Injection Treatment for Tunneling Excavation in Sandy Soils with High Fines Content

Johnatan González-García, Celestino González-Nicieza, Martina-Inmaculada Álvarez-Fernández and María-Belén Prendes-Gero
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Johnatan González-García: Perforaciones Noroeste, S.A., 33002 Oviedo, Spain
Celestino González-Nicieza: DinRock Group, University of Oviedo, 33003 Oviedo, Spain
Martina-Inmaculada Álvarez-Fernández: DinRock Group, University of Oviedo, 33003 Oviedo, Spain
María-Belén Prendes-Gero: DinRock Group, University of Oviedo, 33003 Oviedo, Spain

Energies, 2021, vol. 14, issue 21, 1-19

Abstract: Instability and high permeability are two of the problems facing tunnelling excavations in soils with high fines content. Among the different techniques used to improve these soils, the injection of cement grouts stands out. In this work, a grouting treatment is designed to ensure the stability of the ground during the construction of two tunnels linking two municipalities in the north of Spain in Biscay, and to reduce the inflow of water from the aquifer located in the vicinity of these tunnels. First of all, the rock mass is analysed and the material to be injected is selected on the basis of the authors’ experience as well as setting time and compressive strength. Subsequently, with a test device designed by the DinRock research group of the University of Oviedo, two types of laboratory tests are carried out in order to analyse the effect of fines migration and washing on the water flows and the effect of re-injections of grouts with different densities on the permeability value. The results show that, in sandy materials, obtaining high degrees of waterproofing together with large stable zones can only be achieved by a combination of treatments and stages with different materials and densities. In addition, maximum values for both injection pressure and flow rate must be established depending on the type of grout and the permeability of the soil. Once the problem has been analysed, the injection treatment is designed and executed. The treatment consists of one pre-injection in four stages with 30 boreholes drilled in the top heading, 19–20 boreholes drilled in the bench, and one post-injection with boreholes drilled around the perimeter of the tunnel in those areas where the pre-injection does not achieve the desired degree of waterproofing.

Keywords: tunnelling excavation; injection treatment; cement grouting; ground stability; waterproofing (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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