Hydrogeochemical study of the clastic aquifer in the Umm Gudair field,Kuwait

The Kuwait Group aquifer is a major source of brackish groundwater in the State of Kuwait. The aquifer ranges in thickness from 150–400 m. In the Umm Gudair well field, the water has total dissolved solids ranging from 3,130 to 4,790 mg/l. According to the Sulin classification, all the Kuwait Group aquifer samples are characterized as Cl–Mg or Cl–Ca genetic water types. The chemical data indicate that the aquifer is generally in equilibrium with respect to calcite, dolomite and gypsum but undersaturated with respect to halite and polygorskite. The study has indicated that de-dolomitization is the major geochemical process controlling the chemistry of this aquifer, increasing the major complexes of sulphate and carbonate due to the dissolution of gypsum. The ratio of Cl/Na indicates that the Na⁺ ions have been taken from the Kuwait Group aquifer by reverse ion exchange.      

Engineering geology and future stability of the El Risco landslide,NW-Gran Canaria,Spain

A 200 m long segment of the only main road in NW-Gran Canaria is built on landslide deposits near the village of El Risco. Structural mapping and analysis of the topography reveal that the N–S striking landslide head scarp is the upper part of a sub-circular failure surface. The southern side of the landslide is delimited by a much older E–W strike-slip fault. Prior to pavement resurfacing in 2006, cracks in the road tarmac at the northern and southern sides of the landslide suggested ongoing creep movement. Slope stability analyses suggest that peak ground acceleration (PGA) was the most likely trigger for the initial failure.      

Hydrogeochemistry: an investigation tool to evaluate infiltration into large moving rock masses (case study of La Clapière and Séchilienne alpine landslides)

Isotopic and hydrogeochemical methods have been used to investigate groundwater movement inside the La Clapière and Séchilienne alpine landslides in southern France. The δ¹⁸O data were used to determine the infiltration altitudes of the two areas. The infiltration results indicate that the landslides are recharged from beyond the landslides' perimeters. Hydrogeochemical data on major ions were collected from springs. Numerical simulations of water–rock interactions were then undertaken. The major petrographic contrast between the limited sedimentary rocks and the more common micagneiss/micaschist results in a marked change between the measured and calculated groundwater contents. This contrast of 800 mg/l of SO₄ in the Triassic rocks but only 100 mg/l for the waters from the metamorphic strata at La Clapière is significant. Two different groundwaters have been identified in both landslides: (1) a perched shallow saturated zone near the slope summit; and (2) a deep saturated zone located at the foot of the slope. Chemical monitoring of spring waters in the two zones has allowed an assessment of the infiltration within the slope over time. There is a good correlation between the sulphate content of the perched waters and rate of slope movement, with a sulphate dilution peak corresponding to an acceleration in the movement of the landslip. However, there is no correlation between the chemistry of the deep aquifer and the speed of movement. It would appear therefore that the hydromechanical behaviour of the landslide depends on the vertical leakage from the perched aquifer down to the basal aquifer and the near-surface effects of the water movement. Electronic Publication     

Local labor markets in U.S.–Mexican border cities and the impact of maquiladora production

Shift-share decompositions of employment positions created over 1990–2002 at U.S.–Mexico border cities show that El Paso employment change has been overwhelmingly attributed to national forces, while local and national forces roughly match employment creation at Brownsville. With such fast growing U.S.–Mexico border area as background, we implement time series labor demand models to these cities (El Paso and Brownsville) and compare movements in Mexican maquiladora production against U.S. employment and wages. Cointegration methods confirm that local shocks are more important in Brownsville than in El Paso. Specifically, 10% increases in Juárez maquiladora production lead to increases of 1.21% in El Paso’s government employment and of 0.88% in overall employment. Similar increases in Matamoros lead to gains of 1.59% in Brownsville’s trade, transportation and utilities employment and of 1.41% in overall employment. These results support shift-share findings and are generally consistent with a more diversified industry-mix promoting higher employment creation.

