Search

The construction time and cost of a rock tunnel project are highly dependent on the rock mass quality and encountered ground behaviour. In most rock tunnel projects, the knowledge about the ground conditions along the tunnel is limited, making it difficult to predict accurately the construction time and cost. The KTH model takes a probabilistic approach to address this problem; however, it does not account for the spatial variability of the ground conditions. This paper investigates an alternative probabilistic ground model to be used within the KTH model that enables accounting for the spatial variability through Markov random field theory. The new ground model employs a parametric approach to describe the properties of the Markov field, hence, enabling the simulation of the ground conditions with limited data, but does not consider the epistemic uncertainty in the model parameters. This will be the addressed in future research., QC 20240625

Rock tunnel construction is associated with considerable geotechnical uncertainty, often due to limited knowledge about the ground conditions. This warrants the use of stringent risk management procedures to reduce the likelihood of cost increases, delays, and structural failure events. The observational method is often promoted as a tool to achieve cost-effective designs in cases of large geotechnical uncertainty, but its practical use is still limited. One reason may be the lack of guidelines and experiences from previous projects where the observational method has been used. In this paper, we therefore present a case study of the design and construction of the tunnel under the Hvalfjörður fjord in Iceland, where the observational method played a key role in the risk management that was performed to deal with the challenging geological conditions at the site. The project was a success and completed four months earlier than originally planned. In light of the case study, we discuss the definition of the observational method in Eurocode 7 and the related contractual aspects to consider in such projects., Not duplicate with DiVA 1553241QC 20221129

Modern tunnelling in rock relies heavily on information from monitoring and observations during construction as a means to reduce the considerable uncertainty that originates from a lack of knowledge about the ground conditions. By formally integrating the monitoring information into the structural safety evaluation, a comprehensive risk-based design framework can be achieved. The establishment of relevant thresholds against unacceptable structural behaviour is a key aspect of this work. This paper presents an extensive application example based on real-case data, showing how a reliability-based threshold can be established to ensure the serviceability of a shotcrete lining in a rock tunnel in a challenging geological setting. The authors address and discuss practical approaches to consider the model uncertainty related to the confinement loss caused by the tunnel front advance, as well as the transformation uncertainty related to the use of indirect monitoring information. The established threshold is discussed in the context of the observational method., QC 20221125

This paper explores the use of probabilistic design for mining activities and how to integrate probabilistic design into decision making in mining engineering. Mining design differs from civil rock engineering design with respect to exhibiting more demanding, and continuously changing, stress conditions, different excavation/extraction methods, and a larger scale of the operations. Relevant examples on the use of probabilistic-based design methods in civil and mining engineering are presented together with commonalities and case-specific characteristics. The acceptance level for the probability of failure is a part of the risk-based design process and needs to be selected together with decision-makers from other disciplines in the mine. Based on experience from, and commonalities with, civil engineering, the integration of probabilistic design in underground mining should focus on the uncertainty of material properties (e.g., effect of spatial variability, parameter distribution, etc.) and on how to implement theoretical findings into engineering practice. The probabilistic design assessment methods should be further evaluated by applying them to real mining cases., Part of ISBN 978-0-7844-8498-2QC 20230911

The construction of rock tunnels is inherently associated with large geotechnical uncertainty, which not only affects the structural safety and other design requirements but also causes challenges in meeting time plans and budgets. Time and cost estimations of tunnel projects are however still mainly deterministic. The introduction of the contractual document called Geotechnical Baseline Report highlights, however, a need for clients and contractors to address how geotechnical uncertainty affects time and cost estimations. Using probabilistic time and cost estimation methods, a key parameter is the proportion of different construction classes along the tunnel. This paper introduces the Dirichlet distribution (a.k.a. multivariate beta distribution) as a suitable probabilistic model for this epistemic uncertainty and discusses its potential for Bayesian updating and risk assessments of Geotechnical Baseline Reports., Part of ISBN 978-0-7844-8498-2QC 20230911

Decision making in geotechnical engineering is characterized by considerable uncertainty. To find optimal solutions in such an environment, an iterative decision-making process, which includes new information as it becomes available, is required. In this contribution we extend the risk-based framework of Bismut et al. (2023) for optimal planning of a geotechnical construction to include predictions, which are based on a linear regression analysis of monitoring data. This approach is illustrated for the design of a surcharge on an embankment in clayey soil, as the optimal preloading sequence is searched. We demonstrate that by increasing the amount of information considered more cost efficient strategies can be identified and outcome uncertainties can be reduced., QC 20230823

