Road Pavement Failure Research Articles

A Review of Road Pavement Failure: A Case Study of Nigerian Road

A Review of Road Pavement Failure: A Case Study of Nigerian Road

Compaction and strength characteristics of lead contaminated lateritic soil treated with eco-friendly biopolymer for use as road foundation material

Reuse of unwanted soil material due to contamination is one of the available alternative to mitigate the depletion of natural construction material like lateritic soil. Lateritic soil can become contaminated as a result of mining activities. However, assessment of such soil for adequate compaction and strength development is a critical requirement for establishing foundation for road pavement failure of which can result in rapid deterioration of structural integrity of pavement. The research paper investigated the efficacy of Gum Arabic biopolymer (GAB) as eco-friendly additive, in enhancing strength development of lead-contaminated lateritic soil (LCLS) for use as foundation material for road pavement. Varying contents of GAB up to 25% of the dry weight of soil in 5% succession was used in treating LCLS. Compaction characteristics, Maximum Dry Density (MDD) and Optimal Moisture Content (OMC), and California Bearing Ratio (CBR) with microstructural analysis of the treated soil were assessed using three distinct compactive efforts: British Standard Light (BSL), West African Standard (WAS), and British Standard Heavy (BSH). With increase in GAB content, there is a corresponding rise in MDD, while OMC decreased across all three compaction efforts. Optimal CBR values were obtained at 10% GAB content across the three compactive efforts. The Scanning Electron Microscopic (SEM) analysis revealed modifications in the surface morphology occurring at the peripheries of clay particles. The R-squared (R2) values of the regression models derived from statistical analysis of all dependent variables revealed that GAB, MDD, OMC and CE (compactive effort) collectively exert considerable significant effect over CBR values. However, the ultimate strength values fall short of the recommended thresholds for sub-base stabilization. This suggests that a GAB content of 10% enhances the characteristics of contaminated lateritic soil. However, it should not be employed as a sole stabilizer; instead, it could be considered as a potential admixture in cement stabilization.

Comparison of Costus dewevrei De Wild. and T. Durand Admixture with Lime and Cement in Soil Stabilization

The study investigated the use of cement and lime as composite mixture with Costus dewevrei De Wild. & T. Durand as for soil stabilization aimed at improving the properties of expansive soils used for road pavement. The maximum dry density (MDD), optimum moisture content (OMC), consistency limits, California bearing ratio (CBR) and unconfined compressive strength (UCS) of the soil were subjected test to ascertain the performances of the cement and lime with bagasse composite. The results showed that the composite materials improved the soil properties, but the maximum dry density (MDD), optimum moisture content (OMC), liquid limit (LL), plasticity index (PI), California bearing ratio (CBR) and unconfined compressive strength (UCS) of the expansive soil stabilized with cement and bagasse ash composite were greater than the soil samples stabilized with lime and bagasse ash composite. Meanwhile, the value of plastic limit (PL) obtained from the soil sample stabilized with lime and bagasse ash was higher than the value recorded in the soil sample stabilized with cement and bagasse ash. The optimum values UCS and CBR were recorded at 8% combined proportion of bagasse ash with cement and lime. Therefore, the improvement recorded in the soil properties proved that the combined effect of bagasse ash obtained from Costus dewevrei De Wild. & T. Durand and cement or lime, is effective and can be applied as stabilization material to reduce shrinkage and swelling of expansive soil that often lead to road pavement failure.

