基于宏观实验数据的岩土材料细观参数反演

发布时间：2018-03-05 17:00

本文选题：离散单元法　切入点：颗粒流　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：岩土材料不同于一般的宏观连续介质材料,其在细观组构上是颗粒堆积体,内部普遍存在着裂纹、孔洞及结构面等构造。离散单元法于1971年被引入,其将岩土材料视为由圆形颗粒构成的颗粒集合体,在细观层次上模拟岩土材料受力、运动及变形状态,受到十分广泛的应用及进一步的研究。二维颗粒流程序pFCD基于离散单元法而开发,被广泛应用于隧道开挖、基坑支护、边坡稳定性、土工试验模拟、岩石破碎、渗流、动载问题等诸多岩土工程领域。颗粒流模拟的精度主要取决于其细观参数的确定,也称作标定,细观参数的标定通常采用常规“试错法”,即通过不断改变细观参数值直到模拟值与试验值基本吻合,其偶然性较高,理论性欠缺,标定难度较高。本文针对上述岩土材料细观参数标定方法的不足,结合试验设计、响应面法及BFGS优化算法,提出了一种岩土材料细观参数反演辨识方法。使用线性接触模型模拟堆石料,根据堆石料三轴压缩实验室试验观测数据及先验信息对堆石料细观参数进行了初步标定,设计了批量颗粒流模拟试验,基于响应面函数建立了堆石料宏观偏应力与细观参数之间的非线性映射关系,采用BFGS优化算法对堆石料细观参数进行了反演。使用平行粘结模型模拟改性渣土,根据改性渣土三轴压缩实验室试验观测数据及先验信息对改性渣土细观参数进行了初步标定,设计了批量颗粒流模拟试验,基于响应面函数建立了改性渣土宏观偏应力与细观参数之间的非线性映射关系,采用BFGS优化算法对改性渣土细观参数进行了反演。研究表明,结合响应面法和BFGS优化算法,基于宏观实验数据的岩土材料细观参数反演方法具有较高的预测精度。根据估计的岩石平行粘结模型细观参数,对压头作用下岩石破碎过程进行了颗粒流模拟,并与已有研究结果取得了定性上的一致。研究表明,PFC2D可从细观角度再现压头破岩过程,平行粘结模型可用来模拟岩石材料细观破坏行为。
[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.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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