| Summary: | 碩士 === 淡江大學 === 土木工程學系 === 89 === The purposes of this research is to investigate the behavior of soil nailing structure in gravel formation by numerical analysis, and discuss the effect of designing parameter on its mechanical behavior.
Firstly, according to the field conditions, builds up the numerical model of a soil nailing and ground anchors retaining structure, then simulates the behavior during excavating procedure with the finite difference program FLAC, and compares the results with the measured data in field to confirm the adequacy of numerical model.
Finally, according to the numerical model built up previously, aiming at the gravel formation to proceed a series of parameters study to investigate the influences on the soil nailing structure behavior.
Research result shows that: (1) When the ratio of nail length and excavation depth(L/H) is greater than 0.75, the decrease of the maximum tensile force of nail and horizontal wall displacement are limited. And when the ratio of L/H is greater than 0.31, the failure mechanism transfers from nail pull-out to nail breakage. (2) Decreasing nail spacing makes averagely the maximum tensile force and raise the global stability. When spacing equal 3 and 2.1m, the horizontal wall displacement is decrescent downward from the top of wall, but increases gradually from half excavation depth; when spacing equals 1m, the horizontal wall displacement is similar as sandy soil. (3) Raisng the density of nail, the lateral earth stress behind wall will approach to rest lateral earth stress. (4) As nail inclination increases, the global pull-out safety factor decreases, but the global breakage safety factor increases. (5) When the inclination of nail is smaller than 15o, the variance of wall displacement is small.
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