離散元素法數值模擬平面應變試驗與土壤微觀參數標定

Numerical Simulation of Plane Strain Testing and Calibration of Micro-Parameters of Soils through Discrete Element Method

黃任中(Ren-Chung Huang) ； 張睦雄(Muh-Siung Chang)

《中國土木水利工程學刊》 23卷2期 (2011/06) Pp. 119-130

https://doi.org/10.6652/JoCICHE.201106_23(2).0001

摘要

本文進行平面應變試驗求取試驗砂土之巨觀參數（摩擦角φ'），接著利用離散元素法軟體PFC（上標 2D）進行該試驗之數值模擬分析，藉以標定數值分析中砂土所需之微觀參數，如顆粒間摩擦係數（fric）、正向接觸勁度（K（上標 n））、與剪切接觸勁度（K（上標 s））等，並以模擬結果呈現試驗室不易觀察的現象，如受剪時土體內部剪斷面的發展、土體受剪顆粒位移與試體內部接觸應力分佈等。本研究結果發現：（i）顆粒之間設置平行鍵結（parallel bond）可以有效模擬柔性邊界；（ii）數值顆粒的旋轉與否應視顆粒的形狀來決定，使之符合砂土顆粒實際的受力行為；（iii）試體內部剪斷面的生成，均由試體上半部開始發展，進而斜下貫穿整個試體；（iv）當單一剪斷面產生之後，共軛剪斷面才會隨著軸向應變之增加而逐漸發展完整。研究結果所標定之砂土數值微觀參數，將可作為未來進階研究之重要參考依據。

關鍵字

離散元素法 ； 數值模擬 ； 平面應變試驗 ； 微觀參數標定

並列摘要

The study herein conducts a series of plane strain compression tests to obtain macro-parameters (i.e., friction angle φ') of two test sands. The macro-parameters are then employed to calibrate the micro-parameters of the sands, such as friction coefficient (fric), normal and tangent stiffnesses of particle contacts (K(superscript n) and K(superscript s)), etc., which are required in numerical simulations by a discrete element code PFC(superscript 2D). The simulations would show details of the observations (e.g., shear plane development, particle movements, and contact stress distribution) that are not easily detected during the tests. Findings of the study generally indicate: (i) installation of parallel bonds among particles could effectively model the flexibility of test membrane; (ii) selection of particle spinning in numerical simulation depends on the shape of real particles; (iii) development of shear plane starts from upper portion and then propagates to the lower portion on other side of the sample; (iv) initiation of conjugate shear plane is apparent after the occurrence of the first shear plane in the sample. The calibrated micro-parameters of the test sands could provide a sound basis for future studies on numerical simulation of more complicated engineering problems encountered in the field.

並列關鍵字

discrete element method ； numerical simulation ； plane strain testing ； micro-parameter calibration