New developments in the Integrated Stress Determination Method and their application to rock stress data at the Äspö HRL, Sweden

The Integrated Stress Determination Method (ISDM) is a powerful tool for estimating the regional stress tensor from in-situ measurements of local stress tensors using a wide variety of stress measuring techniques. This study presents new developments of the ISDM: The stress field may be described with up to 12 model parameters; and is applicable to data from CSIR- and CSIRO HI-type of overcoring devices, hydraulic fracturing, hydraulic tests of pre-existing fractures (HTPF), as well as to combined data sets. Furthermore, in combined data sets, the hydraulic fracturing and/or HTPF data may be used to constrain the average elastic parameters, Young's modulus and Poisson's ratio.The new ISDM developments were applied to the extensive and recently re-analysed rock stress data at the Äspö Hard Rock Laboratory. The results reveal a good fit of the re-analysed data. Overall, the re-analysis indicates that the stress field at Äspö HRL is relatively well constrained and consistent with depth. The NE-2 Fracture Zone influences the stresses, and dividing the regional stress field into a NW and a SE stress domain. When the hydraulic fracturing data were used to constrain the average elastic parameters, Young's modulus, E, and Poisson's ratio, ν, quite similar results were obtained ( and ν=0.33) compared with results from biaxial tests of overcore samples ( and ν=0.26).     

Evaluation of measurement-related uncertainties in the analysis of overcoring rock stress data from Äspö HRL, Sweden: a case study

A re-evaluation of overcoring results from the Borre Probe and the CSIRO HI cell was carried out at the Äspö HRL. The re-analysis revealed a number of measurement-related uncertainties for the two cells, e.g. bonding, temperature effects and identification of elastic parameters. These uncertainties were corrected and the re-analyzed strains were then used to determine the in situ stress field using standard least-squares technique. The results indicate lower stress magnitudes compared to the original interpretations and the results are in good agreement with existing hydraulic fracturing data as well as with theoretical vertical stress. Overall, the re-analysis indicates that the stress field at Äspö HRL is well constrained and relatively consistent with depth.     

Äspö Hard Rock Laboratory-Research, development and demonstration for deep disposal of spent nuclear fuel

The Äspö Hard Rock Laboratory (Äspö HRL) provides an important scientific and technical basis for the programme o f implementation and operation of a future deep repository for spent nuclear fuel in Sweden. A major milestone has now been reached with the completion of the pre-investigation and construction phases. The comprehensive research conducted has permitted valuable development and verification of site characterization methods applied from the ground surface, boreholes and underground excavations. The present database of the crystalline rock at the Äspö area is one of the most comprehensive databases in the world, containing data from a large number of investigation methods from the surface down to 1700 m below ground level.Site characterization in conjunction with construction work at Äspö has basically confirmed the pre-construction models. The work at Äsp has shown that such pre-construction models can be obtained for the studied key issues through the application of “standard methodology of good quality” for measurements, data analyses, modelling and evaluation The site characterization at Aspö has been a realistic “adress-rehearsal” that will be invaluable for planning and executing surface and underground site characterization for the deep repository for spent fuel in Sweden.     

Seismic characterization of fracturing at the Äspö Hard Rock Laboratory, Sweden, from the kilometer scale to the meter scale

In 1986, the Swedish Nuclear Fuel and Waste Management Co. (SKB) decided to build an underground research laboratory, the Äspö Hard Rock Laboratory (HRL). The Äspö HRL offers the possibility to test and demonstrate a full site investigation sequence. As part of this work, various seismic techniques were tested and demonstrated, from the kilometer to the meter scale. The preliminary investigation stage comprised surface reflection profiling and VSP. The VSP measurements, though limited to one borehole, played an important role in defining the site model. Shallow reflection surveys in crystalline rock have been judged as basically feasible, but further development is required to reduce costs. During the construction of the laboratory, the objective of the seismic investigations was to check and refine the site model. Within the zone of excavation disturbance experiment project, seismic tomographic analyses were made for P- and S- wave velocity and attenuation, at 5–15 m scale. Crosshole reflection imaging was also performed. The tracer retention understanding experiments project also included transmission and reflection tomography but on a 100–300 m scale. For the experiments where both transmission and reflection measurements were processed, the seismic surveys also produced information regarding the intrinsic mechanical properties of the rock besides inferring a geometrical model of the rock structures.     

