A city is considered to be safe when people can move freely, without being concerned about being subjected to any crime. CPTED is a way to work with crime prevention in the society. Although safety and security are two distinct concepts, they can interact with each other in the work towards a more sustainable society. This bachelor essay explores how the perception of safety, regarding common anxiety, is distributed between men and women in Stockholm City. Furthermore, the perception of safety within the female group is examined in terms of age. This has been conducted in the form of a quantitative analysis, based on data from Stockholm’s safety survey in 2014. The results showed that the perceived safety, in a general sense, is very low among the Stockholm residents. In all but one of the cases, the proportion of women who claimed to be unsafe was bigger than the proportion of men. Most women, who felt unsafe in the neighborhood or transit environment, were between the ages of 25 and 44 years. The results were analyzed in a more qualitative form, by an assessment of its reasonableness and feedback with relevant theory that has been presented. This led to the conclusion that there are differences in people’s perceived safety, which can be explained by its individual characteristics like gender and age. / En stad anses vara trygg när människor kan röra sig fritt utan att vara rädda att utsättas för brott av något slag. CPTED är ett sätt att jobba med brottsprevention i samhället. Trots att trygghet och säkerhet är två säregna begrepp, kan de samverka med varandra vid arbetet mot ett mer hållbart samhälle. Denna kandidatuppsats undersöker huruvida människors upplevda trygghet, rörande allmän oro, är fördelad mellan män och kvinnor i Stockholm. Vidare undersöks också trygghetskänslan inom den kvinnliga könsgruppen, med avseende på ålder. Denna undersökning har genomförts i form av en kvantitativ analys, vilken baserades på data från Stockholms trygghetsmätning år 2014. Resultaten visade att den upplevda tryggheten generellt sett var väldigt låg hos invånarna i Stockholm. Vid alla utom ett av de undersökta fallen, var andelen kvinnor som uppgett sig vara otrygga större än andelen män. De flesta kvinnor som kände sig otrygga i bostadsområdet respektive transit miljön var mellan 25-44 år. Resultaten analyserades i form av en mer kvalitativ karaktär, genom utförandet av en rimlighetsbedömning och återkoppling till relevant teori om trygghet. Detta ledde till slutsatsen att det finns skillnader i människors upplevda trygghet, som kan förklaras av dess individuella egenskaper såsom kön och ålder.

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This thesis explores the development of an automated re-synthesising tool, called EasySynth, to generate a Swiss synthetic population and travel diaries from publicly available data. The aim is to overcome the limitations of restricted-access real population data while maintaining control over anonymisation and statistical accuracy. The research addresses the need for reproducibility and limited data in transportation modelling and thus may be employed in contexts outside Swiss borders where data is not as ample. The methodology involves direct data manipulation and calculation using weighted probabilistic sampling to generate synthetic travel data representative of the real Swiss behavior. The results indicate a close match between the synthetic population and the real Swiss population in terms of age, sex, canton,purpose, and mode of travel. This study aims to contribute to the Eqasim pipeline for Switzerland whereby raw synthetic data is prepared for MATSim and other activity-based microsimulators. In so doing, the project demonstrates the potential of utilising open data to generate a synthetic population and travel behaviour in an automated fashion.

