Groundwater control for construction purposes: a case study from Kuwait

One of the major rehabilitation projects in Kuwait during the 1990s was improvement of the wastewater treatment plant at Jahra, a town 30 km north of Kuwait City. The project incorporates construction of a pumping station to collect the sewage via a network of sewer lines throughout the city. Groundwater occurs 4 m below the ground surface and construction specifications required lowering the groundwater table by 16 m to the foundation grade, 20 m below the ground surface. Open excavation with four stage well point system of dewatering was selected to ensure dry foundation conditions; but the system failed to lower the groundwater table down to the desired depth. Review of site investigation records and recalculation of field hydraulic conductivity resulted in design changes, augmenting the well point system with a number of deep wells and sumps to lower the water table down to the foundation grade. The paper discusses subsurface conditions and presents an analysis of the cause of failure of the well point system. The actual hydraulic conductivity proved to be several folds higher than the calculated one that was determined using Hazen’s formula. It was found that use of Hazen’s formula led to serious underestimation of field hydraulic conductivity. It is advised not to use such formulas without thorough investigation and proper interpretation of borehole data.     

Uniform investigation of hydraulic fracturing propagation regimes in the plane strain model

The hydraulic fracturing propagation regimes in the plane strain model are uniformly investigated using a numerical method based on the finite element method. The regimes range from toughness‐dominated cases to viscosity‐dominated cases, covering zero leak‐off situations and small leak‐off situations. Unlike the asymptotic solutions, the numerical method is independent of the energy dissipation regimes and fluid storage regimes. The numerical method pays no special attention to the fracture tip, and it simulates fracture tip behaviors by increasing the number of functions in a natural and uniform manner. The numerical method is verified by comparing its results with the asymptotic solutions. The effect of the model sizes on the numerical method is discussed along with the robustness of the numerical method. Copyright © 2014 John Wiley & Sons, Ltd.     

Spatial analysis of groundwater quality for drinking purpose in Sirjan Plain,Iran by fuzzy logic in GIS

At present,due to shortage of water resources,especially in arid and semiarid areas of the world such as Iran,exploitation of groundwater resources with suitable quality for drinking is of high importance.In this regard,contamination of groundwater resources to heavy metals,especially arsenic,is one of the most important hazards that threaten human health.The present study aims to develop an approach for presenting the groundwater quality of Sirjan city in Kerman Province,based on modern tools of spatial zoning in the GIS environment and a fuzzy approach of evaluating drinking water in accordance with the standards of world health organization(WHO).For this purpose,qualitative data related to 22 exploitation wells recorded during 2002 to 2017 were used.In addition,fuzzy aggregate maps were prepared in two scenarios by neglecting and considering arsenic presence in groundwater resources.The results showed a decrease in groundwater quality over time.More specifically,neglecting the presence of arsenic,in 2002,all drinking wells in the area were located in an excellent zone,while in 2017 a number of operation wells were located in the good and medium zone.Also,the final map,considering the presence of arsenic as a limiting factor of drinking water,indicated that parts of the southern regions of the plain would be the best place to dig wells for drinking water.Therefore,the use of new methods can contribute significantly to the usage of groundwater aquifers and provide a good view of the aquifer water quality.     

The aqueous oxidation of complex sulfide concentrates in hydrochloric acid

Complex sulfides containing sphalerite, galena, chalcopyrite, and small amounts of silver in a matrix of pyrite can be decomposed at 120°C and oxygen pressure of 1000 kPa in 1–2 N HCl for 90 min to yield > 97% of the zinc and > 95% of the copper in solution while about 83% of the lead remains in the residue as PbCl₂ and PbSO₄ and 85% of the silver, together with most of the pyrite. The recovery of elemental sulfur is nearly 100% with respect to ZnS, PbS, and CuFeS₂. Leaching in HCl is faster than in H₂SO₄ at the same acid normality, and the process is diffusion-controlled (strongly dependant on agitation speed and having an activation energy of 3.6 kcal/mole). Lead jarosite, Pb_0.5Fe₃ (SO₄)₂?(OH)₆, is mainly formed when H₂SO₄ is used as a leaching agent.     

Drinking water treatment residuals as an amendment to alkaline soils: Effects on the growth of corn and phosphorus extractability

Drinking water treatment residuals (alum) are waste products of water purification that have potential for environmental remediation as a soil amendment and a potential plant growth medium. In this study, the influence of added Drinking water treatment residuals on the extractability and availability of phosphorus to plants; determination of the agronomic rate of alum to different agricultural soils and evaluation of the alum as ameliorating material for soil conditions and plant growth were investigated. In all studied soils, increasing drinking water treatment residuals rate up to 30 g/kg significantly increased dry matter yield. Application of 10, 20 and 30 g/kg alum significantly increased plant P concentrations in the plant materials (shoots and roots) taken from clay, sandy and calcareous soils. Further increase in alum application rate has resulted in negative significant impact on plants P concentration, especially in clay and calcareous soils, but in sandy soils the increase in phosphorusconcentration extended to 40 g/kg alum rate. Application of alum at rates up to 30 g/kg significantly increased available phosphorus concentrations of the three studied soils. However, application of alum at a rate of 40 g/kg to clay and calcareous soils significantly decreased available phosphorus concentrations. Combined analyses of all soils and alum rates studied clearly indicated significant relationship between available phosphorus concentration and phosphorus uptake (r = 0.87, P < 0.001). Based on our experiment results, the rate of 30 g/kg is considered the best application rate of alum because of its positive effects on plant dry matter. Our study clearly demonstrates that alum has potential as a soil amendment to increase plant growth; however, more research is needed to determine beneficial and / or detrimental aspects of this practice under field conditions.     

Geotechnical and mineralogical characteristics of marl deposits in Jordan

Marls and marly limestone deposits cover most of Northern Jordan, where Amman City and its suburbs are located. These deposits serve as foundations for most buildings and roads as well as fill material for structural back filling, especially road bases and sub-bases. The present study aims at investigating the geotechnical characteristics and mineral composition of the marl units of these deposits through field investigations and laboratory testing. Using X-ray diffraction technique along with chemical analysis, representative samples of marl horizons were tested for mineral composition, and for a set of index and geotechnical properties including: specific gravity, grain size, Atterberg limits, Proctor compaction and shear strength properties. The test results show a positive linear relationship as expected between the clay content and both liquid and plastic limits. The tests results also show an inverse linear relationship between the clay content and the maximum dry density in both standard and modified compaction. This is attributed to the adsorption of water by the clay minerals. The relationship is more prominent in the case of modified compaction test. The results also indicate a similar relationship for the angle of internal friction. No clear correlation between cohesion and clay content was apparent.