干燥和饱水状态下炭质板岩流变力学特性与模型研究

发布时间：2018-03-13 22:16

本文选题：炭质板岩　切入点：干燥和饱水状态　出处：《长安大学》2013年博士论文　论文类型：学位论文

【摘要】：开展不同含水状态下岩石流变力学特性与模型研究，对于正确预测和有效控制岩石工程的安全与稳定具有重要的理论价值和工程实践意义。本文以兰渝铁路木寨岭隧道炭质板岩为研究对象，采用试验研究、理论分析相结合的方法，基于炭质板岩在干燥和饱水状态下的力学特性以及蠕变规律，建立适用于炭质板岩的非线性流变理论模型，结合粒子群算法(PSO)和非线性最小二乘法对流变参数进行辨识，并将建立的流变模型嵌入FLAC3D，完成数值程序的二次开发。本文主要研究工作如下： (1)开展干燥和饱和状态下炭质板岩单轴和三轴试验、楔形剪切试验、巴西圆盘劈裂试验，以及单轴循环加卸载瞬时力学特性试验，掌握了两种状态下炭质板岩的瞬时力学特性，也为开展岩石蠕变试验提供了试验基础。试验结果表明：水对炭质板岩强度和变形的影响是显著的，而在单轴循环加卸载条件下的影响更为突出； (2)采用全自动伺服流变仪，对干燥和饱和炭质板岩开展分级加载和分级增量循环加卸载蠕变试验，研究两种状态下炭质板岩的蠕变特点，以及水对岩石在各级压力下的蠕变量、蠕变速率的影响。在中、低应力水平下，岩石蠕变变形主要呈现出衰减蠕变和稳态蠕变2个阶段，当加载应力增加到较高应力水平时，岩石轴向变形急剧增长，表现出加速蠕变阶段；相同应力水平下的饱水岩样的蠕变量为干燥岩样的3倍以上；加卸载蠕变试验表明：水对岩石瞬时变形的影响主要表现在瞬时塑性变形方面，对瞬时弹性变形的影响不大，而对岩石蠕变变形的影响则主要体现在粘弹性应变方面； (3)根据炭质板岩在干燥和饱水状态下的蠕变特点，在Burgers流变模型的基础上，结合一个非线性粘塑性体，和Burgers流变模型相串联，构建适于炭质板岩蠕变特点的改进Burgers非线性粘弹塑性流变模型，导出了模型的本构方程、蠕变方程、卸载方程以及蠕变模型的三维形式； (4)在粒子群算法的基础上，将线性递减权重粒子群算法和Levenberg-Marqud非线性最小二乘法相结合，先采用线性递减粒子群算法对流变模型参数进行初步辨识，将其结果作为初始值，再采用L-M算法进行辨识，参数辨识后的相关系数均在0.94以上； (5)针对目前建立的能反映蠕变加速阶段的流变模型元件和参数较多的问题，借鉴经典元件组合模型的建模思路，将含分数阶微积分的软体元件与弹簧元件串联，结合一个幂函数粘塑性体，提出一种新的四元件非线性粘弹塑性流变模型，并给出该模型的本构方程和蠕变方程。利用炭质板岩蠕变试验结果，将该模型与改进Burgers非线性流变模型进行对比拟合分析，表明该模型能够有效地描述岩石的三阶段蠕变特性，在满足拟合精度的前提下，能够减少组合模型中的元件个数和参数数量； (6)岩石的蠕变过程是岩石内部应力不断调整，硬化和损伤效应不断发展并共同作用的结果。以经典元件模型为基础，将岩石的初始屈服强度作为蠕变硬化的应力阈值，岩石的长期强度作为损伤软化的应力阈值，引入能反映岩石蠕变硬化的硬化函数和损伤效应的损伤变量，建立了一个能够全面反映蠕变机制的岩石非线性蠕变模型。利用蠕变试验数据对所提出的模型进行辨识，，结果表明该模型不仅能够很好地描述三阶段蠕变特性，而且可以全面反映岩石蠕变过程中的蠕变硬化和损伤软化机制； (7)依据FLAC3D提供的内置本构模型源代码，在Burgers蠕变模型有限差分形式的基础上，导出了改进Burgers非线性蠕变模型的三维差分形式。借助C++语言将改进Burgers非线性蠕变模型的三维差分形式编译成动态链接库，嵌套到FLAC3D中，实现了本构模型的二次开发，并利用新开发的流变模型进行单轴压缩蠕变模拟试验，验证了程序二次开发的正确性。
[Abstract]:Study on characteristics and model of rock rheological mechanics under different moisture conditions, has important theoretical value and practical significance for the safety and stability of correct prediction and effective control of rock engineering. In this paper, Muzhailing tunnel on Lanzhou Chongqing railway carbonaceous slate as the research object, based on the experimental results, the theoretical analysis method of combining, carbon slate in mechanical properties of dry and saturated state and creep law based on nonlinear rheological theory model for carbonaceous slate, combined with particle swarm algorithm (PSO) on the rheological parameters identification and nonlinear least square method, embedded FLAC3D rheological model and the establishment of the completion of the two numerical procedure is developed. This paper the research work is as follows:
(1) to carry out dry and saturated carbonaceous slate single axis and three axis wedge test, shear test, Brazil disk split test, and uniaxial cyclic loading and unloading transient mechanical properties test, grasp the two conditions of carbonaceous slate instantaneous mechanical properties tests provide a basis for carrying out the creep test of rock. The experimental results show that the water has a distinct effect on the strength and deformation of the carbonaceous slate, the impact of the uniaxial cyclic loading and unloading conditions is more prominent;
(2) using automatic servo rheometer of dry and saturated carbonaceous slate to carry out graded loading and multi-step incremental cycling loading and unloading creep test, the creep characteristics of carbonaceous slate of two states, as well as at all levels under the pressure of water on rock creep, the creep rate of the impact. In the low stress under the rock creep deformation mainly presents 2 stages of decay creep and steady creep. When the loading stress increases to a higher stress level, axial deformation increased sharply, showing accelerated creep stage; under the same stress level of creep deformation of water saturated rock samples for dry rocks indicate that more than 3 times; unloading creep test: influence of water on rock instantaneous deformation mainly in instantaneous plastic deformation, has little effect on the instantaneous elastic deformation, and the influence on the creep deformation of rock is mainly embodied in the viscoelastic strain;