Comparative study on organic constituents in polluted and unpolluted inland aquatic environments—II: Features of fatty acids for polluted and unpolluted waters

Fatty acids were analyzed for polluted river waters from the Tokyo area and unpolluted river, brook, reservoir and pond waters from the Ogasawara (Bonin) Islands to elucidate their features for polluted and unpolluted waters. Fatty acids ranging from the carbon chain length of C₈-C₃₄ including unsaturated and branched acids were found with the great predominance of even-carbon numbers and lower molecular weight ranges (C₁₃–C₁₉) in the water samples from the Tokyo area and Ogasawara Islands. It was thus confirmed that no marked changes in fatty acid composition between polluted and unpolluted waters are absent. However, the total contents of the acids (average, 270 ± 120 μg 1⁻¹ at 90% confidence limits) as well as the FAC (fatty acids as carbon)/TOC (total organic carbon, 2.6 ± 0.93%) and FAC/EOC (extractable organic carbon with ethyl acetate, 16 ± 6.7%) of river water samples from the Tokyo area were considerably higher than those of the waters from the Ogasawara Islands (58 ± 29 μg 1⁻¹, 0.79 ± 0.48% and 2.1 ± 0.51%, respectively). These higher values for the Tokyo area should be due to sewage.A filtering method showed that most of fatty acids (>95%) was present in particulate fractions. In addition, the content of free fatty acids was fairly lower than that of combined fatty acids. Further, unsaturated fatty acids were detected only in combined forms both in particulate and dissolved fractions. They are considered to be present as esters in polluted and unpolluted waters.     

Detoxification of seawater used for gas scrubbing in the steel industry

Cyanide ion present in seawater after scrubbing blast furnace and coke ovens gases can be removed by sedimentation of hexacyanoferrate complexes followed by oxidation of residual cyanide with Caro's acid. Zinc ion is removed at the same time by adsorption on the hexacyanoferrate/hydrous ferric oxide precipitate.Sulphide is precipitated as ferrous sulphide, then oxidised by atmospheric oxygen. At 25°C and using an Fe/CN ratio of 1·00, initial concentrations of 50 mg l⁻¹ of CN⁻ and 10 mg l⁻¹ of Zn²⁺ in seawater are reduced to 5–7 mg l⁻¹ and 0·1 mg l⁻¹. Subsequent treatment with H₂SO₅/CN = 1·2 reduces the [CN⁻] to 0·1 mg l⁻¹.Treatment of a combined blast furnace/coke ovens effluent ([CN⁻] = 24 mgl⁻¹, [Zn²⁺] = 4·0 mgl⁻¹) with Fe/CN = 1·5 reduced [CN⁻] to 0·2 mg l⁻¹ and [Zn²⁺] to <0·1 mgl⁻¹. Subsequent treatment with H₂SO₅/CN = 2·0 reduced [CN⁻] to 0·2 mg l⁻¹. The process operates best in the pH range 7–9 and so is not affected by the buffer characteristics of seawater.     

pH adjustment in anaerobic digestion

In the pH range 6·0–7·5, the pH in anaerobic processes is controlled by the interaction of the carbonic system and a net strong base. The acid-base state of a digestor can be monitored by only measuring pH and CO₂ partial pressure. Shock doses of strong bases and carbonates causes temporary undersaturated CO₂ conditions and excessively high pH. Bicarbonate dosing leaves the CO₂ solubility equilibrium unchanged. In the absence of a CaCO₃ precipitation inhibiting agent. CaCO₃ solubility limits the pH, and Ca(OH)₂ dosing is unable to raise the pH significantly. Orthophosphates inhibit CaCO₃ precipitation. With [PO₄] > 1·0 × 10⁻³mole·1⁻¹. CaCO₃. precipitation is partially inhibited. Ca(OH)₂ dosing being approximately 45 per cent effective for doses up to 15000 mg 1⁻¹ as CaCO₃. At [PO₄] < 1·0 × 10⁻³moles·1⁻¹ orthophosphates eventually precipitate out during Ca(OH)₂ dosing, thus removing the inhibition mechanism: pH is then limited by the CaCO₃ solubility. Most wastes contain [PO₄] > 2·0 × 10⁻³moles·1⁻¹ making pH adjustment with Ca(OH)₂ possible to a pH of about 7·2 although the dosages will be very high. The pH changes in a process following dosing can be predicted by the graphical representation of the carbonic and net strong base systems.     