Undermarksprojekt är ofta tekniskt komplicerade, samtidigt som de kännetecknas av stora geologiska och geotekniska risker. Riskerna har sitt ursprung i att det för bergbyggande är svårt att i förväg fastställa vilka tekniska egenskaper som berget har. Denna osäkerhet ger inte bara tekniska, utan även juridiska och ekonomiska utmaningar. Ofta hamnar man i frågan vem som ska stå för den ekonomiska risken om kostnaderna blir högre än väntat. Om riskfördelningen mellan parterna inte är tydligt reglerad i kontraktet, kan det uppstå en både arbetsam och kostsam tvist. Ett relaterat problem är hur riskerna presenteras i förfrågningsunderlaget. Ett otydligt förfrågningsunderlag försvårar för entreprenadbolagen att komma fram till en rimlig prissättning. Internationellt finns ett kontraktsdokument som kallas Geotechnical Baseline Report (rapport för geotekniska bedömningsgrunder), som tagits fram för att tydliggöra parternas ansvar för geologiska och geotekniska risker i geotekniska byggprojekt. I en ny BeFo-rapport har vi introducerat principerna för hur detta kontraktsdokument kan förstås, tolkas och tillämpas i upphandling och utförande av svenska undermarksprojekt. Denna artikel och tillhörande presentation på Bergdagarna ger ett sammandrag av rapporten. Särskild vikt läggs vid definitionen av geoteknisk bedömningsgrund och hur sådana kan användas för att uppnå en tydlig riskdelning i förfrågningsunderlag och kontrakt i praktiken., Underground excavation is often technically complex, as well as associated with large geological and geotechnical risk. The risks originate from the rock engineer’s challenge to determine in advance the technical properties of the rock mass. This uncertainty gives not only technical, but also legal and economic challenges. It is often unclear which party shall own the economic risk, if there is a cost increase. If the risk ownership is not clear from the contract, a time-consuming and costly dispute may occur. A related issue concerns how risks are presented in the tender documents. Vague tender documents make the bidder’s task to find a reasonable price more challenging. Interna-tionally, a concept known as Geotechnical Baseline Report (GBR) is often used to clar-ify the risk allocation in geotechnical engineering projects. In a new research report published by BeFo (Rock Engineering Research Foundation), the authors have intro-duced the principles of GBR in a Swedish context, focusing on Swedish underground excavation projects in rock. This article and accompanying presentation at the Rock Engineering Days provide the main points from the research report, focusing on the defi-nition of a geotechnical baseline and its potential use to achieve a fair risk allocation in tender documents and contracts., QC 20230615

QC 20230601

riven piles can be severely damaged during driving into soil with high boulder content and can potentially lose their structural integrity, resulting in pile refusal. This can consequently aggravate project cost, delays and environmental impact. Pile drivability assessments during the design stage are frequently carried out by designers or contractors, to ensure that the selected foundation system is suitable for the given soil conditions. Such assessments rely heavily on their expertise regarding specific soil conditions, pile properties and installation methods. This procedure is often not documented in detail, which can cause disagreements with the client when significant pile refusal occurs. At the tender stage, the type of contract should identify the risk owner for piling design and installation; however, due to the complexity of the problem, the risk is not distinctly quantified and the risk ownerremain unclear for most projects. The urgency to optimize the design and minimize pile refusal in Sweden is evident, as more than 80 % of all the piles in 2021 were installed by impact driving. The intent of the presentation is to show the limitations and the effects of using the current assessment method, and how the research is currently aiming to develop new probabilistic methods. A transparent methodology to support the decision-making in pile design is in fact necessary for a cost-effective driving strategy and optimal design solutions. Results from geotechnical investigation are also discussed, in order to understand their potential contribution in a pile drivability assessment. This presentation is based on the research work of an ongoing PhD project supported by the Swedish Transport Administration through Better Interactions in Geotechnics (BIG) and by SBUF (Development Fund of the Swedish Construction Industry)., QC 20230516

Genom att tillämpa livscykelberäkningar där man utvärderar hela konstruktionens livscykel, från råmaterialutvinning till slutskedet, kan ett mer hållbart val av en konstruktions utformning göras. I syfte att skapa förutsättningar för att minska både konstruktionens miljöpåverkan och kostnader utvecklar man nu på avdelningen för Jord- och bergmekanik på KTH just sådana beräkningsmetoder. Här skriver forskarna på KTH om det pågående projektet som sker med finansiering från Sven Tyréns Stiftelse och Trafikverket., QC 20230320

