural (deep-seated pavement failure). There are many factors that can influence the performance of highway pavement s t r uc ture . T hese inc lude : g eo log ica l , geomorphological, geotechnical, design, material selection, construction practices, maintenance and usage factor.

Many studies have been carried out on flexible pavement designs in general and on its failure in particular. Adeyemi and Oyeyemi (2000) examined the geotechnical basis for failure of sections of the Lagos-Ibadan expressway southwestern, Nigeria. The authors concluded that the soils beneath the unstable zones are more mechanically stable than those beneath stable

zone, hence opined that mechanical properties cannot be used to predict the stability of road pavements and recommended that further investigation of the geotechnical properties of as many subgrade soils as possible is undertaken in order to elucidate the influence of geotechnical and geological factors. Oladeji and Adedeji (2001) used environmental observations in addition to geotechnical test to study the causes of non-uniform occurrence of deformation features on highway pavement in Ogbomoso Township. It was concluded that the observed localized failure is primarily due to shallow groundwater level. Adewole et al. (2004) reported on the Oyo-Ogbomoso Road southwestern Nigeria. They concluded from geotechnical points of view that flexible highway failure, which manifested on the road like waviness/corrugation rutting and potholes are due to environmental factors like poor drainage, lack of maintenance and misuse of the highway pavement and that seepage of runoff, due to precipitation, largely finds its way into the pavement structure damaging them in the process.

APPRAISAL OF THE CAUSES OF PAVEMENT FAILURE ALONG THE ILESA - AKURE HIGHWAY, SOUTHWESTERN NIGERIA USING REMOTELY SENSED AND

GEOTECHNICAL DATA

1 1 2Akintorinwa, O. J., Ojo J. S. and Olorunfemi M. O.1Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria

2Department of Geology, Obafemi Awolowo University, Ile-Ife, Nigeria

(Received: October, 2010; Accepted: January, 2011)

Remotely sensed and geotechnical data have been used to establish some of the causes of perpetual pavement

failure along the Ilesa Akure highway in the southwestern part of Nigeria. Four failed segments and two control

stable segments were selected for the geotechnical study. The remote sensing investigation involved the

processing and interpretation of Landsat-7 ETM+ images covering the study area and it's environ for

lineaments. The geotechnical investigation involved grain size analyses, Atterberge Limits, Compaction Test and

California Bearing Ratio (CBR) determination. Lineaments were identified across virtually all the failed localities

with a predominantly N-S structural trend. The geotechnical properties of the soils beneath the stable and failed

segments of the highway show significant overlap which suggests that the cause of road pavement failure along

the highway may be due to factors other than or complimentary to the geotechnical factors. The pavement

failure may have resulted from suspected near-surface linear (geological) features such as faults/fractures and

lithologcal contacts beneath the highway pavement. Clayey substratum and ponded embankment toe could also

have contributed to the pavement failure.

Keywords: Remote Sensing, Geotechnical Investigation, Road Pavement Failure, Basement Complex

Environment

ABSTRACT

185Ife Journal of Science vol. 13, no. 1 (2011)

Bala et al. (2000) used Landsat 5 imagery in the assessment of groundwater resources in the crystalline rocks around Dutsin-Ma, northern Nigeria. With this approach they mapped lineaments and areas of lush vegetation on the basis of which they were able to divide the study area into three main hydrogeological zones. Onyedim and Ocan (2001) used SPOT-XS imagery to map the two major sets of fracture in part of Ilesa area, southwestern Nigeria. They drew the conclusion that the NE-SW and NNE-SSW trending structures were responsible for the emplacement of the Itamerin granite and the formation of the Ifewara fault zone respectively. Awoyemi et al. (2005) extracted structural and drainage lineament from enhanced SPOT-XS imagery and topographic maps of the Ilesa area southwestern Nigeria. The authors obtained a positive above average correlation coefficient between structural and drainage linear, indicated that there is a significant control of drainage in the area by geological structures. A lineament analysis using a LANDSAT Thematic Mapper (TM) dataset of the Gölmarmara (Manisa) region was performed by Kavak and Cetin, 2007 to identify linear geological features that could be attributed to paleotectonic and/or neotectonic structures. There results shows that extensive NE and ENW trending lineament systems have developed in the region and most of ENW-SSE trending lineaments are associate with the recent normal faulting of the western Anatolia after the middle

Miocene Period.