Studiens syfte är bland annat att undersöka och redogöra för skillnader och likheter mellan rättelse och ändring av detaljplan. Arbetet syftar också till att identifiera konsekvenser av uppkomna felaktigheter, och hur kommuner hanterar dessa. Målet med studien är att lämna ett kunskapsbidrag av vad som sker när felaktigheter uppstår i en detaljplan och vad som krävs för att kunna tillämpa rättelse. Studien har genomförts till största del genom kvalitativ metod med litteraturstudie och intervjuer som kompletteras med ett kvantitativt bidrag i form av sammanställda rättelser. Urvalet till intervjuerbaserades på tjänstepersoner som jobbar i en kommun med detaljplaner dagligen. Kommunernas spridning var blandad runt Västra Götalandsregionen från landsbygdskommun till storstad. Rättelserna redovisas i ett diagram och användes för att visa vilken typ av rättelser kommuner utför. Rättelserna var 20st till antal och valdes ut genom dess tillgänglighet via sökmotorer. Kriterierna var att rättelserna skulle vara gällande och inte överklagade och fick inte vara äldre än 2011. Inga rättelser sållades bort. Resultatet delades in i kapitel om gällande rätt och empiri. I gällande rätt redovisas svar på frågeställningarna ur juridisk vinkel, vilka lagstiftningar som är aktuella för studiens syfte. PBL redogör för en ändring och vilken process som krävs. Enkelt förfarande, standardförfarande och utökat förfarande redovisas ihop med vad förarbeten avsåg vid tillämpning. En ändring i en detaljplan ska genomgå något av förfarandet även om det bara är en del av planen som ändras. FL redogör för vilka kriterier som ska uppfyllas för att en rättelse får ske. Felet ska bland annat vara av uppenbar karaktär och tillkommit genom ett skrivfel, räknefel eller tekniskt missöde. Rättsfall från MMD och MÖD redovisar hur domstolen tolkat 36 § FL, där MÖD 2018 gav en dom som kan vägleda kommuner i tolkning av lagtext. MÖD dömde mot kommunen och angav som skäl att rättelsen som avsågs innebar en ändring i sak i detaljplanen, dessutom till nackdel för en enskild, och inte uppfylldede kriterier som lagstiftarna ansett som rättelse. I analys och diskussion, analyseras rättelserna från kommuner ihop med material från intervjuer, gällande rätt och rättsfall. Analysen påvisar att kommunerna har tolkat FL på olika sätt och att demotiverat beslut om rättelse olika utförande. Majoriteten av de rättelser som studerats visar sig inte uppfylla de minimikrav som FL ställer för rättelse och det visade sig inte heller finnas stöd i form av rättsfall för majoriteten av rättelserna. Resultatet från tjänstepersonernas intervjuer visar sig däremot för det mesta ligga i linje med vad lagstiftaren avsåg. Tjänstepersonerna var eniga om att en plan inte får rättas om det innebär en förändring i planen, då ska planen genomgå en ändring genom PBL. Det har genom studien visat sig vara svårt att dra en rak skiljelinje mellan rättelse enligt FL och ändring genom PBL. Kommuner tolkar en uppenbar felaktighet och förändring i sak på olika sätt vilket resulterat i de rättsfall som presenterats i studien. Slutsatser som har dragits är att FL är allt för generell och PBL allt för snäv för att enkelt genomföra mindre korrigeringar. FL tillåter enbart bagatellartade felaktigheter medan PBL ställer allt för stora krav vid justering av småfel. / The purpose of the study is to investigate and account for differences and similarities between correction and change of detailed development plan. The work also aims to identify the consequences of errors that have arisen, and how municipalities handle these. Furthermore, the survey aims to investigate who are the stakeholders and what communication takes place between the municipality and the stakeholders. The aim of the study is to provide a knowledge contribution of what happens when errors occur in a detailed development plan and what is required to be able to apply correction. The study has been carried out largely through a qualitative method with a literature study and interviews that are complemented with a quantitative contribution in the form of collected corrections. The selection for interviews was based on officials who work in a municipality with detailed development plans daily. The spread of municipalities was varied around the Västra Götaland region from country municipality to bigcity. The corrections are presented in a chart and were used to show the type of corrections municipalities make. The corrections were 20 pcs in number and were selected through its availability via search engines. The criteria were that the corrections should be valid and not appealed and could not be older than in 2011. No corrections were filtered away. The result was divided into chapters on current law and empirical evidence. Current law presents answers to the questions from a legal point of view, which legislation is relevant for the purpose of the study. The PBL describes a change and the process required. Simple procedure, standard procedure and extended procedure are accounted for in the context of the application of preparatory work. An amendment to a detailed plan shall undergo some of the procedure even if only part of the plan is amended. FL explains the criteria that must be met for a correction to be implemented. The error must, among other things, be of an obvious nature and caused by a typing error, arithmetic error or technical error. Legal cases from MMD,RR and MÖD report how the court interpreted § 36 FL, where MÖD 2018 gave a judgment that can guide municipalities in the interpretation of legal text. MÖD ruled against the municipality and stated as a reason that the correction in question entailed a change in substance in the detailed plan, also to the detriment of an individual, and did not meet the criteria that the legislators considered a correction. In analysis and discussion, the corrections from municipalities are analyzed together with material from interviews, applicable law and court cases. The analysis shows that the municipalities have interpreted FL in different ways and that they have justified decisions on correction of different designs. The majority of the corrections studied do not turn out to meet the minimum requirements set by FL for correction, nor did it turn out that there was support in the form of legal cases for the majority of the corrections. The results from the officials' interviews, on the other hand, mostly turn out to be in line with what the legislator intended. The officials agreed that a plan may not be corrected if it involves a change in the plan, then the plan must undergo a change through PBL. Through the study, it has proved difficult to draw a straight line between correction according to FL and change through PBL. Municipalities interpret an obvious error and change in substance in different ways, which has resulted in the legal cases presented in the study. Conclusions that have been drawn are that FL is far too general and PBL far too narrow to easily implement minor corrections. FL only allows trivial errors while PBL makes excessive demands when adjusting small errors.

