| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 97 === In order to simulate construction-related hazards caused by tunnel-digging in shallow-covered or unsymmetry joint formations, in this study the trapdoor test was adopted to discuss the characteristics of the sinking and formation-changes caused by the digging of single or twin tunnels. Close-range photo-grammetry was also utilized as a measurement tool to examine the scope of the changes in the sinking and the rocks above the arch of the tunnel after digging begins. A numerical simulation was then carried out to test and compare the results.
The test result indicates that the scope of influences is at its largest, being 3.5D, when the sinking is at a joint angle of 45° in the digging of a single-tunnel in a shallow-covered terrain. Of the characteristics of formation changes, the heights of the arching effect’s influence zone are respectively 05D and 0.25D when the joint angles are 0° and 30°; no arching effect takes place when the joint angles are 45° and 60°.In the case of the digging of a twin-tunnel, influences on the degree of sinking and formation changes are most significant when the distance between the twin channels is S=0.0D. If the diggings of the twin channels took place when the distance is S=1.0D, did not interfere with each other, and were independent from each other, a disturbed zone each would occur above the arches of the twin channels at the height of 0.5D. In addition, when the distance between the twin channels is 0.5D, the height of the disturbed zone occurred by the digging of the new channel on the left side would be lower than the counterpart on the right. If tunnel-digging were to take place when different joints angles exist in an anaclinal slope with biased formations, the scope of the influences of the formation would differ depending on the location of the tunnel and the joint angle. The higher the average height of the ground surface where the tunnel is
located is, the broader of the scope of the influences that follow. The greater the joint angles, the broader the scope of the influence on the entire formation-changes – as well as the influences on the ground surface. The numerical simulation reveals that the simulations and testing in DDA small displacement tend to overestimate; the simulations for all other stages, however, show good results. Using a joint angle of 60° as an example, the result of the Phase2 simulation is ideal when the amount of digging is δ=2, 4mm; underestimation tends to occur when the amount of digging is at its maximum.
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