分離元素法探討卵礫石層中管道開挖形狀及支撐之穩定

Modeling of Pipeline Excavation Shape and Support in Gravel Formation Using Distinct Element Method

陳學禹(Syue-Yu Chen)

指導教授 ： 徐松圻

朝陽科技大學/理工學院/營建工程系/碩士(2011年)

摘要

由於卵礫石層為大小不同顆粒所組成之複合土層，其性質乃顆粒間之相互滑動、滾動及顆粒間之互鎖及粒徑大小分佈等所控制，應視為不連續體來分析模擬。卵礫石其力學行為主要與卵礫石顆粒形狀、大小、排列方式、細料含量及性質有密切的關係，而且粗、細顆粒含量之多寡對於卵礫石層之工程性質也有影響。
本研究主在模擬分析卵礫石層中開放式管道開挖，以不同開挖面進行開挖時之破壞機制，藉由改變不同開挖面型式及限制不同百分比顆粒不旋轉性，來探討土體之穩定性破壞影響範圍及支撐方式，而數值模擬方法則採用分離元素法為主之數值程式 PFC2D及PFC3D做一比較，探討不同階段時，顆粒滑動、滾動之位移影響情形。
由分析結果顯示，開挖面主要破壞由管道開口接近頂拱處先產生滑動及滾動崩塌，逐漸向上延伸崩塌，並有可能導致地表下陷。當現地卵礫石愈趨近於圓形顆粒，開挖時極易崩塌，由限制不同百分比顆粒之可得知，當卵礫石顆粒形狀愈趨向橢圓或微扁平狀時，在弧形開挖面且限制20%以上粒徑不旋轉時，顆粒間排列之互鎖效應最明顯也最接近現地情況。而增加支撐之角度越小時，崩塌範圍會較小且不易向上延伸。

關鍵字

PFC ； 管道開挖 ； 支撐 ； 分離元素法 ； 卵礫石

並列摘要

The gravel formation in Taichung consists of granular materials with various sizes and can be considered as a compound material. The properties of the formation are mainly determined by slipping, interlocking, and rolling between particles and grain size distribution. The gravel formation can be regarded as a discontinuous material for simulation and analysis. The mechanical behavior exhibited by the gravels is closely related to gravel size, gravel shape, size distribution, and percentage of fines content. The percentage of coarse and fine particles has a great impact on its engineering properties.
In this study, simulation analysis gravel in an pipeline excavation, excavation face a different failure mechanism for the excavation, excavation face by changing the different types and limits of different percentages of particles to be not rotate, to explore the soil the extent of damage to the stability and support methods, and numerical simulation method is applied to individual elements of value-based program PFC2D and PFC3D to do a comparison of different stages, particle sliding, rolling effect of the displacement situation.
The analysis showed that the main damage from the pipeline excavation near the top of the arch openings have sliding and rolling at the first collapse, and gradually extended upward collapse, and may lead to surface subsidence. When are increasingly close to the gravel particles in the round, excavation can easily collapse, the percentage of particles of different restrictions can be learned, when gravel particles tend to shape more oval-shaped or slightly flattened, in the curved surface and excavation 20% limit to be not rotate when the particle size, arrangement of interlocking between the particles the most obvious effect is also the closest to the situation. Increased support of the angle the more hours, the range will be small and difficult to collapse upward.

並列關鍵字

support ； distinct element method ； PFC2D ； underground pipe excavation ； gravel

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