Optimisation of a geodetic network is performed to provide its pre-set quality requirements. Today, this procedure is almost run with the aid of developed analytical approaches, where the human intervention in the process cycle is limited to defining the criteria. The existing complication of optimisation problem was terminated by classifying it into several stages. By performing these steps, we aim to design a network with the best datum, configuration and the observation weights, which meets the precision, reliability and cost criteria. In this thesis, which is a compilation of four papers in scientific journals, we investigate the optimisation problem by developing some new methods in simulated and real applications. On the first attempt, the impact of different constraints in using a bi-objective optimisation model is investigated in a simulated network. It is particularly prevalent among surveyors to encounter inconsistencies between the controlling constraints, such as precision, reliability and cost. To overcome this issue in optimisation, one can develop bi-objective or multi-objective models, where more criteria are considered in the object function. We found out that despite restricting the bi-objective model with precision and reliability constraints in this study, there is no significant difference in results compared to the unconstrained model. Nevertheless, the constrained models have strict controls on the precision of net points and observation reliabilities. The importance of optimisation techniques in optimal design of displacement monitoring networks leads to the development of a new idea, where all the observations of two epochs are considered in the optimisation procedure. Traditionally, an observation plan is designed for a displacement network and repeated for the second epoch. In the alternative method, by using the Gauss-Helmert method, the variances of all observations are estimated instead of their weights to perform the optimisation. This method delivers two observation plans for the two epochs and provides the same displacement precision as the former approach, while it totally removes more observations from the plan. To optimise a displacement monitoring network by considering a sensitivity criterion as a main factor in defining the capacity of a network in detecting displacements, a real case study is chosen. A GPS displacement monitoring network is established in the Lilla Edet municipality in the southwest of Sweden to investigate possible landslides. We optimised the existing monitoring network by considering all quality criteria, i.e. precision, reliability and cost to enable the network for detecting 5 mm displacement at the net points. The different optimisation models are performed on the network by assuming single baseline observations in each measurement session. A decrease of 17% in the number of observed baselines is yielded by the multi-objective model. The observation plan with fewer baselines saves cost, time and effort on the project, while it provides the demanded quality requirements. The Lilla Edet monitoring network is also used to investigate the idea, where we assume more precise instruments in the second of two sequential epochs. In this study, we use a single-objective model of precision, and constrained it to reliability. The precision criterion is defined such that it provides the sensitivity of the network in detecting displacements and has a better variance-covariance matrix than at the first epoch. As the observations are GPS baselines, we assumed longer observation time in the second epoch to obtain higher precision. The results show that improving the observation precision in the second epoch yields an observation plan with less number of baselines in that epoch. In other words, separate observation plans with different configurations are designed for the monitoring network, considering better observation precision for the latter epoch. / <p>QC 20150603</p> / Formas

A majority of the direct and indirect maintenance costs in the life cycle of aircraft stems from the consequences of decisions taken during the initial maintenance program development. In particular, the preventive and corrective maintenance requirements, which greatly influence both the system availability and life cycle cost, need to be defined in order to perform only those preventive actions that are absolutely necessary and costeffective. Reliability-Centered Maintenance (RCM) is a systematic methodology used to identify the preventive maintenance tasks that are necessary to realize the inherent reliability of equipment at the lowest possible cost. Developing a scheduled maintenance program by means of