基于细观数值试验的非饱和土石混合体力学特性研究

 从土石混合体细观结构出发，融合细观结构模型生成技术、主–从接触面模型及非饱和土渗流与强度理论，建立非饱和土石混合体的细观数值模拟方法。通过与非饱和土石混合体室内试验结果进行对比，验证所建立的细观数值模拟方法的可行性和合理性。利用该细观模拟方法，分析土–石界面接触特性、含石量及饱和度等因素对非饱和土石混合体力学特性与破坏机制的影响。结果表明：(1) 非饱和土石混合体在低围压下表现出明显的剪胀性，且受含石量和饱和度影响显著；在较高围压下基本上表现为剪缩变形，随含石量的增大其剪缩变形减小，饱和度对剪缩性的影响较小。(2) 土石混合体的峰值强度和变形模量随土–石界面摩擦因数的增大呈非线性增长，在界面摩擦因数大于0.6以后，两者基本趋于稳定值。(3) 含石量越大，非饱和土石混合体的峰值强度和变形模量越大，应变硬化特征更为显著，在含石量增加到58%后峰值强度和变形模量趋于稳定值。在低围压下剪胀变形随含石量的增加而增大；在较高围压时，剪缩变形随含石量的增大而减小。(4) 饱和度越大，基质吸力越小，非饱和土石混合体的峰值强度越低，但变形模量变化不大。

RESEARCH ON MECHANICAL CHARACTERISTICS OF UNSATURATED SOIL-ROCK MIXTURE BASED ON NUMERICAL EXPERIMENTS OF MESOSTRUCTURE

The mesoscopic numerical method for simulating unsaturated soil-rock mixture is presented based on its mesostructure features. This method includes the technique for generation of mesostructural model，master-slave contact surface algorithm，and seepage and strength theory of unsaturated soil. The feasibility and rationality of proposed method are validated by comparing the numerical results to the results obtained in laboratory experiments of unsaturated soil-rock mixture. The proposed method is then used to analyze the factors，such as the contact behaviours of soil-rock interface，rock block content and saturation degree，and their influences on the mechanical characteristics and failure mechanism of unsaturated soil-rock mixture. It is found that：(1) Under low confining pressure，unsaturated soil-rock mixture exhibits remarkable shear dilatancy，which are influenced significantly by rock block content and degree of saturation at this time. Under high confining pressure，unsaturated soil-rock mixture exhibits shear contraction. As rock block content increases，the deformation of shear contraction decreases；and the influence of saturation degree is small. (2) The peak strength and deformation modulus of soil-rock mixture increase nonlinearly as the friction coefficient of soil-rock interface increases. When friction coefficient is above 0.6，values of peak strength and deformation modulus tend to be stable. (3) The increase of rock block content will lead to the increases of peak strength and deformation modulus of unsaturated soil-rock mixture. Strain-hardening feature at this time becomes more remarkable. When rock block content exceeds 58%，values of peak strength and deformation modulus tend to be stable. Under low confining pressure，the increase of rock block content will lead to the increase of shear dilatancy deformation. Under high confining pressure，the increase of rock block content will lead to the decrease of shear contraction deformation. (4) The increase of saturation degree will lead to the decrease of matric suction and peak strength of soil-rock mixture but have little influence on deformation modulus.