層間剪動下砂顆粒之粒徑級配演變研究

Evolution of Sand Grain Size Distribution during Bedding Shear

林庭鞍(Ting-An Lin)

指導教授 ： 楊長義

淡江大學/工學院/土木工程學系碩士班/碩士(2016年)

https://doi.org/10.6846/TKU.2016.00565

摘要

順向坡的特性是具順層的結構，且因受到層間之錯動(bedding shear)常存在層間摩擦剪動的「泥縫(seam)」，其被蹍碎後的顆粒常比上下母岩更細微化或成黏土等級，因此其摩擦角常又比原來母岩更低、且更易吸水。因此，本文主要以兩片粗糙花崗岩面對夾層砂顆粒材料進行磨碎試驗，目的是在探討砂土顆粒材料受剪後顆粒大小、形狀、級配與顆粒間距離分佈特性之改變與產生細粒料(小於#200)的量變化。
結果得致下列主要結論：(1) 本文自製的簡易型梳尺儀可用以量測岩面粗糙度，以利計算JRC。係採用108根直徑0.88 mm測釘排列於兩片鐵片中，再置放於花崗岩粗糙面上量測高程，量測後拍照各測釘高度投影剖面匯入繪圖軟體，標定基準線，可連接108個高程點即可繪出岩面剖面，並計算其JRC值。文中亦使用手機結合新式顯微鏡，可將手機顯微鏡應用於觀察砂顆粒細粒化後之形狀。 (2) 施加正向應力階段，顆粒就會破碎使粒徑變小，但粒徑尚皆大於#200尺寸；粒徑小於#200的細粒料則是在受剪後隨著剪動位移才變多。因在層間受剪破碎愈來愈小，故其整體抗剪摩擦角將漸低。 (3) 夾層顆粒於低正應力(?n=0.5 MPa)下，受剪幾乎不出現粒徑小於#200之細粒料，在拍攝其顆粒間之質點分佈，統計顆粒間之距離分佈特性後，發現顆粒與顆粒間之平均距離隨著剪位移之增加而相互靠近。但大約於尖峰剪應力後達於一固定狀態，粒間距離不再有變化。 (4) 若將每一顆粒視為一個質點，由其質點分佈圖，引用雙點相關維度Dcorr值記錄其變化，可用以反映受剪中顆粒間排列之疏密程度變化，即排列越均勻者其Dcorr值愈大，而排列越叢集者其Dcorr值愈小。依此觀點，本文夾層未受剪時Dcorr值為1.36，受剪至尖峰剪應力前，Dcorr值降至1.3，顯示顆粒受剪後排列漸趨於叢集狀態，但在受剪至尖峰剪應力後Dcorr值則趨於固定值(Dcorr=1.27)。 (5) 從顆粒間分佈平均距離與雙點相關維度值兩者之分析結論，可知層間夾層顆粒之粒徑分佈及其排列距離於尖峰剪應力後已達於穩定，不再改變，此一現象或可說明本文夾層顆粒於低正向應力(?n=0.5 MPa)下之抗剪應力已趨於一固定值之穩定狀況。

關鍵字

層間剪動 ； 砂顆粒 ； 粒徑級配演變 ； 碎形維度

並列摘要

Consequent slope is a smooth layer structure and because by the bedding shear between the layers, there is often present interlayer friction shear move called "seam", which the particle broken after often than upper and lower rock more or a level of fine clay, so often surpasses the original rock friction angle lower and more absorbent.Therefore, this paper mainly two rough granite face sandwich sand particulate material grinding test, the purpose is to explore the distribution characteristics of sand particulate material change of distance between the after shear particle size, shape, gradation and fine particles produced by the amount of material (less than #200) change.
The results obtained to the following main conclusions:(1) Simple homemade comb foot instrument used to measure the surface roughness of the rock, in order to facilitate the calculation JRC. 108 diameter 0.88 mm using soil nails arranged in two iron sheet, and then placed in a granite surface roughness measuring height, measured after each soil nail pictures sectional height of the projector into graphics software, calibration baseline, 108 soil nails can be connected elevation points to draw a cross-section of rock face, and calculate the value of JRC. The paper also use the new handsets combined with the microscope, the microscope can phone the shape of fine sand particles are applied after the observation.(2) Stress is applied to the positive phase, the particles will be broken so that the particle size becomes smaller, but still larger than in particle size # 200; fine aggregate size of less than #200 is in the shear with only dynamic displacement increases. Because the interlayer shear crushing smaller and smaller, so the overall shear angle of friction will gradually lower.(3) Interlayer particles under low normal stress (?n = 0.5 MPa), shear hardly appear fine aggregate size of less than # 200, the shooting between the particle distribution of the particles, after the distance between the statistical distribution characteristic particles, particles found the average distance between the particles with increasing shear displacement of close to each other. But after about shear stress to peak reached in a fixed state, there is no change in the distance between the grains.(4) If each particle as a particle, its particle distribution, citing double-point correlation dimension Dcorr record its value changes that can be used to reflect the degree of change in density between the particles are arranged in the shear, that arrangement more uniform by its value Dcorr The larger, the more clusters are arranged by their Dcorr value is smaller. On this view, the time of this Interlayer were not shear Dcorr is 1.36, before shear to the peak shear stress by, Dcorr value to 1.3, the display by the particles arranged after getting shear tends to cluster state, but after the peak shear stress to shear by Dcorr value tends to a fixed value (Dcorr = 1.27).(5) From the distribution of the average distance between the particles with a double point correlation dimension value analysis of two conclusions, we can see between the floor and the particle size distribution of the particles are arranged from the Interlayer after the peak reached in the shear stress stability, not change, this phenomenon may account This article Interlayer particles in low forward stress (?n = 0.5 MPa) under shear stress condition has stabilized a constant value.

並列關鍵字

Bedding Shear ； Sand ； Evolution of Sand Grain Size Distribution ； Fractal

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