Investigation of Road Pavement Failures Using Active and Passive Surface Wave Methods in Parts of Calabar Municipality, Cross River State, Nigeria

The active and the passive techniques of surface wave were employed to investigate some major road pavement failures within the Calabar metropolis, Cross River State. The dispersion curves from MASW (active) and ReMi (passive) were inverted to give a 1D shear wave velocity model. The aim of this study was to comparatively investigate the major causes of the incessant road pavement failures especially few months after its construction and repairs within the study area using the shear wave velocity and blow count (N values). These roads are all located within the same geologic setting of the Calabar Coastal Plan Sand and showed evidence of road failures ranging from pot holes, alligator cracking, rutting and shear failure cracking etc. For each site, two sets of data were collected; the Passive and the Active seismic surface wave data. The survey was able to gather the following data from each location; shear wave velocity, primary wave velocity, N-values for both the active and the passive data which were both derived by the Seisimager surface wave software. The software was used to delineate low velocity layers within the depth of 4m – 6m at the failed portions of the survey sites exception of location 1 (the control site) which showed an ideal situation of increasing velocity with depth. These low velocity layers were inferred to be the major cause of the incessant failure of the pavements in the survey areas. These velocities and the N- values (blow count) were used to classify each location into sites C, D and E, according to the 1997 National Earthquake Hazards Reduction Program (NEHRP).

Performance of Sustainable Road Pavements Founded on Clay Subgrades Treated with Eco-Friendly Cementitious Materials

Clays encountered during road construction are mostly weak and result in major pavement failures due to their low California bearing ratio (CBR) and high swelling potential. In this study, sustainable and eco-friendly waste materials including brick dust waste (BDW), ground granulated blastfurnance slag (GGBS), recycled plastic (RP) and recycled glass (RG) at varying proportions of 11.75% and 23.5% were used as partial replacement for cement and lime in clay treatment. After determining the water content by conducting Atterberg limit and compaction test, A CBR and swell characteristics of treated and untreated clay were also conducted. A road pavement design was conducted using the Design Manual for Road and Bridges (DMRB) as a guide to determine the performance of treated clay with varying CBR values. A road pavement failure analysis was also conducted to understand the defect formation within pavement structures supported by eco-friendly treated clay. The embodied carbon of treated clay was calculated and a life cycle cost analysis (LCCA) of flexible pavement with treated clay and road with imported materials was conducted. The results show a liquid limit of 131.26 and plastic limit of 28.74 for high plasticity index (clay 1) and liquid limit of 274.07 and a plastic limit of 45.38 for extremely high plasticity index (clay 2). An increase in CBR values from 8% and 9% to 57% and 97% with a reduction in swell values from 4.11% and 5.03% to 0.38% and 0.56% were recorded. This resulted in a reduction in pavement thickness and stresses within the road pavement leading to reduced susceptibility of the pavement to fatigue, rutting and permanent deformation. Very low embodied carbon was recorded for eco-friendly treated clay and a high life cycle cost (LCC) with clay removed and replaced with imported materials compared with clay treated using eco-friendly waste materials. The study concluded that carbon and overall construction costs can be reduced using waste materials in road construction. Owners and operators can save money when clay is treated and used in road construction instead of removing clay and replacing it with imported materials.

Geotechnical Evaluation of the Causes of Road Pavement Failure Along the Mbaitoli-Ikeduru-Mbaise Highway, Southeastern Nigeria

The incessant failed spots in the road pavement along the 27.61km Mbaitolu-Ikeduru-Ahiara Mbaise highway in Imo state, southeastern Nigeria, has necessitated this geotechnical study to evaluate the impact of the subgrade material quality on the road pavement failure. The study entailed both physical and geological assessment of the predominantly sandy to clayey silt Benin Formation underlying the area, as well as field and laboratory engineering tests on the subgrade materials underlying the road alignment. The engineering tests carried out included the grain size distribution, specific gravity, natural moisture content, Atterberg (liquid and plastic) limits, compaction (to determine maximum dry density and optimum moisture content), California bearing ratio (CBR), and shear strength (to determine cohesion and angle of internal friction). The engineering test results indicate that the natural moisture content values range between 10.4 and 18.9%, liquid limit between 36.0 and 48.6%, plastic limit ranges from 26.1 to 31.6, with corresponding plasticity index values that range from 9.2 to 17.0%. The grain size distribution test results connote the predominance of sand, with number of fines-sized particles that ranges from 22 to 38% and amount coarse to medium sand-sized particles ranging from 62 to 78%.Maximum dry density ranges from 1.29to 1.93 kg/m3. (CBR) ranges from 3.7 and 91.9%. Specific gravity ranges between 2.56and 2.61, while cohesion and angle of internal friction range from 39 to 42 kPa, and 14 to 20°, respectively. Some failed portion especially in Inyishi area were likely due to moisture fluctuation in the subgrade due to closeness of the water table. Proper compaction, chemical stabilization, and appropriate drainage would likely boost the efficiency of the subgrade material and the durability of the road pavement.

