一般在邊坡穩定分析中，考量滑動破壞面的剪力抵抗時，常將破壞面上材料的剪力強度以殘餘剪力強度為之，因此，探討坡地材料的殘餘剪力強度是相當重要的。在實驗室內求取邊坡材料的殘餘剪力強度一般多以傳統直接剪力試驗來求取，但傳統直接剪力試驗在剪動過程中，受剪面積不斷變小且剪動位移量受到試體尺寸的限制，而得不到材料真正的殘餘強度。
Bishop et al. (1971)開發使用環形剪力儀，應用於原狀與重模黏土的剪力試驗改善傳統直接剪力的缺點，使試驗中剪動面積維持不變並可進行大剪動位移的試驗，環形剪力儀雖然可改善傳統直接剪力試驗的兩大缺點，但其在儀器操作上較為困難、儀器設備複雜、價格高昂，一般實驗室較少見。
為了免除環形剪力儀的昂貴與複雜又能改善傳統直剪試驗的缺失，本文嘗試使用反覆剪力試驗，來探討大型岩盤邊坡地滑的殘餘剪力強度，主要以草嶺地滑為對象，研究草嶺地滑之卓蘭層砂岩的殘餘剪力強度，以不同尺寸大小具人工節理面岩塊試體檢討剪斷面積、剪動位移量對於殘餘剪力強度的影響。並且利用雷射剖面儀來掃描剪力試驗前、後之節理剖面試體，計算其節理剖面之JRC值，以了解在剪力試驗前、後之卓蘭層砂岩節理剖面粗糙變化情況。此外，透過Sufer軟體將節理剖面繪製立體圖，展現節理剖面的情況，再使用ArcGIS地理資訊系統分析節理剖面的坡高、坡度、坡向資料，可知各剖面之各項資料。

本研究結果如下：
1. 各尺寸節理剖面岩塊在殘餘狀態下，摩擦角與凝聚力值。
尺寸 正向應力 累積剪位移量 殘餘摩擦角 凝聚力
(MPa) (mm) (°) (MPa)
A(10cm×10cm×10cm) 0.5、1、2、4 200 34.8 0.100
B(20cm×10cm×10cm) 0.5、1、2、4 200 39.1 0.233
C(30cm×10cm×10cm) 0.5、1、2 240 31.8 0.473
A(10cm×10cm×10cm) 0.4、0.6、0.8 200 39.7 0
D(20cm×20cm×10cm) 0.4、0.6、0.8 200 42.8 0
由於人工節理剖面的異質性，剪力強度受剖面起伏影響大，本研究結果之殘餘摩擦角並沒有隨著試體尺寸變大，而有明顯的增加或減少。
2. 具節理剖面試體，當正向應力越大時，需要較大的剪位移量，剪力強度才會進入殘餘狀態；在正向應力0.5MPa、1MPa下，試體呈現剪脹行為，剪力強度來源為節理剖面沿剖面爬升之摩擦力；在正向應力2MPa與4MPa下，試體呈現剪縮的行為，剪動過程試體節理剖面不斷的被剪斷、壓碎，較大的正向應力剪縮量越大，即正向應力越大，節理剖面被剪斷、壓碎行為越劇烈。
3. 具節理面岩塊之JRC值在剪力試驗前後變化情況，在相同尺寸下，正向力越大，JRC減少越劇烈；在相同正向應力之下，尺寸越大，JRC減少越劇烈。
4. 節理岩塊剖面之JRC值與試體長度有關，尺寸A與尺寸B計算JRC值時，試體長度在10cm左右時，JRC有收斂的情況；尺寸C的JRC與試體長度之關係，試體長度則是在15cm左右時，JRC也有收斂的情況。
5. Barton之經驗公式預測剪應力值，當JRC值範圍在18以上，節理剖面較粗糙時，預測誤差大；當正向應力0.5MPa下，預測誤差大，隨著正向應力增加，誤差值減少。
6. 卓蘭層砂岩在尺寸A下，剪力試驗之剪動過程中，節理面爬升與節理面剪斷的正向應力門檻值，經過實驗迴歸後計算為1.386MPa。
7. 透過ArcGIS地理資訊系統，可以將3D節理剖面資料，進行坡高、坡度、坡向進行資料分析，可以藉此了解各尺寸試體剖面起伏情況。各節理剖面的坡向分析中可知，剖面在各方向的比例並不相同，顯示剖面起伏的各方向比例不同。
8. 從ArcGIS地理資訊系統的坡向、坡度資料分析，本試驗剖開岩塊的方法，其尺寸大小不同時，節理剖面的起伏情況並不相同，節理剖面試體的異質性，剪力強度並無規則的尺寸效應。