Hydrogeochemistry along the flow path of a confined aquifer,Düzce plain,north western Turkey

The Düzce plain is formed of Quaternary deposits derived from the surrounding hills, which feed water to three aquifers. The groundwater flow direction in the first confined aquifer is towards Efteni Lake and the Büyük Melen River. Generally the waters have a low concentration of minerals adjacent to the hills from which they are recharged while the groundwater increases in mineral content as it passes through the confined aquifer. Although Ca²⁺, HCO₃ ⁻, total hardness, TDS-EC and Na⁺ values increase along the groundwater flow path, they remain within the limits specified by standards related to drinkability and industrial/agricultural usages.      

Upslope plume migration and implications for geological CO2 sequestration in deep,saline aquifers

Recent investigations regarding CO₂ sequestration in deep saline aquifers have focused on characterization of the injected plume, its migration within the aquifer over time, and possible leakage out of the aquifer. To study these complex flow systems, simplified models are sometimes used to describe both plume evolution and the amount of leakage. Simplifications may include an assumption of perfectly horizontal geological formations, negligible capillary pressure, and symmetry of the injection plume. In this study, we explicitly test the limits of the assumption of a horizontal aquifer through numerical simulation of typical injection scenarios in continental sedimentary basins. Our approach is to simulate injection of CO₂ into a confined saline aquifer for an extended period (we have used 15 years) and examine the effect of different degrees of slope, as well as other system parameters, on plume asymmetry using measures such as the location of the centroid of the CO₂ plume. Dimensional analysis of this system shows that the centroid migrates upslope in proportion with buoyancy, aquifer permeability, and slope, whereas increased porosity and CO₂ viscosity mitigate upslope migration of the centroid. The results of this study show that the effect of slope can be ignored for many aquifers likely to become CO₂ sequestration sites in North America. However, slope will be more important for higher permeability aquifers, such as the site used in the Sleipner sequestration project in the North Sea.     

Hydrogeological behaviour of an unsaturated waste rock pile: a case study at the Golden Sunlight Mine,Montana, USA

Parent geology, mining operation, construction practice and weathering processes govern the hydrogeological behaviour of waste rock piles. Variable heterogeneity in such earth structures requires site specific correlations. Based on field investigation and laboratory characterization, this paper developed a physical model for the unsaturated East Pile at the Golden Sunlight Mine in Montana, USA. Results indicate that the pile had interfingered dipping beds characterized by a matrix-supported structure in the fine grained layers and a clast-supported structure in the coarse grained layers. Waste rock with at least 45% sand retained water (ψ _a = 2–4 kPa, ψ _r = 20–40 kPa, k _sat = 3.5 × 10⁻³ cm/s, k _unsat = 2–3 orders of magnitude lower at 100 kPa) whereas materials with less than 45% sand drained rapidly (ψ _a < 1 kPa, ψ _r < 10 kPa, k _sat = 1 × 10⁻¹ cm/s, k _unsat > 6 orders of magnitude lower at 10 kPa).      

Circular tunnel in a semi-infinite aquifer

The steady gravity flow that is generated by a circular tunnel disturbing the hydrostatic state of a semi-infinite, homogeneous and isotropic aquifer is solved exactly. Many aspects of the flow are found in closed analytical forms such as the water inflow, pressure, leakage and recharging infiltration, which give a complete view of the aquifer in the drained steady state. It is found that the maximum value of the recharging infiltration does not exceed the hydraulic conductivity allowing stating a criteria for recharge intervention to ensure the stability of the aquifer. In addition to the main results, two aspects of the water inflow are treated. These are the necessary modifications that are to be considered in the case of an inclined water table and in the case of a lined tunnel that develops a constant internal pressure. It is also found that under an inclined water table a tunnel may cease to drain on its complete circumferential edge and a limiting condition is stated. Furthermore, the Muskat–Goodman and other water inflow predictions are compared to the exact gravity water inflow.     

