| 1. |
- Carlsson, Mats, et al.
(författare)
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On risk management in large infrastructure projects
- 2005
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Ingår i: Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Vols 1-5. - 9789059660274 ; , s. 2785-2788
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Konferensbidrag (refereegranskat)abstract
- Large infrastructure projects are in general unique as the conditions and demands vary from one project to another. Furthermore, these projects are often related to risks of different nature due to high technological level, high environmental, public and political focus, long lead and project times, large and complex organizations, complex contracts etc. This paper aims to give some guidelines how to perform a successful management of risks in a large infrastructure project. The main conclusion is that the key to a successful risk management in a large infrastructure projects is early planning and a strict and continuous execution during the entire life-cycle of the project. Good planning and control of the risks enable an organized, comprehensive and iterative approach for identifying and evaluating the risks and give handling options necessary to optimize the project strategy. The management of risks should be performed as early as possible in the life-cycle of a project in order to ensure that critical risks are incorporated into the project plan and addressed with mitigation actions.
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| 2. |
- Hintze, Staffan, et al.
(författare)
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Effektivare hantering av geotekniska risker i infrastrukturprojekt
- 2006
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Ingår i: Bygg och Teknik. - 0281-658X .- 2002-8350. ; :2, s. 22-28
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Under de senaste årtionden har många infrastrukturprojekt blivit väsentligt dyrare och tagit längre tid att genomföra än beräknat. En stor del av projekten har dessutom orsakat kostsamma tvister för flera parter i projektet och för samhället. Kostnaderna för skador på grund av bristande hänsyn till de geotekniska faktorerna står för en betydande del av totalkostnaden.
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| 3. |
- Johansson, Teddy, 1960-
(författare)
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Artificial Ground Freezingin Clayey Soils : Laboratory and Field Studies of Deformations During Thawing at the Bothnia Line
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial ground freezing as a method to temporarily stabilize and create hydraulic sealing in urban as well as in rural areas has been used in a number of Swedish construction projects, particularly during the last decade. One problem with the freezing of soil and rock is that fine-grained clayey types of soils have showed a tendency to under certain circumstances, during the thawing process, create a pore water overpressure and to consolidate, despite a change in the external loading conditions. In certain cases, this condition can be a desired effect as the soil mass after a freeze- and thaw cycle acquires overconsolidated properties. The main objectives of this study are, to describe and review the knowledge and current state of practice of artificial ground freezing, to increase the understanding about the conceptual behaviour for prognosis of the vertical deformation concerning artificial ground freezing and to compare and discuss results from laboratory and field studies concerning vertical deformation during thawing process for Bothnia soil. The field studies and the laboratory tests in this research study have been performed with soil from the freezing of the Bothnia Line in the vicinity of Stranneberget. The Bothnia Line is the railway link between Nyland, north of Kramfors, and Umeå. This thesis relates to a part of the Bothnia Line. It deals with the behaviour of soil during thawing by means of temporary stabilization and hydraulic sealing of fine-grained soil through artificial freezing using brine as the cooling agent. However, the reason behind the problem consists of the final deformations due to the thawing process. The general conclusions of this study are; the Bothnia soil water content decreased in mean approximately 14 % after a freeze-thaw cycle, which approximately corresponds to; wth = 0.8w – 1.5 the decrease of the water content has no correlation to the depth below ground surface, in contrast, there is a strong correlation between the undisturbed soil water content and the magnitude of the decrease in water content the soil liquid limit decreases after a freeze-thaw cycle, simultaneously as the relative share of clay and fine silt grains decreases while the relative share of more coarse grains increases the coarser and denser soil created after a freeze-thaw cycle obtains an increased preconsolidation pressure and an increased undrained shear strength.
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| 4. |
- Lucian, Charles
(författare)
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Geotechnical Aspects of Buildings on Expansive Soils in Kibaha, Tanzania : Preliminary Study
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this study is on potential problems resulting from construction on expansive soils in Kibaha region, Tanzania. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the soil behaviour and their interaction with structures, specifically as they relate to shallow foundations, has been of more interest to the study in order to evaluate properly the source of the problem. The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area. The geotechnical results are linked with the performance of the foundation as well as structures. Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples. The collected samples were submitted to soil laboratories at KTH and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests (free swell and swelling pressure). The results of this investigation indicate that soil in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell. Since swell potential and swell pressure are key properties of expansive soils, the swell parameters were measured by free swell tests and one-dimensional oedometer swell tests respectively. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa. The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of montmorillonite in the soil. It is from this fact that the source of the problem is in the expansive soils coupled with poor building materials. Physical conditions of the surveyed properties in the area confirmed the hypothesis of building damages due to poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations is supplemented with prototypes of strip foundations whose performances are to be monitored over a long period. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil.
