Experimental comparison of active seismic surface wave tests on shallow and deep bedrock sites

Active seismic surface wave tests are seismic tests for which the signal is generated by artificial sources as opposed to passive tests where the signal is generated by natural source. Active tests are widely used around the world due to among other factors their non- intrusive nature. However, the use of these tests in different parts of the world is based on availability and experience. Practitioners do not always consider the technical abilities of a test relative to others, but they rather select the test based solely on the availability of that tests in that specific region. Thus, few unbiased technical comparisons of these tests have been done to date. This study investigated the comparison of three active seismic surface wave tests, spectral analysis of surface waves (SASW) test, multi-channel analysis of surface waves (MASW) test, and the continuous surface wave (CSW) test. The objective was to compare these three tests in terms of repeatability (reliability), susceptibility to near field effects, and maximum and minimum investigation depth. The tests were carried out in the field on shallow and deep bedrock sites. Midpoint SASW configuration was used with source offsets ranging from 1 m, 2 m, 4 m, 8 m, 16 m and 32 m. As there is currently no standard configuration for conducting MASW tests, MASW tests were performed using two different array configurations of 24 geophones spaced at 1 m and 2 m respectively. The source offsets used for the 1 m geophone spacing were as follows: 1 m, 2 m, 4 m, 8 m and 16 m and for the 2 m geophone spacing the offsets were set up as follows: 2 m, 4 m, 8 m, 16 m, and 32 m. CSW tests were performed using five geophones spaced at 1 m and the source offsets used were 1 m, 2 m and 4 m. 2.2 kg, 6.3 kg and 9.2 kg sledgehammers were used as energy sources for the SASW and MASW tests whereas high and low frequency shakers were used as energy sources for the CSW tests. The geophones used to detect the signal of propagating Raleigh waves were 4.5 Hz natural frequency and a PASI GEA 24 (24 bit) seismograph was used to log the signals. After the evaluation and analysis of the shallow bedrock results, all the tests were found to be repeatable (reliable) though the repeatability of CSW was better than that of SASW and MASW. MASW was found to be more prone to near field effects with the configuration of 1 m geophone spacing being affected more than the 2 m geophones spacing configuration. SASW was the second most affected and hence CSW was the least affected. Furthermore, SASW was able to sample deeper and shallower than both MASW and CSW. MASW was second best for sampling deeper and CSW was the second best for sampling shallower. At the deep bedrock site, the repeatability of the tests was better than on the shallow bedrock site however, the repeatability of MASW and CSW was better than that of SASW. With regards to near field effects, MASW test with 1 m geophones spacing configuration was affected the most, followed by SASW, then CSW. CSW was also affected by multiple modes (far field) effect. MASW test with 2 m geophones spacing configuration was affected the least. Lastly, SASW was able to sample deeper, followed by MASW and then CSW. However, SASW and MASW were able to sample to virtually the same minimum depth which was in turn shallower than that achieved by the CSW test.Dissertation (MEng (Geotechnical Engineering))--University of Pretoria, 2022.Civil EngineeringMEng (Geotechnical Engineering)Unrestricte

Exploring ways of assisting Lesotho educators to offer care and support to children orphaned and rendered vulnerable by HIV and AIDS

The HIV and AIDS pandemic has resulted in 14 million children being orphaned worldwide. In Lesotho alone, where this study was carried out, there are about 180 000 of these children (UNAIDS, 2007). Teachers, especially in Lesotho‘s primary schools need to be equipped to better deal with the challenges that result from having these children in their classrooms. At the Lesotho College of Education, where I have worked for 12 years as a teacher educator, pre-service and in-service student teachers are not trained to offer care and support to orphans and vulnerable children. They experience problems in the classroom emanating from the needs of these children. This study followed an action research design to find ways to support teachers to better deal with the issues they face as a result of having orphans and vulnerable children in their classes. Using a qualitative approach, educators perceptions, feelings, attitudes and experiences in dealing with orphans and vulnerable children in their schools were identified, and it became apparent that educators were negatively affected on a personal and professional level. It was concluded that the development of resilience in educators would help them to better cope with orphans and vulnerable children in their classes. The chosen intervention Resilient Educators Programme (REds) was implemented and evaluated and findings revealed that it was beneficial in increasing educator resilience. Recommendations, based on the findings of the study, were made for future teacher education in this area

Experimental comparison of active seismic surface wave tests on shallow and deep bedrock sites

