Validation of Hyperbolic Model by the Results of Triaxial and Direct Shear Tests of Municipal Solid Waste

The increasing demand of engineering landfills requires that designers propose a framework for landfill design, construction, repair and maintenance. As municipal solid waste (MSW) is a major part of a landfill, the analysis should consider MSW mechanical behavior using a constitutive model. To investigate this, 18 direct shear (DS) and triaxial (TX) tests were conducted on MSW samples with different fiber contents. Different shearing mechanisms lead to understand effects of fibers on stress–strain response. Based on obtained results the hyperbolic model Duncan and Chang (J Soil Mech Found Div 96(5):1629–1653, 1970) has been employed to simulate the TX results indicating the ability of the model to predict stress–strain behavior of MSW. This model could also be employed to the DS test results with some assumptions. The model can capture DS stress–strain response well whereas for TX tests the predictions were just enough. The experimental results and two sets of proposed MSW parameters of hyperbolic model have been compared and discussed.     

Ground improvement and foundation practice for Persian Gulf Bridge (causeway); Bandar Abbas Harbor–Qeshm Island

National Persian Gulf Bridge is a communication route between Bandar Abbas port and Qeshm Island located on the southern border of Iran. This causeway has important role for facilitating the transportation system between Qeshm Island and mainland, i.e., Bandar Abbas. Based on geotechnical and geological site investigation records, the bridge is located on the deposits with high seismic possibility and subsequently significant dynamic loading. Therefore, adequate substructure design of this bridge as an offshore project is realized as a major requirement. The geophysical and geotechnical investigations have been done to obtain the subsoil characteristics of the project site. For this purpose, 18 boreholes have been performed to do in situ tests and extract samples for laboratory testings. Data synthesis indicates that in the zones close to Qeshm Island and in the deeper parts of the sea, the strata is made of clay with loose sands and some depths, with silty sands. Hence, instability issues, including the low bearing capacity and the high differential settlement, are significant aspects in analysis and design of substructure for this project. Also, in this paper, the subsoil conditions have been studied from in situ tests such as standard penetration test (SPT) and cone penetration test (CPT) results in order to achieve an appropriate foundation system. Moreover, the necessity of the ground improvement of the site has been investigated to propose an efficient technique for safe and secure construction. Based on the analysis and methods screened, the vibro-replacement method is considered as a suitable and efficient ground improvement method for this project.     

Investigation of fiber effect on the mechanical behavior of municipal solid waste by different shearing test apparatuses

This paper embraces the results of a study on the mechanical behavior of municipal solid waste, MSW, and the effect of shearing mechanism on its mechanical response. Totally, 9 drained direct shear tests and 9 drained triaxial tests have been performed on fresh MSW samples with fiber contents of 0, 6 and 12%. Each apparatus represents a different shearing mechanism. The composition and compaction condition for MSW samples in each fiber content, employed in both shearing test devices, were the same. In triaxial tests, since the shear plane was cutting through the fibers, with increase in the fiber content, an increasing trend of strength was observed; on the contrary, this trend was decreasing in direct shear tests because fiber alignment was parallel to the shear plane. Test results show that the effect of fibers in the triaxial tests depends on the level of imposed axial strain on the samples as well as the confining stress. Based on the findings of this paper, hardening behavior of MSW is attributed to reinforcement action of fibers and particle compressibility.     

Vulnerability assessment of urban groundwater resources to nitrate: the case study of Mashhad,Iran

Groundwater vulnerability assessment of urban areas is a challenging task in the fast trend of urbanization around the globe. This study introduces a new approach for modifying well-known parameters of common vulnerability indexes to adjust them for urban areas. The approach is independent of a specific weighting system. The aquifer of Mashhad city, contaminated by domestic wastewater, is selected as a case in this study. In order to evaluate the aquifer vulnerability due to anthropogenic activities, at first, parameters of depth to groundwater, recharge, land use, and soil are modified based on their basic concepts and their influences on contamination attenuation. Then, the modified parameters are used simultaneously in several index methods to investigate the capability of the modified parameters to increase correlation coefficient of all employed index methods with the measured nitrate concentration. Accuracy of the modified methods is evaluated by Spearman nonparametric correlation. It is shown that considering the wastewater discharge into recharge parameter leads to an increase of 20% in correlation coefficient. Also, level difference technique shows that more than 70% of the vulnerable areas are predicted correctly in all utilized methods. The accurate prediction in all employed methods indicates that these modifications are independent of the type of index method. Moreover, sensitivity analysis reveals that the recharge and the land use are both the most significant parameters for evaluating the vulnerability.     

How Viable will the Agricultural economy be in the New State of Palestine?

A key objective of the Israeli occupation of the West Bank and Gaza Strip in Palestine has been to render the economy of these regions dependent on the Israeli economy and thus hamper their economic development. Large areas of land have been confiscated or expropriated by the Israeli authorities to establish Jewish settlements. Other severe measures imposed include control of irrigation water and obstacles for the Arab agricultural and industrial sector in the Occupied Territories aimed at preventing Arab competition with Israeli products.Palestinian agriculturalists have met this challenge and have worked to achieve higher production levels in agriculture. Nonetheless, economic development there was blocked, and many agriculturalists sought employment inside Israel. The Intifada since December 1987 has aimed at encouraging Arab economic independence and intensification of efforts to meet national requirements of greater self-sufficiency in subsistence crops and stimulation of agriculture-related industries. The Intifada is thus functioning as a stimulus to development and economic viability.     

