STRESS STATE OF TRANSVERSELY ISOTROPIC ROCKS NEAR PRESSURIZED HYDRAULIC TUNNEL OF HORSESHOE CROSS-SECTION

Vestnik MGSU 10/2017 Volume 12
  • Bautdinov Damir Tahirovich - Russian State Agrarian University - Moscow Timiryazev Agricultural Academy (RSAU - MTAA or RSAU - MAA named after K.A. Timiryazev) Candidate of Technical Sciences, Associate Professor, Department of Technical Mechanics and Construction, Russian State Agrarian University - Moscow Timiryazev Agricultural Academy (RSAU - MTAA or RSAU - MAA named after K.A. Timiryazev), 49 Timiryazevskaya str., Moscow, 127550, Russian Federation.
  • Atabiev Umar Ishakovich - Russian State Agrarian University - Moscow Timiryazev Agricultural Academy (RSAU - MTAA or RSAU - MAA named after K.A. Timiryazev) Postgraduate, Department of Hydro-technical Construction, Russian State Agrarian University - Moscow Timiryazev Agricultural Academy (RSAU - MTAA or RSAU - MAA named after K.A. Timiryazev), 49 Timiryazevskaya str., Moscow, 127550, Russian Federation.

Pages 1172-1179

The parametric analysis of the stress state of a transversally isotropic rock mass near a pressurized hydraulic tunnel of a box-shaped form is carried out. Pressurized hydro-technical tunnels of box-shaped cross-section are widely used in the field of hydraulic engineering construction and are one of the complex, labor-intensive and expensive types of structures that make up the main structures of waterworks, melioration systems and water supply systems. As a culvert and water supply facilities they are built underground if the open excavation is impossible or not economical, or when the tunnel runs through a densely populated or densely built-up area, or when landslides, screes, rockfalls are possible. Violation of integrity of the rock mass, in particular, caused by tunneling, modifies the stress-strain state (SSS) of the rock mass, which leads to appearance of tensile stresses in some places, and in some cases, to significant compressive stresses. If these stresses exceed the design strengths of rock to tension and compression, respectively, then the collapse of the working roof and buckling of the side walls and the bottom of the tunnel may occur. Subject: analysis of the stress state of transversally isotropic rocks near the pressurized hydraulic tunnel of horseshoe cross-section caused by the internal head of water. Research objectives: determination of real values of circumferential stresses along the development contour. Materials and methods: solution of the problem of plane deformation of the theory of elasticity for a transversely isotropic medium containing tunnel excavation cannot be obtained by analytical methods, and therefore the stress-strain analysis was carried out by the finite element method using the ANSYS software package, MCE. Results: determination of stresses along the development contour, construction of diagrams and graphs showing the effects of the anisotropy conditions and Poisson’s ratio. The tangential stresses along the contour of hydraulic tunnel development for various values of deformation modulus and Poisson’s ratio are determined, which makes it possible to estimate the strength of the rock mass for different tunnel depths. The analysis of a long hydro-technical tunnel, laid in a strong, transversally isotropic rock, is reduced to the problem of plane deformation of the theory of elasticity for a transversely isotropic medium containing tunnel excavation. The size and type of the finite element suitable for analysis were determined in advance based on the solution of the test problem. Conclusions: it is necessary to determine the physical and mechanical properties of rocky soils more accurately, paying special attention to elastic characteristics; calculations should be performed taking into account the anisotropy of elastic properties.

DOI: 10.22227/1997-0935.2017.10.1172-1179

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WELDING STRESSES IN DOUBLE-TEE BARS OF BUILT-UP CROSS SECTION WITH ELEMENTS OF LARGE THICKNESS

Vestnik MGSU 2/2017 Volume 12
  • Vershinin Vladimir Petrovich - Moscow State University of Civil Engineering (National Research University) (MGSU) Associate Professor, Department of Metallic Structures, Moscow State University of Civil Engineering (National Research University) (MGSU), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation.

Pages 150-156

Procedure of calculation of temporary and residual stresses in welding of double-tee bars with elements of large thickness, i.e. at an uneven distribution of welding stresses as per a thickness of flanges, is set forth. This procedure is based on analytical solution of the temperature problem. Solution of the problem on determination of fields of temporary and residual stresses amounts to determination of temperature and stress-strain state (SSS) in the flange and in the wall as separately existing systems, and then to a solution of the problem of compatibility of deformations in the line of conjugation thereof. Factors making the most influence on the intensity of residual welding stresses (RWS) in the flanges of double-tees, are noted. The intensity of RWS is most significantly influenced by the chord thickness variation tf , strength of steel σт, and heat input of welding. The flange width variation bf influences the distribution of RWS to a lesser degree. Components of RWS have a complex pattern of distribution in the direction of thickness. Longitudinal component of RWS reaches a considerable value (yield strength of material). Value of thickness and transverse components of RWS with thickness of flanges of double-tees not more than 40 mm, and with respective minimal weld legs turns out to be insignificant. Growth of the yield strength of steel (as applied to low-carbon and low-alloy steels) leads to increase of level of RWS. Increase of thickness of the flange leads to a growth of unevenness of distribution of RWS in thickness and to increase of the thickness component of RWS. Welding heat input enhancement results in a more uniform heating of the flange in thickness and, therefore, a more uniform distribution of residual stresses in the flange thickness, hereat the stressed state in the flanges of double-tees comes close to uniaxial.

DOI: 10.22227/1997-0935.2017.2.150-156

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