2001 Fiscal Year Final Research Report Summary
Mechanism of germination of underground cavities and its influence on pavement
| Project/Area Number |
11450182
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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 | The University of Tokushima |
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Principal Investigator |
MOCHIZUKI Akitoshi The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (40047345)
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| Co-Investigator(Kenkyū-buntansha) |
JING-CAI Jiang The University of Tokushima, Faculty of Engineering, Research associate, 工学部, 助手 (10284308)
UENO Katsutoshi The University of Tokushima, Faculty of Engineering, Lecturer, 工学部, 講師 (70232767)
YAMAGAMI Takuo The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (90035642)
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| Project Period (FY) |
1999 – 2001
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| Keywords | pavement / under-road cavity / CBR test / cenrifuge model test / compaction / erosion due to water permeation |
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| Research Abstract |
The following themes were objects in this project using experimental and analytical procedures: Theme-1 Simulation of a process to form a cavity in a sandy layer due to water permeation by experiments in laboratory. Theme-2 Development of Stability Test Method of back filling materials for a road excavation, and a guideline of the degree of compaction to avoid subsidence of a road due to a cavity underneath pavements. Theme-3 Development of a centrifugal apparatus for soil model tests with observing systems for deformation of models and distribution of stresses in the centrifuge. Theme-4 Performance of centrifugal model tests to simulate a process of failure of a clayey pavement with a cavity by self-weight. Theme-5 Bearing capacity tests of a clay ground with a cavity. Theme-6 Analyses of bearing capacity of clay ground with a cavity.
Firstly, the process to form a cavity was demonstrated in a series of model tests. Then Stability Test of back-fill materials using a compaction mold wit
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h 13 holes measuring 10 mm in diameter at the bottom plate was developed. The results showed that the resistance of materials for de-compaction depended on basically grain size distribution, and that over 85 % of the degree of compaction of material is effective to prevent de-compaction.
A new centrifuge apparatus with a 400 g-t capacity and an effective radius of 1.55 m was developed with a support from this grant aid. The relationship between the tensile strength and the width of collapsed underground cavities was investigated and an equation to predict the shape of collapsed ceiling was proposed. In theme-5 and 6, bearing capacity tests for model ground on an artificial clay with/without a cavity were performed in the gravitational field, and a chart was obtained, which shows a relationship of bearing capacity to depth and width of a cavity in the ground.
Analyses for the footing tests on model clay were performed, and obtained result that if a cavity locates over three times of a footing width, bearing capacity of the ground is, the same as that on a clay ground without any cavity. The same conclusion was obtained in the bearing capacity tests on the artificial ground. According to the conclusions, a risk chart for under-road cavity was presented based on data sampled in Osaka city area. Less
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