(3) according to the creep characteristics of carbonaceous slate in the dry and saturated state, based on Burgers rheological model, combined with a nonlinear viscoplastic body, and Burgers rheological model are suitable for constructing carbon slate creep characteristics of modified Burgers nonlinear visco elastoplastic rheological model, constitutive equation the model, derived creep equation, equation and three-dimensional form creep model;
(4) on the basis of particle swarm optimization, combining the linear decreasing weight PSO and Levenberg-Marqud nonlinear least square method, the linear decreasing particle swarm algorithm for preliminary identification of the parameters of rheological model, the results as the initial value, then the L-M algorithm for identification, parameter identification of the correlation coefficient in the more than 0.94;
(5) aiming at the establishment of the problem can reflect the accelerated creep rheological model of components and parameters more stage, from the classic element combination modeling ideas, the fractional calculus software element and spring element in series, with a power-law viscoplastic body, put forward a new four component nonlinear visco elasto plastic rheological model, and gives the model of the constitutive equation and creep equation. Using carbon slate creep test results, the model with improved Burgers nonlinear rheological model comparison fitting analysis show that the model can effectively describe the three stages of creep of rock, in order to meet the demand of the fitting precision, can reduce the the number of components and the number of parameters in the model;
(6) the creep process of rock is the rock internal stress hardening and damage effect of continuous adjustment, development and result of the interaction. Based on classical element model as the foundation, the rock initial yield strength as creep hardening stress threshold, the long-term strength of rock softening stress as the damage threshold, the damage variable can reflect the hardening function and damage effect of rock hardening, establish a fully reflect the creep mechanism of the nonlinear creep model of rock. To identify the model proposed by the creep test data, the results show that the model can well describe the creep characteristics of the three stage, but also can reflect the creep process of rock creep hardening and damage softening mechanism;
(7) on the basis of the built-in FLAC3D provides the constitutive model of the source code, in the Burgers creep model of finite difference based on improved Burgers derived three-dimensional nonlinear creep model of the three-dimensional form. The improved Burgers nonlinear creep model with the aid of the C++ language form is compiled into a dynamic link library, nested FLAC3D to achieve the two development, constitutive model, and the uniaxial compression creep simulation experiments using the new rheological model developed, verified the correctness of the two development program.

【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU45

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