The Fe3O4-formation by the ‘Ferrite Process’: Oxidation of the reactive Fe(OH)2 suspension induced by sucrose

A mechanism of the formation of small particles of iron oxide in the wastewater treatment system ‘Ferrite Process’ is described. Small particles consisting of the Fe₃O₄−γ-Fe₂O₃ solid solution having slightly higher content of γ-Fe₂O₃ were obtained by the aerial oxidation of Fe(OH)₂ suspension in the presence of a weak dispersing reagent, sucrose, at pH 9.0. The increase of γ-Fe₂O₃ content is caused by a further oxidation of the Fe₃O₄ particles in the course of the reaction. The further oxidation was accelerated below 1000 Å of the particle size. When SO²⁻₄ ion coexisted with sucrose in the reaction medium, the further oxidation was reduced and the treatment of the wastewater was improved. At a temperature interval of 40°–65°C, the formation of α-FeOOH was completely inhibited by a small amount of sucrose and only Fe₃O₄ was obtained.     

Effects of confining pressure and temperature on mixed-mode (I–II) fracture toughness of a limestone rock

Studying fracture toughness behavior at elevated temperatures and confining pressures is valuable for a number of practical situations such as hydraulic fracturing used to enhance oil and gas recovery from a reservoir, and the disposal or safe storage of radioactive waste in underground cavities. Mixed-mode (I–II) fracture toughness under simulated reservoir conditions of high temperature and confining pressure was studied using straight notched Brazilian disk (SNBD) specimens under diametrical compression. Rock samples were collected from a limestone formation outcropping in the Central Province of Saudi Arabia. Tests were conducted under an effective confining pressure (σ₃) of up to 28 MPa (4000 psi), and a temperature of up to 116°C. The results show a substantial increase in fracture toughness under confining pressure. The pure mode-I fracture toughness (K_IC) increased by a factor of about 3.7 under a σ₃ of 28 MPa compared to that under ambient conditions. The variation of K_IC was found to be linearly proportional to σ₃. The pure mode-II fracture toughness (K_IIC) increased by a factor of 2.4 upon increasing σ₃ to 28 MPa. On the other hand, K_IC at 116°C was only 25% more than that at ambient conditions. Some ductile behavior was displayed by the rock samples at a high temperature and confining pressure.     

Water inflow into excavations in fractured rock—a three-dimensional hydro-mechanical numerical study

Water inflow into rock excavations is a complex three-dimensional (3-D) problem influenced by a number of processes, such as stress–permeability coupling, groundwater degassing, bubble trapping, temperature effects or turbulence effects. Results from inflow experiments in the field show that when going from a slim borehole to a larger diameter hole, the inflow into the larger hole is often less than predicted; the explanation for this is not yet fully known. A single process or a combination of processes may be responsible for reduction of inflow into the larger diameter holes. In this study, a coupled hydro-mechanical, 3-D discrete element analysis has been conducted with the objective of gaining a better understanding of the influence of effective stress redistribution induced by excavation and related inflow into a cylindrical opening in a fractured rock mass. Matrix and fracture data from the Äspö Hard Rock Laboratory in Sweden have been used as input for the model. Several aspects related to fracture inflow into underground excavations have been studied (hydro-mechanical coupling, uncertainty in rock mass characteristics, relevance of non-linear fracture behaviour and influence of the excavation diameter). Results of this study show that stress–permeability coupling is one of the causes for the usually less than expected inflow into larger diameter holes.     

