GEOPHYSICAL INVESTIGATION OF ROAD FAILURE USING ELECTRICAL RESISTIVITY IMAGING METHO A CASE STUDY OF UHIELE – OPOJI ROAD EDO STATE

ABSTRACT

A  shallow geophysical investigation for  road surface  failure  using  2D  electrical  resistivity imaging profiling was conducted to produce an approximate model of the subsurface resistivity. This study was done with the aim of revealing the horizontal and vertical geological discontinuities using electrical resistivity, an intrinsic property of all materials. Probable zones of untimely failure along the road are then investigated by variation in resistivity. Four traverses were established on the road with one parallel to the road segment. The Electrical Resistivity Imaging (ERI) Profiling involving the Wenner array 2D Imaging was adopted for the resistivity survey. The Pseudosection results revealed that the road structure is founded on a near homogeneous substratum indicating that the road is situated on a better geology than those from previous studies done in this geologic environment. The apparent resistivity values for all the profiles ranged from 273.94 Ωm – 3566.7 Ωm for profile I; 1561.2 Ωm – 4062.4 Ωm for profile II; 714.36 Ωm – 3856.4 Ωm for profile III and 700.06 Ωm – 3994.65 Ωm for profile IV. Apparent Resistivity values of Area Studied ranged from 273.94Ωm to 4062.4Ωm with an average of 2168.17Ωm which characteristically placed the studied area in a sedimentary basin with the presence of clay- sandstone intercalation. The low apparent resistivity values between

273.93 Ωm to 979.64 Ωm were obtained alternately with high apparent resistivity values along all the profiles investigated and were also obtained where there were major cracks, accentuated by water ingress. Geotechnically, it was inferred that highly resistive soils, usually at most times correlate with competent zones and the low resistive zones correlate to the incompetent soils. The engineering properties of soils using Weaver’s rippability rating chart (seismic velocity and hardness)  of  soils,  showed  that  the  low  resistive  soils  were  incompetent  for  engineering structures like road pavement etc. The causes of road pavement failure on the studied road was found to be majorly as a result of a combination of clayey topsoil/sub grade soils, water-logged sands due to ingress with characteristically low resistivity values and thin pavement thereby unable to withstand pressure exerted on the road.

CHAPTER ONE

1.0       INTRODUCTION

The incessant incidence of pavement failure of road structure is becoming alarming and has  become  a  common  phenomenon  in  many  parts  of  Nigeria.  These  failures  have  been attributed to a number of factors such as inadequate information about the soil and the incompetence of these subsurface geologic materials.  Failures are not limited to any particular geologic setting.  Failures  have  been recorded on crystalline,  basement,  complex rocks and sedimentary formations.

The state of Nigerian roads had remained poor for a number of reasons. The number one problem is  poor quality roads, resulting from faulty designs, lack of gutters and  very thin coatings that are easily washed away by floods and hardly withstand heavy traffic. Secondly, funding of road maintenance has been grossly inadequate. From 1999 to 2002 in retrospect, less than 10 per cent of the funding request made by the Federal Ministry of Works and Housing (FMW&H, 2002) for road maintenance was appropriated by the Federal Government of Nigeria (CBN, 2002). Even at this, only about 53.5 per cent of the appropriation was released. These were the collections from tollgates across the country – N569.29 million, N742.72 million and N779.84 million in 2000, 2001 and 2002 respectively (FMW&H, 2002, CBN, 2002). For each year, tollgates collections alone were much higher than the total funds released for road maintenance. Third is the excessive use of the road network, given the undeveloped state of waterways  and  the  poor  state  of  the  railways,  which  are  alternative  transport  modes.  In particular, the railways serve the purpose of transporting bulky goods, which are not good for road haulage. Fourth, information from the Chief Highway Engineers in Nigeria showed that there  is  no  articulated  programme  for  road  maintenance.  (Federal  Ministry of  Works  and

Housing, 2002; CBN. 2002). Road maintenance decisions are taken at the headquarters and are in most cases influenced by politics and not necessarily on the actual maintenance needs. For this reason most of the roads have been neglected.