Generally in the stability of slope analysis,when consideration of slideing failure surface shear force resistance is often using the residual shear strenght for the failure surface on the material shear strenght. Therefore, the discussion on slopes material's residual shear strenght is quite important. To find the slope on the material shear strenght,it is often using the tradition direct shear test in the laboratory. But the tradition direct shear test in the shaering process, there is changeing small in the area of cross section ofthe shear plane and to limit the shear displacement by the specimen size, can't obtain true residual strength.
Bishop et al. (1971) development use ring-shear apparatus, applies in the original condition and the remolded clay shearing test improvement tradition direct shear shortcoming, there is no change in the area of cross section of the shear plane and it can do big shear displacement test. Although ring shear apparatus can improvement tradition direct shear two shortcoming, it is more difficult in the instrument operation, the instrumentation equipment to be complex, the price is soaring, generally the laboratory is rare.
In order to avoid the ring-shear apparatus expensive and complex can improve the tradition direct shear test the shortcoming,this article attempts the cyclic shear test to discuss the large-scale siding slope's residual shear strenght. Mainly take the Tsaoling landslide as the object, researching into Tsaoling landslide's Chaolan formation sandstones of residual shear strenght.It has artificial jointed rock by different size specimen to discuss the area of cross section of the shear plane and shear displacement which regarding residual shear strenght influence. And scans the shearing test before and after jointing using the laser profiler to jointed specimen, calculating JRC of value its jointed specimen,which understand in the shearing test before and after Chaolan formation sandstones of jointed specimen rough change situation. In addition, by Sufer software jointing section plane plan block diagram, development jointing section plane situation, and using the geography information system analysis jointing section plane's height, slope and aspect, may know different section planes each item of data.
This research are as follows:
1. Different sizes jointed section plane rock under residual condition, angle of friction and cohesive of value.
size normal stress Shear displacement residual angle of friction cohesive
(MPa) (mm) (°) (MPa)
A(10cm×10cm×10cm) 0.5、1、2、4 200 34.8 0.100
B(20cm×10cm×10cm) 0.5、1、2、4 200 39.1 0.233
C(30cm×10cm×10cm) 0.5、1、2 240 31.8 0.473
A(10cm×10cm×10cm) 0.4、0.6、0.8 200 39.7 0
D(20cm×20cm×10cm) 0.4、0.6、0.8 200 42.8 0
Because the non-homogeneous of the artificial joint surfaces of the specimens, the profile fluctuations of the joint surfaces affect the shear strengths of the specimens. Meanwhile, the residual friction angle has no obvious variation as the size of the specimen varies.
2. Higher the normal stress, higher the shear displacement for the specimen gets into the residual condition. When the normal stress is 0.5MPa and 1MPa, specimens present shear dilation and the shear strength originates from the friction as the specimen moves along the joint profile. When the normal stress is 2MPa and 4MPa, specimens present shear compaction and the joints of the specimen are cut off and broken to pieces. Higher normal stress indicates larger shear compaction and the joints of the specimen are cut off and broken more violent.
3. After the cyclic shear test, the JRC of the specimen with the same specimen size reduces more violent as the normal stress increases gradually. Meanwhile, under the same normal stress, the JRC of the specimen reduces more violent as the specimen size enlarges gradually.
4. The length of the specimen would affect the JRC of the specimen. In size A and size B specimens, as the JRC calculation length of the specimen closes to about 10cm, the JRC of the specimen becomes stable. In size C specimens, as the JRC calculation length of the specimen closes to about 15cm, the JRC of the specimen also becomes stable.
5. This study uses the Barton empirical formula to forecast the shear stress of the joint in the specimen. When the JRC of the specimen is higher than 18, which means the joint surface is rougher, the shear stress prediction error is getting higher. When the normal stress is lower than 0.5Mpa, the shear stress prediction is not stable and the prediction error is huge. However, the shear stress prediction error would reduce as the normal stress increases.
6. The joint of the specimen would be cut off and leads to the shear stress decreasing as the normal stress is over the normal stress threshold during the shear test process. When the specimen size of the Chaolan formation sandstone is in size A, the normal stress threshold of the Chaolan formation sandstone is 1.386Mpa by applying the regression analysis on the cyclic shear test results.
7. Through the geographic information system, the height, slope, aspect of the 3D joint surface data can be calculated and may take advantage of understanding the joint surface roughness fluctuation in different specimen sizes. In the slope analysis of the joint surface, the proportion of the slope in each direction is quite different which reveals the slope distribution is dissimilar in different joint surfaces.
8. According to the slope and aspect analysis of the joint surface acquired by the geographic information system, the splitting rock specimen method utilized in this study would lead to the different joint surface and joint roughness. The non-homogeneous of the joint surfaces in different specimens result in the shear strength of the specimen would not be affected by the scale effect obviously.

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