RCM consists of identifying those preventive tasks which are both applicable (technically feasible) and effective (worth doing). An applicable maintenance task must satisfy the requirements of the type of failure to restore the item's initial performance capability. To be effective, a preventive maintenance task must lead to a reduced risk (or expected loss) of the consequence classes to a level which is acceptable to the user. In the design development phase, in order to identify the most cost effective solution, a design trade-off study is needed. This involves choosing the correct balance of the cost of consequences of failure and its correction, with their cost of prevention. However, during initial aircraft maintenance program development, lack of a methodology that supports the assessment of the operational consequences of failures has made the costeffectiveness analysis of maintenance tasks a challenging issue. This might reduce the accuracy of the analysis, which results in higher maintenance costs and may decreases the punctuality of operation, which ultimately increases the total aircraft life cycle cost. The purpose of this study is to develop a methodology for identifying different operational consequences and associated costs caused by aircraft system failure, in order to facilitate and enhance the capability of taking correct and efficient decisions when analyzing the cost-effectiveness of maintenance tasks. Some empirical studies of possible scenarios involving aircraft failures and their operational consequences for a commercial airline have been performed. Empirical data were extracted through document studies and interviews, guided by the application of an Event Tree Analysis (ETA). The analysis was performed together with experienced practitioners from both an aircraft manufacturer and commercial airlines, which contributed to a continuous verification of the outcomes of the study. Finally, the study has also estimated the associated cost of the identified operational consequences of failures. In order to quantify the operational consequences of failures, in the absence of adequate and reliable data, a methodology using pair-wise comparison technique has been applied to extract judgments of experts efficiently / Godkänd; 2007; 20071203 (ysko)

Big Data analytics has attracted intense interest from both academia and industry recently for its attempt to extract information, knowledge and wisdom from Big Data. In industry, with the development of sensor technology and Information &amp; Communication Technologies (ICT), reams of high-dimensional data streams are being collected and curated by enterprises to support their decision-making. Fault detection from these data is one of the important applications in eMaintenance solutions with the aim of supporting maintenance decision-making. Early discovery of system faults may ensure the reliability and safety of industrial systems and reduce the risk of unplanned breakdowns. Both high dimensionality and the properties of data streams impose stringent challenges on fault detection applications. From the data modeling point of view, high dimensionality may cause the notorious “curse of dimensionality” and lead to the accuracy deterioration of fault detection algorithms. On the other hand, fast-flowing data streams require fault detection algorithms to have low computing complexity and give real-time or near real-time responses upon the arrival of new samples. Most existing fault detection models work on relatively low-dimensional spaces. Theoretical studies on high-dimensional fault detection mainly focus on detecting anomalies on subspace projections of the original space. However, these models are either arbitrary in selecting subspaces or computationally intensive. In considering the requirements of fast-flowing data streams, several strategies have been proposed to adapt existing fault detection models to online mode for them to be applicable in stream data mining. Nevertheless, few studies have simultaneously tackled the challenges associated with high dimensionality and data streams. In this research, an Angle-based Subspace Anomaly Detection (ABSAD) approach to fault detection from high-dimensional data is developed. Both analytical study and numerical illustration demonstrated the efficacy of the proposed ABSAD approach. Based on the sliding window strategy, the approach is further extended to an online mode with the aim of detecting faults from high-dimensional data streams. Experiments on synthetic datasets proved that the online ABSAD algorithm can be adaptive to the time-varying behavior of the monitored system, and hence applicable to dynamic fault detection.