Byggande av geotekniska konstruktioner innebär ofta stora investeringar av samhällets resurser, ofta i form av skattemedel. Myndigheter som byg­ger och förvaltar stora geotekniska anläggningar har därför ett ansvar att fatta genomtänkta beslut avseende utformning, byggande och förvaltning. Med ett riskbaserat beslutsfattande kan kostnaderna över tid minimeras. I praktiken kräver detta att man kan ta fram modeller dels för sannolikheten för olika framtida scenarier, dels för de kostnader som de olika scenarierna medför. Detta blir ofta avancerade beslutsteoretiska problem, vars lösning dock sällan studerats inom geotekniken. Denna förstudie syftar till att undersöka potentialen i bayesiansk beslutsteori för att lösa praktiska geotekniska dimensioneringsfrågor. För­studien ger dels en översikt över hur bayesiansk beslutsteori principiellt kan tillämpas på geoteknisk dimensionering, dels ett omfattande praktiskt beräkningsexempel för optimeringen av en överlast för en bank på lera. Författarnas bedömning är att den beslutsteoretiska analysmetoden som användes i exemplet är generellt tillämpbar på liknande problem där många beslut fattas i sekvens, givet att det finns en probabilistisk modell av den geotekniska konstruktionen. Slutligen noteras att det inte föreligger något större behov av att utveckla själva de beslutsteoretiska modellerna. Forskningsarbetet bör därför framöver riktas mot att försöka beskriva van­ligen förekommande geotekniska frågeställningar som beslutsteoretiska problem och därefter utveckla probabilistiska geotekniska modeller som möjliggör deras lösning., Construction of geotechnical engineering structures often requires large societal investment of resources, often in terms of tax funds. Public author­ities that construct and manage large geotechnical engineering structures therefore have a responsibility to make well thought out decisions concern­ing design, construction, and operation. Making risk-based decisions can over time minimize costs. This requires in practice that probabilistic mod­els of future scenarios and associated costs are developed, making up advanced decision theoretical problems, the solution of which rarely has been studied in geotechnical engineering. This prestudy aims to investigate the potential of using Bayesian statis­tical decision theory to solve geotechnical design issues in practice. The prestudy provides first an overview of how Bayesian statistical decision theory can be applied to geotechnical design, followed by an extensive practical calculation example concerning the optimization of a surcharge for an embankment founded on soft clay. The authors’ find that the deci­sion theoretical analysis method used in the example should be generally applicable to similar issues, where many decisions are made in sequence, given that there exist a probabilistic model of the geotechnical engineering structure. Finally, the authors note that there is no imminent need to develop the decision theoretical models per se; research effort should therefore be directed toward describing common geotechnical design issues as decision theoretical problems and developing geotechnical mod­els that allow their solution., Två vetenskapliga artiklar är kopplade till denna rapport:Artikel A: https://doi.org/10.1680/jgeot.22.00408Artikel B: https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-334482QC 20231123

Unexpected and unforeseen geotechnical events cause large cost increases in geotechnical engineering projects and threaten construction workers’ health and safety all around the world. Practical tools and guidelines for how to implement structured and effective risk management methods in geotechnical engineering projects are however few and rarely applied. The Swedish Geotechnical Society has therefore published a methodology for this issue. A key activity in this methodology is to create an understanding of and to interpret the geotechnical context in which the project is to be carried out. This paper presents a guide for how practising geotechnical engineers, hydrogeologists, and other related professionals can perform this activity in a structured way. The procedure is illustrated through the foundation design for a new office building in a geotechnically challenging environment., QC 20220815

