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- Axelsson, Magnus, 1974, et al.
(författare)
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The PenetraCone, a new robust field measurement device for determining the penetrability of cementitious grouts
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 25:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- One of the most crucial parameters for successful grouting is to ensure that the grout can penetrate the necessary apertures. For the most commonly used grout, cementitious grout, the available methods for determining the ability to penetrate apertures involves several measurements with different meshes or similar, which need to be evaluated. However, during the grouting process in the field there is rarely any time for evaluation and the most commonly used field method today stipulates a mesh width through which a certain volume need to pass. This implies that only an indirect measurement of the penetrability is performed. In order to perform direct and fast field measurements of the penetrability, a new, robust measuring device has been developed at Chalmers University of Technology in Gothenburg, Sweden. The device is named PenetraCone and the measuring part consists of a gap that is formed between two conical cylinders. The penetrability characteristics are measured by decreasing this gap as grout flows through. The gap is measured using a dial indicator gauge. Initial tests with the PenetraCone show that two characteristic gaps or widths can be evaluated. The width as the grout flow goes from continuous flow to dripping is termed bfilter and when the flow stops completely it is termed bstop. The parameter bfilter is related to the commencement of clogging or filtration of the cementitious grout. This means that for apertures larger than bfilter the cement passes unrestricted but for narrower apertures filtration will commence. This filtration process will occur in apertures down to bstop, which indicates the smallest aperture that the cement can pass through and for apertures below bstop the cement will not penetrate at all. The device is easy to use and the tests show that consistent values are obtained. The accuracy seems good enough for use as a control of the penetrability of cementitious grouts in the field. For use in production, the PenetraCone should be placed on the grouting rig, after the mixer, so that direct measurements can be performed on the grout that will actually be used for grouting. By relating the measured parameters to the penetrability requirements, quick decisions regarding the quality of the grout can be made directly on the grouting rig.
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| 2. |
- Butron, Christian, 1978, et al.
(författare)
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Drip sealing of tunnels in hard rock: A new concept for the design and evaluation of permeation grouting
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 25:2, s. 114-121
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new pre-excavation grouting concept to prevent dripping and reduce the inflow into a railway tunnel. For this purpose, the tunnel's roof was drip-sealed using colloidal silica and the walls and invert of the tunnel were grouted with cement. The grouting design process followed a structured approach with pre-investigations of core-drilled boreholes providing parameters for the layout. Water pressure tests and pressure volume time recordings were used for the evaluation. Results showed that the design was successful: the total transmissivity was reduced from 4.9 x 10(-08) m(2)/s to the measurement limit (1.6 x 10(-08) m(2)/s), and the dripping was reduced to eight spots from the roof. Improved rock characterisation showed that the grout hole separation was within the transmissivity correlation length and that grouting efficiency depends to a large extent on the dimensionality of the flow system of the rock mass. (c) 2009 Elsevier Ltd. All rights reserved.
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| 3. |
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| 4. |
- Fransson, Åsa, 1971, et al.
(författare)
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Estimation of deformation and stiffness of fractures close to tunnels using data from single-hole hydraulic testing and grouting
- 2010
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Ingår i: International Journal of Rock Mechanics and Minings Sciences. - : Elsevier BV. - 1365-1609. ; 47:6, s. 887-893
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Tidskriftsartikel (refereegranskat)abstract
- Sealing of tunnel sin fractured rocks is commonly performed by pre- or post-excavation grouting. The grouting boreholes are frequently drilled close to the tunnel wall, an area where rock stresses can be low and fractures can more easily open up during grout pressurization. In this paper we suggest that data from hydraulic testing and grouting can be used to identify grout-induced fracture opening, to estimate fracture stiffness of such fractures, and to evaluate its impact on the grout performance. A conceptual model and a method are presented for estimating fracture stiffness. The method is demonstrated using grouting data from four pre-excavation grouting boreholes at a shallow tunnel (50 m) in Nygard, Sweden, and two post-excavation grouting boreholes at a deep tunnel (450 m) in Aspo HRL, Sweden. The estimated stiffness of intersecting fractures for the boreholes at the shallow Nygard tunnel are low (2-5 GPa/m) and in agreement with literature data from field experiments at other fractured rock sites. Higher stifness was obtained for the deeper tunnel boreholes at Aspo which is reasonable considering that generally higher rock stresses are expected at greater depths. Our method of identifying and evaluating the properties and impact of deforming fractures might be most applicable when grouting takes place in boreholes adjacent to the tunnel wall, where local stresses might be low and where deforming (opening) fractures may take most of the grout. (C) 2010 Elsevier Ltd. All rights reserved.
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| 5. |
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| 6. |
- Stille, Björn, 1969, et al.
(författare)
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A review of the Namntall Tunnel project with regard to grouting performance
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 25:4, s. 346-356
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Tidskriftsartikel (refereegranskat)abstract
- The 6 km tunnel under the Namntall hill is a part of the Botniabanan railway project in northern Sweden. The tunnels were excavated by means of drilling and blasting and with, for Scandinavian conditions, a normal grouting routine. The grouting is performed to reduce water ingress into the tunnel to the level defined in the contract. When the water ingress requirements proved difficult to meet, it was obvious that the geological and the hydrogeological conditions in the tunnel would dictate the work processes. A distinctive change in rock conditions influenced both grouting performance and seepage into the tunnel. The rock conditions and the grouting were quantified throughout the project and these are summarized in this paper. It can be concluded that the strongest correlation is between the water ingress, the hydrogeological conditions and the density of the zones and the conditions in and around these zones. The paper suggests a different approach to hydrogeological prognosis and the grouting process, such as distribution of grouting classes, increased mixer capacities and regular use of two grouting rounds. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Stille, Björn, 1969, et al.
(författare)
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Experiences With Real Time Grouting Control Method
- 2010
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Ingår i: Bergmekanikdag : föredrag vid Bergmekanikdag i Stockholm 8 mars 2010.. - 0281-4714. ; , s. 119-132
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In the paper the concept of “Real Time Grouting Control Method” is described in order to calculate the grout penetration and to control grouting in real time by applying developed theories for grout spread. The stop criterion can with this method be related to achieved groutspread such as the fact that grouting is completed when the grout penetration for the smallest fracture that has to be sealed is above a certain minimum value (target value) or before the grout penetration for the largest fracture aperture reaches a certain maximum value (limitingvalue).It might also be possible by following the ongoing grouting minute by minute to predict the course of the grout flow and spread and also analyze the risk for uplift and jacking. These issues will also be discussed in the paper.Verification of the “Real Time Grouting Control Method”, with field data from four tunnel projects in Sweden is presented in the paper. The calculated flow dimensionality, the calculated fracture apertures and the calculated grout flows were quite close to thosemeasured. This indicates that the “Real Time Grouting Control Method” may be applicable to real grouting design and control.
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