Today's highly advanced technological flying platforms, such as aircraft, helicopters and Unmanned Air Vehicles (UAVs), are characterised by a high degree of complexity. Simultaneously, they are used in different operational and mission profiles, and also in multiple operational environments and geographical settings. In addition, the interaction between major stakeholders, such as operators and support providers, has been drastically changed by concepts such as Performance-Based Logistics (PBL), where the support providers' commitment increases through the offering of availability performance at a fixed price. These changes put new and stringent requirements on dependability analysis to make efficient use of field data (e.g. generated by built-in tests, operation and maintenance) to sustain, improve and predict the availability performance of flying platform fleets. The purpose of the research presented in this thesis is to explore and describe methodologies and tools for dependability analysis, modelling and simulation of fleets of complex systems, in order to support improvement decisions throughout the fleets' whole lifecycle. More specifically, the objective of the research is to contribute to the development of a tool for modelling and simulation of multiple parallel lifecycle phases of complex technical systems in a fleet. The focus is on the assessment of field data and the extraction and prediction of information for continuous improvement of subsystem reliability performance, organisational maintenance support performance and fleet availability performance. The empirical work focuses on the Swedish military aeronautics community. The data has been collected through interviews, observations, document studies and archival records, such as recordings of in-flight parameters and maintenance actions. The data has been analysed to investigate critical aspects, such as the perfect repair assumption, the appropriateness of decisions about changes of maintenance intervals and of the No Fault Found (NFF) phenomenon. Through a literature study and practical efforts, this thesis also outlines and exemplifies methodologies and tools that support dependability analysis of an aircraft fleet. In addition, modelling and simulation efforts have been made to enable prediction of aircraft fleet performance and beneficial adjustments of support resources during the fleet retirement phase. The results act as input to a conceptual model that describes the phasing-in, operation and retirement of an aircraft fleet. The model aims to identify when it is cost-effective to consider the Remaining Useful Life (RUL) of individual repairable components comprising aircraft being retired, and utilise these components as spare parts for the aircraft staying in service. In summary, the performed work indicates that, in today's context with PBL and excessive amount of available data, dependability analysis, modelling and simulation must become more transparent, traceable and intersubjective.

The understanding of the fracture mechanisms and failure processes of the rock is an important requirement for the design of mining excavations and civil engineering constructions. The fracture process is necessary for the excavation and fragmentation of rock, but fracture of rock must be avoided and controlled to preserve the integrity of the construction. This licentiate thesis work is focused on hard rock masses and conditions typical on Fennoscandia. This work was initiated with a review of literature. Following the literature review, information about real underground excavations with deformation monitoring was collected. Laboratory test data was also collected after the survey of cases. The last task for the licentiate work was to perform numerical analysis simulation using the program Phase2 and evaluate the strains due to possible failure. The literature review showed that fracture of brittle rock is the process by which new surfaces in the form of cracks are formed in rock-like material, or existing crack surfaces are extended. Five stages of deformation are distinguished in the fracture process of brittle rock: crack closure, linear elastic deformation, fracture initiation, fracture propagation and post-peak behaviour.The most common reason for stability problems in underground excavation is structurally controlled failure and stress-induced failure. The ground response curve is a technique for describing the response of rock under parameters such as deformation and stress. Thus, the response of the rock mass response can be evaluated and related to the distance to the face of the excavation. The failure criteria reported in the literature are formulated in terms of stresses and include one or several parameters that describe the rock mass properties. Only a few failure criteria were formulated in terms of strains. Since macroscopic failure surfaces are characterized by strain concentrations, fallout criteria should be expressed in terms of strain quantities. Further studies have to be done in order to be able to formulate strain-based fallout criteria.The four underground cases with hard rock mass and conditions typical of Fennoscandia are: Mine-by Experiment, Instrumented drift at the Kiirunavaara mine, Arlandabanan tunnel and Äspö Pillar