Active seismic surface wave tests are tests during which signals are generated by artificial sources such as sledgehammers, drop weights and fixed or variable frequency shakers. A number of active seismic surface wave tests have become popular in the geotechnical industry. Interestingly, different surface wave tests are popular in different regions of the world, presumably because the tests require different equipment, expertise and numerical analysis techniques. Few studies have been done to compare seismic surface wave tests directly. This study investigated the performance of three active seismic surface wave tests, namely the spectral analysis of surface waves (SASW), multi-channel analysis of surface waves (MASW) and continuous surface wave (CSW) tests. This paper reports the performance of the three tests with regard to repeatability, susceptibility to near-field effects, and maximum and minimum measurement depths at both a shallow and a deep bedrock site.http://www.journals.co.za/ej/ejour_civileng.htmlam2024Civil EngineeringSDG-09: Industry, innovation and infrastructur

Activated Carbon from Paper Waste as Potential Adsorbents for Methylene Blue and Hexavalent Chromium

Environmental pollution is a significant problem and is increasing gradually as more and more harmful pollutants are being released into water bodies and the environment. Water pollutants are dangerous and pose a threat to all living organisms and the ecosystem. Paper waste is one of the most widespread and largest wastes in the world. This research aims to address two important problems simultaneously: the reduction in solid waste in the environment using activated carbon from paper waste as potential adsorbents and the removal of harmful contaminants from water. Carbon from paper waste was activated with H2O2, HNO3, and KMnO4 for the adsorption of Cr(VI) and MB. SEM, EDX, FTIR, Raman, and BET were used to determine the properties of the materials. The surface morphology of the materials consisted of amorphous particles. EDX shows that all activated samples have a higher content of (O) than carbon paper waste. Adsorption studies showed that there was a stronger interaction between the pollutants and the adsorbent at a higher initial concentration (200 mg/L) than at the lower initial concentrations. The contact time data show that uptake increases when the interaction time between the contaminant and the adsorbent is increased. The tests for the pH of the solution show that the adsorption of Cr(VI) decreases when the pH is gradually increased, whereas the adsorption of MB increases when the pH of the solution is increased. The results fit better with the Freundlich isotherm and PSO models. The temperature studies show that the enthalpy was positive, indicating that the uptake process is endothermic. The Gibbs free energy values were all negative, indicating that adsorption between the adsorbents and the pollutants was favored. After four consecutive cycles, all the samples retained more than 60% of their uptake capability

The Adsorption of Copper, Lead Metal Ions, and Methylene Blue Dye from Aqueous Solution by Pure and Treated Fennel Seeds

This research work reports on pure and acid-treated fennel seed biomaterials for the removal of metal ions of copper Cu(II), lead Pb(II), and methylene blue (MB) dye from aqueous solution by batch adsorption. Pure fennel seeds were labelled as PFS; nitric and sulphuric acid-treated seeds were designated as NAFS and SAFS, respectively. The adsorbents were characterised by SEM, EDX, FTIR, XRD, and BET. The SEM images revealed that the surface of the adsorbents was porous. However, physicochemical characterization further revealed that BET surface area, pore size, and pore width increased for NAFS and SAFS compared to PFS. FTIR results revealed that the peaks for cellulose −COC and −OH decreased considerably for NAFS and SAFS; this indicated that cellulose was hydrolyzed during acid treatment. Adsorption data showed that all biomaterials had a higher affinity for MB dye more than Pb(II) and Cu(II) metal ions. The maximum adsorption capacities onto PFS were 6.834, 4.179, and 2.902 mg/g and onto NAFS are 15.28, 14.44, and 4.475 mg/g, while those onto SAFS are 19.81, 18.79 and 6.707 mg/g respective for MB dye, Pb(II), and Cu(II) ions. Postadsorption analysis revealed that adsorption of Pb(II) and Cu(II) was controlled mainly by the electrostatic attraction, while that of MB was synergistic of electrostatic attraction, π-π interaction, and hydrogen bond. It was found that the uptake processes of MB dye onto all adsorbents fitted Freundlich while both cations were described by Langmuir model. The thermodynamic parameters ΔHo and ΔGo indicated the endothermic nature and spontaneity of the processes, respectively

Magnetite Functionalized Nigella Sativa Seeds for the Uptake of Chromium(VI) and Lead(II) Ions from Synthetic Wastewater