1.1       ROAD DEVELOPMENT IN NIGERIA

The Government of Nigeria is committed to improve road network within the country and this venture is laudable since to a great extent, it will enhance her economic development. Recent years have seen a major development in the infrastructure of this area, including several new roads linking the towns and villages. The road network is currently estimated at about

194,000 kilometers, with the Federal Government being responsible for about 17 percent, State Governments 16 percent  and  local Governments 67 percent  (FMW&H). This has led  to  a situation, whereby for a variety of reasons, roads were constructed in areas with a history of surface and subsurface geological degradation. In spite of various rehabilitation efforts, several segments of our highways fail perpetually soon after commissioning. Such rehabilitation has become an annual ritual and a big financial burden on various tiers of Government (Adiat et al.

2009). This has resulted in the need for reparations and the use of remedial measures to ensure the usability of the transportation network (Hadjigeorgiou, 2006).

As more roads are envisaged in the near future, it is necessary to learn from past failures so as to avoid repeated problems in the future, resulting in a waste of the limited economic resources (Onita, 1985). Some huge amount of money allocated towards rehabilitating and maintenance of roads throughout the country which were over laid with asphaltic concrete in order to increase their strength could have been reduced if adequate geological and geophysical advice were sought prior to the construction of these roads. It is a problem that every right

thinking person should be concerned about, since the large sum of money spent on road repairs could have been injected into other vital sector of the economy (Aigbedion, 2007).

If this must be achieved, sufficient technological, geophysical and environmental data on the causes of road failures must be provided for both, in the maintenance of these roads and the construction of other roads on similar soils. The need for pre-foundation studies has therefore become very imperative so  as to  prevent  loss of valuable lives and properties that  always accompany  such  failure.  Foundation  studies  usually  provide  subsurface  information  that normally assists civil engineers and geologists in the design of foundations of civil engineering structures (Akintorinwa and Adeusi, 2009).

1.2      DEFINITION OF ROAD PAVEMENT FAILURES

Road pavement failure can be defined as a discontinuity in a road network resulting from cracks, potholes, bulges and depression. A road network is supposed to be a continuous stretch of asphalt layer for a smooth ride. Visible cracks, potholes and depressions generally regarded as road  failure  may  punctuate  such  smooth  ride  (Rahaman  1976,  Aigbedion  2007).  Flexible highway (i.e. good and well developed  interconnectivity of roads) aids easy and smooth’s vehicular movement, and have been very useful for transportation of people, goods and services from  one  point  to  another,  especially  in  developing  countries  where  other  means  of transportation  such  as  rail,  underground  tube,  air,  and  water  transportation  systems  have remained largely undeveloped. However, bad portions of road, many of which result from poor construction or being founded on incompetent sub-grade and sub-base materials had been found to do more harm than good. They have been responsible for many fatal accidents, wearing down of vehicles and waste of valuable time during traffic jams (Osinowo, 2011). The various types of road failure identified in the study area (see plate 1, plate 2), include failure of the black top

surfacing, pitting or minor dent, shear or massive failure (pot-holes) extending through the pavement, and occasionally to the subgrade etc. (Plate 1) (Osinowo, 2011).

A                                                B

C                                                 D

PLATE 1: (A) Failed section of Opoji old road along Opoji – Irrua road (B) Pavement surface removal after rehabilitation along Uhiele – Opoji road (C) Zoomed section showing very thin coating of the pavement surface (D) Longitudinal view of Uhiele – Opoji road with very thin surface coating.

1.3      INSTABILITY OF UNDERGROUND

Recent studies in the area show that the physically obvious road failures witnessed in almost all roads in this terrain are not only as a result of factors like drainage and quality of materials used for construction alone, but also as a result of instability in the underground geology as well as sub standard materials used in pavement construction (Aigbedion 2007).

1.4        MINERALOGY OF SUBBASE

Geological factors are rarely considered as precipitators of road failure even though the highway pavement is founded on the geology. (Momoh et al., 2008, Ozegin et al., 2011). Some sections of major roads failed because their soil properties were not thoroughly investigated at the initial state. In fact, little or no consideration was given to the effect of clay mineralogy and the associated engineering soil behaviour, as highway foundation materials. The bearing capacity of rocks in relation to traffic  is one the essential parameters to be reckoned with, in road construction projects. Some major Nigerian highways are known to fail shortly after construction and well before their design ages.