Stability Experiment. These cases contain very good information regarding rock properties, geology and stress state. These cases are a good example of in situ deformation measurement. For some cases, the failure occurred and the measured deformation is related to the failure. Laboratory tests of hard rock specimens were performed at Luleå University of Technology and by Posiva Oy. The tested rocks are Fennoscandian types such as limestone, quartzite, diorite, norite, gabbro, diabase, syenite porphyry, mica gneiss, tonalite gneiss and a variety of granites. In these tests, the rock properties and stages of deformation (crack closure, crack initiation and crack damage) were measured and determined. The evaluation of the laboratory tests showed that the stages of deformation vary between rock types and depend on factors such as grain size and mineral composition. Therefore, it may be better if each rock type is treated individually.Failure (i.e., intersection of shear bands forming a v-notch) of a real case and fictitious case was simulated using Phase2. The evaluation of predicted quantities such as maximum and minimum principal, volumetric and maximum shear strains along the depth of the v-notch showed good agreement with the point where the v-notch ended. Furthermore, the comparison between the predicted lateral strains related to failure and the critical lateral strains of rock tested in laboratory showed good agreement as well. / Förståelsen av brottmekanismerna och brottsprocesserna i berg är mycket viktig vid utformning och dimensionering av t ex orter, schakt, brytningsrum, tunnlar och bergrum. Brottsprocessen är en nödvändig del av drivnings- och fragmenteringsprocessen men skador på den blivande bergkonstruktionen bör minimeras för att inte bärförmågan ska reduceras och stabiliteten riskeras. Denna licentiatavhandling fokuserar på hårda bergmassor och förhållanden typiska för Fennoscandia. Detta arbete startade med en litteraturstudie och en studie av verkliga fall där deformationsmätningar genomförts. Hållfasthetsdata från två laboratoriestudier studerades därefter. Den sista delen av avhandlingsarbetet omfattade numeriska analyser med programmet Phase2 med utvärdering töjningstillståndet kring två olika underjordsöppningar. Litteraturstudien visade att brottsprocessen i berg omfattar bildandet av nya sprickor och propagering av existerande sprickor. Fem stadier kan identifieras under brottsprocessen: slutning av existerande sprickor, linjär elastisk deformation, sprickinitiering, spricktillväxt och efterbrottsbeteende. Den vanligaste orsaken till stabilitetsproblem i underjordskonstruktioner är strukturstyrda utfall och spänningsinducerade utfall. Bergets responskurva (Ground Reaction Curve, GRC) kan användas för att beskriva utvecklingen av deformationen som funktion av förstärkningstrycket/stödtrycket (inre övertryck), för en given insituspänning. Bergmassans respons som funktion av avståndet från tunnelgaveln kan studeras med denna metod. Brottkriterierna rapporterade i litteraturen är huvudsakligen formulerade i termer av spänningar och inkluderar även olika typer av hållfasthetsparametrar (kohesion, friktionsvinkel, enaxiell tryckhållfasthet etc.). Endast ett fåtal kriterier är baserade på töjningar. Eftersom makroskopiska brottytor karakteriseras av töjningskoncentrationer bör kriterier som förutsäger utfall uttryckas i termer av töjningar. Ytterligare studier är dock nödvändiga för att kunna föreslå ett utfallskriterium. De fyra underjordsfallen som karakteriseras av hårt berg och förhållanden typiska för Fennoscandia är Mine-by Experiment, en instrumenterad ort i Kiirunavaaragruvan, Arlandabanan och pelarstabilitetsexperimentet i Äspö. Dessa fall ger en mycket god information om bergmassans egenskaper, geologin, spänningstillståndet och bergets deformationer. I några av fallen skedde brott. Detta gör det möjligt att studera deformationerna under brott. En utvärdering av laboratorietester på hårda bergarter utförda av Luleå Tekniska Universitet respektive Posiva Oy utfördes. Testerna utfördes på bergarter av typen kalksten, kvartsit, diorit, norit, gabbro, diabas, syenitporfyr, glimmerskiffer, gnejs och ett antal graniter. I dessa tester utvärderades de olika deformations- och brottstadierna (sprickslutning, sprickinitiering och starten på instabil spricktillväxt (eng. crack damage)). Utvärderingen av laboratorietesterna visade att de töjningsnivåer som definierade de olika deformations- och brottstadierna varierade mellan bergarterna. Faktorer som kornstorlek och mineralinnehåll visade sig ha stor betydelse. Därför måste bergarterna studeras individuellt. Brott (d v s, skjuvband eller makroskopiska brottytor som definierar en utfallsvolym) i ett verkligt fall och ett fiktivt fall studerades med hjälp av Phase2. Studierna av minsta och största huvudtöjningarna samt maximala skjuvtöjningen som funktion av avståndet från bergöppningens rand visade att absolutbeloppen av töjningsstorheterna har lokala maxima där där analysen indikerar en brottyta. Jämförelser mellan den beräknade minsta huvudtöjningen och den laterala töjningen (minsta töjningen) från laboratorietesterna visade att töjningarna i modellerna var av samma storlek som de kritiska töjningsvärden som representerar begynnande instabil spricktillväxt.