Evaluation of the long-term durability of yellow travertine using accelerated weathering tests

The study investigated the long-term performance/durability of yellow travertine against various environmental processes using several accelerated weathering tests: wet–dry, freeze–thaw and salt crystallization. Prior to the accelerated weathering tests, the specimens were separated into two groups based on their porosities. The re-crystallization pressure of Na₂SO₄ salt was found to be the most destructive factor in the deterioration of the yellow travertine, with a maximum of 50% loss of integrity recorded. The recurrent cycles of wetting–drying and freezing–thawing caused relatively minor damage. After the experimental studies, the disintegration rate was statistically evaluated using the alteration index–alteration velocity and the decay function approaches. Both statistical models confirmed that the rate of disintegration was higher with salt re-crystallization pressures in the less porous yellow travertines compared with that resulting from wet–dry and freeze–thaw cycles.     

The effect of mineralogy,texture and mechanical properties of anti-skid and asphalt aggregates on urban dust,stages II and lll

Urban road dust is formed during wintertime when cars use studded tyres and when anti-skid aggregate particles are being crushed under tyres. A road simulator fitted with studded and friction winter tyres was used in three test series in order to investigate dust formation at tyre and pavement interface with various anti-skid materials and tyre types. The bedrock and glaciofluvial anti-skid aggregates tested had variable mechanical–physical and mineralogical properties. A special emphasis was put on the particle size distribution of anti-skid materials and on asphalt aggregate characteristics. The proportions of particles <10 μm from asphalt vs anti-skid aggregate was defined with SEM/EDX. The results of this study indicate that the particle size distribution is the most important property of anti-skid aggregates, and that the wearing process of asphalt pavement “is not homogenous” with friction and studded tyres, and with various anti-skid aggregates. The mechanical–mineralogical relationship between anti-skid and asphalt aggregates is one decisive factor in PM₁₀ formation and these properties affect the proportions of PM₁₀ (anti-skid vs asphalt aggregate). Friction tyres and anti-skid aggregates with lower average hardness compared to asphalt aggregate cannot wear harder minerals (e.g., quartz) of the pavement aggregate homogeneously.      

Seismic Performance Evaluation of SSMF with Simple Beam–Column Connections Under the Base Level

Simple beam–column connections are simpler and cheaper in construction than rigid beam–column connections, moreover, beams under the base level are only carrying gravity loads because of high rigidity of basement walls; therefore, seismic performance of special steel moment frame with basement wall is investigated in two cases in this paper. First, as the normal case of design, rigid beam–column connections are used under the base level, then all of the beam–column connections under the base level are changed to simple connections. The seismic performance of these two types is evaluated by FEMA P695 method. For predicting the collapse capacity of each archetype, adjusted collapse margin ratios are evaluated based on several nonlinear analyses and compared to acceptance criteria. Finally, seismic performance of these two kinds of structures is compared with each other. Despite the structural system’s change in height, seismic performance factors of special steel moment frames are considered for designing whole of the structures. Finally all two types of structures pass the acceptability checks and all the initial assumption are proved.     

Evaluating landslide deposits along the Tsurukawa fault zone, Japan, using magnetic susceptibility

 This paper describes the results of in-situ measurements of magnetic susceptibility in landslide deposits along the Tsurukawa fault zone in central Japan. The measured magnetic susceptibility values range from 0.4 to 9.6×10^–3 (in SI) and correspond to the proportions of the two component materials, weathered volcanic ash and faulted rock fragments. The study shows that landslide deposits along the Tsurukawa fault zone are composed of varying proportions of weathered volcanic ash. The results contrast with some general assumptions concerning landslides along fault zones in Japan. Received: 16 April 1999 · Accepted: 10 August 1999     

Migration of As, and H/He ages, in groundwater from West Bengal: Implications for monitoring