The aim of the present study was to utilise pristine and magnetite-sucrose functionalized Nigella Sativa seeds as the adsorbents for the uptake of chromium(VI) and lead(II) ions from synthetic wastewater. Prestine Nigella Sativa seeds were labelled (PNS) and magnetite-sucrose functionalized Nigella Sativa seeds (FNS). The PNS and FNS composites were characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The FTIR analysis of both adsorbents revealed the presence of vibrations assigned to 1749 and 1739 cm-1 (-C=O) for ketonic group for both adsorbents. The amide (-NH) peak was observed at 1533 and 1527 cm-1 on FNS and PNS composites, respectively, whilst the carboxyl group (-COOH) were observed at 1408 cm-1 on both adsorbents. The XRD results of FNS and PNS composites showed a combination of spinel structure and y-Fe2O3 phase confirming the formation of iron oxide. The influence of operational conditions such as initial concentration, temperature, pH, and contact time was determined in batch adsorption system. The kinetic data of Cr(VI) and Pb(II) ions on both adsorbents was described by pseudo-first-order (PFO) model which suggested physisorption process. The sorption rate of Cr(VI) ions was quicker, it attained equilibrium in 20 min, and the rate of Pb(II) ions was slow in 90 min. Freundlich isotherm described the mechanism of Pb(II) ions adsorption on PNS and FNS composites. Langmuir best fitted the uptake of Cr(VI) ions on PNS and FNS. The results for both adsorbents showed that the removal uptake of Pb(II) ions increased when the initial concentration was increased; however, Cr(VI) uptake decreased when the initial concentration increased. The adsorption of Cr(VI) and Pb(II) ions on both adsorbents increased with temperature

Equilibrium, kinetic and thermodynamic studies of the uptake of copper by layered double hydroxide

This study explored the adsorption capacity of Mg/Al layered double hydroxide (LDH) for the removal of Cu2+ from aqueous solutions after synthesis and characterization. The effect of various operational parameters such as concentration, temperature and sorption time on the adsorption of Cu2+ was investigated using batch adsorption process experiments. It was found that layered double hydroxide (LDH) can be used as adsorbent for the removal of copper ions in aqueous solution containing low concentration of the metal salt. The average values of activation energy, isosteric heat of adsorption, entropy and enthalpy were 1.447, 12.9, 0.0137 and –4.8390 kJ/mol, respectively. This shows that the adsorption of the metal ion on the adsorbent follows a physical adsorption mechanism. The kinetic results conform to pseudo-second order model (R2 = 0.9959) and second order kinetic model (R2 = 0.9952) while the adsorption characteristics of the adsorbent followed both Langmuir and Freundlich adsorption isotherm models

Multi-application of fennel (Foeniculum vulgaris) seed composites for the adsorption and photo-degradation of methylene blue in water

This work reports on synthesis of fennel-based composites and their feasibility to remove and photo-degrade methylene blue dye from aqueous solution. Pristine fennel seeds (PFS) was impregnated with iron(III) oxide nanoparticles (Fe2O3 NP) and iron(III)-1,2,3,4-tetracarboxylic acid (Fe-TCA) to yield the composites fennel seeds-nanoparticles (FS-NP) and fennel seeds-tetracarboxylic acid (FS-TCA), respectively. Scanning electron microscope (SEM) images revealed that the surface of the adsorbents appeared to have a rough texture with cavities. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of −OH, −C=O, −COC, −COOH and −CO groups that could easily bind to the dye. The physicochemical characteristics such as cation exchange capacity (CEC) and Brunauer, Emmett and Teller (BET) surface area were enhanced after impregnation compared with PFS. The maximum adsorption capacity recorded at pH 10 for PFS was 13.2 mg/g while for FS-NP and FS-TCA was 32.8 and 42.9 mg/g, respectively This was ascribed to chemical interaction such as hydrogen bond, electrostatic attraction and π-π stacking. The isotherm and kinetic data were best described by Freundlich and pseudo-first order models. Thermodynamic parameters (∆Ho and ∆Go) showed spontaneity and endothermicity respectively. The positive values of ΔSo suggests that there was increased level of freedom at solid/liquid interface. PFS showed no activity for photocatalytic degradation properties while PF-NP and PF-TCA recorded 58.9 and 48.6% efficiencies, respectively. The data revealed that pseudo-second order described the photocatalytic processes of MB better than pseudo-first order kinetics

Additional file 1: Figure S1. of Novel PVA/MOF Nanofibres: Fabrication, Evaluation and Adsorption of Lead Ions from Aqueous Solution

The Langmuir isotherm plots, M/X against 1/C e. (a) PVA nanofibres, (b) PVA/Sb-TBC nanofibres, (c) PVA/La-TBC nanofibres and (d) PVA/Sr-TBC nanofibres. Figure S2. The Freundlich isotherm plots, InX/M against InC e. (a) PVA nanofibres, (b) PVA/Sb-TBC nanofibres, (c) PVA/La-TBC nanofibres and (d) PVA/Sr-TBC nanofibres. Figure S3. Plots of t/q t vs. t for adsorption of Pb2+ onto (a) PVA nanofibres, (b) PVA/Sb-TBC nanofibres, (c) PVA/La-TBC nanofibres and (d) PVA/Sr-TBC nanofibres. (DOCX 74 kb