Soil Investigation On Failed Portions Of Nta Road

INTRODUCTION 

1.1 Background of study

Road networks play a vital role in the economy of any nation especially in developing ones like Nigeria, which require good roads for transportation of goods and services. Roads aid easy and smooth vehicular movement. In developing countries where other means of transportation such as rail, underground tube, air and water transport systems have remained largely under-developed, roads remain indispensable in the transportation of people, goods and services from one point to another. Oguntuase [2018] and Igwe et al. [2016] broadly classified the road network in Nigeria into three distinct groups namely: 

o Urban Roads, 

o Inter-State and 

o Inter-City Highways and the Rural Roads. 

Urban roads are wide paved roads found within cities and towns. The inter-state and inter-city highways are those that connect two or more States together. The third category of roads is the rural roads which are mainly earth roads. These roads connect farms and villages with inter-city roads. Ozuoba, NTA road Port-Harcourt falls within the third category of roads (Rural roads which are mainly earth roads.). A sub-division of the Nigerian road system was done by Fadaka [3]; Nnama [4] and Akobi [5] considering important details such as ownership, construction and maintenance responsibility. The road serves as inter-links between towns, states and countries and therefore is known as the common means of transportation.

Road failure is generally detected and observed as cracks, depressions and removal of the bituminous pavement, which exposes the subbase. The punctuation in a smooth ride is generally regarded as road failure. Consequently, the pavement will no longer be able to absorb and transmit the wheel loading through the fabric of the road without causing a fairly rapid deterioration of the road pavement. The rate at which roads (highways) fail in Nigeria is quite alarming in recent times and this has been causing concerns among the stakeholders in the maintenance of Nigerian highways. Most of these roads have become death traps in many places across the country with the attendant loss of lives and properties. The failed segments of major highways across the country usually display a variety of failed pattern ranging from pitting, rutting and waviness patterns. A number of contributing factors have been identified, such as mis-use of highways or over-use of highway, lack of maintenance culture, poor construction practices and geotechnical factors [Adele 2016].

Engineering properties have been identified as the major factors influencing the failure of many roads within and outside the country and side country, of which Rivers State is among them, that each government that comes in may be called Mr Project. Despite the technological improvement in the country, the cause of pavement failures has remained a serious concern in almost all the major roads in Nigeria. Pavement or terms base and sub- base are sometimes used interchangeably to refer to the sub-surface layers of a pavement, sub-base is the layer of aggregate material laid on the sub-grade on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. The base and sub-base layers at the study area were exposed by the different grades of pitting along the road. Road failures are almost invariably linked directly to the underlying soil (sub-grade soil) which usually bears the load carried by the road. The term “sub-grade” as used in Civil Engineering refers to the in-situ material upon which the pavement structure is placed. It may be the material reworked in-situ or even the imported material from another source such as a cut. Sub-grades are also considered layers in the pavement design, with their thickness, assumed to be infinite and their material characteristics

assumed to be unchanged or unmodified. The sub-grade serves as the foundation for the highway pavement and distributes the load from the upper layers to the soil underneath. A satisfactory sub-grade is able to resist the effect of both traffic and weather. Under heavy traffic loads, sub-grade soils may deform and contribute to distress in the overlying pavement structure manifesting as failure. It is therefore very important to adequately prepare this layer if the road is to last.

The causes of roads failure in Nigeria have been attributed to several factors such as poor construction materials, poor design and specification, road usage, poor drainage, geological and geotechnical factors. Geological factors are usually not considered as precipitators of road failure even though the highway pavement is founded on the geology. The proper design of road requires adequate knowledge of subsurface conditions beneath the road route. Previous studies have revealed that the integrity of the road pavement can be undermined by the existence of geological features and/or engineering characteristics of the underlying geologic/geoelectric sequences. Field observations and laboratory experiments carried out by Ajayi [2019] showed that road failures can arise from inadequate knowledge of the geotechnical characteristics and behaviour 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.It is crucial to develop a sub-grade with a California Bearing Ratio (CBR) value of at least 10. Islam [2013] reported that if a sub-grade has a CBR value less than 10, the sub-base material will deflect under traffic loadings in the same manner as the sub-grade and cause pavement deterioration. The stability and durability of pavement depends on the traffic load or intensity and the strength of pavement layers [14]. Pavement failure is certain to occur if the pavement is not perfectly designed with the present traffic condition being considered. If it is designed without considering incremental traffic in the near future, the pavement life will be successively reduced. A flexible pavement surface reflects the entire behaviour of the sub grade layer, it thereby, emphasises more attention on making the soil sub-grade of superior soil properties. In previous research, road failure occurred due to the following reasons: Inadequacies in pavement structural design [15,16], poor sub-grade soil properties [17], insufficient pavement drainage [18] and effect of seasonal fluctuations of temperature over base course aggregates [19] and poor visco-elastic properties of asphalt binder [20]. Adewoye et al. [21] observed that the flexible highway failures along the OyoOgbomoso road, which manifested as waviness/corrugation rutting and potholes were due to environmental factors such as poor drainage, lack of maintenance and misuse of road pavement. It was also noted that runoff due to precipitation, largely found its way into the pavement structure damaging them in the process. A road is usually divided into different parts namely: pavement, base, sub-base and sub-grade. Sub-grade is the soil foundation which directly receives the traffic loads from the pavement and a satisfactory subgrade resists the effects of both traffic load and weather.

