Investigation into the effects of two component grout properties on surface settlements


Sharghi M., Chakeri H., ÖZÇELİK Y.

TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY, cilt.63, ss.205-216, 2017 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 63
  • Basım Tarihi: 2017
  • Doi Numarası: 10.1016/j.tust.2017.01.004
  • Dergi Adı: TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY
  • Sayfa Sayıları: ss.205-216

Özet

Ground displacement is an inevitable problem in the excavation and construction of tunnels and underground spaces near the surface of the earth. In urban areas, this displacement can affect surface and subsurface constructs. In fact, there is no possibility of boring underground space and the installation of support systems, simultaneously. Therefore, some ground displacement will happen at the level of the tunnel and eventually this displacement will also lead to surface settlement. Surface settlement becomes more important by reducing the depth of the tunnel. When settlements greater than the limit value are created they can damage surface and subsurface constructs. Therefore, identification of factors affecting the settlement of the tunnel is important and one of these factors is grouting behind the segmental lining of the tunnel. In tunneling by the shield, due to differences in the diameter of cutter head and tail shield, empty space is created around the segmental lining of the tunnel. This void is usually the ratio of the cross sectional area that is being drilled in soil and soft ground and will cause problems such as settlement of surface, displacement and damage to the lining of the tunnel and unsuitable sealing. Therefore, this empty space must be filled immediately after the drilling operation. There are different methods to fill any given empty space. One of them, in excavation by EPB-TBM, is the injection of two component grout with suitable pressure to the back of the segment (simultaneously with moving ahead of the shield of the excavator). Grout used must have the appropriate performance and mechanical properties. There is still no certain standard for the compressive strength of two component grout and the compressive strength of grout proposed is variable with different values in projects and researches. In this study, grout mechanical properties such as compressive strength, modulus of elasticity and Poisson's ratio were studied. Thus, more tests were performed with different proportions of ingredients and finally the effect of each of the components on the properties were examined. Then, to study the effect of the grout properties on surface settlement until introduction of the appropriate amount and compressive strength of two component grout a numerical modeling of Tabriz subway line 2 by FLAC3D software were completed. For this purpose, the results of the laboratory tests for numerical modeling of grout were used in software. Finally, with regard to the obtained numerical results, the conclusion that excessive increased resistance were came and thereby the amount of cement of grout will only result in additional costs and in terms of settlement control has little effect. Therefore, create a grout with resistance as the resistance of the soil is sufficient to fill the empty space and surface settlement control (part of the settlement due to lack of suitable filler material occurs). (C) 2017 Elsevier Ltd. All rights reserved.