Numerical strength calculations of underground gas pipelines in undermining areas

Introduction. Various calculation methods, including empirical, analytical, and numerical ones, are used to assess the effect of undermining on base deformations and force variations in the structures of existing and projected pipelines. Empirical methods are typically developed using an experimental analysis of numerous results obtained during the engineering and geodetic observations of settlements and surface terrain shifts in undermining areas. However, such methods fail to take into account all the factors affecting settlements and shifts during underground excavations, including the vertical heterogeneity and physicomechanical properties of soils, etc.
Aim. To determine the advantages of numerical methods and to develop a methodology for using numerical calculations in the Plaxis and Midas GTS NX geotechnical software applications. Compared to empirical and analytical methods, numerical approaches have the advantage of simulating the bedding heterogeneity of geological engineering elements and their physicomechanical properties, ensuring joint calculations of the “underground excavation – soil massif – existing structure” system, considering the gradual character and undermining technology, as well as providing the possibility to search through a large quantity of variants over a short period of time. The principles of numerical calculations of the strength of underground main gas pipelines during the arrangement of closed underground excavations for mineral mining are considered.
Methods. The developed methodology is based on the degree and nature of effects produced by various factors on numerical modeling results, including the presence of a pipeline in the design model, width of the model calculated area, finite element mesh sizes, parameters of the soil geomechanical model, width, bedding depth, dip angle, thickness, and number of mineral mined formations, as well as the problem statement type (2D or 3D).
Results. The results of the study are presented in the form of a methodological verification, performed on the basis of a comparison between the calculated and actual parameters of rock shifts.
Conclusions. The presented methodology reliably predicts base deformations and force variations in the structures of existing and projected pipelines during the excavation of a coal seam at one of the mines of the Moscow lignite basin.

1. State Standard 27751-2014 Reliability of building structures and foundations. The main provisions. Moscow: Standartinform Publ.; 2015 (in Russian).

2. State Standard R 53778-2010 Buildings and structures. Rules of inspection and monitoring of technical condition. Moscow: Standartinform Publ.; 2010 (in Russian).

3. SP 36. 13330. 2012 Trunk pipelines. Updated version of SNiP 2.05.06-85*. Moscow: Ministry of Regional Development of Russia; 2012 (in Russian).

4. RD 07-166-97 Instructions for observing the movements of the Earth’s surface and objects located on it during the construction of underground structures in Moscow. In: Protection of mineral resources and geological surveying control: a collection of documents. Episode 07. Issue 8. Moscow: CJSC “Scientific and Technical Center for Industrial Safety Research”; 2010, p. 102–176 (in Russian).

5. State Standard 31937-2011 Buildings and constructions. Rules of inspection and monitoring of technical condition. Moscow: Standartinform Publ.; 2014 (in Russian).

6. NIIOSP named after N.M. Gersevanov JSC “SIC “Construction”. Development of a methodology for calculating the strength of underground main gas pipelines in the territories under development. Report on the research work. Moscow; 2021 (in Russian).

7. Avershin S.G. Displacement of rocks. Moscow: Ugletekhizdat Publ.; 1947 (in Russian).

8. Einbinder A.B., Kamerstein A.G. Calculation of trunk pipelines for strength and stability. Moscow: Nedra Publ.; 1982 (in Russian).

9. Bogomolova O.A., Zhidelev A.V. The influence of the parameters of underground mining on the amount of precipitation of the daily surface of the moonlit area. Construction and Geotechnics. 2020;11(2):5–18 (in Russian). https://doi.org/10.15593/2224-9826/2020.2.01

10. Geniev G.A. A practical method for determining the movements of the earth’s surface and the stressed state of soils caused by underground workings. Stroitel’naya mekhanika i raschet sooruzhenii = Structural Mechanics and Analysis of Constructions. 1977;(3):10–14 (in Russian).

11. Ilyichev V.A., Nikiforova N.S., Tupikov M.M. Study of deformation of soil massifs during the construction of shallow communication tunnels. Osnovaniya, fundamenty i mekhanika gruntov = Soil Mechanics and Foundation Engeneering. 2011;(3):8–15 (in Russian).

12. Iofis M.A., Konovalov P.A., Mayorov S.G. Instructions for observing the movements of the Earth’s surface and objects located on it during construction. Moscow: IPKON RAS Publishing House; 1997 (in Russian).

13. Longjid Ehtur. Forecast of displacements and deformations of rocks and the Earth’s surface when crossing the subway tunnels of heterogeneous layered rocks with different lithology [dissertation]. Saint Petersburg: Saint Petersburg Mining University; 2018 (in Russian).

14. Petrukhin V.P., Isaev O.N., Sharafutdinov R.F. Modeling of deformations of a soil massif during tunneling. Part 1: Studies of the influence of calculated parameters. Transportnoe stroitel’stvo = Transport construction. 2014;(9):7–11 (in Russian).

15. Petrukhin V.P., Isaev O.N., Sharafutdinov R.F. Modeling of deformations of a soil massif during tunneling. Part 2: Methods for selecting numerical simulation parameters. Transportnoe stroitel’stvo = Transport construction. 2014;(10):14–15 (in Russian).

16. Polyak Z.I. Displacement of rocks in the coal basin near. Moscow: Ugletekhizdat Publ.; 1947 (in Russian).

17. Sheinin V.I., Pushilin A.N. Evaluation of efforts in building structures arising from the penetration of underground workings. In: Collection of scientific works of N.M. Gersevanov NIIOSP: 75 years. Moscow: Ekonomika, stroitel’stvo, transport Publ.; 2006, p. 66–73 (in Russian).

18. Pushilin A.N., Sheinin V.I. Development of an engineering scheme for calculating building structures taking into account the displacements of the Earth’s surface caused by tunneling. Moscow: RAT Publ.; 2002 (in Russian).

19. Pushilin A.N., Favorov A.V., Sheinin V.I. Method for calculating forces in building structures when the base is deformed due to tunneling underground workings. Osnovaniya, fundamenty i mekhanika gruntov = Soil Mechanics and Foundation Engeneering. 2007;(3):2–6 (in Russian).

20. Strokova L.A. Numerical modeling of surface subsidence during subway sinking. Osnovaniya, fundamenty i mekhanika gruntov = Soil Mechanics and Foundation Engeneering. 2009;(3):29–31 (in Russian).