單一岩石弱面動態剪力強度尺度規模效應

A study on the scale effect of dynamic shear strength between single rock joint

陳立偉(Li-Wei Chen)

指導教授 ： 鄭富書

國立臺灣大學/工學院/土木工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.00135

摘要

岩石邊坡上的岩體常存在不同組數的節理面，這些節理面也成為岩塊可能滑動的平面，又依不同的節理交集狀況，岩坡破壞的型式也不同，如多組滑動面的楔型滑動，或是單一滑動面的順向坡滑動(如：草嶺順向坡滑動)。
順向坡這類型的岩坡，在受震滑動過程中的特性，受兩項主要因素影響1. 岩覆正向應力2.岩體的滑動速度，當雨水入滲至滑動面或地震來臨時，即有可能產生大規模滑動破壞，然本研究中先以簡化的室內實驗，以模擬砂岩試體探討岩石邊坡界面「受震滑動」之「乾摩擦」特性，暫不考慮「濕摩擦」及「雨水入滲」之情形。
本研究將探討岩塊受震滑動時界面摩擦的動態行為。影響節理面摩擦特性之影響因子眾多，此先針對「正向應力」及「剪動速率」對平滑節理面摩擦影響進行研究，並依據實驗結果與現象了解其摩擦特性。
此外，本研究也將探討室內實驗尺度的結果如何推展至現地尺度的應用，期望能求得可考量尺度效應的摩擦曲線及剪力強度，對應用至實際岩坡滑動的案例有所幫助。
於室內實驗現地尺度直接剪力實驗下，進行水平剪動，改變正向應力及剪動速率並求得剪力強度。
於室內實驗小尺度振動台實驗下，分為水平受震與斜坡5度、10度受水平震動三種情形，再改變正向應力及震動頻率下，探討變位、速度、加速度歷時差異，於動態下由靜到動的趨勢與滑動歷程，以及摩擦係數隨相對速率或相對變位的變化，並進一步與前人所做綜合討論。
於本研究中尺度規模效應，剪動速率、正向應力之尺度差異影響再同一尺度下，求得水平受剪之剪力強度尺度規模效應。

關鍵字

小尺度振動台實驗 ； 直接剪力實驗 ； 正向應力 ； 剪動速率

並列摘要

There are different numbers of joints, which may be formed a sliding plane, for rock mass of rock slope. Depend on the intersection of different joints, the failure type of rock slope are usually quite different, such as the wedge failure which includes multiple sliding planes or a dip slope failure which includes a specific sliding plane. (Ex. Tsao-Ling rockslide.).
The sliding process of a dip slope under seismic excitation has two main factors: 1) normal stress applied on the sliding surface; 2) sliding velocity of rock block along a plane. A severe rock sliding failure could be induced by an infiltration of rain or by an earthquake. In this research, several simplify laboratory experiments are conducted to simulate and to investigate behaviors of “dry fiction” at a sliding interface between two rock blocks. However, the “lubrication effect of friction” and “effect of rain infiltrating into rock” are not included in this thesis.
The friction behavior of sliding block under dynamic condition are presented in this thesis. Nevertheless, there are many influence factors of friction, so the first part of this study is focus on “effect of normal stress” and on “effect of dynamic shear rate” and all the characteristics of experiment results are discussed in this research.
Moreover, the application from results of the laboratory scale tests to the in-situ slope failure analysis is also investigated here. This study could be applied on an analysis of rock slope failure by considering the scale effect on dynamic shear strength.
The direct shear test, which is simulated an in-situ scale test, is conducted with three kinds of conditions which are 1) horizontal dynamic shear test 2) different applied normal stress test and 3) different dynamic shear rate test.
About the small scale shaking table test, three kinds of tests are conducted which are “different slope angle test”, “different applied normal stress” and “different shaking frequency.” In addition, the influences of sliding process of a rock block is also presented here, which includes the trend of friction behavior of a block from static to slide on a plane under seismic excitation and the relationship between a friction coefficient and relative velocity of sliding block or relative displacement of sliding block.
Under these test conditions, such as difference of scale effects, different dynamic shear rate, and different applied normal stress, how to get the scale effect on shear strength using horizontal shear test are presented in this thesis.

並列關鍵字

small scale shaking table test ； direct shear test ； normal stress ； shear rate

參考文獻

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6. Mendez, B.C., Botero, E. and Romo, M.P., “A new friction law for sliding rigid blocks under cyclic loading.” Soil Dynamics and Earthquake Engineering 29, pp. 874-882. 2009.

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