Developing a Maintenance Model for Pavements Vulnerable to Climate Change in South Eastern Nigeria

The South East region of Nigeria faces widespread flood during rainy seasons as a result of inadequate drainage channels, poor drainage management and most often the absence of drainage. The increase in rainfall can be attributed to climate change. Climate change has become one of the most common sources of road pavement failure in the region which leads to rapid need of maintenance as a result of flooding and this problem is becoming worse yearly. Most roads in the region suffer submergence because of flooding. In this research work, a predictive model will be developed to control maintenance of road infrastructural systems in the South-East in terms of fatigue. This work is limited to pavement behavior with respect only to fatigue life using the mechanical/elastic properties as the input parameter using additives in the established failure conditions considering Federal roads in the South East as case studies. It is also important to note that the research has a well-defined assumption within the scope to expectancy is 20 years. The loads causing pavement failure are ≥80 KN single axle. Passenger cars will not be included in the passenger. The performance of flexible pavement in real life is synonymous with performance of hot mix asphalt concrete (HMA) in the laboratory. The fatigue life of a pavement is the number of load repetitions ≥80 KN single axle load and finally, traffic loads and moisture are the only contributors to pavement damage.

Investigating Road Pavement Failure in Oworonshoki, Kosofe Area of Lagos, Using Geophysical and Geotechnical Methods

An assessment of the immediate causes of persistent road pavement failure in Oworonshoki, Koshofe area of Lagos, Nigeria using geophysical and geotechnical methods was carried out. Six traverses were occupied in the study area along the alignment of the road. Electrical Resistivity Imaging (ERI) data using the Wenner array were acquired along the six traverses. These were followed by six (6) Vertical Electrical Sounding (VES) data along the traverses. On traverse 1 are VES 1 and 2, on traverse 2 are VES 3 and 4, on traverse 3 are VES 5 and 6. One boring and three Cone Penetration Testing (CPT) were conducted along traverse 6 while the three CPTs were carried out on traverse 3, 4 and 5 respectively. The inverted 2D results reveal that resistivity values vary from 6.74 – 1333 Ωm in the study area. Four resistivity structures are delineated which are peat, clay/sandy clay, clayey sand and sand. The peat has resistivity values ranging from 6.74 – 17.7 Ωm, clay/sandy clay (20.9 – 86.9 Ωm), clayey sand (96.3 – 194 Ωm) and sand (245 – 1333 Ωm). The peat is laterally extensive and occurs from the surface to a depth of 25 m. The peat is underlain by the clay which is fairly extensive across the area of study with a thickness of 2.5 – 20 m in most location. The Cone Penetration Tests (CPT) reveal cone resistance values that progressively varies from 0 – 101 kg/m2 from the surface to a depth of 17 m, indicating dense earth materials at deeper depth while at near surface, they are incompetent soft clayey earth materials. The laterally extensive peat and clay units underlying the road pavement, extending up 30 m depth as revealed from the 2D ERI, the geoelectric investigation and the borehole are suspected to be responsible for the persistent settlement, rutting and pitting of the road pavement. The thickness of the peat/clay and the lateral extent may not be economically admissible for excavation during construction. Pile foundations to the dense gravely sand at 40 m depth along the stretch of the road is therefore recommended for stable road pavement.

