轉盤直徑影響砂土盤剪行為之實驗研究

A Study of the effect of diameter on the Disc Shearing Behavior of Sand

曾鈐頌(Chain Sung-Tzean)

指導教授 ： 馮道偉

中原大學/工學院/土木工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000860

摘要

盤剪可讓砂土顆粒產生錯動而位移並有壓實的效果，促使砂土顆粒與顆粒之間更為緊密，提高砂土之強度。
本研究探討轉盤直徑對砂土盤剪行為之影響，早期的小型盤剪試驗所使用的土樣環直徑為200 mm且圓盤直徑為198 mm ，使得土樣環中之砂土受到側向束制。近期使用的中型土槽直徑加大為600 mm，且圓盤直徑為200 mm，使得土樣槽中的砂土受到側向束制的情形大為降低。本研究亦使用直徑600 mm之土樣槽，且新做一直徑150 mm之圓盤，加上既有的200 mm直徑圓盤，用之於進行盤剪試驗。
本研究以麥寮砂與渥太華砂二種不同粒徑特性之砂土為土樣，土樣直徑為600 mm，高度為150 mm，初始相對密度為50％。透過盤剪儀施加靜壓載重和盤剪單位轉角，觀察圓盤沉陷量、土樣表面隆起量、側向土壓改變量及圓錐貫入阻抗值。
試驗結果顯示，當盤轉累積角相近時，圓盤直徑對試體體積壓縮之影響與砂土粒徑特性有關。當試體分層霣降並加入加勁材(本研究以濾紙為加勁材料)，對於圓盤盤剪時所造成之沉陷量有明顯降低之效果。由側向土壓力變化來看，累積轉角到達30°之前，側向土壓力隨累積轉角之增加而增加；累積轉角到達30°之後，側向土壓力約略保持定值。由於200 mm直徑圓盤較靠近土槽邊界，其盤剪造成之側向土壓力增加大於150 mm直徑圓盤所造成之側向土壓力增加。由圓錐貫入阻抗qc數據來看，盤剪造成不均勻的qc值變化，於圓盤正下方的qc值增加，於圓盤邊緣下方的qc值則降低。整體來看，200 mm直徑圓盤造成之qc變化減去150 mm直徑圓盤造成之qc變化多為正值，且呈不均勻分佈，其大小亦與砂土粒徑特性有關。

關鍵字

土壤改良 ； 轉盤直徑 ； 砂 ； 盤剪

並列摘要

Disc shearing may produce lateral displacement of sand particles to enhance the sand strength and to make the sand grains closely packed.
The study is to investigate the effect of disc diameter on the disc shearing behavior of sand. In previous small size disc shearing experiments, the specimen ring is 200 mm in diameter and the disc diameter is 198 mm. This provide the sand specimen a laterally confined condition. In previous mid-size disc shearing experiments, the specimen diameter increases to 600 mm and the disc diameter is 200 mm. These reduce the lateral confinenet condition in the sand specimen. This experimental study use the 600 mm test tank and a new disc of diameter
of 150 mm, together with the 200 mm diameter disc.
Mai-Liao and Ottawa sand are used as soil samples with different grain characteristics. The specimen is 600 mm in diameter and 150 mm in hight, and the initial relative density is 50%. The disc shearing
is operated under both constant static load and unit angle of rotation. The disc settlement, the amount of sand surface heaving, the change in lateral
earth pressure, and cone penetration resistance are observed.
The test results show that, as the accumulated angle of rotation is the same, the effect of disc diameter on the specimen compression is a function of sand grain characteristics. Multilayer sand sample with reinforced material (i.e. filter paper), has smaller settlement as result
of disc shearing.
For the change in lateral earth pressure, when the accumulative angle of rotation less than 30°, the lateral earth pressure increases with increasing accumulated angle of rotation； when the accumulated angle of rotation exceeds 30°, the lateral earth pressure keeps about the same. The 200 mm disc is close to the side of the tank so that the change in
lateral earth pressure is higher than that induced by the 150 mm disc.
The cone penetration resistance data show that disc shearing causes an unern change；qc increases under the disc center and qc decreases under the disc edge. The qc after 200 mm disc rotation is higher than the
qc after 150 mm disc rotation.

並列關鍵字

Sand ； Disc Shearing ； Disc Diameter ； Soil Imporvement

參考文獻

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