The Ilesa-Akure highway (Fig. 1) which is underlain by the Basement Complex rocks (Fig. 2) is a major road that links the southwestern part of Nigeria with the northern and eastern parts of the

0 country. The highway lies within latitudes 7 14' N 0 0 0and 7 45' N and longitudes 4 45' E and 5 15' E

(Fig. 1). Ten segments of the Akure-Ilesa highway (Fig. 3) as at the time of study have experienced perpetual failure after several rehabilitations. The topography of the highway is relatively flat with mean elevation ranging between 300m and 400m along the 70 km long highway. The investigated failed segments are neither previously sand fill nor cut into clayey saprolite.

These failed segments have been responsible for many tragic human and material losses. Enormous amount of money had been spent on for the rehabilitation works without any success. The various types of highway failures identified along the highway are: (a) Distress arising from the failure of the bitumen layer, especially along wheel tracks, (b) 'Wavy' or heaving surface due to settlement of the pavement material causing frequent bumps on the highway, (c) Pitting or minor dent, longitudinal cracks running more or less parallel to central line of the roadway and (d) Shear or massive failures (potholes) extending through the pavement, occasionally to the subgrade. This study attempts to identify possible geological and geotechnical factors that may be

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Fig. 1: Road Map of Part of Southwestern Nigeria Showing the Ilesa Akure Highway(Modified After Spectrum Road Map, 2002)

186 Akintorinwa et al.: Appraisal of the Causes of Pavement Failure

responsible for the road pavement failure.

MATERIALS AND METHODSThe study involved interpretation of Landsat images, geotechnical investigation and subsoil condition review along the highway. Based on spatial resolution, satellite data can be classified into three types: low-resolution data (e.g. NOAA/AVHRR), medium-resolution data (e.g. Landsat, SPOT, IRS) and high-resolution data (e.g. IKONOS, SPIN-2). The cost of the satellite data

increases with resolution (Janssen and Bakker, 2001). For this reason, to meet the information requirements for geological application in developing countries, satellite data of medium-resolution are often used. Thus, Landsat-7 ETM+ imagery was acquired for this research. The sub-scene covering Ilesa-Akure area (Fig. 4) was created from the full scene Landsat-7 ETM+ image. Image pre-processing involving geometric correction and digital image enhancement of the created sub-scene image were carried out in order

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L o c a l i t y U n d i f f e r e n t i a t e d O l d e r

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w i t h p o r p h y r o b l a s t i c & s o m e

m i g m a t i t e P e l i t i c

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Fig. 2: Geological Map of the Area around Ilesa-Akure Showing the Ilesa-Akure Highway(Modified After Geological Survey of Nigeria, 19 76)

187Akintorinwa et al.: Appraisal of the Causes of Pavement Failure

to create better and improved images from the original image. The image acquired already georeferenced with the reference datum and ellipsoid of the 1984 World Geodetic System (WGS). The original image was georeferenced using the UTM zone number 31 map projection and the subscene covering Ilesa-Akure area was created and resampled to 20 m pixel size. Because of the large variations in the spectral response as shown by band 7, which was selected during the preprocessing phase for the mapping of linear features, image histogram equalization was carried out with 10% stretching interval. The stretched image was then sharpened through filtering in order to emphasize the linear features (e.g., edges) with high spatial frequency. Using the convolution method, directional filters of 3x3

kernels were used to enhance linear trends with different orientations. The resulting enhanced image (Fig. 5) revealed most of the lineaments in the study area which were digitized using 'Acrview GIS 3.2a' computer software to produce the lineament map of the area. This was realized from the combination of the principal linear features and the delineated traces of the strong curvilinear geomorphic trend. A total of 167 lineaments were identified, interpreted and used to generate an Azimuth- Frequency diagram (Rose Diagram),

0showing the number of the lineaments in each 10 azimuth class.