Integrated magnetic and electrical resistivity investigation for assessment of the causes of road pavement failure along the Ife-Osogbo Highway, Southwestern Nigeria

This study combined magnetic and electrical resistivity investigations to assess the reasons for the persistent failure of road pavement along the Ife-Osogbo highway, southwestern Nigeria. Three traverses, each covering both stable and failed road segments, were established for ground magnetic, 2D dipole–dipole electrical resistivity imaging (ERI) and 1D Schlumberger vertical electrical sounding (VES) surveys. Data correction involving diurnal effect and offset were carried out on the magnetic data and the corrected data were presented as profiles and then modeled for 2D subsurface images. The VES and 2D ERI data were respectively modeled for layer geoelectric parameters and 2D resistivity images. The magnetic profiles and 2D magnetic subsurface models identified geologic structures (fault/fracture/contact zones) that are inimical to road pavement foundation beneath the investigated traverses. Subsurface sequences underlying the road segments are topsoil, lateritic layer, weathered layer, partly weathered/fractured basement and the fresh basement rock. Laterite, typical of competent subgrade for road pavement foundation, was generally observed beneath the stable segments while clayey weathered layer characterized the failed segments. From 2D resistivity images (upper 5 m), low resistivities (< 100 Ωm), typical of expansive clay, were observed partly beneath the stable but predominately beneath the failed road segments. Generally, it was observed that road segments founded on relatively high resistivity/lateritic layer were stable while the failed segments were associated with significantly thick and low resistivity weathered layer with thin/no lateritic topsoil cover. It was therefore concluded that the persistent road pavement failure along the Ife-Osogbo highway were caused by the clayey nature of the subsoil and the underlying geologic features.

Road Pavement Failure and Exploratory Analysis of Requirements for Effective Management of Highway Maintenance Projects

Feedback information from investigating causes of Road Pavement Failure (RPF) will provide guidelines for requirements definition and management system for effective delivery of Highway Maintenance Projects (HMP) in Imo State Nigeria. This paper investigates the causes of RPF and explores the requirements needed for effective delivery of HMP to enhance sustainable thoroughfare assets. Expository field surveys with cluster sampling were adopted in the study. A sample size of five dilapidated highways with 78 target respondents and 6 factors in each of the 3 cluster groups of requirements formed the basis for primary data generation. The instrument of data collection and measurement was questionnaire designed in Likert five points scale. The methods of data analysis were the Relative severity index, Kendall’s coefficient of concordance and Pearson correlation analysis. The results and findings from the analysis found that poor side drainage system, poor quality of construction design and materials are the severest causes of RPF. The coefficient of concordance W from three raters indicate significant agreement of the three cluster groups of technical, financial and institutional requirements with,W= 70.60%, 62.40% and 61.50% respectively. Similarly, the result of correlation analysis shows that technical and financial requirements correlate significantly with effectiveness of HMP delivery with coefficients of 69.20% and 52.40% respectively. However, institutional requirement through important, did not correlate very strongly in this study. The results suggest that RPF analysis mitigates complexities of figuring out HMP requirements definitions and management system and hence, ensures meeting up with the acceptance criteria, change control and user’s satisfaction.

Geotechnical investigation of road pavement failure along arigidi / oke - agbe akoko, southwestern, Nigeria

Twenty soil samples collected from the failed portions in the study area were air dried for two weeks before analyses. Each soil samples were subjected to eight engineering tests which include: natural moisture content, atterberg limit, specific gravity, compaction, unconfined compressive strength, California bearing ratio, grain size and hydrometer analysis. Results showed that the natural moisture content ranged from 17.7% to 37.8%, liquid limit from 48.5% to 62.4%, plastic limit from 18.3% to 26.8%, plasticity index from 25.7% to 37.7%, shrinkage limit from 5.8%-12.5%, optimum moisture content from 14.2% to 32.4%, maximum dry density from 1301 Kg/rn3 to 2002 Kg/rn3. Soaked California bearing ratio ranged from 5% to 17%, unsoaked from 15% to 38%, specific gravity from 2.5 to 2.68, unconfined compressive strength r from 112.8 Kpa to 259.7 Kpa, shear strength from 56.4 Kpa to 129.9 Kpa and hydrometer analysis from 48.5% to 72.1%. Based on the Federal Government specifications for pavement construction, for the soil to be suitable, stabilization with bitumen, Portland cement, lime, coal fly ash, and saw dust should be done. Road pavement failure along Arigidi – Oke Agbe road was due to poor engineering geological condition of the sub-grade soils and poor drainage systems. Â