QC 20220208

Following an increased focus on societal sustainability, life-cycle considerations have become more important for owners of geotechnical engineering structures. A structural design shall not only perform well at the completion of the structure, but facilitate structural performance over the whole service life. A sustainable geotechnical design should therefore strive to minimise the total life-cycle cost of the structure. As a consequence, the design needs to consider the effect of potential future hazards and allow for cost-effective maintenance. This report takes a first step toward risk-based life-cycle assessments in geotechnical design. The report reviews the current state of the art of probabilistic life-cycle assessments in civil engineering, with a focus on geotechnical design. Based on this, a probabilistic decision tool for geotechnical design from a life-cycle perspective is proposed. The applicability of the tool is then illustrated for a practical case, where different design alternatives for an embankment foundation on soft clay (vertical drains or dry deep mixing columns) are evaluated with respect to a potential groundwater drawdown event, occurring during the service life of the embankment. To facilitate this life-cycle cost assessment, novel reliability-based design methodologies were developed both for surcharges on vertical drains and for dry deep mixing columns. The research results are summarised in this final report and in six scientific articles, which have been appended., Samhällets ökade intresse för hållbar utveckling har gjort livscykelanalyser alltmer relevanta för ägare av geotekniska anläggningar. Konstruktionens utformning ska inte bara avse förhållandena vid invigning, utan även fungera under konstruktionens hela dimensionerande livslängd. En geotekniker bör därför sträva efter att konstruktionens livscykelkostnad minimeras. Utformningen behöver därför väljas med beaktande av såväl framtida hot från extrema laster som kostnadseffektiva möjligheter till underhåll. Denna rapport tar ett första steg mot riskbaserade livcykelkostnadsanalyser inom geotekniken. Rapporten redogör för det nuvarande forskningsläget kring sannolikhetsbaserade livscykelanalyser inom anläggningsbyggande, med särskilt fokus på geotekniken. Utifrån detta har ett sannolikhetsbaserat beslutsverktyg tagits fram. Verktyget analyserar val mellan olika möjliga designalternativ utifrån möjliga effekter under hela livscykeln. Verktygets användbarhet visas genom ett illustrativt beräkningsexempel, där olika grundläggningsalternativ för en vägbank (vertikaldräner med överlast och kalkcementpelare av olika längd) utvärderas med avseende på effekten av en extrem grundvattensänkning, som potentiellt kan inträffa under vägbankens livslängd. För att kunna förse verktyget med relevant indata har även nya sannolikhetsbaserade metoder utvecklats för dimensionering av dessa grundläggningsalternativ. Forskningsresultaten sammanfattas i denna slutrapport, som även inkluderar sex vetenskapliga artiklar., This report has six scientific articles appended, accessible in the following links:Paper A: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293858Paper B: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290364Paper C: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264902Paper D: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-316339Paper E: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290163Paper F: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-320072QC 20230120

This bright spark lecture opens by noting that geological and geotechnical uncertainty affects not only a tunnel's structural safety but also its cost and time plan. Cost overruns and delays of underground excavation projects in rock are, in fact, a huge problem worldwide, and neglecting the effect of geological uncertainty in the project planning can be an important reason for this. As a consequence, both clients and contractors need sensible risk management tools and contractual frameworks that facilitate fair risk sharing between the involved parties and reduce the number of contractual disputes. The lecture will highlight a number of such tools, like probabilistic time and cost assessments and Geotechnical Baseline Reports, as well as discuss their use from a risk management perspective., This is a Bright Spark Lecture, awarded by the ISSMGEPart of proceedings: ISBN 978-981-18-5182-7, QC 20230308

Observationsmetoden framhålls ofta som ett viktigt verktyg för dimensionering av tunn­lar i hårt berg. Genom att observera konstruktionens beteende under byggtiden kan man minska den så kallade epistemiska osäkerheten, som är kopplad till bristen på kunskap om de verk­liga geotekniska förutsättningarna. Detta medför att man kan tillåta mindre konservativa designlösningar än vad som annars skulle krävas ifall man inte beaktade sådana observa­tioner. Tack vare de senaste årens utveckling av nya sannolikhets­baserade verktyg och beräkningsmetoder, är det idag möjligt att använda observations­metoden i ett sannolikhets­baserat ramverk. Därmed kan mätdata användas för att for­mellt uppdatera den beräknade brottsannolikheten för konstruktionen. Det saknas dock idag både riktlinjer, rekommendationer och praktiska exempel på hur detta kan utföras i verkliga projekt. Detta forskningsprojekt har därför syftat till att visa hur det sannolikhetsbaserade ramverket för observationsmetoden kan användas vid dimensionering av bergtunnlar. En central del av observationsmetoden utgörs av hur man ska fastställa de larmgränser som anger oacceptabelt beteende hos konstruktionen och vars överskridande innebär att åtgärder behöver sättas in för att säkra konstruk­tionen. Denna slutrapport ger en överblick över den konceptuella idén för det sannolikhets­baserade ramverket för observationsmetoden (då teorin presenteras i detalj i Spross doktors­avhandling som publicerats som BeFo-rapport 163). En utredning ges därefter av hur sannolikhetsbaserade larmgränser kan fastställas inom ramen för detta. Den teo­retiska bak­grunden och praktiska tillämpningen utvecklas i detalj i två bifogade veten­skapliga artiklar. Artikel I är publicerad i Structural Safety och presenterar en beräk­ningsalgoritm för fast­ställandet av sannolikhetsbaserade larmgränser. Algoritmen använder sig av delmängds­simulering (eng. Subset Simulation) och fungerar med både analytiska och numeriska (finita element-)modeller i, The observational method is highlighted commonly as an important tool for the structural design of tunnels in hard rock: by observing the structural behaviour during construction, a large portion of the epistemic uncertainty (lack of knowledge) that was present in the design phase can be eradicated. This allows for less conservative design solutions, which in many cases can lead to more economic designs. Following the development of new reliability-based tools and calculation procedures, it is today possible to apply the observa­tional method within a reliability framework. This means that measurement data can be used to formally update the probability of unsatisfactory structural behaviour. There is however a lack of guidelines and recommendations for how to use these new tools in practice. This research project has therefore aimed to address this issue by showing how the reliability-based framework for the observational method can be implemented into the design of rock tunnels. A key issue for the observational method is the establishment of thresholds toward unacceptable structural behaviour, as the vio­lation of such a thresholds requires that prepared safety-enhancing design modifications are put into operation. This final report outlines the conceptual idea of the reliability framework for the obser­va­tional method (as it was previously published in Spross Ph.D. thesis from 2016) and discusses in detail how reliability-based alarm thresholds can be established. In two appended journal articles, the scientific basis for the procedure is elaborated in detail. Article I is published in Structural Safety and presents a computational algorithm for estab­lishment of reliability-based alarm thresholds. The algorithm employs Subset simulation and can be used with both analytical and numerical (finite element) models in the evalua­tion of the considered limit state function. Article II presents a comprehen­sive calculation example inspired by the ground conditions pre, QC 20230131