Cadmium in the Rhône river

The distribution of cadmium in the Rhône river was studied using differential pulse anodic stripping voltametry with a static mercury drop electrode. For 11 potentially contaminated river stations, the Cd in true solution averaged 39 ± 23 ng kg⁻¹, adsorbed on suspended matter was 19 ± 22 ng kg⁻¹ (liquid phase) and suspended matter content was 2.4 ± 1.5 mg kg⁻¹ (solid phase), equivalent to 40 ± 24, 22 ± 24 and 38 ± 31%, respectively, of the total carried under these conditions. For sediments the mean Cd content was 0.9 ± 0.6 mg kg⁻¹. The water values are low by world standards, even though sampling was biased towards sites potentially contaminated. This could be partially due to the unusual water pH of 7.8–8.5.     

Persistent organic pollutants and mercury in dead and dying glaucous gulls (Larus hyperboreus) at Bjørnøya (Svalbard)

Dead and dying glaucous gulls (Larus hyperboreus) were collected on Bjørnøya in the Barents Sea in 2003, 2004 and 2005. Autopsies of the seabirds only explained a clear cause of death for three (14%) of the 21 birds. A total of 71% of the birds were emaciated. Liver and brain samples were analysed for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ether (PBDEs), hexabromocyclododecanes (HBCDs) and mercury (Hg). High levels of ΣOCPs, ΣPCBs, ΣPBDEs and α-HBCD were found in liver and brain. Compared to the dead and dying glaucous gulls found 1989, the congeners' composition tended to change toward more persistent compounds in the 2003–2005 samples. The brain levels of OCPs and PCBs did not differ between 1989 and 2003–2005, while the liver levels were significantly lower. The brain/liver ratio for PCB and PBDE significantly decreased with halogenations of the molecule, indicating a clear discrimination of highly halogenated PCBs and PBDEs entering the brain. There was further a clear negative correlation between contaminant concentrations and body condition. The brain levels were not as high as earlier published lethal levels of p,p′-DDE or PCB. However, more recent studies reported a range of sub-lethal OCP- and PCB-related effects in randomly sampled glaucous gulls. An additional elevation of pollutants due to emaciation may increase the stress of the already affected birds. The high brain levels of OCP, PCB and PBDE of present study might therefore have contributed to the death of weakened individuals of glaucous gull.     

Acute toxicity and behavioral responses of coho salmon (Oncorhynchus kisutch) and shiner perch (Cymatogaster aggregata) to chlorine in heated sea-water

The acute toxicity and behavioral response to chlorinated and heated sea-water was determined for coho salmon smolts and 1–3 month old shiner perch. LC₅₀'s were determined for 7.5, 15, 30 and 60 min exposure times; 13, 16 and 20°C (Δt = 0, 3, 7°C) temperatures and total residual oxidant (TRO) concentrations ranging from 0.077 to 1.035 mg l⁻¹. The mean 60 min LC₅₀ for shiner perch was significantly reduced (P ≤ 0.05) from 308 μg l⁻¹ TRO at 13°C to 230 μg l⁻¹ TRO at 20°C. The 60 min LC₅₀ for coho salmon decreased from 208 μg l⁻¹ TRO at 13°C to 130 μg l⁻¹ at 20°C. The LC₅₀'s for coho salmon in chlorinated sea-water averaged 55% of those for shiner perch. The relationship between TRO concentration, exposure time, and percent survival in chlorinated sea-water at 13°C is presented for both species.A significant (P ≤ 0.01) avoidance threshold for coho salmon occurred at 2 μg l⁻¹ TRO and was reinforced with increasing temperature. A significant (P ≤ 0.01) avoidance threshold for shiner perch occurred at 175 μg l⁻¹ TRO, while a significant preference (P ≤ 0.05 or 0.01) response at 16°C and 20°C occurred at 10, 25, 50 and 100 μg l⁻¹ TRO. The ecological implications of the toxicity tests and the behavioral responses are discussed.     