A                                             B

C                                             D

PLATE 2: Major Highways failing before their design age within the state. (A) A Federal highway route in the country (B) and (C) Roads collapsing due to lack of proper drainage system within the state in Benin metropolis (D) Benin – Ore road (2010) (Wednesday, 13 July 2011, Nigerian Compass)

1.5      LACK OF ADEQUATE GEOPHYSICAL SURVEY

The factors responsible for road failures are traceable to lack of adequate geophysical survey before commencement. Such preliminary studies are capable of delineating structures such as unconsolidated soil formations with varying resistivity and conductivity (Sikdar, et al,

1999; Praveen, and Ankit, 2010). They can also detect naturally occurring underground water channels which may expedite weathering and surface deformation. A number of important engineering problems which include dams, reservoirs, huge and heavy constructions that can cause road failure have been identified in which geophysical methods find extensive application (Aigbedion, 2007), since geophysics offers a unique window into the earth as a  means of detecting subsurface conditions in which its relevance lies in the concrete and cost effective benefits it delivers.

Several  factors  are  considered during  investigation  for  road  failures,  which  include geological, geomorphological, geotechnical, road usage, construction practices, and maintenance (Adegoke,  et  al,  1980;  Ajayi,  1987,  Adiat  et  al.  2009).  Field  observations and  laboratory experiments carried out by Adegoke, et al, (1980), Mesida (1981), and Ajayi (1987), Adiat et al. (2009), showed that road failures are not primarily due to usage or design construction problems alone but can equally arise from inadequate knowledge of the characteristics and behavior of residual soils on which the roads are built and non-recognition of the influence of geology and geomorphology during the design and construction phases.

1.6      INTEGRITY OF GEOPHYSICAL SURVEY

For the past two decades, geophysics has proved quite relevant in road and site investigations and several of these engineering and geological problems have been successfully solved by geophysical methods (Nelson and Haigh, 1990, Adiat et al. 2009). The integrity of

near surface geophysical investigation methods to complement geotechnical studies in some foundation engineering problems cannot be overemphasized (Osinowo et al. 2011).

The non recognition of this fact has led to loss of integrity of many highway routes and other engineering structures across the country as observed by (Olorunfemi et al., 2000 a, b, Ozegin et al., 2011). This research therefore tries to use Electrical Resistivity Imaging surveying method to study the causes of consistent failure of Uhiele-Opoji road. It involves a longitudinal probe of the failed, fairly stable, and stable portion of the road as well as perpendicular probe using a two dimensional (2D) imaging profile, in order to characterize the near surface geologic materials that constitute the sub-grade, sub-base and the foundation upon which the pavement was founded.

1.7      SAND AND SANDSTONES AS ROAD BUILDING MATERIALS

Soil  is  formed  by the  process of ‘Weathering’ of rocks,  that  is,  disintegration and decomposition of rocks and minerals, at or near the earth’s surface through the actions of natural or  mechanical  and  chemical  agents  into  smaller  and  smaller  grains.  Sand  is  an  important economic resource. The uses of sand are many. In some purposes, sand is used an abrasive to clean a skillet or mess kit. Other uses require a particular kind and quality of sand (Broswell,

1989). Sands are sources of silica for making sodium silicate, for manufacturing carborundum, for silica brick, for the manufacture of both common and optical glass. Sand is an ingredient in plaster, in concrete, in addition to clay to reduce shrinkage and cracking in brick manufacture and then is mixed with asphalt to make road dressing. It is used in foundries as moulding and parting sand, and it is used as an abrasive sand paper and sand blast. Sands are exploited for rare minerals and rare elements, which they contain. Some are gold bearing, others contains gem, platinum uranium etc. Sandstones are used for building, stone construction as flagstone and if

crushed as road fill, road metal and railroad ballast. There are three basic types of sand materials used for construction of roads: gravel, sand, and fines (listed in order from largest to smallest particle size). Gravel and sand particles, coarse material, are readily distinguishable to the naked eye. Fines (silts and clays) are generally comprised of particles too small for the eye to see. Each soil material has specific properties that make it useful for different aspects of road building. Coarse material provides strength and has large voids between the particles that provide good drainage. Fines fill the voids between the coarse material particles holding them together, and on the road surface, decrease infiltration of water into the road. An ideal road bed should have two layers; a base layer that provides strength and is free draining and a surface layer that is strong and dense, shedding rainfall and preventing it from infiltrating into the bed. When selecting road bed material, it is important to have a range of different sizes of gravel and sand so that the particles “lock” together. This is called well-graded. If they are all the same in size, they are more apt to move around, causing a rut.

