1996 Fiscal Year Final Research Report Summary
Study on Hydraulic Fracturing of Filltype Dams During Earthquake
| Project/Area Number |
07455194
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Aichi Institute of Technology (A.I.T.) |
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Principal Investigator |
OHNE Yoshio A.I.T., Fac.of Eng., Prof., 工学部, 教授 (00064931)
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| Co-Investigator(Kenkyū-buntansha) |
OKUMURA Tetsuo A.I.T., Fac.of Eng., Ass.Prof., 工学部, 助教授 (70078913)
TATEBE Hidehiro A.I.T., Fac.of Eng., Prof., 工学部, 教授 (10064940)
NARITA Kunitomo A.I.T., Fac.of Eng., Prof., 工学部, 教授 (90064956)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Filltype Dam / Collapse / Hydraulic Fracturing / Compaction / Hydraulic Gradient / Effective Vertical Stress / FEM Analysis / Centrifuge Model Test |
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| Research Abstract |
Hydraulic fracturing (Seepage failure) tests were conducted on compacted actual core materials to investigate the relationship between the effective vertical stress sigma_V' and the hydraulic gradient at failure i_f. Results are summarized as follows : (1) sigma_V' has a very close relation to i_f and can be the most effective parameter to explain the phenomenon of Hydraulic Fracturing (H.F.), and (2) the resistance against H.F.depends on the initial degree of saturation of compacted soil.
In the centrifuge model tests of investigating the relationship between configuration of abutment foundation and internal deformation of embankment, it is recognized that (1) distribution of the maximum shear strain gamma_<max> depends much on the abutment configuration and large value of gamma_<max> appears in the vicinity of the turning point of foundation slope, and (2) a simple gravity turn-on FEM calculation can be a useful tool to evaluate such mechanical aspects qualitatively.
In another centrifuge deformation tests on model rockfill dams, results presented that (1) large value of gamma_<max> appears irrespective of the core width in the upper part of the core and in the vicinity of core trench, and (2) area of low factor of safety against H.F.then concentrates near the core trench.
In the centrifuge H.F.model tests on a rockfill dam with a centrally located core, a 27cm high model fill was loaded in 20G and 30G,and settlement and stress distributions in the core were measured by using appropriate transducers. Concluding remarks drawn in the test are as follows : (1) differential settlement and stress redistribution in the core due to the first filling of the reservoir causes reduction in confining pressure in the core, and (2) this directly leads to an internal erosion and associated seepage failure in embankments in a similar manner as observed in actual dams.
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