Att bygga undermarksanläggningar är ofta tekniskt komplicerat, samtidigt som dessa byggprojekt kännetecknas av stora geologiska och geotekniska risker. Riskerna har sitt ursprung i att det för bergbyggande är svårt att i förväg fastställa vilka tekniska egen­skaper som berget har. Men detta ger inte bara tekniska utmaningar utan även juridiska och ekonomiska: vem ska stå för den ekonomiska risken om kostnaderna blir högre än väntat? Denna fråga regleras i kontraktet mellan beställare och entreprenör. Om kon­traktet visar sig vara otydligt beskrivet när kostnader väl ska regleras, hamnar man ofta i en juridisk tvist. Ett relaterat problem är hur riskerna presenteras i förfrågnings­underlaget. Om detta är otydligt avseende riskerna försvårar det för entreprenadbolagen att göra sin kalkyl och komma fram till en rimlig prissättning. Internationellt finns ett kontraktsdokument som kallas Geotechnical Baseline Report (rapport för geotekniska bedömningsgrunder) och som tagits fram för att tydliggöra parternas ansvar för geologiska och geotekniska risker i geotekniska byggprojekt. Syftet med denna förstudierapport är att introducera principerna för hur detta kontrakts­dokument kan förstås, tolkas och tillämpas i upphandling och utförande av svenska undermarksprojekt. Rapporten är tänkt att utgöra en teoretisk grund för fortsatt forsk­ning och utveckling kring dessa frågor i Sverige. Rapporten ger dels en överblick över hur valet av affärsform (entreprenadform och kon­traktstyp och dyl.) kan förstås ur ett riskperspektiv, dels en teoretisk analys av begreppet geoteknisk bedömningsgrund och hur det fungerar som ett verktyg för riskdelning mel­lan byggprojektets parter. Ett praktiskt tillämpningsexempel presenteras och diskuteras också. Rapporten avslutas med en diskussion av det fortsatta forsknings- och utveck­lingsbehovet som kvarstår innan geotekniska bedömningsgrunder kan börja användas i praktiken i Sverige., Constructing underground structures is often technically challenging and characterised by large geological and geotechnical risk. These risks originate from the fact that it is difficult to predict the properties of the rock mass before the construction has started. But this does not only give technical challenges, but also economic and legal: who shall own the economic risk if the final cost is larger than expected? This issue is regulated in the contract between the client and the contractor. If the contract is vague, claims and disputes often arise. A related issue concerns how risks are presented to the bidders in the tender documents. If the tender documents are vague regarding the risks, it becomes more difficult for the bidders to come up with a reasonable bid amount. Internationally, there exist a contractual document called Geotechnical Baseline Report (GBR), which was created to clarify the contractual parties’ ownership of geological and geotechnical risks in geotechnical engineering projects. The purpose of this prestudy report is to introduce the principles of how this contractual document can be understood, interpreted and applied in procurement and execution of Swedish under­ground excavation projects. The report is intended to be a theoretical basis for future research and development in this field. The report first gives an overview of how the client’s considerations of different contract types can be understood from a risk perspective, which is followed by a theoretical analysis of geotechnical baselines as a concept as well as how these baselines can serve as a tool for risk sharing between the project parties. An application example is also presented and discussed. The report ends with a discussion of the research and development need that remains before geotechnical baselines can be used in the Swedish practice., QC 20230214