| 1. |
- Al-Gburi, Majid, et al.
(author)
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Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks
- 2018
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In: European Journal of Environmental and Civil Engineering. - : Taylor & Francis. - 1964-8189 .- 2116-7214. ; 22:2, s. 226-245
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Journal article (peer-reviewed)abstract
- Estimation of restraint is very important for accurately predicting the risk of early thermal and shrinkage cracking in concrete structures. The stress in young concrete is affected by changes in its dimensions during hydration and the restraint imposed by adjoining structures. In concrete culverts, the restraints from existing structures acting upon the first and second casting sections to be cast are different, causing them to exhibit different early cracking behaviour. This work presents a new method for predicting restraint in complex concrete structures using artificial neural networks (ANNs). Finite element calculations were performed to predict restraint in 108 slabs, 324 walls and 972 roofs from second sections of concrete culverts, and the results obtained were used to train and validate ANN models. The ANN models were then used to study the effects of varying selected parameters (the thickness and width of the roof and slab, the thickness and height of the walls, and the length of the culvert section) on the predicted restraint. Mathematical expressions for predicting restraint values in slabs, walls and roofs were derived based on the ANN models’ output and implemented in an Excel spreadsheet that provides a simple way of predicting restraint in practical applications. Restraint values predicted in this way agree well with the results of finite-element calculations
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| 2. |
- Amavasai, Amardeep, 1988, et al.
(author)
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Towards consistent numerical analyses of embankments on soft soils
- 2022
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In: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 2116-7214 .- 1964-8189. ; 26:7, s. 2616 -2634
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Journal article (peer-reviewed)abstract
- A consistent automated parameter derivation method for an advanced constitutive model, Creep-SCLAY1S, which considers anisotropy, structure and creep in soft soil is presented. The algorithms are implemented in a general purpose numerical framework and are robust for noisy data. The accuracy of the derived parameters are benchmarked against a well known test case: the Haarajoki test embankment. The results show that using the proposed methodology, a consistent parameter set is derived that enables accurate laboratory data and boundary value level simulations with limited to no major user intervention. The only remaining user input relates to the adjustment of the pre-consolidation pressure with 3 kPa. This difference between the laboratory and boundary value simulations is attributed mainly due to somewhat low quality of the samples.
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| 3. |
- Chen, Xu-Guang, et al.
(author)
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Analogical model test and theoretical analysis on zonal disintegration based on filed monitoring in deep tunnel
- 2013
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In: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 1964-8189 .- 2116-7214. ; 17:Suppl. 1, s. 33-52
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Journal article (peer-reviewed)abstract
- Field monitoring carried out in a deep tunnel of the Dingji coal mine in China confirmed the zonal disintegration phenomenon by using the borehole TV. Based on field monitoring, an analogical model test was conducted to research the fracture shape and forming conditions of the rock mass in the Dingji mine. To perform the model test, an analogical material and optical sensor were developed independently. Through the test, the occurrence of zonal disintegration was confirmed and the forming process was monitored. The fracture pattern of zonal disintegration was determined, and the radii of the fractured zones were found to fulfil the relationship of geometric progression. The displacement laws of surrounding rocks during zonal disintegration were obtained and found to be non-monotonic. The test results are in agreement with the field-monitoring results. Through a theory analysis based on fracture mechanics, the mechanism of zonal disintegration was revealed. The fracture zones occur as circles concentric to the cavern periphery, which is the “false face”. Each fracture zone ruptures at the elastic–plastic boundary of surrounding rocks and then coalesces into a circle. The geometric progression ratio was determined; it is related to the mechanical parameters and ground stress of the surrounding rocks and calculated as follows: And the mechanism of the non-monotonic displacement law is revealed; the continuous formation of the “false face” causes the geostress redistribution and crack opening.
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| 4. |
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| 5. |
- Jostad, H. P., et al.
(author)
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A procedure for determining long-term creep rates of soft clays by triaxial testing
- 2022
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In: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 2116-7214 .- 1964-8189. ; 26:7, s. 2600-2615
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Journal article (peer-reviewed)abstract
- The paper presents a procedure for determining a significantly larger range of creep rates (isotaches) of soft clays than found from standard incremental loading oedometer tests. The test is performed in a triaxial apparatus by first loading up to the virgin compression line at a relevant effective stress level and then determine the creep rates at different stress states along an unloading branch keeping the horizontal to vertical effective stress ratio constant. The test procedure is tested on a soft Norwegian plastic marine clay. Challenges due to the non-linear behaviour of natural soft clays where the standard creep and compression indexes are not constant values are demonstrated, and recommendations for how to account for this effect are given. The obtained results from the test are also compared with results from a parallel long-term creep phase in a standard oedometer apparatus taken from the same block sample.
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| 6. |
- Mangraviti, Viviana, 1991, et al.
