拉压循环荷载下砂岩的力学及蠕变特性研究

发布时间：2018-06-12 22:16

本文选题：砂岩 + 拉压循环　；参考：《重庆大学》2015年硕士论文

【摘要】：在岩体工程中岩石承受的应力环境非常复杂,受到拉伸与压缩反复加卸载作用的情况经常发生,如地下油气注采过程中注采荷载对围岩的作用等。本文以砂岩为例进行拉伸与压缩循环荷载下的疲劳和蠕变试验,研究砂岩在拉压循环荷载作用下的力学特性,揭示砂岩加载-卸荷-卸荷拉伸下的变形规律,并深入探讨砂岩在这种复杂应力路径下的蠕变特性,建立非线性蠕变模型。论文主要研究工作如下:①运用改进的拉压连接装置在INSTRON 1342试验机上进行砂岩定应力和增应力拉压循环荷载试验,探讨了砂岩在拉压循环荷载作用下的主要力学特性,如轴向应变、变形模量和能量损伤随应力水平和循环次数的变化规律等。②利用设计开发的杠杆式岩石拉压流变试验仪对砂岩进行定应力和增应力拉压循环蠕变试验,研究砂岩在拉压循环荷载作用下的蠕变特性,如瞬时应变、蠕变变形、蠕变速率和体积蠕变变形与应力水平和循环次数之间的关系等。③基于拉压循环试验结果,得到砂岩拉压循环破坏门槛值的一个范围。根据应力应变曲线,计算变形模量和能量损伤,基于能量耗散分析建立能量损伤与压应力和循环次数之间的关系式,该方程能够很好的描述砂岩能量损伤演化过程。④基于拉压循环蠕变试验结果,分析应力和循环对瞬时应变和蠕变量的影响,研究了增应力蠕变试验的体积蠕变,以及每一级荷载的蠕变速率随时间的变化规律,比较了最后一级荷载下长时蠕变的衰减蠕变、稳态蠕变和加速蠕变三个阶段,以及最终的蠕变破坏特性。⑤根据砂岩增应力拉压循环蠕变试验结果,比较试验曲线与Burgers蠕变模型拟合曲线。基于岩石拉伸加速蠕变试验结果,提出了一个岩石非线性粘弹塑性蠕变模型。采用基于MATLAB程序的quasi-Newton算法(BFGS算法)对砂岩拉伸状态下的蠕变曲线进行了参数的识别。
[Abstract]:In rock mass engineering, the stress environment of rock is very complex, which is often subjected to repeated loading and unloading under tension and compression, such as the effect of injection-mining load on surrounding rock in the process of underground oil and gas injection and production. In this paper, the fatigue and creep tests of sandstone under tensile and compressive cyclic loads are carried out to study the mechanical properties of sandstone under tension and compression cyclic loads, and to reveal the deformation law of sandstone under load-unloading tension. The creep characteristics of sandstone under this complex stress path are discussed, and a nonlinear creep model is established. The main research work of this paper is as follows: 1. Using the improved tension-compression connection device to carry out the cyclic load tests on sandstone under constant stress and increasing stress on the Instron 1342 testing machine, the main mechanical properties of sandstone under the cyclic load of tension and compression are discussed. For example, the variation of axial strain, deformation modulus and energy damage with stress level and cycle times, etc. 2. The cyclic creep tests of sandstone under constant stress and increasing stress are carried out by using the levered rock tensile compression rheometer developed in this paper. The creep characteristics of sandstone under tension and compression cyclic loading, such as instantaneous strain, creep deformation, the relationship between creep rate and volume creep deformation, stress level and cycle number, are studied based on the results of tensile compression cycle tests. A range of the failure threshold of sandstone under tension and compression cycles is obtained. According to the stress-strain curve, the deformation modulus and energy damage are calculated. Based on the energy dissipation analysis, the relationship between energy damage and compressive stress and cycle number is established. The equation can well describe the energy damage evolution process of sandstone. Based on the results of tensile compression cyclic creep test, the influence of stress and cycle on instantaneous strain and creep is analyzed, and the volume creep of stress-increasing creep test is studied. The creep rate of each stage load varies with time, and the three stages of long term creep attenuation creep, steady state creep and accelerated creep under the last stage load are compared. Finally, the creep failure characteristics of sand are compared with those of Burgers creep model according to the cyclic creep test results of sandstone under increased stress, tension and compression. Based on the results of tensile accelerated creep test, a nonlinear viscoelastic-plastic creep model for rock is proposed. The quasi-Newton algorithm based on MATLAB (BFGS algorithm) is used to identify the parameters of creep curve in sandstone tensile state.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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