1.2 Statement of Problem

Road construction have become an issue in Rivers State, in that it have increased lack of employment in the State, because any sitting governor must based it's governance on road construction and will for fit all other sector and job creation. The researcher observe this scenario and choose to research on the soil investigation on the fail portions alone NTA, Ozuoba road. The major components of several typical flexible road pavements from the base to the top include the subgrade, sub-base, base course and riding surfaces (Gupta and Gupta 2003 ; Adeyemi 2013 ). However, loss of lives and properties has been linked to the poor design and substandard construction activities arising from non- compliance with the recommended standards. However, road failures are usually followed by the following signs such as rutting, potholes, differential heave, deformation, peeling and cracking (Gidigasu 1976 ; Alexander and Maxwell

1996 )This road has been characterized by bad spots, road damage, which lead to road parchment, go slow, or holdup, accidents that took life some times etc.  The researcher did it necessary to deepout most of the causes of failure portions alone the study area to enable good access road. 

The objective of this study is to determine the engineering geological properties of the soils in the study area using integrated geotechnical and geophysical investigations and their contribution to road failure.

1.3 Aim of Study

The aim of this research is to examine the effect of rock fines on the geotechnical properties of sub-grade soil materials along failed portions of Ozuoba, NTA road, South-western Nigeria in order to reassess their direct productive application as soil materials or the need for incorporating the stabilisation method to enhance their properties for flexible road construction. This will be summarized with the following Objectives. 

1. Causes of Soil failure of soil in Ozioba NTA road Port-Harcourt Rivers state 

2. Soil investigation of fail portions along Ozioba, NTA Road Port-Harcourt Rivers state

3. The remedy to Soil failure in Ozioba NTA road Port-Harcourt Rivers 

1.4 Research Questions 

1. What is the Causes of Soil failure of soil in Ozioba NTA road Port-Harcourt Rivers state

2. What method could be used in Soil investigation of fail portions along Ozioba, NTA Road Port-Harcourt Rivers state

3. What are the remedies to Soil failure in Ozioba NTA road Port-Harcourt Rivers 

1.5 Significance of Study

This study is significant very because construction company will use the result and recommendations of this research to adopt insulation requirement in road construction, while the lecturers, staff and students will also use the research to adopt the development/improvement of knowledge about the causes of soil failure and the remediation especially in road construction and sits for building.

Furthermore, the study will be used for further research for any professional and also, for external use like the government.

1.6 Scope of Study

The study was carried out within Obio-Akpor Local Government Area, Rivers State, Nigeria. The study tailored on the cause of soil failure and how to investigation the soil fail portions and the remedy, using Ozioba NTA road as a case study.    

1.7 The limitation of the Study

In the study, Soil investigation of failed portions along Ozioba NTA road Port-Harcourt Rivers state, the researcher encountered some difficulties in the course of carrying out this research work, notable among them include:

The non-cooperation nature of many lab attendance in carrying out adequate practicals for the research, thinking that the researcher has something else to do with the information given other than for academic purpose. Owing to time frame given for this study, it was not easy for the researcher to bring the work to the best standard.

Financial constraints also contributed immensely to limit the extent to which data are collected..

1.8 Definition 

1. PAVEMENT. A pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as road or walkway.

2. SUB-GRADE. sub-grade as used in Civil Engineering refers to the in-situ material upon which the pavement structure is placed. It may be the material reworked in-situ or even the imported material from another source such as a cut.

3. Investigation 

4. Fail

5. portion

6. Soil