Correlation between geological units and mineralized zones using fractal modeling in Zarshuran gold deposit (NW Iran)

In this study, the relation between ore grade and geological characteristic has been studied as a principle and also important conceptual in Zarshuran gold deposit in NW Iran. The main subject in this study was identifying a correlation among the ore grade populations and rock types which could be used in other steps of local estimation in the deposit concentration–number (C–N) fractal model and logratio matrix. The C–N log–log plot reveals six geochemical zones defined by Au?<?0.02 ppm as non-mineralized zone and Au?>?0.02 ppm as mineralized zones. According to geological logging and field geology inspection, black gauge, jasperoid, fault gauge and breccia, and carbonaceous rocks are considered as main rock types which contain major Au mineralized zones. The correlation between geological and fractal modeling by logratio matrix shows that there is a good correlation between geological assumed host rocks and C–N fractal modeling. Black gauge rock type with 93.48 % of overall accuracy shows a significant correlation with supergene zone of fractal model, and jasperoid with 92.5 % and carbonaceous rock type with 52.90 % have a decent correlation with highly and lowly mineralized zone of fractal model relatively. Black gauge, jasperoid, and fault gauge and breccia have an approximately near cooperation in this zone for mineralization.     

Stress studies in the Central Alborz by inversion of earthquake focal mechanism data

The Alborz is one of the most important seismotectonic provinces in Iran. Furthermore, emplacement of Tehran as a mega city in southern part of the Alborz intensifies the seismic vulnerability in this area. In this study, the focal mechanism data from teleseismic and local seismic networks are used for stress tensor inversion. The earthquake focal mechanisms in the Central Alborz are divided into several groups with respect to their location. Two different stress tensor inversions, linear and nonlinear, are used for obtaining the principal stress orientations. The results show spatial variations in tectonic stress field, consistent with fault orientations and faulting mechanisms. The maximum compressional stress directions obtained in this study are confirmed by fast S-wave polarization axes reported by a previous shear wave splitting study. The maximum horizontal stress directions are also compared with GPS strain rates. The results indicate a partitioning of deformation in the area due to regional stresses along preexisting faults.     

Assessing the footprint and volume of oil deposited in deep-sea sediments following the Deepwater Horizon oil spill

The lateral and vertical extents of Macondo oil in deep-sea sediments resulting from the 2010 Deepwater Horizon oil spill were determined using chemical forensics and geostatistical kriging of data from 2397 sediment samples from 875 cores collected in 2010/2011 and 2014. The total mass of Macondo-derived hopane on the seafloor in 2010/2011 was conservatively estimated between 2.00 and 2.26 metric tons, derived from 219,000 to 247,000 barrels of oil; or 6.9 to 7.7% of the 3.19 million barrels spilled. Macondo-derived hopane was deposited over 1030 to 1910 km² of the seafloor, mostly (> 97%) in surface (0–1 cm) and near-surface (1–3 cm) sediments, which is consistent with short-term oil deposition. Although Macondo oil was still present in surface sediments in 2014, the total mass of Macondo-derived hopane was significantly lower (~ 80 to 90%) than in 2010/2011, affirming an acute impact from the spill and not long-term deposition from natural seeps.     

3D numerical simulation of flow field around twin piles

In this study to identify the flow pattern and local scour mechanism around pile groups, the flow field was simulated using FLOW-3D software. A pair of pile on a flat-bed channel with side by side and tandem arrangements was investigated. To establish Navier–Stokes equations, the RNGk-ε turbulence model was used and the results were verified using experimental data. In case of FLOW-3D capability, it was found that the software was able to properly simulate the expected interaction between the pile groups. The results of flow field simulation showed that Reynolds number and the pile spacing are the most influential variables in forming vortices. The flow around tandem pile and the downward flow around wake vortices were more intense and complicate in comparison with side by side arrangements and single pile.     

Petrography, mineralogy and geochemistry of the Zarshuran Carlin-like gold deposit, northwest Iran

Gold mineralisation at Zarshuran, northwestern Iran, is hosted by Precambrian carbonate and black shale formations which have been intruded by a weakly mineralised granitoid. Granitoid intrusion fractured the sedimentary rocks, thereby improving conditions for hydrothermal alteration and mineralisation. Silicification is the principal hydrothermal alteration along with decalcification and argillisation. Three hydrothermal sulphide mineral assemblages have been identified: an early assemblage of pyrrhotite, pyrite and chalcopyrite; then widespread base metal sulphides, lead-sulphosalts and zoned euhedral arsenical pyrite; and finally late network arsenical pyrite, massive and colloform arsenical pyrite, colloform sphalerite, coloradoite, and arsenic–antimony–mercury–thallium-bearing sulphides including orpiment, realgar, stibnite, getchellite, cinnabar, lorandite and a Tl-mineral, probably christite. Most of the gold at Zarshuran is detectable only by quantitative electron microprobe and bulk chemical analyses. Gold occurs mainly in arsenical pyrite and colloform sphalerite as solid solution or as nanometre-sized native gold. Metallic gold is found rarely in hydrothermal quartz and orpiment. Pure microcrystalline orpiment, carbon-rich shale, silicified shale with visible pyrite grains and arsenic minerals contain the highest concentrations of gold. In many ways Zarshuran appears to be similar to the classic Carlin-type sediment-hosted disseminated gold deposits. However, relatively high concentrations of tellurium at Zarshuran, evidenced by the occurrence of coloradoite (HgTe), imply a greater magmatic contribution in the mineralising hydrothermal solutions than is typical of Carlin-type gold deposits. Received: 13 May 1999 / Accepted: 2 February 2000