2007 Fiscal Year Final Research Report Summary
IMPROVEMENT OF EVALUATION METHOD FOR ROCK MASS STRENGTH BY NONLINEAR MULTI-SCALE ANALYSIS
| Project/Area Number |
17560440
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geotechnical engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
KYOYA Takashi Tohoku University, TOHOKU UNIVERSITY, GRADUATE SCHOOL OF ENGINEERING, PROFESSOR (00186347)
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| Project Period (FY) |
2005 – 2007
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| Keywords | discontinuous rock mass / thin laver crack model / multi-scale analysis / strength evaluation / primal-dual finite element analysis |
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| Research Abstract |
A strength evaluation method based on the multi-scale analysis for discontinuous rock mass has been improved. Discontinuities in rock mass such as cracks and joints are treated as thin layers and modeled by ordinary solid finite elements, which enables utilization of graphical image of rock mass surface in the analysis. Nonlinear stress-strain relation of crack closing has been carefully observed in a series of compression tests of gypsum mortar specimen, and their nonlinear relation has been formulated in a form of constitutive equation. Cracks are represented by thin layers with the nonlinear constitutive law, instead of complicated contact analysis model, and their nonlinear closing and opening behaviors are expressed by hardening and softening of its stiffness. The nonlinear deformation behavior of rock mass that includes many cracks are therefore appropriately simulated by suing the thin layer model only from graphical image of crack distribution and mechanical properties of intact rocks. In addition, a powerful limit load analysis has also developed by utilizing formulation of the primal-dual optimization and incorporated into the thin layer analysis system. Thus the nonlinear multi-scale analysis system for discontinuous rock mass has been made in a form of prototype. Validation analyses have been done for direct shear test of cracked gypsum mortar specimen and an actual rock mass shearing test in site. Results agreed with measurements fairly well, and revealed the validity of the multi-scale analysis system.
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