Geotechnical Evaluation of Road Pavement Failure along the Awotan-Akufo Road, Oyo State Southwestern Nigeria

In order to access the cause(s) of road failure and proffer preventive measures for the future reconstruction of the Awotan-Akufo road, southwestern Nigeria, the geotechnical engineering properties of the subgrade soil, asphalt pavement thicknesses, drainage and traffic load were evaluated. Soil samples were collected from test pits 1 m deep and at an interval of 50 m and subjected to geotechnical analyses in accordance to AASTHO specification. The grain size distribution revealed that 70% of the entire samples from Awotan-Lifeforte and Adaba failed sections along Akufo road contain amount of fines more than 35% passing through sieve No. 200. The Natural Moisture Content range from 5.73 - 20.21% (Awotan-Lifeforte section) and the entire samples from Adaba failed sections have high natural moisture content ranging from 16.20 - 23.20%. From Atterberg limit test, the Liquid limit of 12 - 56% (Awotan-Lifeforte section) and 26.00 - 40.00% (Adaba Section) were obtained. The Plastic Limit and Plasticity Index of the soils ranges from 8.43 to 49.10% and 1.01 to 7.0% (Awotan-Lifeforte section), and 23.10 - 35.50% and 1.50 - 7.10% (Adaba Section) respectively. Linear shrinkage varies from 0.80 to 9.60% and from 3.10 to 8.80% for Awotan-Lifeforte and Adaba sections, respectively. The Maximum Dry Density of the soils ranged from 1.625 - 1.835 mg/m3 at Optimum Moisture Content of 13.4 - 17.3% (Lifeforte-Awotan section), and MDD of 1.752 - 1.975mg/m3 at Optimum Moisture Content of 13.4-17.3% (Adaba section). The unsoaked California Bearing Ratio are 30.08, 70.14, 39.08%, and the soaked California Bearing Ratio values are 26.17, 11.41, 33.41% (Lifeforte-Awotan section) respectively. At Adaba section of the road, the unsoaked California Bearing Ratio is 3.46, 87.70, 70.14%, and soaked California Bearing Ratio values are 3.42, 32.56, 39.83%. The average asphalt pavement thicknesses around Awotan-Lifeforte section range from 0.60 - 1.10 inches, and that of Adaba section range from 0.57 to 1.46 inches. The study concluded that the road pavement subgrade is silty clay and the geotechnical properties rated below the specifications of the Federal Ministry of Works and Housing at some failed portions. Asphalt pavement thicknesses are grossly inadequate and far below NAPA 2007 recommendation. As such the road cannot withstand the heavily loaded trucks that ply it on regular basis. All aforementioned contributed to the untimely failure of the road.