Prediction of the temperature dependence of electrical conductance for river waters

The application of mixed electrolyte theories to the prediction of the electrical conductivity of 14 river-water samples covering a range of ionic strength and temperatures between 5 and 25°C has been evaluated using a new program, CONCAL. Both the Fuoss-Onsager, FO, and Lee-Wheaton, LW, theories produce better agreement between the measured and predicted conductivities for the majority of the samples than the simple product equation. For river waters with a charge imbalance of less than 10%, the prediction of the simple product, FO and LW equations are on average within 11.1, 3.4 and 3.7%, respectively, of the experimental values over the range of temperatures considered. The major error in the predictions of the FO and LW models is associated with the reliability of the chemical analytical data input to CONCAL. The accuracy of the predictions of the models is also discussed in terms of the magnitude and sign of the charge imbalance calculated for each of the samples from the analytical data.Five equations that are available to apply a temperature compensation to conductivity data to predict values at 25°C have been tested over a temperature range of 5–25°C. The best performance is achieved using the modified Walden's product.The relationship between the measured conductivity at 25°C, κ(25), and ionic strength, I, has been calculated to be I = 0.0021 + 0.0148 κ(25) with I in mmol dm⁻³. This observation is discussed by reference to the predicted relationship for simple binary mixtures of NaCl and Ca(HCO₃)₂.     

Temperature and oxygen-nitrogen gas ratios affect fish survival in air-supersaturated water

Juvenile steelhead trout and juvenile chinook, coho and sockeye salmon were tested at different temperatures (8°, 9°, 10°, 12°, 15°, 18° and 20°C) at the same concentration of air-supersaturated water. Supersaturated water concentrations in different tests were 115, 116, 117, 118 and 120% saturation. Increased temperatures caused a significant (P< 0.005) increase in steelhead mortality, a significant increase (P < 0.025) in chinook deaths, but no significant effect on coho or sockeye mortality. Regression model data for steelhead indicate that a 10°C increase in temperature will decrease the time to 50% death by a factor of 2.7, e.g. from 190h at 8°C to 70h at 18°C, when tested at the same total dissolved gas pressure. Effects of different oxygen-nitrogen gas ratios on fish mortality at the same total dissolved gas pressure in supersaturated water were demonstrated with juvenile steelhead trout. Mortality was rapid (time to 50% death in 1–6 h) at 140, 135 and 130% saturation, with fish dying more rapidly as the ratio of oxygen-nitrogen decreased (decrease in O₂, increase in N₂) Mortality patterns were similar at 125%; time to 50% death occurred in 5–20 h, with more rapid deaths occurring as oxygen (O₂/N₂ ratio) was decreased.     

The extent of reversibility of polychlorinated biphenyl adsorption

The extent of reversibility of PCB bonding to sediments has been characterized in studies on the partitioning behavior of a hexachlorobiphenyl isomer. Linear non-singular isotherms have been observed for the adsorption and desorption of 2.4.5.2′,4′,5′ hexachlorobiphenyl (HCBP) to 1100 ppm sediment suspensions. Partition coefficients, π(1 kg−1), for desorption from lake sediments (Saginaw Bay. Lake Huron. Michigan) are substantially greater (π_d 20.000–35.000) than those obtained for adsorption (π₄ 9000–14,000). HCBP was found to be more weakly adsorbed to montmorillonite (π_a − 3000, π_d 9000) and kaolinite (π_a 1000, π_d 3000) clay samples than to the natural sediment samples. Desorption results (π_d) for Saginaw Bay sediments were quite similar to π values (15,000–35.000) calculated from field measurements of aqueous and particulate PCB concentrations. For Saginaw Bay sediments and clay minerals partitioning appeared to be correlated both to sediment surface area and to sediment organic content. A regression analysis using both of these variables explained 90% of the observed variations. HCBP adsorption at 40 C (π_a 14,000) was significantly greater than at 1° C (π_a 6500) resulting in a calculated enthalpy of adsorption of +3.3 kcal mol⁻¹. Non-singular isotherm behavior was not found to be readily attributable to microbiological, kinetic or experimental effects. Evidence from consecutive desorption studies suggests that while HCBP adsorption may ultimately be reversible. release from sediments appeared to involve desorption along two distinct isotherms. These results have been interpreted in terms of possible similarities between the sorption properties observed in the distilled water systems of the present study and PCB bonding processes in natural water systems.     

