Computational Technology Resources - CCP

Keywords: weak sandstones, constitutive model, creep.

Summary

In the western part of Taiwan, weak sandstones are often encountered during tunnel construction, and these materials exhibit relatively low shear strength, enormous dilation, and significant creep deformation. According to the test results of previous researchers [1,2,3], weak sandstones typically exhibit the following behavior:

In the hydrostatic loading stage, the total strain exhibits nonlinear behavior, which indicates that the bulk modulus would increase as hydrostatic stress increases. For the creep deformation, it reveals that an increase of hydrostatic stress would suppress the amount of creep deformation.
In the shear loading stage, the volumetric strain induced by shear is initially contractive, and then gradually becomes dilative upon an increase in the shear stresses. For the creep component, it is also initially compressive and then dilative at later stages of loading. In addition, the greater creep shear strain can be induced, especially when the loading is approaching shear strength.

According to aforementioned deformation characteristics, a time-dependent model based on the concept of shear-induced anisotropic degradation is proposed to represent the key behavior of weak sandstone. The stress-strain relationship of the proposed model was originated from the degradation of moduli K and G subjected to different loading conditions. An anisotropic factor beta is introduced to indicate the tendency of the shear-induced volumetric deformation. Furthermore, to incorporate time-dependent deformation behavior of sandstone, this anisotropic degradation model is further extended using the generalized Burger's model.

As a result, this proposed constitutive model is characterized by the following features: (1) being capable of describing shear-induced volumetric deformation, either compression or dilation, prior to the failure state; (2) being versatile in the time-dependent (creep) deformation (3) the anisotropic factor beta serves as a convenient index regarding whether shear-induced volumetric deformation dilates or not; and (4) the number of material parameters is controlled to be as few as possible. The proposed model has been verified by comparing to experimental results. It is found that the proposed model is versatile in simulating short-term and long-term deformations of sandstone under different stress paths.

References

1: M.C. Weng, F.S. Jeng, T.H. Huang, M.L. Lin, "Characterizing the Deformation Behavior of Tertiary Sandstones", Int. J. Rock Mech. Min. Sci., 42, 388-401, 2005. doi:10.1016/j.ijrmms.2004.12.004
2: L.S. Tsai, Y.M. Hsieh, M.C. Weng, T.H. Huang, F.S. Jeng, "Time-dependent deformation behaviors of weak sandstones", Int. J. Rock Mech. Min. Sci., 45, 144-154, 2008. doi:10.1016/j.ijrmms.2007.04.008
3: M.C. Weng, F.S. Jeng, Y.M. Hsieh, T.H. Huang, "A simple model for stress-induced anisotropic softening of weak sandstones", Int. J. Rock Mech. Min. Sci. 45, 155-166, 2008. doi:10.1016/j.ijrmms.2007.04.004

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £125 +P&P)

	Computational & Technology Resources an online resource for computational, engineering & technology publications
	not logged in - login
Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 94 PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: Paper 124 An Anisotropic Degradation Model for Weak Sandstone considering Time Dependent Deformation M.C. Weng¹, F.S. Jeng², C.Y. Liao³ and L.S. Tsai⁴ ¹Department of Civil and Environmental Engineering, National University of Kaohsiung, Taiwan ²Department of Civil Engineering, National Taiwan University, Taipei, Taiwan ³Sinotech Engineering Consultants, Ltd., Taipei, Taiwan ⁴China Engineering Consultants, Inc., Taipei, Taiwan doi:10.4203/ccp.94.124 purchase the full-text of this paper Full Bibliographic Reference for this paper M.C. Weng, F.S. Jeng, C.Y. Liao, L.S. Tsai, "An Anisotropic Degradation Model for Weak Sandstone considering Time Dependent Deformation", in , (Editors), "Proceedings of the Seventh International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 124, 2010. doi:10.4203/ccp.94.124 Keywords: weak sandstones, constitutive model, creep. Summary In the western part of Taiwan, weak sandstones are often encountered during tunnel construction, and these materials exhibit relatively low shear strength, enormous dilation, and significant creep deformation. According to the test results of previous researchers [1,2,3], weak sandstones typically exhibit the following behavior: In the hydrostatic loading stage, the total strain exhibits nonlinear behavior, which indicates that the bulk modulus would increase as hydrostatic stress increases. For the creep deformation, it reveals that an increase of hydrostatic stress would suppress the amount of creep deformation. In the shear loading stage, the volumetric strain induced by shear is initially contractive, and then gradually becomes dilative upon an increase in the shear stresses. For the creep component, it is also initially compressive and then dilative at later stages of loading. In addition, the greater creep shear strain can be induced, especially when the loading is approaching shear strength. According to aforementioned deformation characteristics, a time-dependent model based on the concept of shear-induced anisotropic degradation is proposed to represent the key behavior of weak sandstone. The stress-strain relationship of the proposed model was originated from the degradation of moduli K and G subjected to different loading conditions. An anisotropic factor beta is introduced to indicate the tendency of the shear-induced volumetric deformation. Furthermore, to incorporate time-dependent deformation behavior of sandstone, this anisotropic degradation model is further extended using the generalized Burger's model. As a result, this proposed constitutive model is characterized by the following features: (1) being capable of describing shear-induced volumetric deformation, either compression or dilation, prior to the failure state; (2) being versatile in the time-dependent (creep) deformation (3) the anisotropic factor beta serves as a convenient index regarding whether shear-induced volumetric deformation dilates or not; and (4) the number of material parameters is controlled to be as few as possible. The proposed model has been verified by comparing to experimental results. It is found that the proposed model is versatile in simulating short-term and long-term deformations of sandstone under different stress paths. References 1 M.C. Weng, F.S. Jeng, T.H. Huang, M.L. Lin, "Characterizing the Deformation Behavior of Tertiary Sandstones", Int. J. Rock Mech. Min. Sci., 42, 388-401, 2005. doi:10.1016/j.ijrmms.2004.12.004 2 L.S. Tsai, Y.M. Hsieh, M.C. Weng, T.H. Huang, F.S. Jeng, "Time-dependent deformation behaviors of weak sandstones", Int. J. Rock Mech. Min. Sci., 45, 144-154, 2008. doi:10.1016/j.ijrmms.2007.04.008 3 M.C. Weng, F.S. Jeng, Y.M. Hsieh, T.H. Huang, "A simple model for stress-induced anisotropic softening of weak sandstones", Int. J. Rock Mech. Min. Sci. 45, 155-166, 2008. doi:10.1016/j.ijrmms.2007.04.004 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £125 +P&P)
Back to top	©Civil-Comp Limited 2023 - terms & conditions