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| 5. |
- Lucian, Charles, 1963-
(författare)
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Geotechnical Aspects of Buildings on Expansive Soils in Kibaha, Tanzania
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this study is on potential damages to buildings resulting from expansive soils in Tanzania, particularly clay soils in Kibaha. For the fact that most of the affected structures are founded on expansive soils, a clear understanding of the behaviour of soils and their interaction with structures has been of interest to the study in order to evaluate properly the source of the problem.The geotechnical behaviour of expansive clay soils is investigated by looking into the geomorphologic, geological and climatic conditions and mineralogical composition of the soils in the study area.Two sites, representative of known problem-areas in Kibaha were selected for geotechnical tests. Geotechnical site investigation consisted of open trial pits, profile description and the collection of both disturbed and undisturbed samples. To extend and amplify the findings, supplementary samples were collected from the environs of the two sites.The collected samples were submitted to soil laboratories at KTH, ARU, SEAMIC and DIT for mineralogical composition tests, natural water content, density, Atterberg limits and swell tests. The results of this investigation indicate that soils in Kibaha contains clay (31%), have high liquid limit (59%) and plastic limit (37%) which indicate high potential swell.Since swell pressure, free swell and swell percent are key properties of expansive soils, the swell properties were measured by free swell tests and one-dimensional oedometer swell tests. The free swell ranged from 100% to 150% and the swell pressure was in the region of 45 kPa. The coefficient of linear extensibility (COLE) was determined for characterizing expansive clays. For all tested samples, COLE ranged from 0.09 to 0.14 indicating that soils fall in the region of high to very high expansion potential rating. The properties of expansive soils were confirmed by the x-ray diffraction test which showed the presence of smectite in the soil. Furthermore, total suction measurement technique using filter paper method indicated that the soils have high suction values, signifying that they have a tendency to swell upon wetting depending on plasticity of particular soil.The depth of the active zone was measured as a function of moisture variations in the profiles during two extreme weather conditions. The active zone depth was found to be between 1.0 and 2.0 m deep. Procedures to assess models to predict swell in the case study were outlined together with their validity.Vertical and horizontal spatial variability in selected soil properties was defined using geostatistical techniques through the fitting of variogram. The indicator semivariograms of both clay contents and free swell gave a range of 20 m horizontally and 1.0 m vertically, with the horizontal variograms exhibiting greater ranges than the dipping variograms.Physical conditions of the surveyed properties in the area confirmed that building damages are associated with poor building materials triggered by expansive soils. In support of the obtained data, the actual behaviour of the foundations was supplemented with prototypes of strip foundations whose performances were monitored over a period of four months. Finally, suggested are the ways forward to solve the problem of foundation on expansive soil
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| 6. |
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| 7. |
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| 8. |
- Ma, Jianqin, et al.
(författare)
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Apparent Earth Pressures of Soft Soils overlying Hard Bedrock at South Link in Stockholm
- 2007
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Ingår i: Proceedings of the 4th International Conference on Soft Soil Engineering - Soft Soil Engineering. - : Taylor & Francis Group. - 9780415422802 ; , s. 299-307
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Konferensbidrag (refereegranskat)abstract
- The apparent earth pressures measured at the South Link Project in Stockholm are used to analyze the pressure on sheet pile walls at deep excavations in soft soils overlying bedrock. The depths of the excavations vary from 3 m to 16 m and the toes of the walls are keyed into bedrock. Measured apparent earth pressures are over the Peck's (1969) envelope for soft clay but approximate to initial stress at rest. The normalized distribution pattern of the pressures indicates a large apparent earth pressure in the upper part of a test section. The well kept anchor load contributes to the large apparent earth pressure. This case indicates that the beneficial effect of the presence of bedrock may be over-shadowed by the low strength of soft soils, especially when the distance from excavation level to bedrock is larger than the depth of excavation.
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| 9. |
- Ma, Jianqin, et al.
(författare)
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Back Analysis on a Deep Excavation in Stockholm with Finite Element Method
- 2006
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Ingår i: Proceedings of the 6th European Conference on Numerical Methods in Geotechnical Engineering - Numerical Methods in Geotechnical Engineering. - : Taylor & Francis Group. - 0415408229 ; , s. 423-429
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Konferensbidrag (refereegranskat)abstract
- A deep excavation section from the South Link in Stockholm is analyzed with 2D PLAXIS. The excavation, protected by anchor back-tied sheet pile walls, is 12-m-deep and 43-m-wide in soft soils overlying bedrock. Except wall installation, six soil excavations, five anchor preloading stages and seven consolidation analysis stages are presented in a Mohr-Coulomb model. The back-calculated lateral displacements in the numerical model are about 15% less than the monitored in the middle and lower parts of the test section, while about 20% larger in the upper part. The analysis results for the stage of soil excavation are closer to the monitoring results than for the stage of anchor preloading. The magnitude of settlement behind the sheet pile wall in the numerical model is less than that of the monitoring result. Negative soil volume strain is selectively used to discuss a possible mechanism with significant settlement increase.
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| 10. |
- Ma, J. Q., et al.
(författare)
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Behavior of sheet pile walls at deep excavations in soft soils overlying hard rock in Stockholm
- 2008
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Ingår i: Int. Conf. Comput. Methods Adv. Geomech.. - 9781622761760 ; , s. 3922-3929
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Konferensbidrag (refereegranskat)abstract
- The deformation of retained soil is of importance for the design of a deep excavation in soft soil. The influence of bedrock underlying the soils on the behavior of the retaining wall needs proper evaluation. This contribution shows a case study on deep excavation in soft soil overlying bedrock at the South Link Infrastructure Project in Stockholm. The behavior of sheet pile walls at the South Link shows that both lateral displacement and settlement are larger than the magnitude from similar case histories. Exemplified by section 1/840N, the features of lateral displacement increment are analyzed with monitoring and PLAXIS simulating results. The analysis results indicate that the beneficial influence of bedrock may be overshadowed by the low strength of soils in which excavation occurs.
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