Idag används ofta ett samband, framtaget av Hanafy och Emery (1980), för att uppskatta deformationer vid tunnelfronten då bergförstärkning ska installeras i närheten av tunnelfronten. Sambandet visar hur deformationerna i ett referensplan utvecklas som en funktion av tunnelfrontens avstånd till referensplanet. I det här examensarbetet studerades deformationsutvecklingen i en tunnel med syftet att utvärdera hur tunnelgeometri, bergtäckning, spänningsfält och bergkvalitet påverkar deformationsutvecklingen under framdriften. I examensarbetet studerades även bergförstärkning under framdriften med syftet att jämföra resultat när hänsyn tagits till sprutbetongens härdningstid relativt när full styvhet antagits direkt vid installation samt studera belastning i bergbultar. Studien visade att analysresultat och samband framtaget av Hanafy och Emery kan återskapas med FLAC3D. Kombination av förändrat spänningsfält, tunneltvärsnitt och/eller bergtäckning medförde att deformationsutvecklingen inte följde sambandet. Resultatet kunde generaliseras till alla fall skilt från ett hydrostatiskt spänningsfält. Baserat på studien rekommenderas att sambandet enbart bör användas när hydrostatiskt spänningsfält och elastiskt materialbeteende kan antas för att uppskatta deformationer i närheten av tunnelfronten. Tredimensionell modellering i närheten av tunnelfronten rekommenderas alltid utföras när spänningsfält ej kan antas hydrostatiskt. Detta för att på ett korrekt sätt uppskatta deformationer och spänningar kring tunneln. Simulering av bergförstärkning bör genomföras baserat på verklig uttagssekvens med projektspecifika indata för att belastningshistorik och deformationer ska kunna uppskattas och användas som grund för dimensionering. / Currently, a correlation developed by Hanafy and Emery (1980), is often used to estimate deformations at the tunnel face for projects where rock reinforcement is to be installed near the tunnel face. It shows how deformations at a reference plane develops as a function of the distance to the tunnel face. In this thesis, the displacements was studied in order to investigate how tunnel geometry, rock coverage, stresses and rock quality affected the accumulation of displacements in a tunnel during excavation. Studies of rock reinforcement were conducted with purpose to compare results from simulations when the shotcrete hardening process had been considered and when maximum stiffness was assumed directly at installation. Load in bolts was also studied. The study showed that elastic analyses with FLAC3D can recreate analysis results and correlation developed by Hanafy and Emery. Combinations of changed stress field, tunnel geometry and/or rock cover resulted in three-dimensional effects which gave a different displacement ratio compared to Hanafy and Emery. This could be generalised to all cases in which the stress field differed from a hydrostatic stress field. Based on the study it is recommended to only use the correlation for estimating displacements near a tunnel face when hydrostatic stress field and elastic material behaviour can be assumed. Three-dimensional modelling should always be carried out in cases where the stress field cannot be assumed hydrostatic in order to correctly estimate displacements and stresses around the tunnel in the vicinity of the tunnel face. Simulation of rock reinforcement should be carried out based on the actual excavation sequence that will take place. Simulations should be performed with project-specific input data so that load history and displacements can be estimated properly and used in design.

Die stetige Weiterentwicklung von Mess- und Überwachungstechnik ermöglicht Setzungsprozesse und Gebirgsdeformationen mit zunehmender Genauigkeit in numerischen Modellen abzubilden. Mit Hilfe von Laserscans, durchgeführt sowohl vor als auch während der Bauarbeiten, können genauere numerische Modelle erstellt werden. Die baubegleitende Anpassung der Modellgeometrie ermöglicht zudem eine weitere Nachkalibrierung der Simulationen und erhöht damit die Zuverlässigkeit von Prognoseberechnungen. Die Simulationsergebnisse können fortlaufend mit den ursprünglichen Planungen abgeglichen und somit Ausbauplanungen angepasst und optimiert werden. / The ongoing development of monitoring and surveillance technology enables us to reproduce subsidence and rock mass deformation in numerical models with increasing precision. Laserscans prior to and during the construction work increase the spatial accuracy of numerical models. Adjustments of the model geometry during the construction work allow a recalibration of models and increase the reliability of forecast simulations. Simulation results can be successively compared to construction plans and allow adjustments and optimizations of support designs.

