| 1. |
- Andrén, Anna, 1970-
(författare)
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Freezing Temperature Flows in Railway Tunnels and its Consequence on the Rock Supporting Structure, the Rock and the Reinforcing Elements
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Water in the surrounding rock mass flows into the tunnel via naturally occurring joints and via cracks caused by the blasting used to excavate the tunnel. The most common method in Sweden to reduce or prevent leakage problems are first and foremost the use of grouting. However, experience shows that despite extensive pre-grouting and supplementary post-grouting, it is difficult to seal the rock mass so that drips and moisture are completely eliminated. Although the water itself causes degradation of the tunnel, the degradation process increases dramatically when the water is exposed to freezing temperatures. Water expands during freezing and due to water migration, which occurs in rock in a similar way as in soil, the ice causes frost shattering of the interface between rock and shotcrete and also to the shotcrete and the rock itself. This can damage the main load-bearing system. The ice formation itself is a maintenance problem, as the tunnels must be kept clear of icicles, ice pillars and ice layers in the tracks or on the roads. One of the main tasks in this research project has been to identify which problems cause the most maintenance work and where and when these problems occur in the tunnel.During the field observations carried out as part of this doctoral study, many problems with water and ice were discovered, all of which contribute to increased maintenance. Many ice problems are directly linked to frost insulated drain mats. Leakage and ice formations occur at the edge of the drains, in mat splices and when brackets for cable racks, handrails or other installations puncture a drain and it has not been properly sealed. In drains covered with shotcrete, frost shattering and cracking in the shotcrete can be a problem. Frost cycles in the tunnel cause the water to freeze and thaw alternately, allowing more water to reach the freezing area due to water migration, resulting in frost shattering of the rock and the shotcrete. If not anchored with bolts, the reinforcing effect and the stability of shotcrete in a tunnel is dependent on the adhesion to the rock surface. It is, therefore, important to take all available measures to ensure good adhesion. Poor adhesion in itself is not a degradation problem, but a void can form in the interface between rock and shotcrete as a result of poor adhesion. If this void is filled with water that cannot drain away, ice pressure can occur in the layer between rock and shotcrete. The ice pressure can cause cracking and degradation of the shotcrete if the pressure exceeds the tensile strength of the adjacent material. In some of the reported fall-outs of rock and shotcrete, an ice layer was discovered between the rock surface and the edges of the remaining shotcrete layer. Therefore, frost shattering is a likely cause of the fall-outs. Many frost cycles combined with water leakage can cause frost shattering. The field measurements conducted as a part of the doctoral study have shown that most frost cycles do not occur closest to the tunnel entrances, but instead about 100 to 200 m into the longer tunnels. The results from the laboratory tests performed as part of the doctoral study showed that the adhesive strength between rock and shotcrete decreased significantly when the test panels were subjected to freeze-thaw cycles. Furthermore, more of the micro seismic events (AE - acoustic emission monitoring) occurred in the test panels that had access to water during freezing. Therefor, maintenance personnel and inspectors should pay particular attention to water leakage in sections that have an increased number of frost cycles, to avoid future problems with frost shattering of rock or shotcrete. In the longer tunnels studied in this work, a greater number of ice formations occurred in the inner parts of the tunnel, than close to the entrances. The rock mass emits heat, which heats up the cold outside air that enters the tunnel. Due to the heat transfer from the rock mass, leakage points located further along the tunnels can remain unfrozen. A leak that is closer to the tunnel entrances in the longer tunnels or a leak in a shorter tunnel are exposed to higher freezing rates. The entire rock mass freezes and the leak ‘freezes dry’, that is, ice forms in the water-bearing fracture, preventing further water leakage.Where and when ice problems occur along a tunnel depends on many factors. Besides the obvious water leakage, the length of frost penetration into the tunnel is the main reason for where and when ice problems occur. The predominant cause of frost penetration in most of the tunnels is the thermally induced airflow. In the longer tunnels, the inclination of the tunnel affects frost penetration the most. The field observations showed that there was a difference in where and when leakage points appear during the year and also in terms of variation in the amount of leakage water. There was also a variation