Investigating causal factors of road damage: a case study

High rainfall leads to flood vulnerability and potentially leads to the failure of road pavement which affects the economic loss for the people. However, such road pavement failures need to be studied more deeply to be able to distinguish whether the failure is solely due to flood natural disaster or other factors, such as overloading and poor construction quality. This research is urgently needed because up to now there is no tool for assessing pavement failure as a tool of decision-making system that is able to distinguish road pavement failure causal factors into category of natural disaster or human negligence factors in accordance with the definition of building failure in Indonesia Law no. 2 year 2017. Assessment of the causal factor of failure is very important because it is closely related to the determination of the parties who must be legally responsible. This research intends to develop methods for assessing the damage and failure of pavement as a tool of rapid and accurate decision-making system to determine the factors of pavement failure. To obtain accurate results, a case study was taken on Kendal Timur road to enable a deep evaluation of the factors that causing failure on the road. The results showed that many factors involved in causing the failure of the road, such as un-functional drainage channel, uncontrolled overload due to the closing of weigh stations around the road, and also low quality of road maintenance work so that repeating similar road damages occurred in the not-too-distant future. Based on functional and structural failure analysis, as much as 71%, 10% and 19% of the road were in failed, critical and not-failed conditions, respectively.

Application of geophysical approach to highway pavement failure: a case study from basement complex terrain southwestern Nigeria

Geophysical survey involving Schlumberger Vertical Electrical Sounding, 2-D imaging dipole–dipole technique and ground magnetic method were carried out along Ibadan-Ife Highway located in the Precambrian Basement Complex of Southwestern, Nigeria to examine the geological factors responsible for Highway pavement failure. This was with the view to detailing the subsurface geoelectric sequence, mapping the subsurface structural features within the sub-grade soil and delineating the bedrock relief as a means of establishing the cause(s) of the road pavement failure. The geoelectric sections, 2-D resistivity structures and modeled magnetic profiles revealed that the stable segments were founded on a shallow/outcropping basement near homogeneous substratum devoid of major geological features while linear features suspected to be fault/fractured zones, buried stream channels, bedrock depressions and lithological contacts were identified beneath the failed segments of the highway pavement. The geoelectric sections generally identified four geologic layers comprising the topsoil, weathered layer, partly weathered/fractured basement and fresh bedrock. Thus, the failed portions of the road are probably precipitated by very thick and low resistive substratum (clay) beneath the highway pavement and the identified suspected linear features are the major geological factors responsible for the highway pavement failure.

Integrated geophysical investigation of the causes of road pavement failure along Ibadan-Lagos dual-carriage, Southwestern, Nigeria

An integrated geophysical study has been conducted in a segment of Ibadan- Lagos Dual-carriage road to examine the geological factors responsible for highway failure. Schlumberger Vertical Electrical Sounding (VES) and Very Low Frequency Electromagnetic Method (VLF-EM) to evaluate the subsurface integrity, mapping out the subsurface structural features within the sub-grade soil and delineating the bedrock relief as a means of establishing the causes of road pavement failure of 1300 m stretch of road from Ibadan axis. Results from VLF-EM showed the presence of near surface linear geologic structures from the surface to a depth of 15 m which suggests probable conductive zones that have devastating effects to the foundation of the road pavement (g1, g2 and g3). VES results showed the presence of four geologic layers while fractured basement were observed with resistivity value generally less than 100 Ωm which indicates the presence of the water table. The unstable segment is characterized by low resistivity of the near surface materials and shallowness of the aquifer zone on which the road pavement was constructed. The failure of the road is caused mainly by geologic sequence and structures such as clayey subgrade soil under the road pavement and some suspected geological features such as faults and fractures. Keywords: Lithologic contacts, aquifferous zone, geoelectric section, linear contact, sub-grade soil

