Geotechnical and environmental problems of the Niger delta

This paper examines the geotechnical and environmental problems arising from the peculiar characteristics (topography, geology, soil types including their properties and their areal distribution) of the Niger Delta area. The area is characterised by the widespread and irregular distribution of weak soils whose strength is further reduced by the presence of expansive clays. This causes foundation problems in roads, houses and embankments. Excavations are unstable because they are either made in very permeable sands which are subject to enormous seepage pressures or in weak, fat clays of low shear strength. Environmental problems include flooding, poor water quality and excessive river bank erosion and recession. While the surface waters are very turbid due to high clay and silt content the ground waters are very acidic (pH 4.5–5.5) and contain high proportions of nitrates, ammonia and chlorides which contaminate aquifers especially in the coastal and central portions of the delta area. River bank failure and recession of up to 2 to 3 m occur annually and continue to pose an enormous threat to the villages along the river banks.     

The 1988 Nanka landslide,Anambra state,Nigeria

In 1988 a major landslide which required the evacuation of more than 50 families occurred in the little town of Nanka in Anambra State, Nigeria. Investigation revealed that the landslides were caused by an overconsolidated, very highly plastic mudstone layer (PI=67) which probably contained quantities of montmorillonite clay. Peak strength values of remolded samples of the mudstone measured in the ordinary shear box test differed from those of non-remolded (intact) samples only in showing zero cohesion. These values probably represent the strength of the mudstone in its normally consolidated condition. Stability analysis indicated that the major slide approximated more to a sliding block than to a circular failure with the mudstone layer as the base. It also showed that the peak strength at which the major slide occurred probably represents the strength of the mudstone in its fully softened or critical state, while the residual strength at which the minor slides occurred probably represents the strength at large displacements when perhaps the clay particles had become highly oriented in the direction of movement. In the present study, for the first time, the landslides in the highly unstable Nanka area are explained by the presence of active clays.     

The Topp–Leone Lomax (TLLo) Distribution with Applications to Airbone Communication Transceiver Dataset

Wireless Personal Communications - The Lomax distribution was extended in this paper using the Topp–Leone family of distributions. Some of its specific structural properties were established...     

Lean Production Principles in Production Management

Russian Engineering Research - The activity of a manufacturing enterprise is considered. The basic losses are identified; the operational efficiency of the assembly department is analyzed; measures...     

Fast and Optimal Path Planning Algorithm (FAOPPA) for a Mobile Robot

Wireless Personal Communications - The compressive sensing method presents itself as a promising technique in many fields specially for the Internet of Things and Wireless sensor networks...     

Closed form expression for the inverse cumulative distribution function of Nakagami distribution

Wireless Networks - Quantile function or inverse cumulative distribution function (CDF) is heavily utilized in modelling, simulation, reliability analysis and random number generation. The use is...     

Nature inspired quantile estimates of the Nakagami distribution

Telecommunication Systems - Nakagami-m distribution is utilized heavily in modelling multipath interferences in wireless networks. However, the closed form of the quantile function of the...     

Engineering properties and slope stability of road cuttings along the enugu-onitsha express road,Southeastern Nigeria

The new express highway linking Enugu (in Enugu State) and Onitsha (in Anambra State) both in Southeastern Nigeria, is plagued with landslides, a few years after completion. The active landslides are concentrated on the road cuttings between Otuocha junction and Awka, specifically between km 29 and km 40 from the Onitsha end of the road. Three of these slides have been studied. The investigation involved detailed field and laboratory studies of the physical conditions and geotechnical properties of the sites and soils therein. The laboratory tests performed included grainsize distribution analysis, Atterberg limits, specific gravity, natural water content, bulk density, permeability and shear strength. Each site was analysed for stability using the strength parameters obtained from laboratory tests and Bishop's 1955 simplified method of analysis. There is evidence from the analyses results that although the cut slopes are vulnerable to toe undermining and over-steepening by runoff, the generally “loose” nature of the soils as evidenced by the low bulk density (1580–1960 kg/cm³), fairly high void ratio (0.53–0.66) but low permeability (2.15–3.25×10^?3 cm/s) and consequent high saturation and strength reduction during the rains, are the major contributors to instability of the cut slopes.     

Geotechnical characteristics of soils susceptible to severe gullying in eastern Nigeria

The geotechnical characteristics of soils that are susceptible to severe gullying in the rain forest zone of Nigeria were studied. The soils are predominantly sands whose fines (silt/clay) contents are very negligible. The sands are loose (dry density 1.42–1.73 g/cm³) and highly permeable (permeability 9.43×10³?3.4×10²cm/s) with permeability increasing with depth. Porosities and void ratios are also high (41.6–50.3% and 0.71–1.01 respectively), while cohesion is small to zero (0–85 kN/m²). It is thought that although these conditions favour less runoff and high infiltration, they lead to high internal flow velocities and seepage pressures, and ultimately high internal erosion. It is concluded that once a gully is initiated, the soil properties become responsible for rapid propagation. Non response of the gullies studied to afforestation control measures is thought to result from these soil properties.     

Disparities in document indexation in two databases (Scopus and Web of Science) among six subject domains,and the impact on journal-based metrics

A previous study (https://doi.org/10.1007/s11192-020-03457-x) found a discrepancy between Elsevier’s CiteScore and Clarivate Analytics’ Journal Impact Factor (JIF) in library and information science (LIS) journals. One possibility to explain this discrepancy may lie in the number and type of documents used to calculate these journal-based metrics. Using the top quartile of Scopus-indexed journals from 2011 to 2018, we assessed the number of documents for each journal and year that were indexed in Scopus and in Web of Science (WoS) in six fields of study: LIS, discrete mathematics and combinatorics (DMC), medicine: epidemiology (ME), agriculture and biological sciences (ABS), social science: demography (SSD), and environmental engineering (EE). The number of documents in WoS was higher than those indexed in Scopus for four fields of study: LIS, ME, SSD and EE, with a difference of 1653, 3931, 635 and 197 documents, respectively. For DMC and ABS, Scopus listed more documents than WoS for the same years and journals, the differential being 7 and 1284, respectively. The greater indexing of documents in WoS than in Scopus in four fields of study may explain why the JIF of top-ranking LIS journals is different than their CiteScore. To verify this possibility, one category (DMC) was examined in detail. Of the 16 DMC journals examined, 91.1% were articles, while 8.9% of missing documents were corrections, an erratum, an editorial, an abstract report and in press articles. There were no significant differences between the citation patterns of the missing DMC journals’ documents in Scopus and WoS. Citations to missing documents may impact the CiteScore and JIF and should thus be properly indexed.