over different years. The conclusions of the field observations are that it is difficult to estimate where the insulated drain mats should be located along a tunnel. Based on experience from this survey, the location of the drains should be determined only after several inspections and especially after a winter period, when the main problems with ice formation occur. Previous perception regarding ice problems have been that ice formation only occurs at the tunnel entrances and in the outer parts of the tunnel. A proposed measure has, therefore, been to cover the first 300 m from each entrance with frost insulated drains to try to completely eliminate the ice problems. However, this is not an effective solution to the problem. The insulation not only prevents the cold from reaching the leakage point, but it also prevents the rock mass from emitting heat that warms up the cold outside air entering the tunnel. Thus, the frost can penetrate further into the tunnel and the problems with ice formation are only moved further into the tunnel. As the amount and location of the frost insulation affects frost penetration, the dimensioning of insulation must, therefore, be carried out in several iterations, where each new distribution of insulation along the tunnel is calculated separately.For the tunnels that have been studied as part of this doctoral study, the following has emerged. The central and southern parts of Sweden have shorter cooling periods and the tunnels are exposed to many temperature fluctuations around 0°C during the winter. The frost does not have time to penetrate as far here as in the tunnels in the northern parts of Sweden. Therefore, more ice problems arise around the entrances of the tunnels in the southern parts of Sweden than for those in the northern parts. For northern parts of Sweden, the problem of growing ice formations in sections near the tunnel entrance usually occurs only during the autumn and spring, but not in winter. The field observations showed that the problems with ice growth and temperature fluctuations around 0°C occur further along the longer tunnels in the northern parts of Sweden. This is because the temperature of the tunnel air is higher due to heat transfer from the rock mass. For shorter tunnels that adopt the same temperatures as the outside air, ice formations can occur along the entire length of the tunnel in the sections that have leakage problems. The Swedish Transport Administration’s regulations are currently being updated and the observations and measurements carried out in this doctoral work are now being used to evaluate new requirements regarding frost penetration in tunnels.
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| 2. |
- Brunström, Mattias, et al.
(författare)
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Association of education and feedback on hypertension management with risk for stroke and cardiovascular disease
- 2022
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Ingår i: Blood Pressure. - : Informa UK Limited. - 0803-7051 .- 1651-1999. ; 31:1, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Education and feedback on hypertension management has been associated with improved hypertension control. This study aimed to assess the effectiveness of such interventions to reduce the risk of stroke and cardiovascular events. Materials and Methods Individuals >= 18 years with a blood pressure (BP) recording in Vasterbotten or Sodermanland County during the study period 2001 to 2009 were included in 108 serial cohort studies, each with 24 months follow-up. The primary outcome was risk of first-ever stroke in Vasterbotten County (intervention) compared with Sodermanland County (control). Secondary outcomes were first-ever major adverse cardiovascular event (MACE), myocardial infarction, and heart failure, as well as all-cause and cardiovascular mortality. All outcomes were analysed using time-to-event data included in a Cox proportional hazards model adjusted for age, sex, hypertension, diabetes, coronary artery disease, atrial fibrillation, systolic BP at inclusion, marital status, and disposable income. Results A total of 121 365 individuals (mean [SD] age at inclusion 61.7 [16.3] years; 59.9% female; mean inclusion BP 142.3/82.6 mmHg) in the intervention county were compared to 131 924 individuals (63.6 [16.2] years; 61.2% female; 144.1/81.1 mmHg) in the control county. A first-ever stroke occurred in 2 823 (2.3%) individuals in the intervention county, and 3 584 (2.7%) individuals in the control county (adjusted hazard ratio 0.96, 95% CI 0.90 to 1.03). No differences were observed for MACE, myocardial infarction or heart failure, whereas all-cause mortality (HR 0.91, 95% CI 0.87 to 0.95) and cardiovascular mortality (HR 0.91, 95% CI 0.85 to 0.98) were lower in the intervention county. Conclusions This study does not support an association between education and feedback on hypertension management to primary care physicians and the risk for stroke or cardiovascular outcomes. The observed differences for mortality outcomes should be interpreted with caution.
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| 3. |
- Brunström, Mattias, et al.