(author)
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Geosynthetic-reinforced and pile-supported embankments: theoretical discussion of finite difference numerical analyses results
- 2023
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In: European Journal of Environmental and Civil Engineering. - 2116-7214 .- 1964-8189. ; 27:15, s. 4337-4363
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Journal article (peer-reviewed)abstract
- Piled foundations are commonly employed to reduce settlements of artificial earth embankments on soft soil strata and geosynthetic reinforcements are installed at the embankment base to increase pile spacing and reduce construction costs. Despite the well-documented effectiveness of this technique, the mechanical processes, developing during the construction in the different elements constituting the 'geo-structure', are not fully understood and the design approaches are based on very simplified assumptions. They disregard the deformability of the various elements constituting the system and cannot be employed to estimate settlements. With the aim of introducing a displacement-based design approach to optimise the use of reinforcements and piles, in this article, the mechanical response of the system during the embankment construction is studied by means of large displacement non-linear finite difference numerical analyses, in which the geosynthetic reinforcement is modelled as an elastic membrane. The arching effect developing within the embankment body is described and the evolution of the process zone, where shear strains localise, is discussed. The global system response is described in terms of (i) average, (ii) differential settlements at the top of the embankment and (iii) maximum tensile force within the geosynthetic reinforcement.
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| 7. |
- Pham, Tuan A., et al.
(author)
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A new index for the strength analysis and prediction of cement-mixed soils
- 2022
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In: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 1964-8189 .- 2116-7214. ; 27:4, s. 1512-1534
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Journal article (peer-reviewed)abstract
- In geotechnical projects involving soft soils, cement-mixed soils are an excellent way to improve the mechanical behaviour and engineering performance of soils. The water-to-cement ratio, cement content, and porosity are the most critical parameters impacting the strength of cement-mixed soils, but their effects are less well understood. The proportional influence of cement amount, porosity, and moisture content on cement-mixed soil strength is investigated in this research. The results showed that as the water-to-cement ratio increases, the influence of cementation and porosity on unconfined compressive strength decreases. The blended volume ratio is proposed as a new and adequate index for evaluating cement-mixed soil strength based on the experimental results. The blended volume ratio is the product of the void/cement volume ratio and the water/cement volume ratio. While the current index has not fully addressed the important effects of the water-to-cement ratio and porosity, the blended volume ratio allows describing the concurrent influences of porosity, cement amount, and water amount on the strength development. The experimental results showed that the cement-mixed soil strength is a function of the blended volume ratio. An empirical equation based on the blended volume ratio was then proposed for predicting the strength of cement-mixed soils. The validation of the proposed equation is verified by strength analysis for several different test data sets. A good agreement between measured and predicted results indicated that the proposed model is applicable to predict well the strength of cement-mixed soils.
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| 8. |
- Wood, Tara, 1974, et al.
(author)
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Modelling the creep of deep foundations in soft Gothenburg clays
- 2022
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In: European Journal of Environmental and Civil Engineering. - : Informa UK Limited. - 2116-7214 .- 1964-8189. ; 26:7, s. 2581 -2599
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Journal article (peer-reviewed)abstract
- The design of deep foundations in areas with significant background creep deformation is a challenge. In Sweden, mainly empirical methods have been used in the design of deep foundations. Generally, the predictions have been highly inaccurate, in particular with regards to the long-term deformations. Therefore, a stepwise approach is proposed, which stems from the concept of performance based design. It is shown that with the proposed approach, it is for the first time possible to perform representative back analyses of the long-term response of deep foundations in an environment with ongoing settlements. This is achieved with simplified 2D finite-element analyses using a commercially available creep model. Design assumptions and simplifications are defined based on careful back analysis of relevant case studies in the area that can be found in literature. Finally, the approach is validated by comparison with long-term monitoring of a 22-storey building on a floating piled raft.
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| 9. |
- Nilsson, Lars-Olof, et al.
(author)
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On uncertainties and inaccuracies in empirical chloride ingress modelling
- 2011
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In: European Journal of Environmental and Civil Engineering. - 2116-7214. ; 15:7, s. 981-990
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Journal article (peer-reviewed)abstract
- This paper gives an overview of the current state-of-the-art of modelling chloride ingress and focuses on identified uncertainties and inaccuracies in the common way of applying the widely used empirical models. Examples are given in order to quantify the inaccuracies. It is also pointed out that inherent model uncertainties are likely to be of great importance due to lack of homogeneity in the data set laying behind the models. A major part of the parameter uncertainties is due to misunderstandings and lack of knowledge of decisive parts of the models, such as the time-dependency of the chloride diffusivity and the time-dependency of the surface chloride content.
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| 10. |
- Rydén, Nils
(author)
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Resonant frequency testing of cylindrical asphalt samples
- 2011
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In: European Journal of Environmental and Civil Engineering. - 2116-7214. ; 15:4, s. 587-600
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Journal article (peer-reviewed)abstract
- There is a need to develop simple and quick non-destructive tests to measure the complex dynamic modulus of asphalt over a wide frequency and temperature range, i.e. mastercurve. In this study results from free-free resonant frequency measurements on cylindrical disk shaped asphalt samples are presented. The resulting mastercurve, obtained by resonant frequency testing at different temperatures, compares well with reference values within the high modulus range. The proposed method is simple and repeatable.
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