Disturbed soil samples were collected from the two control stable segments and four failed segments. The soil samples were taken at a depth of 0.5 m. At each of the stable segments St1 and

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Fig. 3: Map of the Area around Ilesa-Akure Highway Showing the Specific Sites Studied


St2 samples were collected at two different locations and four samples were collected at each of the failed segments FS1, FS5, FS7 and FS10. The moisture content of the samples collected from the field was determined in the laboratory within 24 hours after collection. Methods of soil testing for engineering purposes were conducted in accordance with B.S. 1377 for all the soil samples and the soils were compacted to the West African Standard. The tests included grain size analysis, liquid limit, plastic limit, linear shrinkage, compaction test and California Bearing Ratio (CBR).

RESULTS AND DISCUSSIONLineament MapFigure 6 shows the lineament map of Ilesa-Akure area. Lineaments, because they are presumed to reflect subsurface phenomenon, can generally be

Ilesa- Akure Area

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Fig. 5: Enhanced Landsat ETM + Band 7 of Ilesa- Akure Area

Fig. 4: The full Landsat scene showing the location of Ilesa-Akure area.

equated with structural elements such as folds, fractures, faults and joints (Viljoen et al., 1983). Some of the lineaments in which the road cut across may be fault particularly those that show relative displacement. Other linear features are suspected to be fracture and fissure zones. As shown in the rose diagram (Fig. 7), the four major

structural trends (N-S, NNE-SSW, NW-SE, and E-W) that are typical of the Nigerian Basement Complex (Rahaman, 1989) are represented in this area. The N-S lineament trend constitutes the dominant structural trend. As shown in Figure 6, several of the linear features cut across the highway investigated and most especially within


and around failed segments of the highway. It is suspected that such linear features may be one of the factors responsible for the perpetual failure of the failed segments of the highway, since linear features are characteristic zones of weakness.

Geotechnical ResultsMoisture ContentThe moisture content of the analyzed soil samples from both the control stable and failed segments of the highway are shown in Table 1. The moisture content of soils from the stable segments (control and classified stable (?)) ranges from 4-31%, while that of failed segments ranges from 4-28%. The entire soil samples have moderate to high moisture content. The ranges of moisture content of the soil samples taken from the stable and failed segments of the highway show significant overlap. It is therefore difficult to explain the causes of failure of the failed road pavement from the point

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Fig. 6: Lineament Map of Ilesa Akure Area

Fig. 7: Rose Diagram of the Lineaments


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of the view of the moisture content of the soils only.Grading CharacteristicsThe results of the grain size distribution analyses are presented in Table 1. Typical grading curve is presented in Figure 8. The soils from control stable segments have percentage finer (percentage

passing 0.075mm) ranging from 33 - 83%, while that of failed and classified stable (?) segment ranges from 31-70% and 25 59% respectively. From the grading curves, the soils can be classified as well graded soil. Most of the soils have percentage passing No. 200 (0.075 mm) of more than 35%, hence, the soils range in group

tP

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SILTCLAY SAND GRAVEL COBBLESFine Medium Fine Medium Coarse Fine Medium

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0.002 0.006 0.02 0.06 0.2 0.6 2 6 20 60 200

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ass

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Fig. 8: Grain Size Distribution Curve for Soil Sample taken from Stable Segment 1 (St1a)


classification from A-4 to A-7 and are generally rated as fair to poor sub-grade highway materials (Table 2). Most of the studied soils (stable and failed localities) did not fall within the Federal Ministry of Works and Hosing (FMWH) ( (1972) grading specification (Table 3). The ranges of the percentage finer of the soils beneath the stable and failed segments (Table 1) show significant overlap; hence the perpetual failure of the failed segments of this highway can not be explained base on grain size distribution only.