(författare)
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Association of physician education and feedback on hypertension management with patient blood pressure and hypertension control
- 2020
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Ingår i: JAMA Network Open. - : American Medical Association (AMA). - 2574-3805. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Elevated systolic blood pressure (SBP) is the most important risk factor for premature death worldwide. However, hypertension detection and control rates continue to be suboptimal.To assess the association of education and feedback to primary care physicians with population-level SBP and hypertension control rates.This pooled series of 108 population-based cohort studies involving 283 079 patients used data from primary care centers in 2 counties (Västerbotten and Södermanland) in Sweden from 2001 to 2009. Participants were individuals aged 18 years or older who had their blood pressure (BP) measured and recorded in either county during the intervention period. All analyses were performed in February 2019.An intervention comprising education and feedback for primary care physicians in Västerbotten County (intervention group) compared with usual care in Södermanland County (control group).Difference in mean SBP levels between counties and likelihood of hypertension control in the intervention county compared with the control county during 24 months of follow-up.A total of 136 541 unique individuals (mean [SD] age at inclusion, 64.6 [16.1] years; 57.0% female; mean inclusion BP, 142/82 mm Hg) in the intervention county were compared with 146 538 individuals (mean [SD] age at inclusion, 65.7 [15.9] years; 58.3% female; mean inclusion BP, 144/80 mm Hg) in the control county. Mean SBP difference between counties during follow-up, adjusted for inclusion BP and other covariates, was 1.1 mm Hg (95% CI, 1.0-1.1 mm Hg). Hypertension control improved by 8.4 percentage points, and control was achieved in 37.8% of participants in the intervention county compared with 29.4% in the control county (adjusted odds ratio, 1.30; 95% CI, 1.29-1.31). Differences between counties increased during the intervention period and were more pronounced in participants with higher SBP at inclusion. Results were consistent across all subgroups.This study suggests that SBP levels and hypertension control rates in a county population may be improved by educational approaches directed at physicians and other health care workers. Similar strategies may be adopted to reinforce the implementation of clinical practice guidelines for hypertension management.
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| 4. |
- Andrén, Anna, et al.
(författare)
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Degradation of the Reinforcing Effect of Shotcrete : Freeze-Thaw Tests on Shotcrete-Rock Panels
- 2020
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Ingår i: The Electronic journal of geotechnical engineering. - : Mete Öner. - 1089-3032 .- 1089-3032. ; 25:1, s. 1-30
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Tidskriftsartikel (refereegranskat)abstract
- In rock tunnels in regions with colder climates, the load-bearing structure, including the rock and the reinforcing elements, is exposed to repeated destructive freezing and thawing cycles during the winter. If water accumulates in cracks or in the interface between rock and shotcrete, frost shattering may occur. If there is adequate adhesion between the rock and shotcrete, degradation of the shotcrete as a reinforcement element due to frost shattering should not present a problem. However, if adhesion is poor, a small void will form between the rock and the shotcrete where water can accumulate. If the water in these voids is subjected to freeze-thaw cycles, ice will develop, thus exerting pressure on the interface and causing the shotcrete to crack and degrade. In tunnel sections with complex water conditions, for example, relatively water-bearing open joints and weak zones, the adhesion of the shotcrete and its stability and reinforcing effect may be strongly affected when exposed to freezing temperatures. This article describes a laboratory study that comprised freeze-thaw tests on shotcreterock panels with the objective of studying how water migration affects the growth of ice and the ice pressure in the shotcrete-rock interface to better understand the degradation of the reinforcing effect of shotcrete
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| 5. |
- Andrén, Anna, et al.
(författare)
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Evaluation of a laboratory model test using field measurements of frost penetration in railway tunnels
- 2022
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Ingår i: Cold Regions Science and Technology. - : Elsevier. - 0165-232X .- 1872-7441. ; 204
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive grouting efforts to prevent water from leaking into tunnels, water seepages remain. When exposed to freezing temperatures, ice formations occur. During the winter, the Swedish Transport Administration's railway tunnels are affected by major problems caused by ice, such as icicles from roof and walls, ice loads on installations, ice-covered tracks and roads, etc. To ensure safety and prevent traffic disruptions, many tunnels require extensive maintenance. Improved knowledge about frost penetration in tunnels is required to reduce maintenance of the tunnels. Frost insulated drain mats are often used at leakage spots to prevent ice formation along the tunnels. To find out which parts of a tunnel are exposed to freezing temperatures, the University of Gävle and the Royal Institute of Technology in Stockholm conducted a laboratory model test on behalf of the Swedish National Rail Administration (now the Swedish Transport Administration). The laboratory model test aimed to find a method to determine the expected temperature conditions along a tunnel to decide which parts of the tunnel require frost insulation to protect the drainage system from freezing and prevent ice formation. To evaluate the laboratory model test, the Swedish Transport Administration in collaboration with Luleå University of Technology have performed field surveys in two Swedish railway tunnels. The field measurements involved monitoring temperatures in air, rock surfaces and rock mass, as well as measuring wind direction, wind and air velocity and air pressure. The measurements in the tunnels show that the frost penetrates further into the tunnels than was expected from the laboratory model test, which was based on a completely uninsulated tunnel. Frost insulated drains do not only prevent the cold air from reaching the rock mass, but also prevent the rock from emitting geothermal heat that warms up the cold tunnel air. Consequently, the frost penetrates further into the tunnel than it would do if the heat from the rock mass was allowed to warm up the outside air on its way into the tunnel. The number of frost insulated drains and how much of the tunnel walls and roof are covered thereby affect the length of the frost penetration.
