Mechanism analysis of foam penetration in EPB shield tunnelling with a focus on FER and soil particle size

Abstract

Parameters of foam penetration in earth pressure balance (EPB) shield tunnelling, such as permeability coefficients and penetration distances, significantly impact tunnel face stability. However, existing studies have faced inaccuracies in analysing these parameters due to imitations in experimental methods. This study addresses this issue by employing enhanced methods for a more precise analysis of foam penetration. Experiments involving three distinct sand types (coarse, medium, and fine) and three foam expansion ratios (FER) (10, 15, and 20) are conducted using a modified model test setup. Benefiting from a novel computer vision-based method, the model test outcomes unveil two distinct foam penetration paths: liquid migration (L_w) and bubble migration (L_f). Three penetration phases — namely, injection, blockage & drainage, and breakage — are identified based on L_w and L_f variations. The initial “injection” phase conforms to Darcy's law and is amenable to mathematical description. The foam with FER of 15 has the maximum viscosity and, hence the L_f and permeability in the penetration tests with FER of 15 are the lowest in the same sand. The bubble size distribution of foam with different FER shows minor differences. Nevertheless, the characteristics of foam penetration vary due to the distinct particle size distribution (PSD) of different sands. Foam penetration creates low-permeability layers in both medium and fine sands due to the larger bubble size of the foam compared to the estimated pore sizes of medium and fine sands. While the coarse sand results in a different situation due to its large pore size. The distinctive characteristics of foam penetration in different sand strata are notably shaped by FER, PSD, and pore size distributions. These insights shed light on the complex interactions during foam penetration at the tunnel face, contributing valuable knowledge to EPB shield tunnelling practices.

Keywords

EPB / Soil conditioning / Foam penetration / Permeability / Tunnel face

CRediT authorship contribution statement

He Huang: Conceptualization, Data curation, Writing - original draft, Methodology, Investigation. Quan Sun: Writing - review & editing, Validation. Tao Xu: Conceptualization, Methodology. Wanhuan Zhou: Conceptualization, Funding acquisition, Writing - review & editing, Supervision, Resources, Project administration.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The research was funded by the Guangdong Provincial Department of Science and Technology (Grant No. 2022A0505030019), the Science and Technology Development Fund, Macao, China (File/Project Nos. 0056/2023/RIB2 and SKL-IOTSC(UM)-2021-2023), and the National Natural Science Foundation of China (Grant No. 52022001).

References

[1] Bashir, A., Haddad, A. S., & Rafati, R. (2022). An experimental investigation of dynamic viscosity of foam at different temperatures. Chemical Engineering Science, 248, 117262.

[2] Bezuijen, A. (2012). Foam used during EPB tunnelling in saturated sand, parameters determining foam consumption. In World Tunnel Congress 2012 (WTC-2012) (pp. 267-269). Ghent University, Department of Civil Engineering.

[3] Bezuijen, A., Pruiksma, J. P., & 2020). In Pore pressures in front of tunnel, measurements, calculations and consequences for stability of tunnel face (pp.799-804).

[4] CRC, Press. Bezuijen, A., & Schaminée, P. E. (2020). In Simulation of the EPB-shield TBM in model tests with foam as additive (pp.935-940).

[5] CRC, Press. Borio, L., & Peila, D. (2010). Study of the permeability of foam conditioned soils with laboratory tests. American Journal of Environmental Sciences, 6(4), 365.

[6] Budach, C., & Thewes, M. (2015). Application ranges of EPB shields in coarse ground based on laboratory research. Tunnelling and Underground Space Technology, 50, 296-304.

[7] Chang, C. C., & Cheng, D. H. (2018). Predicting the soil water retention curve from the particle size distribution based on a pore space geometry containing slit-shaped spaces. Hydrology and Earth System Sciences, 22(9), 4621-4632.

[8] de Oliveira, D. G., Thewes, M., & Diederichs, M. S. (2019). Clogging and flow assessment of cohesive soils for EPB tunnelling: Proposed laboratory tests for soil characterisation. Tunnelling and Underground Space Technology, 94, 103110.

[9] Galli, M. (2016). Rheological characterisation of earth-pressure-balance (EPB) support medium composed of non-cohesive soils and foam. [Doctoral Thesis, Ruhr-Universit¨at Bochum, AG Leitungsbau und Leitungsinstandhaltung]. (in German).

[10] Galli, M., Thewes, M., Freimann, S., & Schroeer, M. (2021). Residual water content of excavated soil in EPB tunnelling. Tunnelling and Underground Space Technology, 114, 103991.

[11] Herrenknecht, M., Thewes, M., & Budach, C. (2011). The development of earth pressure shields: From the beginning to the present/Entwicklung der Erddruckschilde: Von den Anfängen bis zur Gegenwart. Geomechanics and Tunnelling, 4(1), 11-35.