Consistency LimitsAs shown in Table 1, the Liquid Limit of the soil samples from the control stable segments ranges from 38-56%, while those from presently classified stable (?) and failed segments range from 24 - 55% and 20-66% respectively. Typical Liquid Limit curve is shown in Figure 9. The Plastic Limit of the soils ranges from 21-38%, 16 - 36% and 10-41% for the control stable, current classified stable (?) and failed segments respectively. The Plasticity Index of soils beneath the control stable segments ranges from 9-21%, while that of the currently classified stable? and failed segment ranges from 8 28% and 1-25% respectively. Most of the soils (stable and failed localities) investigated fall within the FMWH (1972) specification (Table 3), and are suitable sub-grade materials. Using the America Association of State Highway and Transportation Officials (AASHTO) (1962) classification system

shown in Table 2, the soil samples from both the stable and failed segments belong to group A-4 to A-7, hence the soil can be rated to be of fair to poor sub-grade materials. The Casagrande (1948) Chart (Figs. 10a and 10b) generally indicate medium plasticity for both the soils beneath the stable and failed segments, hence , the soils are expected to exhibit low to medium swelling potential (Ola, 1982). The Linear Shrinkage of the soils beneath the stable and classified stable (?) segment ranges from 1-8% and 3-12% respectively, while that of the failed segments ranges from 3-16% (Table 1). The Linear Shrinkage of most of the soils are £ 8% recommended by Brink et. al. (1982) and Madedor (1983) for highway sub-grade, hence the soils are good sub-grade materials. As discussed above, the consistency limits of the soil beneath the stable and failed segments of the studied highway did not exhibit significant difference and generally fall within the recommended specification by FMWH, 1972. Both soils are rated poor to fair for pavement materials, hence, the cause of failure along the failed segments of this highway may be difficult to explained from the point of view of consistency limits only.

Compaction Characteristics The Optimum Moisture Content (OMC) and the Maximum Dry Density (MDD) obtained from the tested soils are presented in Table 1 while Figure 11 shows typical compaction curve. The The

0

5

10

15

20

25

30

35

40 45 50 55 60 65

Pen

etra

tion

(mm

)

Moisture Content (%)

LLLL==

4488%%

Fig. 9: Liquid Limit Graph for Soil Sample taken from Failed Segment 10 (Fs10a)


Optimum Moisture Content (OMC) ranges from 7-28% for soil beneath the control stable segments and 10 -20% for soil beneath the classified stable (?) segments, while that of failed segments ranges from 9-29%. The Maximum Dry Density (MDD)

3 3ranges from1457-1950 Kg/m ,1620 - 1900 Kg/m

3 and 1571-2040 Kg /m for subsoil beneath control stable, classified stable (?) and failed segments respectively. There is significant overlap between the values of compacted parameters of the soils beneath the control stable segments and failed segments; hence compaction characteristic of the soils may not be a good index for the highway pavement stability.

California Bearing Ratio (CBR)The unsoaked California Bearing Ratio (CBR) values for soil beneath the control stable segments ranges from 38 - 55%, while those of the classified stable (?) and failed segments range from 20 to 72% and 25 to 84% respectively (Table 1). Figure 12 shows the CBR curve for sample FS1d. The unsoaked CBR value stipulated by the FMWH standards (1972) for sub-grade soils is 80% minimum (Table 3). The only soil sample with CBR value within this specification is the soil sample FS7b taken from the failed segment at locality 7. There is thus, no clear-cut correlation between the values of CBR of sub-grade soils and the degree of stability of highway pavement. The

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100

FS5dSt2a

FS10a

FS1aSt1b

FS7a

St2b

FS5aFS1d

FS10d

St1a

FS7dLow Plasticity Soil

MediumPlasticity Soil

High Plasticity Soil

Pla

stic

ity

Ind

ex

Liquid Limit (%)

PI = 0.3509LL + 1.482R = 0.50

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80 90 100

FS5b

FS5c

FS7c

FS1b

FS7bFS1c

FS10b

FS10c

Low Plasticity SoilMediumPlasticity Soil

High Plasticity Soil

Pla

stic

ity

Ind

ex

Liquid Limit (%)

PI = 0.4511LL - 2.6658

R = 0.88

Fig. 10a: Casagrande Chart Classification of the Soils beneath Stable Segments (Based on Casagrande, 1948)

Fig. 10b: Casagrande Chart Classification of the Soils beneath Failed Segments (Based on Casagrande, 1948)


cause of perpetual failure of the failed segments along this highway may therefore not be related to the CBR. From the above, there seems to be a poor correlation between the geotechnical properties of soils and the road stability.

