| Summary: | 碩士 === 中華科技大學 === 土木防災工程研究所 === 100 === Theoretically, the soil of sandy stratum doesn’t possess the qualification of operating soil nails deep-excavation construction method because of the lack of cohesion. However, it could be feasible if given appropriate target strength using ground modification method on non-excavated area to provide sufficient cohesion and balance the un-braced gneiss, then followed up by operating soil nails and shotcrete process to stabilize the excavated acting surface. This research is aim to investigate the influence factors of using soil nails on sandy stratum with numerical analysis. In the research, different target strengths are given to the ground improvement on non-excavated area. Through these environmental variable scenarios, the changing of the horizontal displacements on the excavated surface could be searched.
The results indicated that instead of inhibiting the displacement of the gneiss with high-stiffness retaining wall, the concept of soil nails deep-excavated construction method is to strengthen the soil with soil nails and ground modification, and increase the stability on the entire non-excavated gneiss in order to create a stable gravity-typed retaining structure. Different from the traditional method, which the maximum displacement lays in the excavating of the bottom area, the maximum displacement of the soil nails construction method occurred mostly in the area of middle depth. When the excavated depth increase, obvious displacement increments could still been seen obviously on the surface where soil nails were placed. And with the depth gained, the displacement increment increased progressively. In practice, inclinometer tube in soil is often used to monitor the stimulating lateral horizontal displacement of the excavated surface. The analyzed result shows that it would underestimate the lateral horizontal displacement under most circumstances, and the phenomena got more notable with the excavated depth increased.
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