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| 6. |
- Andrén, Anna, et al.
(författare)
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Field Observations of Water and Ice Problems in Railway Tunnels from a Maintenance Perspective
- 2023
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scientific Press International Limited. - 1792-9040 .- 1792-9660. ; 13:1, s. 11-54
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Tidskriftsartikel (refereegranskat)abstract
- During the winter season, ice causes major problems in many Swedish railway tunnels. Ice, rock and shotcrete in the roof and on the walls may come loose and fall down, installations and cables can break due to ice loads and the tracks can become covered with ice. To maintain safety and prevent traffic disturbances, many tunnels require frequent maintenance. The removal of ice, loose rock and shotcrete is expensive and potentially risky work for the maintenance workers. To reduce maintenance costs, it is important to improve our knowledge of frost penetration inside tunnels and investigate the effect of ice pressure and frost shattering on loadbearing constructions. The aim of this investigation was to gather information about the problems caused by water leakage and its effect on the degradation of a rock tunnel when subjected to freezing temperatures. There are many factors that determine whether frost or ice formations will appear in tunnels. To collect information on ice formation problems, field observations were undertaken in five of Sweden’s railway tunnels between autumn 2004 and summer 2005. For one of the tunnels, follow-up observations also took place in March during the years 2005, 2006 and 2007.
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| 7. |
- Andrén, Anna, et al.
(författare)
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Temperature Flows in Railway Tunnels : Field Measurements of Frost Penetration
- 2020
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scientific Press International Limited. - 1792-9040 .- 1792-9660. ; 10:5, s. 161-194
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Tidskriftsartikel (refereegranskat)abstract
- Even though extensive pre-grouting is carried out during the construction of tunnels, certain leakages and drips remain. These remaining leakages are remedied by a combination of post-injection and drainage measures with, for example, frost insulated drain mats, whose function is to prevent the cold tunnel air from reaching a leakage spot and causing water to freeze. Despite these measures, some water may still enter the tunnels and cause problems during winter with ice formations and frost shattering. Icicles, ice pillars and ice-covered roads and railway tracks require constant maintenance. If ice occurs in the fracture network close to the tunnel contour or in the interface between the rock and shotcrete, it can cause degradation of the load-bearing capacity of the tunnel and fall-outs of both materials. In tunnel sections with water leakage problems it is common to protect the load-bearing structure from freezing with insulated drainage systems. To determine where along the tunnel efforts must be made to prevent ice formation, the temperature conditions of tunnels must be investigated. This article presents parts of the results from field measurements in two Swedish railway tunnels. The measurements involves monitoring of air and rock temperatures, air pressure and air velocity.
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| 8. |
- Batra, Gorav, et al.
(författare)
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Association between heart failure quality of care and mortality : a population-based cohort study using nationwide registries
- 2022
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Ingår i: European Journal of Heart Failure. - : John Wiley & Sons. - 1388-9842 .- 1879-0844. ; 24:11, s. 2066-2077
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: To evaluate the quality of heart failure (HF) care using the European Society of Cardiology (ESC) quality indicators (QIs) for HF and to assess whether better quality of care is associated with improved outcomes.METHODS AND RESULTS: We performed a nationwide cohort study using the Swedish HF registry, consisting of patients with any type of HF at their first outpatient visit or hospitalization. Independent participant data for quality of HF care was evaluated against the ESC QIs for HF, and association with mortality estimated using multivariable Cox regression. In total, 43 704 patients from 80 hospitals across Sweden enrolled between 2013-2019 were included, with median follow-up 23.6 months. Of the 16 QIs for HF, 13 could be measured and 5 were inversely associated with all-cause mortality during follow-up. Higher attainment (≥50% vs. <50% attainment) of the composite opportunity-based score (combination of QIs into a single score) for patients with reduced ejection fraction was associated with lower all-cause mortality (adjusted hazard ratio 0.81; 95% confidence interval 0.72-0.91). Attainment of the composite score was less in the outpatient than inpatient setting (adjusted odds ratio 0.85; 95% confidence interval 0.72-0.99). Quality of care varied across hospitals, with assessment of health-related quality of life being the indicator with the widest variation in attainment (interquartile range 61.7%).CONCLUSION: Quality of HF care may be measured using the ESC HF QIs. In Sweden, attainment of HF care evaluated using the QIs demonstrated between and within hospital variation, and many QIs were inversely associated with mortality.