Subsoil Conditions of the HighwayField observation and results of geophysical investigation carried out by Akintorinwa et al. (2010) along the highway showed that failed segments 1 and 10 are underlain by low resistivity

(<100 ohm-m) clay substratum. The toe of the failed segment 1 was also ponded as at the time of the investigation due to poor embankment drainage system.

The highway is underlain by the Okemesi, Ondo, Egbeda and Itagunmodi soil associations (Fig. 13). The Okemesi Association are composed of well-drained coarse texture, very gravelly soils derived from quartz schist and massive quartzite. The soils underlie stable segment 2. The Ondo Assiciation underlie failed segment 1. The soils are well-

Moisture Content (%)

Dry

Den

sity

(Kg/m

3)

1540

1560

1580

1600

1620

1640

1660

1680

1700

1720

1740

0 5 10 15 20 25 30

MDD = 1720 Kg/m3

OM

C=

19.

7%

Fig. 11: Compaction Curve for Soil Sample taken from Failed Segment 1 (FS1d)

Penetration (mm)

Fo

rce

on

Plu

nger(K

N)

0 2 4 6

1

2

3

4

5

6

Fig. 12: Typical CBR Curve Soil Sample taken from Failed Segment 1 (Fs1d)


drained, medium to fine texture soils overlying orange, brown, yellow brown and brown mottled clay derived from medium-grained granitic rocks and gneisse. The Egbeda Association are also well-drained fine textured soils overlying red , brown yellow brown and white mottled clay mainly derived from fine-grained biotite gneiss and schist. The soils Association underlie failed segments 5 and 7. The Itagunmodi Association underlie failed segment 10. The soils are composed of brownish red very clayey soils derived from amphibolites and charnockite rocks. It follows from the above that the failed segments are underlain by clayey subsoils.

CONCLUSIONS Remote sensing and geotechnical methods have been used to study the causes of road pavement failure along the Ilesa-Akure highway. Four failed segments and two stable segments were selected for the study. The two stable segments served as control. The remote sensing derived lineament

map of the area shows that several linear features cut across the highway investigated. Lineament features were identified virtually across all the failed localities with a predominant structural trend in N-S direction. The geotechnical results generally show largely unsuitable geotechnical properties at the stable segments (stable1 and 2) and the failed and classified stable (?) sections of all the failed localities. The geotechnical properties of subsoil beneath both the failed and stable segments show significant overlap. Suspected near surface linear (geological) features may have acted as zones of weakness that enhance the accumulation of water leading to pavements failure as observed in the failed segments. Clay substratum and ponded embankment toe could also have contributed to the pavement failure.

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Adewoye, A.O., Adegbola, A.A., Bolaji, A.A. and

# Y

# Y # Y

# Y

# Y

# Y

# Y

# Y # Y

# Y

%

% %

%

% %

# Y # Y

# Y # Y

# Y # Y # Y

# Y

# Y # Y

# Y # Y

% [

A k u r e

I k e r e

E r i n j i y a n A d o

- E k i t i I l e s h a

I k o g o s i

I g b a r a

- O d o

I g b a r a

- O k e

I s h a r u n

I j a r e

I p e t u

I b u l e

5

1 5 0 0 4

4 3

0 4 4 3 5

1 5 0

7 1 4 0

7 1 4

0

7 3 8

0 7 3 8

0

0 1 0 k m

I t a g u n m o d i

O n d o

E g b e d a O k e m e s s i

M a m u R o a d

u n d e r i n v e s t i g a t i o n

# Y T o w n % I n v e s t i g a t e d

L o c a l i t y # Y F a i l e d

L o c a l i t y # Y S t a b l e

L o c a l i t y

% [ R e f e r e n c e P o i n t

R i v e r

R o a d

L E G E N D

N

E N N E

E

N

E

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