Study on Shear Failure and Crack Propagation Characteristics of Soil-Rock Mixture

Soil–rock mixture is a special geological material between homogeneous soil masses and fractured rock masses. In this study, the shear characteristics, movement and failure characteristics of particles and the evolution law of cracks were studied by direct shear tests and particle flow numerical simulations. The results show that the shear stress-shear displacement curves of the soil–rock mixture can be roughly classified into three stages: elastic stage, plastic stage and strain softening stage, and there was a "jump" phenomenon. The higher the rock content was, the more obvious the phenomenon. The shear strength and its indices of the soil–rock mixture did not increase with increasing rock content, but there was an "optimal rock content". According to the experimental and simulation results, particle breakage can be divided into three types: slight failure, partial failure and complete failure. The crack propagation characteristics can be divided into three stages, and the crack propagation depth increases with increasing shear displacement. It increases with increasing vertical stress and decreases with increasing block rock content.

An Adaptive Filtering Method for Bridge Vibration Signals Based on Improved CEEMDAN and Multi-Scale Permutation Entropy

Aiming at the serious noise of bridge vibration signals in complex environment, this paper proposed an adaptive filtering and denoising optimization method for bridge structural health monitoring. The method took CEEMDAN algorithm as the core, during the step-by-step decomposition of original signals, white noise with opposite signs was added in each stage, meanwhile multi-scale permutation entropy (MPE) was introduced to analyze the mean entropy of each intrinsic mode function (IMF) at different scales, and components with serious noise were eliminated to complete the first filtering; then, in order to optimize the remaining IMFs for signal reconstruction and ensuring the smoothness and similarity of filtering, an optimized reconstruction model was established to complete the second filtering. Compared with the CEEMDAN method, the proposed method could solve the problems of mode mixing and endpoint effect with good completeness, orthogonality, and signal-to-noise ratio. At last, the advantages and application value of the proposed method were verified again by the vibration signal analysis of a real long-span bridge structure.

Infrastructural Challenges in Nigeria and the Effect on the Nigerians Economy: A Review of Literature

Infrastructure development is a critical prelude to economic growth and development on a global scale. Most emerging economies with infrastructure deficits have little chance of establishing a sustainable route to national growth, as attracting FDI and advancing essential and noncritical sectors of the economy are near-impossible. Nigeria is trapped in this heinous predicament. Over the years, various administrations have failed to prioritize the building of critical infrastructure. Budgeting has frequently prioritized recurrent expenditures over infrastructure development, leaving the country in a dismal and awful condition of infrastructural presence. This study examines infrastructural challenges in Nigeria and their effect on the Nigerian economy. The research mainly relies on a secondary data source, employs the descriptive approach, and finds that Nigeria's infrastructural state results from state actors' continual negligence. It thus recommends that effective management fosters accountability, lowers corruption, and minimizes waste of resources due to efficiency.

Women, Development, and Flooding Disaster Research in Nigeria: A Scoping Review

The growing threat of disasters caused by climate change, of which flooding is the most prevalent has led to a call for a change in the design of, and roll-out of disaster mitigation and response policies. A more inclusive approach to Disaster Risk Reduction has been advocated with the Sendai Framework for Disaster Risk Reduction calling for the involvement of women and marginalized groups for more effectiveness and efficiency. The rapidly urbanizing countries of sub-Saharan Africa are particularly vulnerable to the threats and impacts of disasters, including flooding, and women in these countries are differentially vulnerable and marginalized. In response to the call for the inclusion of women in disaster risk management, this scoping review seeks to understand to what extent Nigerian women have been engaged or included in urban flooding research. This review finds that very little research has been conducted on gender and flooding. In addition, 85% of the papers reviewed focus on rural women, while the prevalence and rising threats of flooding in urban areas are given little attention. As urban centers throughout the region are becoming more feminized, a better understanding of urban women’s experiences with flooding will help ensure a more inclusive and effective disaster response.

A New-Type Semi-Rigid Base Layer Structure for Long Service Life Pavement

Targeting at the problem of pavement cracking under long-term load, this study developed a new-type semi-rigid base layer structure based on the CGC (cement stabilized macadam - graded broken stone - cement stabilized macadam) combinations, and used ANSYS to simulate this proposed structure under conditions of different modulus combinations, deflection under different thickness, different vertical strain values on the top surface of roadbed, and different transverse tensile stress values of bottom base layer. The simulation results indicate that, the various mechanical properties of the proposed new structure can well meet the specifications, and the time of crack generation has been slowed down; the use of graded broken stone in the proposed structure has achieved both the purposes of saving construction cost and reducing construction difficulty. By reasonably controlling the CGC structure and modulus, this study has successfully suppressed the generation of reflection cracks, which can provide good theoretical evidence for prolonging the service life of semi-rigid base layer pavement.

