Moisture Transport Through Sprayed Concrete Tunnel Linings

Waterproofing of permanent sprayed concrete tunnel linings with sprayed membranes in a continuous sandwich structure has been attempted since 2000 and has seen increased use in some countries. The main function of a sprayed membrane from a waterproofing perspective is to provide crack bridging and hence prevent flow of liquid water into the tunnel through cracks and imperfections in the concrete material. However, moisture can migrate through the concrete and EVA-based membrane materials by capillary and vapor diffusion mechanisms. These moisture transport mechanisms can have an influence on the degree of saturation, and may influence the pore pressures in the concrete material as well as risk of freeze–thaw damage of the concrete and membrane. The paper describes a detailed study of moisture transport material parameters, moisture condition in tunnel linings and climatic conditions tunnels in hard rock in Norway. These data have been included in a hygrothermal simulation model in the software WUFI for moisture transport to substantiate moisture transport and long-term effects on saturation of the concrete and membrane material. The findings suggest that EVA-based membranes exhibit significant water absorption and vapor transport properties although they are impermeable to liquid water flow. State-of-the-art sprayed concrete material applied with the wet mix method exhibits very low hydraulic conductivities, lower than 10^?14 m/s, thus saturated conductive water flow is a very unlikely dominant transport mechanism. Moisture transport through the lining structure by capillary flow and vapor diffusion are calculated to approximately 3 cm³/m² per day for lining thicknesses in the range of 25–35 cm and seasonal Nordic climate variations. The calculated moisture contents in the tunnel linings from the hygrothermal simulations are largely in agreement with the measured moisture contents in the tunnel linings. The findings also indicate that the concrete material exhibits a reduction of saturation on the immediate inside of the membrane. Near the location of the waterproofing membrane on either side, the concrete material exhibits degrees of capillary saturation between 85 and 95 %. Moisture content in the membrane is found to be consistently in the range of 12–17 % by weight, corresponding to a degree of saturation of 30–35 %. Possible effects of such moisture contents are lower risk of freezing degradation, higher tensile bonding strengths at the membrane interfaces, and a reduced risk of pore pressure in the concrete material.     

Lead in the North Sea and the north east Atlantic Ocean

Lead has been determined in 105 water samples from the north east Atlantic and from the North Sea. Rigorous precautions were applied to avoid contamination during sampling and analysis.Two different analytical methods were used: ASV and AAS. Determinations with ASV were carried out on board, directly after sampling. After two months storage, acidified samples were analysed by AAS after freon dithiocarbamate extraction and nitric acid back extraction. Particulate lead was determined by AAS after an acid digestion.The profiles of lead concentration versus depth show around 160 pM at the surface and around 20 pM at the bottom, both in the Atlantic and in the Norwegian Sea. The shapes of the profiles are different, however, depending on the hydrography of the area sampled. The profiles from the north east Atlantic coincide with a recently published profile from the north west Atlantic. Moreover, these profiles have lead concentrations about a factor of three higher than those in the Pacific.Considering the high lead input to the North Sea, the lead concentrations found there are remarkably low, probably because of scavenging effects in estuaries leading to a short residence time in the water column. The dominant lead input in offshore regions is from the atmosphere. The highest lead levels are found in the northern North Sea, around 300 pM in surface water.In the Atlantic, particulate lead is a minor part of the total lead whereas in the North Sea the particulate fraction is larger, up to 40%.     

Conodont Biostratigraphy of the Middle Cambrian through Lowermost Ordovician in Hunan, South China

Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Cambrian paraconodonts have proved useful for stratigraphic subdivision and correlation. Thirteen conodont zones are proposed in the Middle Cambrian through lowermost Ordovician. The correlation between these zones and those of North China, western U. S.A., western Newfoundland, Canada, and Iran is discussed. In ascending order, these 13 zones are as follows: The Gapparodus bisulcatus-Westergaardodina brevidens Zone, Shandongodus priscus-Hunanognathus tricuspidatus Zone, Westergaardodina quadrata Zone, Westergaardodina matsushitai-W. grandidens Zone, Westergaardodina lui-W. am Zone, Westergaardodina cf. calix-Prooneotodus rotundatus Zone, Proconodontus tenuiserratus Zone, Proconodontus Zone, Eoconodontus Zone, Cordylodus proavus Zone, Cordylodus intermedius Zone, Cordylodus lindstromi Zone, and     

The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part I: geology

The Kristineberg volcanic-hosted massive sulphide (VMS) deposit, located in the westernmost part of the Palaeoproterozoic Skellefte district, northern Sweden, has yielded 22.4 Mt of ore, grading 1.0% Cu, 3.64% Zn, 0.24% Pb, 1.24 g/t Au, 36 g/t Ag and 25.9% S, since the mine opened in 1941, and is the largest past and present VMS mine in the district. The deposit is hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the Skellefte Group, which forms the lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits. The Kristineberg deposit is situated lower in the Skellefte Group than most other deposits. It comprises three main ore zones: (1) massive sulphide lenses of the A-ore (historically the main ore), having a strike length of about 1,400 m, and extending from surface to about 1,200 m depth, (2) massive sulphide lenses of the B-ore, situated 100–150 m structurally above the A-ore, and extending from surface to about 1,000 m depth, (3) the recently discovered Einarsson zone, which occurs in the vicinity of the B-ore at about 1,000 m depth, and consists mainly of Au–Cu-rich veins and heavily disseminated sulphides, together with massive sulphide lenses. On a regional scale the Kristineberg deposit is flanked by two major felsic rock units: massive rhyolite A to the south and the mine porphyry to the north. The three main ore zones lie within a schistose, deformed and metamorphosed package of hydrothermally altered, dominantly felsic volcanic rocks, which contain varying proportions of quartz, muscovite, chlorite, phlogopite, pyrite, cordierite and andalusite. The strongest alteration occurs within 5–10 m of the ore lenses. Stratigraphic younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration, and tectonic folding and shearing. In the vicinity of the ore lenses, hydrothermal alteration has produced both Mg-rich assemblages (Mg-chlorite, cordierite, phlogopite and locally talc) and quartz–muscovite–andalusite assemblages. Both types of assemblages commonly contain disseminated pyrite. The sequence of volcanic and ore-forming events at Kristineberg is poorly constrained, as the ages of the massive rhyolite and mine porphyry are unknown, and younging indicators are absent apart from local metal zoning in the A-ores. Regional structural trends, however, suggest that the sequence youngs to the south. The A- and B-ores are interpreted to have formed as synvolcanic sulphide sheets that were originally separated by some 100–150 m of volcanic rocks. The Einarsson zone, which is developed close to the 1,000 m level, is interpreted to have resulted in part from folding and dislocation of the B-ore sulphide sheet, and in part from remobilisation of sulphides into small Zn-rich massive sulphide lenses and late Au–Cu-rich veins. However, the abundance of strongly altered, andalusite-bearing rocks in the Einarsson zone, coupled with the occurrence of Au–Cu-rich disseminated sulphides in these rocks, suggests that some of the mineralisation was synvolcanic and formed from strongly acidic hydrothermal fluids. Editorial handling: P. Weihed