ABSTRACT
This research is aimed to evaluate stability of the slope of newly constructed railway embankment along Lagos-Ibadan rail line. Soils samples were collected from KM75+500, KM90+500, KM105+500 and KM116+500 at depths ranging from 0m to 5.5m and 5.5m to 10m and taken to laboratory for tests such as particle size analysis, Atterberg limits, standard Proctor and direct shear test. The slope stability assessment was done for the high filled embankments in KM75+500, KM90+500, KM105+500 and KM116+500. Geotechnical parameters were derived from the direct shear test as inputs for slope/W software used for the slope stability assessment. The results showed that the fill materials for the embankments from 0m to 5.5m was characterized as A-2-6 (clayey soil) subgroup in AASHTO classification system comprises of 78% of sand and 17% of fine particles and is considered as average soil according to International Union of Railways specifications. The subgrade materials from 5.5m to 10m consisting of 51% sand and 49% fines is classified as A-6 (clay soil), with high liquid limit of 41% and plastic index of 19% at KM116+500, and is regarded as poor soil according to railway specifications that requires stabilization. The factor of safety of the embankments according U.S. Army Corps of Engineers shows the slope is stable at KM75+500, KM90+500 and KM105+500 has factor of safety greater than 1.3 but slope at KM116+500 is unstable as the factor of safety is less than 1.3. It was also noticed that there was increases in factor of safety with decrease in embankment height. Slope protection and soil treatment be provided KM116+500 embankments.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
As the population grows, so does the demand for quick and safe transportation. The railroad sector grew rapidly as an alternative system, and it now serves as the world’s largest transportation system. In addition to conventional tracks, the introduction of new Significant Speed Trains resulted in a high demand for corresponding railroads capable of tolerating heavier loads and a greater speed.
Because of a multitude of circumstances, effectively modeling slope stability difficulties is difficult. One of the most fundamental concerns is that slope behavior cannot be predicted precisely. Engineers utilize a factor of safety methodology to reduce the danger of slope failure. When dealing with fluctuating uncertainties, such as slope stability, deterministic approaches give a systematic technique. The stability of a slope has a significant impact on the area surrounding it, because when a slope collapses, it frequently endangers human lives or causes significant material damage. As a result, one of the most important areas of practical usage in soil engineering is slope stability analysis (Capper, 1976).
Nigeria’s federal government has recently begun establishing standardized and broad inland transportation networks that are accessible to both passengers and enterprises. The Federal Ministry of Transport planned many high-speed rail lines around the country to achieve this goal. For economic reasons, the Lagos-Ibadan rail line extension to Apapa port from Ebute-Meta is a priority.
Subgrade is a phrase used to describe the grade line that is elevated that is ready to receive subballast in construction (Dingqing et al. 2015). Because it provides a strong foundation for the track superstructure, subgrade is an important feature of railway systems. It is necessary to avoid progressive shear failure, excessive swelling and shrinking, and subgrade attrition (Selig and Waters, 1994)
The Lagos-Ibadan section is part of Nigeria’s 1,343-kilometer Lagos–Kano Standard Gauge Railway, which was been constructed. It is projected to connect the country’s two main cities, Lagos in the southwest and Kano on the Niger border in the north, if completed. It will also connect the country’s third largest city, Ibadan (also in the southwest), and the national capital Abuja. The railway will run parallel to the Cape gauge line, which was built by the British and has a lower design capacity and is in poor condition (Israel, 2014).
The conversion of single tracks to double or multiple lines, as well as the renovation of old rails to allow high-speed trains, necessitates a large number of materials. It has also become critical to ensure that the quality of such construction meets the requirements for safe, comfortable, and cost-effective train passage under specified conditions. Furthermore, with such a large building volume, finding good quality materials at a reasonable price is a difficult task.
The limit equilibrium approach is adopted to assess slope stability based on assumptions about the sliding surface geometry. The method is popular because it is easy and only requires a few parameters (geology, slope geometry, topography, geotechnical factors, static and surcharge loads and hydrogeologic conditions). The stability of natural and artificial slopes, such as road/railway embankments, hydraulically produced dams, earth dams, and so on, is a major concern in geotechnical engineering.
This research aimed to evaluate stability of the slopes of newly constructed railway embankment from KM75+500 to KM116+500 along Lagos-Ibadan rail line. Limit equilibrium approach has been used to examine the slope stability state of the railway embankment, taking into account the strength parameters of the materials of the newly constructed railway embankment located along the study region.
1.2 Problem Statement of the Research Problem
The stability of slope is a main concern where movements of existing slopes would have an effect on the safety of people and property. Although, slope analysis had been carried out during preliminary design of the embankment, but the possible of slope failure is still high after construction. The aforementioned phenomena occur as a result of either an incorrect approach to assessing their stability, or errors made during geotechnical investigations, incorrect assumptions made during the calculation phase, or improper machine placement on the slope surcharge, or material deterioration over time after construction. One of the causes of faulty slope stability assessments could be an incorrect estimation of the slope’s geological structure (Das, 2011)
1.3 Justification of Study
The motivation driving toward this study is closely related to the assessing the slope stability of railway embankment and the important role slope/w plays in stability analysis of slopes in civil engineering applications and design. Furthermore, evaluating the slope stability of newly constructed railway embankment was to provide the current stability status of the embankment.
This study is intended to evaluate the slope stability of the newly constructed railway embankment along Lagos-Ibadan rail line and in the same time, propose some stabilization measures based on the field investigations and stability assessment of the slope. In other to reduce the problems that could occur after the construction of Lagos- Ibadan railway modernization project, it is essential to identify and assess those sections that could be prone to slope failure periodically.
1.4 Aim and Objectives of the Study
The aim of this research is to evaluate stability of the slope of newly constructed railway embankment along Lagos-Ibadan rail line.
This aim has to fulfill these objectives;
1. To determine the geotechnical characteristics of the embankments at KM75+500, KM90+500, KM105+500 and KM116+500
2. To evaluate the safety factor for slopes at chanaige KM75+500, KM90+500 KM105+500 and KM116+500 embankments using Slope/W 2018 from GeoStudio
3. To determine potential failure mechanisms
1.5 Scope of the study
The new railway embankments selected is from KM75+500 to KM116+500 along Lagos-Ibadan rail line. Samples were collected at KM75+500, KM90+500, KM105+500 and KM116+500 at depths ranging from 0m to 10m To determine the factor of safety, the Slope/W software was used to evaluate the slopes of varying heights 10m, 7m and 5m and side slope ratio 1:1.5 and 1:1.75 of berm based on the limit equilibrium of the Morgenstern-Price technique.
This material content is developed to serve as a GUIDE for students to conduct academic research
SLOPE STABILITY EVALUATION OF NEWLY CONSTRUCTED RAILWAY EMBANKMENT ALONG LAGOS-IBADAN RAIL LINE, NIGERIA
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