1.8         ROADBED CLAY

Clays are very small-grained hydrous aluminosilicate with the phyllosilicate structure. Clays  are classified as hydrosilicate, which means that they are formed from the chemical decomposition of pre-existing silicate minerals. Most clays result from the product of weathering and sedimentation, but they are also formed by hydrothermal activities. Clays can occur as part of a soil structure or as independent layers and lenses. They are also commonly found in glacial till, where glacial action has ground the rocks and boulders into fine particles. Clay particle sizes range from 0.002 mm to 0.001 mm diameter for quartz, feldspar, mica, iron, and aluminum oxides. The finer parts (less than 0.001 mm in diameter) are colloidal and consist mainly of layer silicates with smaller amounts of iron and aluminum oxides. Two basic parameters can be used

to estimate the clay content of soils and other geologic layers. These are electrical conductivity and membrane polarization.

The resistivity of soils and rocks vary from 1 – 30,000 ohm-m. Thus, the appropriate geophysical methods are conductivity measurements (or resistivity) and Induced Polarization, measuring  the  membrane  for  some  clays  and  shale’s  to  over  1,000 ohm-m for  limestone, intrusive rocks such as granites, and some metamorphic rocks. However, in sedimentary soils and rocks, where resistivity generally ranges from 10 to 1000 ohm-m, resistivity is also significantly influenced by the porosity and salinity of the water in the pore space. In order to estimate clay content, the resistivity/conductivity of the layer/zone of interest has first to be determined. Then a relationship is needed to convert the conductivity to clay content. However, as mentioned previously, conductivity is strongly influenced by porosity and the salinity of the pore water, thus making the conversion from conductivity to clay content tenuous.  It is possible that the Induced Polarization method may be more successful since it is less influenced by the resistivity of the material. However, the method needs more research before production surveys are undertaken.

Clays  can swell as well as  have  low  shear strength. Swelling  is usually caused by moisture within the clay. Fine grained material such as clay can hold a significant amount of water. Moisture can be acquired from surface runoff or can be drawn from material beneath them because of the small pore size in clays and the resulting strong capillary forces. Shear strength of clays  are  significantly influenced by  moisture  content,  decreasing with  increased  moisture. Furthermore, clays with high swelling potentials are susceptible to extreme volume changes as moisture content changes. The economical importance is that roads constructed over areas of soft clay will result in poorly performing pavement systems and often result in a sub-grade failure.

Sub-grade failure may be visibly observed as pavement deformations over problem areas. Cation

Exchange Capacities of some common clay types are presented in Table below.

PLATE 3: Volume changes of clay beneath road pavement

TABLE 1: CATION EXCHANGE CAPACITIES (CEC) OF COMMON CLAY TYPES.

Clay type	Cation Exchange Capacity
Kaolinite	3 -15
Chlorite	10 -40
Illite	10 -40
Montmorillonite	80 -150
Vermiculite	100 -150

It was observed that majority of roads have failed because clay was used as construction materials (Aigbedion 2007). Also, studies have shown that the area contain near surface low resistivity geologic materials which are highly favourable to road failures (Ozegin et al. 2011). These zones are structurally weak, as a result of fractures, favorably disposed to groundwater seepage and accumulation, thus making them low resistivity zones, with great potential for pavement failure (Osueni, 2009).

1.9      DRAINAGE

Drainage system is another important factor that is responsible for road or pavement failure in Nigeria.  Surface drainage is collection of rain water from the surface of the road to side drains or to lower sides in open terrain. This is possible if the road have sufficient cross slope about 2%, and free from depressions, potholes and cracks otherwise water will enter into the road structure. Subsurface drainage is the collection of that water that has entered into the road structure.  This internal drainage function of a road pavement is usually performed by the GSB (Granular Sub Base, consisting gravel and sand mixed in defined proportion) layer. This layer itself must be drained in some way in order to  keep  the water-table  low,  to  prevent  the moisture content   of  the   subgrade   from increasing   through  capillary  action,   and   hence decreasing the  subgrade strength. Strength of soils decreases with increase in moisture content.

