【作者】 彭从文；

【导师】 朱向荣；

【作者基本信息】 浙江大学 ， 岩土工程， 2010， 博士

【摘要】 岩石是由多种矿物晶粒、孔隙和胶结物组成的混杂体。经过亿万年的地质演变和多期复杂的构造运动,使岩石含有不同阶次随机分布的微孔隙与裂纹。在宏观尺度上天然岩体又为多种地质构造面(节理、断层和弱面)所切割。这些重要特点表征岩石是一种很复杂很特殊的材料,它不是离散介质,也不是连续介质,而是属于连续与离散(或局部离散)的耦合介质。岩石破坏过程也可看成是其内部结构面形成、重构的过程,在这个过程中,微裂纹萌生、宏观裂纹形成、结构面贯通及沿接触面滑移等现象交织在一起。由于破坏过程的跨学科性、多层次性和状态方程不清,岩石破坏问题一直是研究的热点与难点。本文将岩石结构面空间分布的结构性、尺度的结构性与分形特征的结构性称为广义多层结构,分别研究了脆性岩石、岩石节理及非贯通节理岩体的多层结构模型,模型的数值计算通过ABAQUS平台内嵌子程序UMAT与UEL实现。具体内容有:(1)介绍了用户材料子程序(UMAT)与用户单元子程序(UEL)实现方法。包括:弹塑性比例因子计算、变子增量步的修正Euler显式应力积分方法、应力修正方法、刚度矩阵AMATRX与残余荷载矩阵RHS计算方法及计算流程等。为验证UMAT的有效性,将Drucke-Prager模型写入UMAT并与ABAQUS材料库Drucke-Prager模型进行对比,采用UEL将Cosserate介质弹塑性模型嵌入ABAQUS并进行性状分析。(2)介绍了基于渐近展开法的双尺度边值方程、切线模量计算方法及计算步骤,给出了有限元列式及计算流程。将细观统计模型与渐近展开法相结合,提出了脆性岩石双尺度计算模型。模型在细观尺度采用基于Rankine准则的弹脆性本构关系,并考虑材料的统计性,采用切线模量为零作为材料软化判据,软化后采用考虑复合模式的钝断裂带裂纹模型。采用双尺度计算方法不仅能得到非均质材料的有效性能,更重要的是不必引入虚拟的损伤参数,使材料宏观力学性状与材料真实物理进程相对应。(3)基于节理分形特征,将节理面分解为不同层次结构面,结合Plesha节理本构提出岩石节理多层结构模型。采用单层结构时,该模型退化为Plesha节理模型。模型将接触面的损伤与破坏拟为不同层次结构面渐次破坏的过程,能考虑界面滑移、剪损、压碎、分离等作用机理。通过将界面粗糙度定义为等效起伏角,模型能模拟节理循环剪切性状。模型适用于中低压力下岩体节理、也可用于分析结构物与围岩相互作用性状等。(4)基于共线非贯通节理岩体破坏机理,提出非贯通节理岩体多层结构模型。节理贯通时,该模型退化为Zienkiewicz节理材料模型。节理岩体多层结构模型包括节理滑移与节理扩展模型。节理滑移模型考虑节理细观形态;在节理扩展模型中,结构面剪切强度由节理剪切强度与岩桥强度共同组成,节理剪切强度体现为界面基本摩擦角与粗糙角,岩桥强度体现为等效粘聚力,等效粘聚力不断弱化的过程就是结构面由非贯通向贯通转化的过程。非贯通节理岩体多层结构模型假定岩桥为共面剪切破坏,模型适用于岩体节理共面并且岩桥长度远小于节理长度的情形。更多还原

【Abstract】 Rock is a combination of mineral grains, porosity and composition of cement mixed body. After millions of years of geological evolution and a complex multi-stage tectonic movements, the rock contains a random distribution at different levels of sub-micro-pores and cracks. At the macro-scale natural rock is cut by a variety of geological structures (joints, faults and weak-side).The rock is a very complex and very special material, it is not a discrete medium, nor is it a continuous medium, but under the continuous and discrete (or local discrete) coupling medium. Rock failure can also be seen as a process of their internal structure surface formation and reconstruction, the micro-crack initiate, macro-crack formate, structure surface slide along the contact surface in this process. As the failure process involing in cross-disciplinary, multi-level nature and the equation of state is unclear, the study of rock destruction issue has been hot and difficult. This paper define the spatial distribution of structure of rock, scale structure and fractal as the generalized hierarchical, put forward the hierarchical models of brittle rock, rock joints and non-persistent jointed rock mass respectively. The numerical model are implemented by ABAQUS subroutine UMAT and UEL. Details including:(1) Describes the user material subroutine (UMAT) and the user element subroutine (UEL). Including: elastic-plastic scale factor calculation, changing the amendment to sub-incremental-step explicit Euler stress integration method, the stress correction method, stiffness matrix AMATRX and residual load matrix RHS calculation method. In order to verify the validity of UMAT, comparing the results calculated by Drucke-Prager model embedded into the UMAT and the results calculated by the ABAQUS library Drcuke-Prager model. The elastic-plastic constitutive of Cosserate media is embedded into UEL and the behaviors of the Cosserate media is analyzed.(2) Describes the asymptotic expansion method, tangent modulus calculation method and calculation procedures. The two-scale computational model of brittle rock is proposed based on the combination of the micro-statistical model and the asymptotic expansion. Rankine-based criteria for brittle elastic constitutive is adopted in micro-scale , taking into account the statistical nature of materials, using the zero-value of material tangent modulus as the softening criterion, the blunt crack model is used in the softening process. Using two-scale method the effective properties of non-homogeneous material can be gotten easily, more importantly, there is no need to introduce virtual damage parameters, and the macroscopic mechanical behavior of material corresponds to the real physical processes.(3) Based on the fractal characteristics, the joint roughness is decomposed into different levels of structural surface, hierarchical model of rock joints is proposed combined with Plesha joints model. Using single-layer structure, the hierarchical model degenerates to Plesha joints model. the failure of joint is conceived as process of damage and destruction for the different levels of surfacess gradually, this model consider the mechanisms of interfacial slipping, shearing, crushing and separating. After the joint roughness is defined as the equivalent inclination angle, the model can simulate the behaviors of joints under cyclic loading. The model is applicable to analyze the interaction between structures and rock under low pressure.(4) Based on failure mechanism of coplanar non-persistent jointed rock mass, the hierarchical model of non-persistent jointed rock mass is proposed. the model degenerates to Zienkiewicz jointed material model when the joints become persistent. This model includie joints slip model and joints crack model. Joints slip model considers the joint micro-configuration. In the joint crack model, the shear strength constitute the shear strength of joints and rock bridges strength, joint shear strength reflected in the basic friction angle and rough angle, rock bridge stregth reflected in the equivalent cohesion, the continuous weakening process of the equivalent cohesion is the process of the transformation from discontinuous to continuous of joint. This model assumes the coplanar shear failure mechanism of the rock bridge, so it can be used under the circumstance that the length of rock bridges is far less than of the length of the joint.更多还原