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Auxiliary methods technology
Published in Emilio Bilotta, Renato Casale, Claudio Giulio di Prisco, Salvatore Miliziano, Daniele Peila, Andrea Pigorini, Enrico Maria Pizzarotti, Handbook on Tunnels and Underground Works, 2023
G. Cassani, M. Gatti, C.L. Zenti, V. Manassero, S. Pelizza, A. Pigorini
The TAM method is a multiple phase process, which allows several successive injections in the same zone. This involves installing a plastic or steel sleeved pipe (tube à manchettes or TAM) into a grout hole drilled down to the design depth. The pipe is equipped with one-way valves at fixed intervals (0.33 or 0.50 m), each one constituted by small holes, drilled into the pipe to act as outlets for the grout; these holes are tightly covered by rubber sleeves (manchettes), which open only when under pressure and close when pressure ceases. The TAM is permanently sealed in with a sleeve grout composed of a cement-bentonite-water mixture. The sleeve grout seals the borehole between the pipe and the soil to prevent the injection grout from channelling along the borehole. This means that, under pressure, the injection grout breaks through in radial direction and penetrates into the soil. Once the sleeve grout has set, pressure grouting can be performed. In order to inject through a sleeve, a double packer fixed at the end of a smaller-diameter injection pipe is inserted into the sleeved pipe and centred around the sleeve to form a closed chamber with one-way valve outlets (Figure 4.43).
Decommissioning of Groundwater Control Systems
Published in Pat M. Cashman, Martin Preene, Groundwater Lowering in Construction, 2020
The ducting of the wells of sumps through the slab allows them to continue to operate until the structural designer indicates that the concrete structures have sufficient strength and integrity to allow pumping to be stopped. At that point, the wells can be capped off. The flange of the steel duct is below the original groundwater level, so as water levels recover, the duct will begin to overflow. In relatively low-permeability materials and in shallow structures, this can be done by quickly removing the well or sump equipment and rapidly capping the top of the conductor pipe with the blanking flange, bolts and gaskets. Where high-permeability aquifers are present and/or the potential groundwater heads above flange level are high, capping of the ducts may be difficult due to the rapid onset of overflowing conditions soon after the pumps are stopped. One option is, during the pumping period, to attach a large-diameter valve to the top of the duct and pass the pumping equipment through the valve. When pumping is stopped, the equipment can be removed rapidly by a crane or hoist, while the well overflows, with temporary pumps at slab level used to remove the excess water. The valve can then be closed to seal off the flow. If the wells or sumps are to be decommissioned, this will require pressure grouting through the duct to inject grout backfill against the groundwater pressure.
Highway maintenance
Published in Malcolm Copson, Peter Kendrick, Steve Beresford, Roadwork, 2019
Malcolm Copson, Peter Kendrick, Steve Beresford
Although concrete slabs do not require strong sub-base support, they do require reasonably uniform support, in order to prevent eventual tilting or cracking of the slab, under traffic loading. If this uniform support is lacking, pressure grouting is a possible solution to the problem.
Computation of pull-out resistance of pressure-grouted soil nails in sand using cavity expansion and contraction solutions
Published in International Journal of Geotechnical Engineering, 2022
Alpha Lukose, Sudheesh Thiyyakkandi
(II) Pressure grouting: During pressure grouting (i.e. cylindrical cavity expansion), the state of surrounding soil reverses and the confining stress, which was diminished upon drilling, is partially regained depending on the ratio of the grout pressure to the initial overburden stress. Although the response of soil will be elastic at the very beginning of grouting, plastic yielding of soil starts forthwith, and the radius of this plastic zone increases incrementally with the increase of grout pressure. Similar to the hole drilling, the radius of the plastic zone (; Figure 1c) and the cavity radius (i.e. radius of the grout zone, ) at the maximum applied grout pressure are to be known to estimate the corresponding soil state. A recursive approach similar to that adopted for cavity contraction (drilling) was employed to determine all the parameters of interest as discussed below:
Characteristics, numerical analysis and countermeasures of mud inrush geohazards of Mountain tunnel in karst region
Published in Geomatics, Natural Hazards and Risk, 2023
Long-Long Chen, Zhi-Feng Wang, Wu Zhang, Ya-Qiong Wang
Many grouting parameters can affect the grouting reinforcement effect of tunnel surrounding rock, including grouting material type, grouting pressure, grouting amount, grouting range, grouting liquid diffusion radius, etc. Among them, the diffusion radius of grouting liquid is an important parameter affecting the grouting reinforcement effect because it can directly affect the stability of surrounding rock. On the premise that other parameters remain consistent, the discrete element numerical calculation model can be established to analyze the influence of different grouting diffusion radius on the grouting reinforcement effect.