To keep the moisture content low, proper drainage of subgrade and sealing of the crust (to stop ingress of water) is a must. Also the road  pavement  itself must  be  constructed  so  that  it will drain in  the  event  of  a failure of the integrity of the surfacing layers, i.e. if water is able to enter the road  pavement there must be a path for it to exit.  Once water  has  entered  a  road pavement, water damage is initially caused by hydraulic pressure, i.e. vehicles passing over the road  pavement  pass  on  considerable  sudden  pressure  on  the  water  present  in    the    road pavement,  this  pressure  forces  the  water  further  into  the  road structure and breaks it up. This process can be very rapid once it begins. Sooner or  later  the water  will descend  to  the subgrade  layer  below the road pavement and  weaken  this  layer  thus  lowering  the  strength of  the  subgrade,  and  complex failure of the road will begin. Road pavements have failed for various reasons due to poor drainage, caused either by:-

a) Inadequate drainage provision in the original road pavement design,

b)  Lack  of maintenance of the  drainage  so  that  it  no  longer  functions  in  a correct manner.

c)  Rise in water table thus weakening the road pavement,

d)  Failure of the impervious nature of the surface course such as thin layers of  premix carpet  without  proper  sealing  coat,  cracks  and  potholes  and undulations causing pooling, thus allowing the passage of surface water in to the road pavement matrix.

B

A

PLATE 4: Roads with Poor Drainage Systems along Nigerian highways.

(A) Benin – Ore road congested with traffic due to bad sections of the road

(B) Road flooded due to poor drainage system along the road in Benin metropolis.

1.11    STUDY AREA DESCRIPTION

1.11.1  LOCATION

The road investigated, exists within Ekpoma and Irrua towns in Esan West and Central respectively in Edo state. The road serves as a link between the University town of Ekpoma and the major high way leading to the Eastern part of Nigeria. The old road linking Irrua and Opoji joins the Ekpoma – Uhiele road at Ugbegun leading to the Eastern part of the country. At the time of study, these roads are undergoing some major cracks, potholes, rippling and depressions which will in turn lead to a major road failure.

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FIGURE 1: ACCESSIBILITY MAP OF STUDY AREA

1.11.2 PHYSIOGRAPHY AND CLIMATE

The study area, which is Uhiele – Opoji main road in the central part of Edo state, south- south  Nigeria, is situated on a gently undulating terrain with elevation between 296m and 335m above the main sea level on latitude 60  41ʹN, longitude 60  10ʹE (Uhiele), latitude 60  42ʹN, longitude 60  11ʹE (Opoji), and latitude 60  43ʹN, longitude 60  17ʹE (Irrua). The areas lie in a region where typical characteristics of the tropical rain forest are displayed; multitude of evergreen trees, climbing plants, parasitic plants that live on other plants and creepers. Two main seasons exist in the   area, the dry season which lasts from November to March and the rainy season which begins in April and ends in October with a short period of reduced rains in August commonly referred to as “August break”. Temperature in the dry season ranges from 20°C to

38°C, and results in high evapotranspiration, while during the rainy season temperature ranges from 16°C to 28°C, with generally lower evapotranspiration. It has a mean annual rainfall of about 1400mm and the annual mean temperature is between 250C and 300C. These climatic conditions  are  responsible  for  the  development  of thick  lateritic  soils  in  the  area,  due  to transportation and sedimentation of soil particles resulting from weathering.

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FIGURE 2: TOPOGRAPHICAL MAP OF STUDY AREA

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FIGURE 3: DRAINAGE MAP OF STUDY AREA

1.12     GEOLOGY OF STUDY AREA

The Niger Delta in Southern Nigeria has been prograding outward to the Atlantic Ocean since  late  Cretaceous times and  is  in-filled with Tertiary and  Quaternary sediments which decrease in age progressively southwards. The deposit comprise (figure 4) from north-east to south-west, the Imo shale. A unit of Paleocene to Eocene (lower Tertiary) is the blue gray shale with  thin  sandstones  and  limestone.  The  Eocene  to  Oligocene  is  the  Ameki  Formation, comprising clays, sandstones and limestone. Oligocene to Miocene clays, comprises sands and grits with occasional lignite (carbonaceous deposits) of the Ogwashi-Asaba Formation. The Miocene to Pilocene, Benin Formation is composed of coasted-plain sands and pebbly sands with clay lenses and lignite. These sediments were deposited in a variety of environments from marine, through deltaic, estuarine and coastal swamp to lagoon and fluvial. In all, the sediments pile reaches a thickness of around 12,000m (Osueni 2009).