[12] Hu, Q. X., Wang, S. Y., Qu, T. M., Xu, T., Huang, S., & Wang, H. B. (2020). Effect of hydraulic gradient on the permeability characteristics of foam-conditioned sand for mechanized tunnelling. Tunnelling and Underground Space Technology, 99, 103377.

[13] Huang, S., Wang, S. Y., Xu, C. J., Shi, Y. F., & Ye, F. (2019). Effect of grain gradation on the permeability characteristics of coarse-grained soil conditioned with foam for EPB shield tunneling. KSCE Journal of Civil Engineering, 23(11), 4662-4674.

[14] Jing, J. Q., Sun, J., Zhang, M., Wang, C. S., Xiong, X. Q., & Hu, K. (2017). Preparation and rheological properties of a stable aqueous foam system. RSC Advances, 7(62), 39258-39269.

[15] Lee, H., Kim, D. Y., Shin, D., Oh, J., & Choi, H. (2022). Effect of foam conditioning on performance of EPB shield tunnelling through laboratory excavation test. Transportation Geotechnics, 32, 100692.

[16] Maidl, U. (1995). Extension of application ranges of Earth Pressure Balance Shields by soil conditioning with foam. [Doctoral Thesis, Ruhr-Universit¨at Bochum, AG Leitungsbau und Leitungsinstandhaltung]. (in German).

[17] Mori, L., Mooney, M., & Cha, M. (2018). Characterizing the influence of stress on foam conditioned sand for EPB tunneling. Tunnelling and Underground Space Technology, 71, 454-465.

[18] Qin, S., Cheng, Y., & Zhou, W. H. (2023). State-of-the-art review on pressure infiltration behavior of bentonite slurry into saturated sand for TBM tunneling. Smart Construction and Sustainable Cities, 1(1), 14.

[19] Thewes, M., & Budach, C. (2010). Soil conditioning with foam during EPB tunnelling. Geomechanics and Tunnelling, 3(3), 256-267.

[20] Todaro, C., Carigi, A., Peila, L., Martinelli, D., & Peila, D. (2022). Soil conditioning tests of clay for EPB tunnelling. Underground Space, 7(4), 483-497.

[21] Wang, S. Y., Liu, P. F., Hu, Q. X., Wang, H. B., Huang, S., Zhong, J. Z.,... Yang, J. S. (2020). State-of-the-art on Theories and Technologies of Soil Conditioning for Shield Tunneling. China Journal of Highway and Transport, 33(5), 8 (in Chinese).

[22] Wang, S. Y., Huang, S., Zhong, J. Z., Zhang, S., Hu, Q. X., Qu, T. M., & Ye, X. Y. (2021). Permeability stability calculation model of foamconditioned soil based on the permeability constant. International Journal for Numerical and Analytical Methods in Geomechanics, 45(4), 540-559.

[23] Wu, Y., Mooney, M. A., & Cha, M. (2018). An experimental examination of foam stability under pressure for EPB TBM tunneling. Tunnelling and Underground Space Technology, 77, 80-93.

[24] Xu, T., & Bezuijen, A. (2019a). Pressure infiltration characteristics of bentonite slurry. Géotechnique, 69(4), 364-368.

[25] Xu, T., & Bezuijen, A. (2019b). Bentonite slurry infiltration into sand: Filter cake formation under various conditions. Géotechnique, 69(12), 1095-1106.

[26] Xu, T., Bezuijen, A., & Thewes, M. (2022a). Pressure infiltration characteristics of foam for EPB shield tunnelling in saturated sand- part 1:‘clean’foam. Géotechnique, 72(4), 283-294.

[27] Xu, T., Bezuijen, A., & Thewes, M. (2022b). Pressure infiltration characteristics of foam for EPB shield tunnelling in saturated sand- part 2: Soil-foam mixture. Géotechnique, 72(4), 295-308.

[28] Zheng, D. Z., Bezuijen, A., & Thewes, M. (2021). An experimental study on foam infiltration into saturated sand and its consequence for EPB shield tunneling. Tunnelling and Underground Space Technology, 111, 103878.

[29] Zheng, D. Z., Bezuijen, A., & Thewes, M. (2022). Modelling the infiltration behaviour of foam into saturated sand considering capillary resistance for EPB shield tunnelling. Géotechnique, 1-11.

[30] Zhou, X., & Yang, Y. Y. (2020). Effect of foam parameters on cohesionless soil permeability and its application to prevent the water spewing. Applied Sciences, 10(5), 1787.

[31] Zumsteg, R., & Puzrin, A. M. (2012). Stickiness and adhesion of conditioned clay pastes. Tunnelling and Underground Space Technology, 31, 86-96.