Designing a safe and economical mining activity is the main goal of every mine design engineer. With the rise of computer modeling in mine design there is a need for a standardized method to use geologic characterization of rocks in engineering design. In this research, first a review of empirical methods will be conducted and after that a step-by-step method is presented to adequately use FLAC3D, for development pillars, in room and pillar mine in development stage. ARMPS database is used to evaluate the FLAC3D model results. ARMPS database consists of 645 case study in room and pillar mines. 170 of them are mines in development phase. In this research all 170 cases will be analyzed in FLAC3D v4.0 and the results will be compared to actual success and failure from the database. Also, the stability factor found from FLAC3D will be compared to ARMPS. Finally, it is tried to calibrate FLAC3D stability factor so it can be used in room and pillar design.

Frac-pack design is still done on conventional hydraulic fracturing models that employ linear elastic fracture mechanics. However it has become evident that the traditional models of fracture growth are not applicable to soft rocks/unconsolidated formations due to elastoplastic material behavior and strong coupling between flow and stress model. Conventional hydraulic fracture models do not explain the very high net fracturing pressures reported in field and experiments and predict smaller fracture widths than expected. The key observations from past experimental work are that the fracture propagation in poorly consolidated sands is a strong function of fluid rheology and leak off and is accompanied by large inelastic deformation and shear failure leading to higher net fracturing pressures. In this thesis a numerical model is formulated to better understand the mechanisms governing fracture propagation in poorly consolidated sands under different conditions. The key issues to be accounted for are the low shear strength of soft rocks/unconsolidated sands making them susceptible to shear failure and the high permeabilities and subsequently high leakoff in these formations causing substantial pore pressure changes in the near wellbore region. The pore pressure changes cause poroelastic stress changes resulting in a strong fluid/solid coupling. Also, the formation of internal and external filtercakes due to plugging by particles present in the injected fluids can have a major impact on the failure mechanism and observed fracturing pressures. In the presented model the fracture propagation mechanism is different from the linear elastic fracture mechanics approach. Elastoplastic material behavior and poroelastic stress effects are accounted for. Shear failure takes place at the tip due to fluid invasion and pore pressure increase. Subsequently the tip may fail in tension and the fracture propagates. The model also accounts for reduction in porosity and permeability due to plugging by particles in the injected fluids. The key influence of pore pressure gradients, fluid leakoff and the elastic and strength properties of rock on the failure mechanisms in sands have been demonstrated and found to be consistent with experimental observations. / text

The following report is the results of a master thesis project performed on the behalf of Boliden Tara Mines. The work includes a numerical modelling study with the main purpose to evaluate the room- and pillar stability for the mining method "drift-and-slash" mining currently used in the Tara Mine when mining in thin, low-rise lenses. Also, the potential of applying the "drift-and-fill" mining method was studied during the project. The numerical modelling work was performed both two-dimensionally and three-dimensionally, using the Itasca software FLAC and FLAC3D.  The study resulted in recommendations regarding the room- and pillar dimensions, mining sequence, rock support, mining method and further studies. It was concluded that the currently used room- and pillar dimensions could be altered to increase the extraction ratio and that the mining sequence and rock support should be determined depending on the room- and pillar dimensions. Also, that it could be possible to change from the drift-and-slash method to the drift-and-fill method from a stability perspective. Lastly, it was recommended to further study the rock strength and to monitor the pillar behaviour.