In recent years the Swedish Rail Administration has observed an increased incidence of shotcrete and rock fall-outs in its tunnels, for which reason it has initiated several research projects, of which the present project entitled "Degradation of rock and shotcrete due to ice pressure and frost shattering" is one. The aim of this licentiate project was to bring together experience and information relating to ice formation and the effect of ice pressure on fault zones, cracks and, in particular, the shotcrete/rock interface. Furthermore, the hypothesis from the literature review is tested and the results of the laboratory tests are presented.When water freezes, a 9 % volumetric expansion occurs according to the phase transition into ice. This can exert a pressure on the adjacent material. If this ice pressure exceeds the tensile strength of the adjacent material or the adhesive strength of the shotcrete/rock interface, the material will be damaged. The degree of damage depends, among other factors, on the degree of saturation of the material. A partially saturated material can resist breakage despite its low tensile strength, because ice expansion and pore-water distribution can occur in pores which were initially filled with air. A fully saturated material however yields to frost action regardless of its tensile strength, because it has none of the free space this expansion requires.Volumetric expansion is not the only cause of frost shattering and research shows that the frost action in rocks is the same as in soils, when the rock has access to water during freezing. In soil, water is drawn towards the frozen fringe and causes ice lenses to grow. In a similar manner water tends to migrate in rock and causes ice bodies to grow inside pores and cracks. This water migration takes place because a thin film of adsorbed water occurs at the surface of mineral particles and it is in this water film that water is able to migrate towards the frozen zones. Experimental work has shown that a considerable amount of adsorbed water remains unfrozen at sub-zero temperatures not only in soils, but also in rocks, which enable water migration.Water migration and ice growth thus depend not only on access to water and freezing temperatures, but also on the duration of these temperatures and the freezing rate. If rock or shotcrete is subjected to rapid freezing, the thickness of the water film is quickly reduced and the water migration is inhibited, which limits frost damages to rock and shotcrete. By contrast, a slow freezing allows water migration to occur over a longer period, which can result in greater frost damage to rock and shotcrete. The field investigations found changes to the freezing periods as well as their duration to be of major importance to ice formation growth. If the freezing period was of long duration, several of the cracks and the leakage spots freeze. If leakage is subjected instead to short periods of freezing and thawing, the water in the crack will never freeze and will continue to leak, resulting in ice formation growth. In cold areas, such as the north of Sweden, this problem takes place even far inside the tunnels. This phenomenon occurs because the leakage water transports heat from the rock mass to the cold tunnel wall. The heat content of the water keeps the rock around the crack opening from freezing despite sub-zero tunnel air temperatures. Hence, the leakage spot will continue to leak, until a certain temperature and temperature duration is achieved, which results in ice formations when the water meets the cold tunnel air. Another experience in the field investigations was that the rock and shotcrete fall-outs often occurred in areas with leakage problems.The results of the laboratory tests performed in this licentiate project also show that water in combination with freezing temperature can cause degradation problems. The tensile tests undertaken, showed that the adhesive strength decreased about 50 % when the shotcrete/rock samples had been subjected to freeze-thaw cycles. Furthermore, acoustic emission measurements (AE) showed that more events took place when the shotcrete/rock panels had access to free water during freezing. The literature review, field investigations of railway tunnels and the laboratory tests shows that access to water during freezing can cause damage to the shotcrete/rock interface. This confirms the hypothesis that shotcrete and rock fall-outs can occur because ice pressure in a crack or at the interface exceeds the tensile strength of the material or the adhesive strength between rock and shotcrete. One thing that the laboratory tests failed to provide a satisfactory answer to, was whether these fall-outs could occur due to widening of an initially small area of poor adhesion around a rock crack opening. However, the laboratory test showed a lot of activity during freezing in those areas prepared with poor adhesion. It thus it appears that small areas of poor adhesion in some way affect deterioration of the adhesive strength of the shotcrete/rock interface. / Nedbrytning