Sealing narrow fractures with a Newtonian fluid: Model prediction for grouting verified by field study

The increased demand for efficiency when sealing tunnels by grouting has led to a need to seal narrow fractures. The more conductive fractures are sealed by cement-based grouts, however, the limitations in penetrability make these grouts less useful for low permeable rock. Silica sol is an inorganic grouting material with high potential to penetrate narrow fractures. Its two components, silica sol and a salt solution, are both considered harmless. The salt solution (CaCl₂) is the accelerator. The field study investigates whether the penetration of a Newtonian fluid (silica sol) can be predicted and verified using numerical models, based on grout properties and hydraulic tests. The field study was conducted, in 2004, on a pillar located at 0/670 m at Äspö Hard Rock Laboratory (Äspö HRL).One, well characterised and grouted fracture was selected to be grouted with silica sol and analysed. To check the conditions of the fracture hydraulic tests were used, namely, constant head tests with single packer and they were directly followed by pressure logging in the recovery phase. The transmissivity, T, was estimated from the recovery phase of single-hole injection tests using Jacob’s method. Further, the hydraulic aperture was estimated using the well-known cubic law. For the design of the grouting parameters, gel time, injection pressure, and injection time were determined from a one-dimensional model with the penetration length set to 2.2 m. The grout was mixed with optical brightener to make the grout easier to see in the six cores drilled. The grouted borehole was over-cored, and specimens from the grouted fracture were analysed by microscope. Hydraulic tests were made after grouting to estimate the sealing efficiency of the rock mass. The penetration was also estimated in a two-dimensional model to verify length for selected grouting times.Visual observation and the hydraulic properties of two boreholes show that the penetration length is at least 1.0 m. For the numerical model in 2D, a good agreement is found. The final penetration is underestimated by the model underestimates. The hydraulic tests show that at least two boreholes were sealed with silica sol within the predicted penetration radius. The sealing efficiency was approximately 70%.     

Acute toxicity of unbleached kraft mill effluent (UKME) to the opossum shrimp, Neomysis americana smith

Ninety-six hour TL₅₀ values of unbleached kraft mill effluent (UKME) for Neomysis americana were found to range from concentrations of 3.29–6.85 per cent at 26–28°C and 3.90–7.30 per cent at 16–18°C. Differences between batches of effluent proved insignificant in experiments at each temperature regime. Furthermore, UKME did not lose its toxicity when stored for 5–7 days at 4°C. A concentration of 20 per cent effluent killed 100 per cent of the organisms in 8 of the 12 bioassays. Slope functions and confidence limits of TL₅₀ were calculated. Toxicity did not appear to be correlated with the Biochemical Oxygen Demand (BOD) of individual batches of raw effluent.     

Stress–strain–electrical resistance effects and associated state equations for uniaxial rock compression

This paper reports stress–strain–electric resistance experiments for diabase, limestone and marble containing NaCl solution during the whole process of uniaxial compression. We obtained the complete testing data for the stress–strain curve and the associated electrical resistance–strain curve. The change caused by internal cracking of the rock causes the corresponding variation of rock electrical resistance. There is a minimum value for all the electric resistance–strain curves, corresponding to the cracking stress σ_c or the initial cohesion c_i. Based on the experimental results and stochastic property analyses of the rock fracture variation, we put forward a group of state equations for rock in sections to express the characteristics of rock during the whole process of uniaxial compression. The three variables, stress, strain and electrical resistance, together with data-fitted parameters, α₁,α₂ and β, are contained in the equations. The equations are used to express the inelastic response which intensifies with the propagation of cracking.     

Determination of chloride in water with a HgS/Hg2Cl2 electrode

The application of a new type of solid state chloride ion sensitive electrode, based on HgS/Hg₂Cl₂ has been investigated for manual and automated measurements of chloride in natural, industrial and waste water. The electrode displays Nerstian response for the range 0·05–3·500 ppm of chloride and can be used for concentrations down to 0·05 ppm (5 × 10⁻⁷m). Achieved values of standard deviation, recovery and comparative tests from a variety of water samples are highly satisfactory. Inherent simplicity and sensitivity together with obtained results demonstrate the usefulness of the proposed method in routine analyses.