Detection of Trace Metal Contamination Around a Dumpsite in Iyara Area Warri Nigeria Using Geoelectrical and Geochemical Methods

Trace metal concentration in soils of Iyara area of Warri, Delta State was studied using geophysical and geochemical techniques. Eight vertical electrical sounding (VES) using SAS 1000 Terrameter with maximum current electrode spread of 150 m in the Schlumberger configuration was carried out. The geoelectric layers obtained are topsoil, clay, sand and fine-medium grained sand. The fine to medium grained sand of the third and fourth layers mainly constitute the aquifer with a depth ranging from 4.8 - 11.0 m. Soil samples were collected at three of the VES stations covering the dumpsite and stations away from the dumpsite. The trace metal content was higher than the maximum allowable levels in soils as specified by the World Health Organisation (WHO) and Department of Petroleum Resources of Nigeria (DPR) except for Pb with undetected concentration in VES 3, Mn with 135 mg/kg in VES 1 and undetected in VES 3 and VES 7. The Multiple pollution index, Enrichment factor, and Non-carcinogenic hazard decreases with increasing distance from the dumpsite. The soil around the dumpsite has been impacted and the results of this study will serve as background information for soil studies and groundwater development in the area.

Sensor Network Based Testbench Implementation of Landslide Early Warning System

The paper presents an implementation of prototype based Early Warning System (EWS) to detect and provide early warning of Landslide activities. The main aim of this work is to implement the prototype with low cost sensor network. A simulation setup and a table based prototype setup was implemented to study the capability and effectiveness of the system. The setup consists of table based setup of landslide with multiple/changing angle from 30° to 90°. Multiple sensing elements including rain sensor to detect presence of rain, soil moisture sensor to detect the moisture content, temperature and humidity sensor to detect humidity in the environment and vibration sensor to detect movement in the soil was implemented. The data captured by the sensing element is transmitted to a microcontroller which sends early warning signal represented by LED, Buzzer and sending of SMS or call. Through the setup, it is found that the sensitivity of the moisture sensor is rather limited however the range of moisture content detected by the sensor is functional. The vibration sensor can be tuned to have high sensitivity to the movement of the soil however, a number of false positive outcome may be detected. The early warning system is still possible by using multiple sensing element and averaging over their outcomes. The early warning system using low cost components as prototype has been successfully demonstrated. This setup can be scaled up to a real field implementation after careful tuning.

Incorporation of Innovative Mechanisms for Greenhouse Gas Emission Reduction

Spiraling continued increase in Emission of Green House Gases [GHG] play a significant role in impacting the environment and also human beings at large. Although recent studies have concentrated to an extent on developing schemes for reduction of Carbon dioxide emission and have identified methodologies in implementing the same, sufficient amount of studies have not been done on other greenhouse gases which also have adverse global impact as Carbon dioxide. Applications where methane and, nitrous oxide are emitted in abundance have continued to flourish. This work focuses on select methodologies in reducing all types of Greenhouse gases giving a larger amount of importance to ones which are more severe and the ones that cause depletion of ozone layer. Research findings have shown that majority of greenhouse gas emissions occur as a result of industry advances. Hence, as time is running out, there is an urgent need in identifying ways to mitigate these GHG emissions, thereby contributing to cleaner and healthier environment.

Assessment of a Photoreactor with Immobilized Nanoparticle TiO2 Films for the Purification of Rainwater

The heterogeneous photocatalysis consists of the generation of reactive oxygen species (•OH, •-O2) from a catalyst, UV light, and oxygen; these reactive species can degrade contaminants and eliminate microorganisms. The purpose of this research was to evaluate a heterogeneous photocatalysis system and an UV light disinfection system for the elimination of total coliforms and Escherichia coli bacteria present in rainwater stored in five cisterns in Mexico City. The elimination of total coliforms (MPN/100 mL) and Escherichia coli (CFU/100 mL) were evaluated both in the rainwater treated with TiO2/UV and UV (in time periods of 30 and 60 minutes), according to the treatments established in the statistical model 22. The results show that although complete elimination of initial total coliforms (9.3 x 104 MPN/100 mL) and E. coli bacterium (1.5 x 103 CFU/mL) was achieved in one of the samples of rainwater using only UV light at 254 nm for 30 minutes, the use of 8 films coated with Degussa P-25 titanium dioxide, UV light at 254 nm and 1.5 vvm air in a reactor, achieves a total pathogen removal in a shorter time of 15 minutes. Thus, we anticipate that the combined treatment could be an alternative disinfection process for rainwater stored in cisterns, reducing costs and making the treatment viable for a larger-scale application.