av berg och sprutbetong på grund av istryck och frostsprängningPå senare år har Banverket märkt en ökning av inrapporterade nedfall av berg och sprutbetong i sina järnvägstunnlar. I och med detta så startades en rad forskningsprojekt kring problemen med vattenläckage och isbildning i tunnlar. Detta projekt "Nedbrytning av berg och sprutbetong på grund av istryck och frostsprängning" är ett av dessa. Syftet med detta licentiatprojekt var att samla erfarenhet och information om hur is bildas samt hur istryck påverkar krosszoner, sprickor och framför allt skiktet mellan berg och sprutbetong. Vidare testas hypotesen från litteraturstudien och resultaten från laborationsförsök redovisas.När vatten fryser till is sker en 9 % volymsutvidgning och denna expansion kan orsaka att ett tryck uppstår mot det omgivande materialet. Det omgivande materialet kommer att utsättas för brott om trycket från isen överstiger materialets draghållfasthet eller vidhäftningshållfasthet i skiktet mellan berg och sprutbetong. Storleken på skadan är bland annat beroende av materialets vattenmättnad. Ett delvis vattenmättat material kan klara sig från brott, trots att dess draghållfasthet är låg, genom att expansionen av isen och omfördelning av porvatten kan ske i de porer som från början var fyllda med luft. Ett helt vattenmättat material ger istället efter för frostsprängningen oberoende av sin draghållfasthet, på grund av att materialet inte har något fritt utrymme som kan ta upp expansionen.Det är inte bara isens volymsutvidgningen som orsakar frostsprängning. Forskning visar att om berg har tillgång till fritt vatten under nedkylningen sker en process som liknar den i jord, där vatten vandrar fram mot frysfronten och bildar islinser. På ett liknande sätt vandrar vatten i berg och orsakar tillväxt av isskikt i exempelvis en por eller spricka, vilket kan orsaka att istrycket ökar. Vattenvandringen sker på grund av att det finns en tunn vattenfilm av adsorberat vatten längs mineralkornens ytor och i denna vattenfilm finns möjlighet för vatten att vandra mot frysfronten. Experimentellt arbete har visat att en betydande del av det adsorberade vattnet förblir ofruset vid negativa temperaturer, inte bara i jord utan även i berg och detta möjliggör vattenvandringen.Vattenvandring och istillväxt är inte bara beroende av tillgången till vatten och frystemperatur, utan även av fryshastighet och varaktighet av köldgrader. Om berg och sprutbetong utsätts för snabb nedkylning minskar vattenfilmens tjocklek och vattenvandringen förhindras, vilket begränsar frostsprängningen av materialet. Om istället berget kyls ned långsamt, tillåts vattenvandringen att ske under en längre period, vilket kan resultera i större frostsprängning. I de utförda fältundersökningarna visade det sig att varaktigheten och förändring av frysperioderna var av stor vikt för tillväxten av isformationer. Om frysperioden hade lång varaktighet frös vissa av sprickorna och läckagepunkterna. Om läckagen istället utsattes för kortare perioder av frysning och tining frös aldrig sprickorna och vatten fortsatte att läcka med växande isformationer som följd. För kalla områden, som i de norra delarna av Sverige, uppstår dessa problem även långt in i tunnlarna. Problemen uppstår på grund av att läckagevatten transporterar fram värme från bergmassan till den kalla tunnelytan. Värmen från läckagevattnet håller bergmassan kring spricköppningen ofrusen trots att tunnelluften är kall. Därför fortsätter sprickan att föra fram vatten med konsekvensen att det bildas is när vattnet väl kommer ut i den kalla tunnelluften. En annan erfarenhet från fältundersökningarna var att utfallen av berg och sprutbetong ofta förekom i sektioner som hade problem med vattenläckage.Resultaten från laborationsförsöken utförda i det här licentiatprojektet visar också att vatten i kombination med negativa temperaturer kan orsaka nedbrytningsproblem. De utförda dragtesterna visade att vidhäftnings-hållfastheten minskar med ungefär 50 % när sprutbetong/bergproverna hade utsatts för frysning. Vidare visade mätningarna av akustisk emission (AE) att fler AE-händelser skedde när sprutbetong/bergproverna hade tillgång till vatten under frysningen. Litteraturstudien, fältundersökningarna i järnvägstunnlarna och laborationsförsöken pekar på att tillgången på vatten under frysning kan orsaka skador på skiktet mellan berg och sprutbetong. Detta bekräftar hypotesen att utfall av berg och sprutbetong kan uppstå på grund av att istryck i en spricka eller i skiktet mellan berg och sprutbetong överskrider draghållfastheten för materialet eller vidhäftningshållfastheten mellan berg och sprutbetong. En sak som laborationsförsöken inte kunde ge ett bra svar på var ifall utfallen kunde ske på grund av spridning av en liten yta som redan från början hade dålig vidhäftning runt en spricköppning. Men försöken visade att det förekom mycket aktivitet under frysningen i de områden som preparerats med dålig vidhäftning. Så det verkar som att små områden med dålig vidhäftning kan påverkar försämringen av vidhäftningen mellan berg och sprutbetong.