O uso de fundações por estacas helicoidais tem aumentado consideravelmente nos últimos anos, devido às suas vantagens comparadas a outros tipos de fundação, como a sua rápida instalação e sua capacidade de resistir simultaneamente a esforços de tração e de compressão. No entanto, os métodos de previsão do comportamento deste tipo de fundação submetida a esforços de tração (denominadas ancoragens helicoidais neste caso), ainda são insatisfatórios, e normalmente são observadas discrepâncias entre os resultados estimados por métodos teóricos e medidos em provas de carga. Entre outras razões, estas diferenças ocorrem principalmente pelo fato dos efeitos da instalação destas ancoragens no solo não serem considerados nos métodos de previsão disponíveis. No momento da instalação, os parâmetros do solo atravessado são modificados, e como é o volume de solo alterado que deve resistir ao carregamento da ancoragem sob tração, é essencial entender e quantificar este efeito de instalação para uma previsão adequada da capacidade de carga deste tipo de ancoragem. Para contribuir com o entendimento deste efeito, no presente trabalho foram realizadas simulações numéricas com o software FLAC3D, para se conhecer as modificações ocorridas no solo devido à instalação de uma ancoragem helicoidal em areia compacta. Para este fim, na simulação do solo penetrado pela hélice, foram reduzidos os valores de ângulo de atrito e do módulo de elasticidade da areia. O modelo foi validado por meio da comparação com a curva carga-deslocamento obtida experimentalmente em ensaios realizados em centrifuga. Após o ajuste do modelo numérico, foi realizada uma análise paramétrica com o objetivo de investigar o efeito da instalação no fator de capacidade de carga (Nq). Por meio da análise paramétrica também foram avaliados o deslocamento da ancoragem sob carga máxima e as tensões horizontais atuantes na superfície de ruptura. Os resultados estimados de Nq foram comparados com estudos anteriores, e mostraram um bom ajuste com resultados de provas de carga in situ e em centrifuga. Além disso, o estudo paramétrico indicou que as tensões horizontais atuantes na zona de ruptura são distribuídas em forma de tronco de cone, e variam de acordo com o diâmetro da hélice. / The use of helical foundations has increased considerably in recent years due to its advantages compared to other types of foundations, such as rapid installation and the capacity of resisting tensile and compressive loads. However, the methods normally used to predict the behavior of this type of foundation under tensile loads (called helical anchors in this case), are still unsatisfactory, and discrepancies are usually observed between the results estimated by theoretical methods and measured in load tests. Among other reasons, these differences occur mainly because the effects of helical anchor installation in the soil are not considered in the available predicting methods. During installation, the parameters of the soil penetrated are modified, and since it is this disturbed soil volume that must support the loading of the anchor under tension, it is essential to understand and quantify this installation effect for an adequate prediction of the uplift capacity of this type anchor. In order to contribute to the understanding of this effect, in the present work numerical simulations with the software FLAC3D were performed to evaluate the modifications occurred in the soil due to the installation of a helical anchor in dense sand. For this purpose, in the simulation of the soil penetrated by the helices, the values of friction angle and modulus of elasticity of the sand were reduced. The model was validated by means of the comparison with a load-displacement curve obtained experimentally in centrifuge model tests. After adjusting the numerical model, a parametric analysis was carried out to investigate the effect of the installation on the breakout factor (Nq). The parametric analyses were also used to investigate the anchor displacement at the peak load and the horizontal stresses acting on the failure surface. The estimated Nq values were compared with previous studies, and showed a good agreement with experimental results obtained by field and centrifuge tests. Additionally, the parametric study indicated that the horizontal stresses acting on the failure zone are distributed in the shape of a truncated cone, and vary with the helix diameter.

