本文選題：離散單元法　切入點：顆粒流　出處：《大連理工大學》2015年碩士論文　論文類型：學位論文

【摘要】：巖土材料不同于一般的宏觀連續(xù)介質材料,其在細觀組構上是顆粒堆積體,內部普遍存在著裂紋、孔洞及結構面等構造。離散單元法于1971年被引入,其將巖土材料視為由圓形顆粒構成的顆粒集合體,在細觀層次上模擬巖土材料受力、運動及變形狀態(tài),受到十分廣泛的應用及進一步的研究。二維顆粒流程序pFCD基于離散單元法而開發(fā),被廣泛應用于隧道開挖、基坑支護、邊坡穩(wěn)定性、土工試驗模擬、巖石破碎、滲流、動載問題等諸多巖土工程領域。顆粒流模擬的精度主要取決于其細觀參數(shù)的確定,也稱作標定,細觀參數(shù)的標定通常采用常規(guī)“試錯法”,即通過不斷改變細觀參數(shù)值直到模擬值與試驗值基本吻合,其偶然性較高,理論性欠缺,標定難度較高。本文針對上述巖土材料細觀參數(shù)標定方法的不足,結合試驗設計、響應面法及BFGS優(yōu)化算法,提出了一種巖土材料細觀參數(shù)反演辨識方法。使用線性接觸模型模擬堆石料,根據(jù)堆石料三軸壓縮實驗室試驗觀測數(shù)據(jù)及先驗信息對堆石料細觀參數(shù)進行了初步標定,設計了批量顆粒流模擬試驗,基于響應面函數(shù)建立了堆石料宏觀偏應力與細觀參數(shù)之間的非線性映射關系,采用BFGS優(yōu)化算法對堆石料細觀參數(shù)進行了反演。使用平行粘結模型模擬改性渣土,根據(jù)改性渣土三軸壓縮實驗室試驗觀測數(shù)據(jù)及先驗信息對改性渣土細觀參數(shù)進行了初步標定,設計了批量顆粒流模擬試驗,基于響應面函數(shù)建立了改性渣土宏觀偏應力與細觀參數(shù)之間的非線性映射關系,采用BFGS優(yōu)化算法對改性渣土細觀參數(shù)進行了反演。研究表明,結合響應面法和BFGS優(yōu)化算法,基于宏觀實驗數(shù)據(jù)的巖土材料細觀參數(shù)反演方法具有較高的預測精度。根據(jù)估計的巖石平行粘結模型細觀參數(shù),對壓頭作用下巖石破碎過程進行了顆粒流模擬,并與已有研究結果取得了定性上的一致。研究表明,PFC2D可從細觀角度再現(xiàn)壓頭破巖過程,平行粘結模型可用來模擬巖石材料細觀破壞行為。
[Abstract]:The geotechnical material is different from the general macroscopic continuum medium material, its mesoscopic fabric is the grain accumulation body, the interior generally exists the structure such as the crack, the pore and the structure plane and so on. The discrete element method was introduced in 1971. It regards the geotechnical material as a particle aggregate composed of circular particles, and simulates the stress, movement and deformation of the geotechnical material at the meso level. The two-dimensional particle flow program pFCD is developed based on discrete element method and is widely used in tunnel excavation, foundation pit support, slope stability, geotechnical test simulation, rock fragmentation, seepage, The precision of particle flow simulation mainly depends on the determination of its meso-parameters, also known as calibration. The calibration of mesoscopic parameters usually adopts the conventional "trial and error method", that is, by constantly changing the values of mesoscopic parameters until the simulated values basically coincide with the experimental values, the contingency is relatively high and the theory is deficient. It is difficult to calibrate. In this paper, according to the shortcomings of the methods mentioned above, the response surface method (RSM) and the BFGS optimization algorithm are combined with the experimental design. In this paper, a method for the inversion identification of mesoscopic parameters of rock and soil materials is presented. Using linear contact model to simulate rockfill, the mesoscopic parameters of rockfill are preliminarily calibrated according to the experimental data and prior information of triaxial compression laboratory test of rockfill. Based on the response surface function, the nonlinear mapping relationship between macroscopic deflection stress and mesoscopic parameters of rockfill is established. The BFGS optimization algorithm was used to invert the meso-parameters of rockfill. The modified residuum was simulated by parallel bonding model, and the meso-parameters of modified residuum were preliminarily calibrated according to the experimental data and prior information of triaxial compression laboratory test of modified residuum. A batch particle flow simulation test was designed, and the nonlinear mapping relationship between macroscopic deflection stress and mesoscopic parameters of modified residuum was established based on response surface function, and the BFGS optimization algorithm was used to invert the meso-parameters of modified residuum. Combined with response surface method and BFGS optimization algorithm, the meso-parameter inversion method of geotechnical materials based on macroscopic experimental data has high prediction accuracy. The particle flow simulation of rock breakage process under pressure head is carried out, and it is qualitatively consistent with the existing research results. The results show that PFC2D can reproduce the rock breaking process of head rock from a meso point of view. Parallel bond model can be used to simulate the mesoscopic failure behavior of rock materials.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU45

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