砂土顆粒形狀影響淺基礎承載力之實驗研究

A laboratory study on the effects of particle shape on the bearing capacity of shallow foundation on sands

簡廷達(Ting-Da Jian)

指導教授 ： 馮道偉

中原大學/工學院/土木工程研究所/碩士(2013年)

https://doi.org/10.6840/cycu201300145

摘要

淺基礎的承載力與許多因素有關，一般所知的影響因素包括基礎形狀、基礎埋設深度及載重傾斜度三種，皆與基礎特性有關，而淺基礎下方土壤對承載力的影響通常只考慮內摩擦角及凝聚力兩項數，可能有其他因素值得探討。本研究主要在探討砂土顆粒的形狀及礦物成分對淺基礎承載行為的影響，用顆粒形狀為次圓狀的標準砂、板狀的麥寮砂及顆粒表面光滑且硬度較低的白雲母製作試體，試體相對密度為30%~80%，以直徑50mm高50mm之圓柱形鋁塊模擬基礎，置於砂土表面，加上垂直正向應力進行靜壓加載試驗。
試驗結果顯示，板狀顆粒較次圓狀顆粒在承載能力上較佳，且隨相對密度增加，極限承載力差距越明顯，在相對密度80%時可相差90%。麥寮砂添加粗白雲母後，受其顆粒表面光滑之影響，降低顆粒間摩擦力而降低承載能力，但標準砂添加粗白雲母則會提高其承載能力，是受片狀顆粒令次圓狀顆粒不易移動的影響。標準砂與麥寮砂各混合細白雲母時，細白雲母因顆粒細小而主要產生填充作用，進而提升承載力。綜合以上所述，砂土之顆粒形狀與礦物成分對淺基礎承載力之影響與其相對密度有很大的關係；當相對密度小於50%時，試體所受影響較不明顯，在相對密度50%以上就可觀察到顯著影響。

關鍵字

砂土顆粒形狀 ； 淺基礎 ； 承載力

並列摘要

Bearing capacity of shallow foundation is related to many factors, generally known factors include shape, depth of embedment and load inclination.There may be other factors worth exploring. This study aimed to explore the particles shape and mineral composition effects bearing on behavior of shallow foundation on sand. The that particle shape of Ottawa sand is sub-rounded and of Mailiao sand is plate-like. Ottawa sand , Mailiao sand, and muscovite are used to prepare specimens. With relative densities ranging for 30% to 80%. In the tests a 50mm diameter and 50mm high cylindrical aluminum block is placed on the sand surface and then loaded to failure.
The test results show that the plate-like particles is better then the sub-rounded particles on bearing capacity and the difference increases with increasing the relative density when both Ottawa sand and Mailiao sand have a relative density of 80%, the difference in ultimate bearing capacity can reach 90%. When Mailiao sand is added with coarse muscovite, the friction between the particles and the bearing capacity are both reduced. But for Ottawa sand the coarse muscovite will increase its bearing capacity. It is the flaky particles affect sub-rounded particles so that particles can not move easily. Both Ottawa sand and Mailiao sand mixed with fine muscovite. Because fine muscovite particles are small, it provides primarily a padding role and thus enhances the bearing capacity. In summary, the particle shape and mineral composition and relative density has a great effect on the bearing capacity of shallow foundations on sand; When the relative density is less than 50% the effect is less obvious ;when the relative density is more than 50%, the effect is significant .

並列關鍵字

particle shape ； bearing capacity ； shallow foundation ； sands

參考文獻

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