O uso de fundações por estacas helicoidais tem aumentado consideravelmente nos últimos anos, devido às suas vantagens comparadas a outros tipos de fundação, como a sua rápida instalação e sua capacidade de resistir simultaneamente a esforços de tração e de compressão. No entanto, os métodos de previsão do comportamento deste tipo de fundação submetida a esforços de tração (denominadas ancoragens helicoidais neste caso), ainda são insatisfatórios, e normalmente são observadas discrepâncias entre os resultados estimados por métodos teóricos e medidos em provas de carga. Entre outras razões, estas diferenças ocorrem principalmente pelo fato dos efeitos da instalação destas ancoragens no solo não serem considerados nos métodos de previsão disponíveis. No momento da instalação, os parâmetros do solo atravessado são modificados, e como é o volume de solo alterado que deve resistir ao carregamento da ancoragem sob tração, é essencial entender e quantificar este efeito de instalação para uma previsão adequada da capacidade de carga deste tipo de ancoragem. Para contribuir com o entendimento deste efeito, no presente trabalho foram realizadas simulações numéricas com o software FLAC3D, para se conhecer as modificações ocorridas no solo devido à instalação de uma ancoragem helicoidal em areia compacta. Para este fim, na simulação do solo penetrado pela hélice, foram reduzidos os valores de ângulo de atrito e do módulo de elasticidade da areia. O modelo foi validado por meio da comparação com a curva carga-deslocamento obtida experimentalmente em ensaios realizados em centrifuga. Após o ajuste do modelo numérico, foi realizada uma análise paramétrica com o objetivo de investigar o efeito da instalação no fator de capacidade de carga (Nq). Por meio da análise paramétrica também foram avaliados o deslocamento da ancoragem sob carga máxima e as tensões horizontais atuantes na superfície de ruptura. Os resultados estimados de Nq foram comparados com estudos anteriores, e mostraram um bom ajuste com resultados de provas de carga in situ e em centrifuga. Além disso, o estudo paramétrico indicou que as tensões horizontais atuantes na zona de ruptura são distribuídas em forma de tronco de cone, e variam de acordo com o diâmetro da hélice. / The use of helical foundations has increased considerably in recent years due to its advantages compared to other types of foundations, such as rapid installation and the capacity of resisting tensile and compressive loads. However, the methods normally used to predict the behavior of this type of foundation under tensile loads (called helical anchors in this case), are still unsatisfactory, and discrepancies are usually observed between the results estimated by theoretical methods and measured in load tests. Among other reasons, these differences occur mainly because the effects of helical anchor installation in the soil are not considered in the available predicting methods. During installation, the parameters of the soil penetrated are modified, and since it is this disturbed soil volume that must support the loading of the anchor under tension, it is essential to understand and quantify this installation effect for an adequate prediction of the uplift capacity of this type anchor. In order to contribute to the understanding of this effect, in the present work numerical simulations with the software FLAC3D were performed to evaluate the modifications occurred in the soil due to the installation of a helical anchor in dense sand. For this purpose, in the simulation of the soil penetrated by the helices, the values of friction angle and modulus of elasticity of the sand were reduced. The model was validated by means of the comparison with a load-displacement curve obtained experimentally in centrifuge model tests. After adjusting the numerical model, a parametric analysis was carried out to investigate the effect of the installation on the breakout factor (Nq). The parametric analyses were also used to investigate the anchor displacement at the peak load and the horizontal stresses acting on the failure surface. The estimated Nq values were compared with previous studies, and showed a good agreement with experimental results obtained by field and centrifuge tests. Additionally, the parametric study indicated that the horizontal stresses acting on the failure zone are distributed in the shape of a truncated cone, and vary with the helix diameter.

The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods. Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials. Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe. Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively. Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs. Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement. HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.

The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods. Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials. Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe. Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively. Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs. Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement. HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.

This study uses dynamic centrifuge tests and three-dimensional (3D), nonlinear finite-difference analyses to: (1) evaluate the effect of soil-cement grid reinforcement on the seismic response of a deep soft soil profile, and (2) to examine the dynamic response of structures supported by shallow foundations on soft clay reinforced by soil-cement grids. The soil profile consisted of a 23-m-thick layer of lightly over-consolidated clay, underlain and overlain by thin layers of dense sand. Centrifuge models had two separate zones for a total of four different configurations: a zone without reinforcement, a zone with a "embedded" soil-cement grid which penetrated the lower dense sand layer and had a unit cell area replacement ratio Ar = 24%, a zone with an embedded grid with Ar = 33%, and a zone with a "floating" grid in the upper half of the clay layer with Ar = 33%. Models were subjected to a series of shaking events with peak base accelerations ranging from 0.005 to 0.54g. The results of centrifuge tests indicated that the soil-cement grid significantly stiffened the site compared to the site with no reinforcement, resulting in stronger accelerations at the ground surface for the input motions used in this study. The response of soil-cement grid reinforced soft soil depends on the area replacement ratio, depth of improvement and ground motion characteristics. The recorded responses of the structures and reinforced soil profiles were used to define the dynamic moment-rotation-settlement responses of the shallow foundations across the range of imposed shaking intensities. The results from centrifuge tests indicated that the soil-cement grids were effective at controlling foundation settlements for most cases; onset of more significant foundation settlements did develop for the weakest soil-cement grid configuration under the stronger shaking intensities which produced a rocking response of the structure and caused extensive crushing of the soil-cement near the edges of the shallow foundations. Results from dynamic centrifuge tests and numerical simulations were used to develop alternative analysis methods for predicting the demands imposed on the soil-cement grids by the inertial loads from the overlying structures and the kinematic loading from the soil profile's dynamic response. / Ph. D.