From 2002 to 2010 inclusive we monitored concentrations of arsenic (As) and major ions (Ca, Mg, Sr, Na, K, Fe, Mn, Cl, and SO₄) in groundwater from 14 domestic wells and three piezometer nests in a shallow aquifer (<60 m depth), and 3 wells in a deep aquifer (>70 m depth), in southern West Bengal, India. In the deep aquifer, concentrations of As did not change over time despite increases in the concentration of Fe in two wells. The shallow aquifer occurs in two sedimentological settings: palaeo-channel and palaeo-interfluve. At the top of the shallow aquifer of the palaeo-channel, decreases in all constituent concentrations with time, and an ³H/³He age of 1.4 years, proves that the aquifer is beginning to be flushed of pollutants. In As-polluted groundwater (>50 μg/L As) tapped from deeper grey sands of the shallow, palaeo-channel, aquifer, concentrations of As were mostly stable over time, but both increases and decreases occurred with time in response to downward migration of the chemically-stratified water column. In groundwater tapped from Pleistocene brown sands, the concentration of As remained either low and stable (<2 μg/L As), or increased at rates up to 34 μg/L per year. The increases were caused by the flow of As-rich groundwater either downward into brown sand at the base of palaeo-channels, or laterally into a confined, unpolluted, palaeo-interfluvial, aquifer of brown sand that lies regionally beneath a palaeosol.Under the present pumping regime, the prognosis for As-pollution in the shallow aquifer is complex. Wells in brown sand may become polluted over timescales of as little as 2 years, whilst some wells tapping As-polluted groundwater from grey sand will become fit for potable use (<50 μg/L) within a few decades. The evidence of flushing, and of declining As in some of the groundwater from palaeo-channels, which are conduits for recharge of the confined, As-free, palaeo-interfluve aquifer, and probably also the deeper aquifer, offers hopes that the spread of As-pollution will be limited.     

Hydrogeological and Hydrochemical Study of the Al-Shagaya Field-F, Kuwait

The study area, Al-Shagaya Field-F, is located at the south western part of Kuwait and includes twenty-seven production water wells, tapping the Kuwait Group aquifer. The main objectives of this study were to identify the aquifer type, determine its properties, outline the geological factors and the hydrochemical processes that control the quality of the groundwater of the study area, and to assess the water quality of the Kuwait Group aquifer. Analyses of aquifer test data revealed that the Kuwait Group aquifer acts as a semi-confined to confined aquifer, with a range of transmissivity values between 103 and 1,198 m²/day. The initial water level ranges from 70 to 146 m (M.S.L). The estimated quantity of groundwater entering the study area is about 12,950 m³/day. The chemical analyses show that the groundwater of the study area is a brackish water type, with total dissolved solids ranging from 3,586 to 5,334 mg/l. The aquifer salinity increases in the direction of regional flow towards the NE. The average pH value is 7.7 and the average electrical conductivity is 5,349 s/cm. Groundwater is highly concentrated with Na⁺, Ca²⁺, Cl^- and SO₄^2- and is depleted in HCO₃^- and Mg²⁺ ions. It is characterized by secondary salinity, where the alkaline earths exceed the alkalies and strong acids exceed weak acids. Three groundwater chemical types are recognized: NaCl, Na₂SO₄ and CaCl₂. The NaCl water type is the most abundant in the study area. The main genetic types of water are: MgCl₂ and Na₂SO₄. It is found that the groundwater is oversaturated with respect to aragonite and calcite and undersaturated with respect to anhydrite, gypsum, halite and dolomite. A comparison of the hydrochemical coefficients of Na⁺/Cl^-, SO₄^2-/Cl^- and Ca²⁺/Mg²⁺ in the study area with those of seawater and river water shows that the groundwater of the study area is a mixture of marine and continental water.     