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| 9. |
- Becher, Peter Moritz, et al.
(författare)
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Eligibility for sotagliflozin in a real-world heart failure population based on the SOLOIST-WHF trial enrolment criteria: data from the Swedish heart failure registry
- 2023
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Ingår i: European Heart Journal - Cardiovascular Pharmacotherapy. - : OXFORD UNIV PRESS. - 2055-6837 .- 2055-6845. ; 9:4, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- Aims The SOLOIST-WHF trial demonstrated efficacy of sotagliflozin in patients with type 2 diabetes mellitus (T2DM) and recent worsening heart failure (HF) regardless of ejection fraction (EF). Selection criteria in trials may limit their generalizability. Therefore, we aimed to investigate eligibility for sotagliflozin based on the SOLOIST-WHF criteria in a real-world HF population. Methods and results SOLOIST-WHF criteria were applied to patients stabilized after HF hospitalization in the Swedish HF Registry according to (i) literal scenario (all inclusion/exclusion criteria) or (ii) pragmatic scenario (only criteria likely to influence treatment decisions). Of 5453 inpatients with T2DM and recent worsening HF, 51.4% had reduced EF (HFrEF), 19.1% mildly reduced (HFmrEF), and 29.5% preserved EF (HFpEF). Eligibility (literal) was: 27.2% (32.4% in HFrEF, 24.7% in HFmrEF, 19.7% in HFpEF) and eligibility (pragmatic) was 62.8% (69.1%, 60.3%, 53.4%, respectively). In the literal scenario, criteria limiting eligibility were HF duration <3 months, eGFR <30 ml/min/1.73 m(2), age >85 years, acute coronary syndrome <3 months, and insufficiently high N-terminal pro-B-type natriuretic peptide levels. Eligible vs. non-eligible patients had more severe HF, higher cardiovascular (CV) comorbidity burden, higher use of HF treatments, and higher event rates (all-cause death 30.8 vs. 27.2 per 100 patient-years, CV death 19.1 vs. 16.6, and HF hospitalization 36.7 vs. 24.0). Conclusion In this large, real-world HF cohort with T2DM, similar to 1/3 of patients were eligible for sotagliflozin in the literal and similar to 2/3 of patients in the pragmatic scenario. Eligible patients had more severe HF and higher event rates, in particular CV and HF events.
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| 10. |
- Becher, Peter Moritz, et al.
(författare)
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Phenotyping heart failure patients for iron deficiency and use of intravenous iron therapy : data from the Swedish Heart Failure Registry
- 2021
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Ingår i: European Journal of Heart Failure. - : Wiley. - 1388-9842 .- 1879-0844. ; 23:11, s. 1844-1854
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Tidskriftsartikel (refereegranskat)abstract
- Aims Iron deficiency (ID) is associated with poor prognosis regardless of anaemia. Intravenous iron improves quality of life and outcomes in patients with ID and heart failure (HF) with reduced ejection fraction (HFrEF). In the Swedish HF registry, we assessed (i) frequency and predictors of ID testing; (ii) prevalence and outcomes of ID with/without anaemia; (iii) use of ferric carboxymaltose (FCM) and its predictors in patients with ID. Methods and results We used multivariable logistic regressions to assess patient characteristics independently associated with ID testing/FCM use, and Cox regressions to assess risk of outcomes associated with ID. Of 21 496 patients with HF and any ejection fraction enrolled in 2017-2018, ID testing was performed in 27%. Of these, 49% had ID and more specifically 36% had ID-/anaemia-, 15% ID-/anaemia+, 29% ID+/anaemia-, and 20% ID+/anaemia+ (48%, 39%, 13%, 30% and 18% in HFrEF, respectively). Risk of recurrent all-cause hospitalizations was higher in patients with ID regardless of anaemia. Of 1959 patients with ID, 19% received FCM (24% in HFrEF). Important independent predictors of ID testing and FCM use were anaemia, higher New York Heart Association class, having HFrEF, and referral to HF specialty care. Conclusion In this nationwide HF registry, ID testing occurred in only about a quarter of the patients. Among tested patients, ID was present in one half, but only one in five patients received FCM indicating low adherence to current guidelines on screening and treatment.
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