The study area is geologically characterized by deposits, laid during the Tertiary and Cretaceous periods on the South Western extension of the Niger Delta Basin, (Reyment, 1965). The various formations in the geology of Edo State are the Benin, Bende Ameki, Ogwashi- Asaba, Imo, Nsukka Formation and the various Quaternary Deposits. In this study the entire investigated area is underlain by sedimentary rocks of the Niger Delta Basin of southern Nigeria, (Precambrian basement complex of southern Nigeria) with about 90% of sandstone and shale intercalation. It has coarse grained to locally fine grained in some area, poorly sorted, sub- angular to well rounded, which bears lignite streaks and fragments (Figure 5) (Kogbe, 1976). The type of granite mostly found in the area of study is gneiss consisting of feldspar, mica and quartz as dominant minerals. Its origin and evolution have been discussed by several workers including Hospers (1965), Burke et al. (1972) and Nwachukwu (1972). The origin is believed to

be linked to a series of tectonic activities that occurred in the south Atlantic region during the late Cretaceous times (Murat, 1972). The Sediments penetrated by the Gbakebo “B” well located at Okitipupa Ridge on the western flank of Niger Delta form part of the late Cretaceous and Tertiary sequences of the southern Nigerian Basin (Kogbe, 1976). Deposition of sediments in the Niger Delta Basin began in the Tertiary and continued into post Tertiary times. The Niger Delta sediments include Benin, Agbada and Akata Formations and they range in age from Eocene to Recent (Short and Stauble, 1967; Asseez, 1976). The Agbada Formation is a down-dip continuation of Eocene-Miocene Ameki and Ogwashi-Asaba Formations, while the Akata Formation is a down-dip continuation of Paleocene- Imo Formation (Frankland Cordy, 1967). The  geology  of  the  study  area  is  characterized  by  deposits  laid  during  the  Tertiary  and Cretaceous periods. The area is underlain by sedimentary rocks constituting part of the formation which is made up of over 90% massive, porous, coarse sand with clay/shale inter-beds having high ground water retention capacity. Soil particles vary from coarse grained to fine grained is some areas, poorly sorted, sub-angular to well rounded particles with lignite fragments.

State of Study area

FIGURE 4: GEOLOGICAL MAP OF NIGERIA SHOWING THE STATE OF STUDY AREA. Agwae, (2011)

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FIGURE 5: ENLARGED GEOLOGICAL MAP OF STUDY AREA (An extract  from the geological map of Nigeria, Department of Geology). The geological map of the study area shows part of the Precambrian basement complex of Southern Nigeria (pink) prograding through Mamu Formation (light green), Ajali Formation (off green), Nsukka Formation (brown), Umanu Formation (whitish brown), Ameki Formation (yellow), and Ogwashukwu Formation (whitish yellow)  advancing  downwards  as  a  result  of  accumulation  of  sediments.  The  study  area formation falls within the Ameki and Ogwashukwu formations.

1.13    STATEMENT OF THE PROBLEM

The roads to be investigated serve as a link between the University town of Ekpoma and the major high way leading to the Eastern part of Nigeria. The occupation of the people living in this part of the town is predominantly farming. The failures of these roads have generated a lot of problems of which a few are listed below;

i.      Farm produce from these communities hardly get to the outside market as a result of bad road network.

ii.      Commercial road users have totally neglected these roads due to major failure of some parts of the roads. They make use of more distant routes at the expense of the passengers.

iii.      Criminals have taken a great deal of advantage of these failed portions to perpetrate their unwholesome acts by waylaying people when they slow down.

1.14     PURPOSE OF STUDY

This project  work  is  prompted by  lack  of data  on the  geotechnical and  geological properties  of the  subsoil  in  the  study area.  The  objective  of this  project  is  to  appreciate geophysical investigation in identifying weak and competent (that is, conductive and resistive) zones. Geologic factors such as bedrock, subsurface features, like faults, fractures, depressions

and joints that are responsible for these incessant road failures even after rehabilitation. This study expects to correlate geophysical results with geotechnical standards to ascertain the causes of road failures within the project site. The result will aid road construction and maintenance on similar soils by engineers, planners, designers and contractors in the future.

This  practice  is  common  in  developed  countries  where  roads  are  constructed  with detailed information from geophysical investigation of the construction site. This ensures design stability, economical construction, maintenance free roads. Such geophysical investigations provide full details of the area topography, lithological characteristics of the soil or rock and groundwater conditions in that particular construction site. The roads investigated in this study have protracted failure characteristics such as potholes, cracks, depressions and water percolated channels. These failure potentials become incessant despite inadequate previous rehabilitation programs.

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