Influence of CF<Subscript>3</Subscript>I and CBrF<Subscript>3</Subscript> on Methanol–Air and Methane–Air Premixed Flames

The suppression of CH₄ and CH₃OH premixed flames with CBrF₃ and CF₃I is examined, using computational techniques. By combining sensitivity analysis, reaction pathway analysis (based on carbon, hydrogen, bromine and iodine atom fluxes) and heat release estimation, we develop an explanation for the difference of suppression efficiencies which is qualitatively consistent with experimental cup burner data. The key reaction steps and channels responsible for the (apparent) higher inhibition efficiency of CF₃I compared to CBrF₃ in CH₃OH premixed flames are disclosed, by combining reaction pathway and heat release contribution analysis. The reaction of bromine atom dominates the decomposition channel for CH₃OH but plays a relatively minor role in the activation of CH₄, while I atom plays a minor role in CH₃OH or CH₄ activation. Accordingly, the rate of production of flame propagating radicals CH₂O and OH is higher in a CH₃OH–air–CBrF₃ system than in a CH₃OH–air–CF₃I system. The overall conclusion is that CBrF₃ contributes significantly to flame propagation for CH₃OH fuel reactions and consequently more CBrF₃ is required to extinguish a CH₃OH flame than CF₃I. Finally the explanation is validated by applying the reaction “switching-off” test.     

Photometric determination of ammonium nitrogen with the nessler reagent in drinking water after its chlorination

The photometric procedure for determining ammonium nitrogen in the drinking water containing inorganic chloramines has been refined. The preliminary reduction of chloramines at pH 4–9 was performed by using sodium sulfite at the fixed concentration in the interval 0.1–0.2 mM. Thereafter the mixture of solutions K₂HgI₄ (1–2 mM) and NaOH (80–100 mM) was added and the optical density of the resultant colored solution was measured at 440 and 600 nm.     

Collapse deformations of gypsum sands

Conclusion Gypsum silty sands with water-saturation under loading acquire collapsibility properties, whose magnitude depends on the water content, the dry density, the content of water-soluble salts, and the pressure. For sands containing highly soluble salts and gypsum, ε_Sl varies from 0.004 to 0.16, and for sands containing highly soluble salts amounting to 2.5–2.7%, ε_Sl=0.002–0.10. For w₀>0.1, gypsum silty sands are practically noncollapsible. VNIIOSP Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 16–18, May–June, 1991.     

Hydrochemical investigation on the clastic and carbonate aquifers of Kuwait

The field pH and contents of basic cations, anions, total alkalinity and other aqueous species have been measured in 89 groundwater samples collected from clastic sediments and carbonate aquifers of Kuwait. The mean molar ratio of Mg²⁺/Ca²⁺ is 0.63 and 0.48 for the carbonate and clastic aquifers respectively, indicating that the groundwater of the carbonate aquifer is in equilibrium with calcite and dolomite, the calculated mean PCO₂ of the clastic and carbonate aquifers suggesting a deep closed environment system. The clastic aquifer is supersaturated with respect to calcite, aragonite, quartz and chalcedony, undersaturated to near-saturated with dolomite and undersaturated with respect to gypsum, anhydrite and halite, whereas the carbonate aquifer is supersaturated with respect to dolomite, calcite, aragonite and quartz but undersaturated with anhydrite, gypsum and halite. The salinity of both aquifers increases in the direction of flow. The water types are dominantly NaCl and Na₂SO₄ in the clastic aquifer and Na₂SO₄, CaSO₄ and NaCl in the carbonate aquifer. Electronic Publication     

Optimization of dewatering schemes for a deep foundation pit near the Yangtze River,China

A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation(horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d). The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.     

Dynamic response of a long span suspension bridge and running safety of a train under wind action

A dynamic analysis model of a wind-train-bridge system is established. The wind excitations of the system are the buffeting and self-excited forces simulated in time domain using measured aerodynamic coefficients and flutter derivatives. The proposed formulations are then applied to a long rail-cum-road suspension bridge. The dynamic responses of the bridge and the train under wind action are analyzed. The results show that the lateral and rotational displacements of the bridge are dominated by wind, while the vertical by the gravity loading of the moving train. The running safeties of the train vehicles are much affected by wind. Under wind conditions of 30–40 m/s, the offload factors, derail factors and overturn factors of the train vehicles exceed the safety allowances, to which great attention should be paid. Translated from Engineering Mechanics, 2006, 23(2): 103–110 [译自: 工程力学]