An Experimental Approach to the Development of Dynamic Pressure to Improve Grout Spread

Ghafar, Ali Nejad; Mentesidis, Anastasios; Draganović, Almir; Larsson, Stefan

doi:10.1007/s00603-016-1020-2

Cited by 16 publications

(6 citation statements)

References 12 publications

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“…Solving this problem by the complex variable function method can be roughly divided into two categories. The first category is solving double-cavern or multi-cavern problems, and the other category is solving the problems of “one inside another” − Therefore, this paper intends to use the existing grouting diffusion formula to establish the characterization formula of the strength of fractured surrounding rock after grouting reinforcement in the ideal state. − Based on the “one inside another” solution of the complex variable function theory, we derived the analytical formulas of the stress and displacement of the fractured surrounding rock after grouting reinforcement and verified the reliability of the solution by a numerical method. Therefore, we can quantitatively explore the effect of grouting reinforcement on fractured surrounding rock.…”

Section: Introductionmentioning

confidence: 99%

Analytical Solution of the Grouting Reinforcement Response of a Circular Cavern in Deeply Buried Fractured Surrounding Rock under a Nonuniform Stress Field

Liu

Lyu

et al. 2022

ACS Omega

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Grouting is widely utilized to reinforce fractured surrounding rock. However, presently, the secondary stress distribution of fractured surrounding rock after grouting is not distinct, which hinders the accurate evaluation of the grouting effect. Therefore, a complex variable function solution is provided for the evolution of the stress field and the displacement field around the reinforced fractured surrounding rock subjected to a nonuniform load. By comparing the evolution of the stress and radial displacement fields around the cavern, the reinforcement effect on the fractured surrounding rock is quantitatively confirmed. The results show that grouting has an obvious modification effect on fractured surrounding rock: its radial stress and circumferential stress fields are affected to different degrees, and the circumferential stress is more obvious. Grouting makes the circumferential stress peak transfer from the wall of the cavern to the roof and floor of the cavern, which is beneficial to the stability of the cavern. The radial displacement around the cavern also decreases. The displacement of the wall decreases by approximately 24.0%, and the radial displacement of the roof and floor decreases by approximately 61.8%.

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Section: Introductionmentioning

confidence: 99%

Analytical Solution of the Grouting Reinforcement Response of a Circular Cavern in Deeply Buried Fractured Surrounding Rock under a Nonuniform Stress Field

Liu

Lyu

et al. 2022

ACS Omega

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“…In contrast to the previous efforts using high-frequency oscillating pressure, in a recent study [5] a low-frequency rectangular pressure impulse was introduced as a new alternative to increase the efficiency of the method and reduce the dissipation of the pressure impulses along a fracture. The results showed significant improvement of up to 11 times in the total volume of grout take in 30 to 43 mm slots [5]. The dissipation of the pressure impulses was then studied in a considerably longer artificial fracture with 4 m length and apertures of 230 to 10 mm [6].…”

Section: Test Setupmentioning

confidence: 99%

Development of dynamic grouting under laboratory and field conditions

Zirgulis

Ghafar

Chaudhari

2022

Geomechanics and Tunnelling

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When it comes to underground structures, water ingress from the surrounding formations leads to several environmental, economic and sustainability issues. To obtain the sealing, the grouting of rock fractures is done. Today, in the grouting operations, which are commonly conducted in almost all the tunnel and subsurface infrastructure projects, the pressure applied is static. This type of applied pressure might be suitable for the large fracture apertures > 100 μm, but it has been acknowledged that it is difficult to obtain sufficient penetration through smaller apertures, where filtration of cement particles starts to occur. Research is already done to overcome this issue by applying dynamic grouting pressure instead of static. It was proved that this approach erodes the formed filter cakes and improves grout penetrability in fractures below 100 μm. This research focuses on low‐frequency rectangular pressure impulse as an alternative to other methods. The goal is to improve grout spread in micro‐fractures (especially in apertures < 70 μm). During the investigation, a prototype dynamic injection equipment was built and tested under laboratory conditions. The 4 m variable aperture long slot (VALS) was used in the experiments to simulate rock fractures. The test showed better grout penetrability using dynamic pressure approach. At the current time of writing this article, preparation works are done for field test of prototype equipment at SKB Hard Rock Laboratory (HRL) at Äspö, Sweden.

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“…The oscillation in pressure in combination with low sampling frequency, is considered as a negative factor in this study, but it is important to emphasise that the oscillating pressure could give a positive effect on the grouting process with regard to penetration of cement into small fractures (Ghafar et al, 2016).…”

Section: Interpretation Of Real Datamentioning

confidence: 99%

Development of an algorithm to detect hydraulic jacking in high pressure rock mass grouting and introduction of the PF index

Strømsvik

Morud

Grøv

2018

Tunnelling and Underground Space Technology

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Pre-excavation rock mass grouting is a common procedure for reducing water ingress into tunnels during construction in Norwegian tunnelling. The level of grouting pressure is a disputed subject and the knowledge of how the rock mass responds to the high pressure and how this inflicts on the grouting results is sparse and little investigated. For this reason, it is of interest to use data from high pressure grouting performed in Norwegian projects to investigate these matters. This paper presents the development of a method for identifying hydraulic jacking during rock mass grouting and the making of an algorithm to perform computerized detection of hydraulic jacking in grouting logs. The algorithm is the base for a larger study, where screening for hydraulic jacking is performed in over hundred grouting rounds, distributed on several Norwegian tunnels excavated in rock mass. The relation between grout flow and grouting pressure has shown to be vital for the understanding of the grouting progress and events occurring during the grouting. Interpretation of pressure and flow as two separate variables, which are affected by aliasing, caused by low and irregular sampling frequency is a challenging task, and it was found to be helpful to create a parameter to represent this relationship, named the PF index (Pressure Flow index). This parameter has also shown to be useful in other applications such as monitoring the grouting progress on site.

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An Experimental Approach to the Development of Dynamic Pressure to Improve Grout Spread

Cited by 16 publications

References 12 publications

Analytical Solution of the Grouting Reinforcement Response of a Circular Cavern in Deeply Buried Fractured Surrounding Rock under a Nonuniform Stress Field

Analytical Solution of the Grouting Reinforcement Response of a Circular Cavern in Deeply Buried Fractured Surrounding Rock under a Nonuniform Stress Field

Development of dynamic grouting under laboratory and field conditions

Development of an algorithm to detect hydraulic jacking in high pressure rock mass grouting and introduction of the PF index

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