English

As part of effort to examine the factors responsible for highway failure in the sedimentary terrain, geophysical survey involving Very Low Frequency Electromagnetic (VLF-EM), Schlumberger Vertical Electrical Sounding (VES), and dipole-dipole electrical resistivity techniques were carried out along Iruekpen-Ifon highway. This was aimed at using surface geophysics to characterize and identify the factors responsible the for road failures along Iruekpen-Ifon highway. ABEM WADI instrument was used to obtain electromagnetic-Very Low Frequency (VLF) field data, while ABEM resistivity meter was used to obtain electrical resistivity field data. The VLF-EM data were interpreted using the VLF Graphic software, VELFAN 1.0 double plot of filtered real and filtered imaginary against distance. The VES data obtained were interpreted using IP 2 Win software. Geoelectric parameters were used to generate the Dar Zarrouk second order parameters. 2-D inversion modeling of the dipole-dipole data was carried out using ZONDRES window software. VLF-EM result suggested varying degree of conductivity in the area and the wide spread of clay/metallic ore and water in the study area. Results show that the topsoil generally varies in composition from clay to clayey and laterite with resistivity values varying from 89 to 400 Ωm and thickness between 0.2 and 4.0 m. The fractured layers composed of clay and compacted clayey sand which represents the recent alluvial deposits with resistivity values of 2 to 89 Ωm and the thickness between 1.5 and 11 m. The fresh water zone is characterized by low resistivity ranging from 0.5 to 23 Ωm, which is diagnostic of saline water saturated with clay formation, fresh water ingression, and marls. The values of co-efficient of anisotropy (l) range from 1.03 to 2.19. The relatively higher values of λ (1.30 to 2.19) suggest that the subsurface rocks in these areas are likely to be more intensely fractured and more permeable. The saline water saturated with clay formation, fresh water ingression, fracture and marls clearly limit the lithological contacts and enhance high swelling potential which might be responsible for the road pavement failures in the studied area. Key words: Highway, resistivity, troubled roads, Dar Zarrouk, anisotropy.

Evaluation of geotechnical properties and structural strength enhancing road pavement failure along Sylhet-Sunamganj highway, Bangladesh

The study looks at the impact of poor soil properties and improper design on highway pavement failure on critical locations along Sylhet-Sunamganj road, Bangladesh. The entire study was conducted in the month of June to July, 2011 which was usually rainy season in Bangladesh. Pavement structural condition was evaluated by Dynamic Cone Penetrometer (DCP) test and sub-grade soil properties were obtained by laboratory soil tests. The California bearing ratio (CBR) values and thickness of the pavement layers were found as 66, 66 and 47% and 90, 90, and 110 mm for surface, base and sub-base layers respectively. According to Roads and Highway Department, the respective values needed were 100, 140 and 180 mm respectively with CBR values of 90, 55 and 16% respectively. It was clear from such comparison that requisite depth of construction were not maintained in various sections which might assist the pavement to its distressed condition. Sub-grade soil properties were evaluated as sandy soil of category A-3 (According to American Association of State Highway and Transport Officials) having moisture content range from 11.11 to 14.94%, specific gravity ranges from 2.21 to 2.49, optimum moisture content range from 9 to 16% were not appropriate for pavement construction. Clayey soil sample that was found from SUST gate arena having moisture content of 16.51%, specific gravity of 2.3, liquid limit of 40.80%, plastic limit of 17.85%, plasticity index of 22.95% and dry density of 2060 kgm -3 was totally unsuitable for such an important pavement construction. Specially, maintaining of liquid limit < 40 and plasticity index < 15 of soil is a must for such important pavement construction.

Relationship between road pavement failures, engineering indices and underlying geology in a tropical environment

This article presents the results of a study carried out to relate the frequency of pavement failures, the engineering indices of the subgrade materials and the underlying geology. The results show a high variability in the indices such as the liquid limit, LL, the plasticity index, PI, the maximum dry density, MDD, the optimum moisture content, OMC, compressibility and the California Bearing Ratio, CBR, between the different geologic units. Engineering indices having significant correlation with CBR (the major criteria for assessing the quality of subgrade materials), are used to develop a scheme for evaluating the materials at different failure points along the Calabar-Itu Highway in Nigeria. The evaluation shows that locations exhibiting high failure rates are underlain by shaly or marly subgrade whereas locations characterised by low failure rates are underlain by weathered basement or sandy unit as subgrade. It is recommended that maintenance and provision of drainage facilities will go a long way to reducing the rate of failure.Keywords: engineering indices, failure, road pavement, subgrade, NigeriaGlobal Journal of Geological Sciences Vol. 3(2) 2005: 99-108