脆性材料中三维裂隙破坏过程试验与数值模拟研究

发布时间：2018-08-22 14:58

【摘要】：原生裂隙的起裂、扩展和贯通演化特征和破坏规律是研究岩体工程破坏和失稳的基础,渗流对岩体强度的影响也受工程界所重视。由于三维裂隙岩体研究的复杂性,前人研究往往将三维问题简化为二维问题,而在这一简化往往不能全面反映三维裂隙的扩展破坏规律。近年来,研究裂隙的三维扩展形态和破坏机制成为裂隙岩体领域的重要课题,对裂隙岩体三维应力条件下的破裂过程和机理研究仍需深入。此外,很多岩体工程的失稳往往和地下水的作用密切相关。因此,开展裂隙岩体在内含有压水的条件下其破裂规律的变化和新的特征也是十分重要的。本文通过实验研究、理论分析和数值模拟等方法,研究类岩石材料含裂隙试件的裂纹扩展规律和机理,采用细观理论方法,揭示裂纹的扩展过程和破坏形态,对有水压条件的裂隙试件破裂过程和强度规律进行了分析,并将分析方法用于工程实际中,主要完成和开展了以下几方面工作： (1)研制了低温下拉压比为1/6.6的树脂材料用于制作模型试件,该材料脆性高,符合岩石的基本特征,其力学参数大理岩等岩石力学参数接近,可以在很大程度上模拟这些岩石的力学特性；而且其透明度高,能够清晰的用肉眼观察试件内部裂纹的扩展破坏状态,便于人们直观上理解裂纹的扩展规律。同时,作者用该材料研制了含中空裂隙试件,进行了内置裂隙在有水压的条件下的压缩试验。采用该中空裂隙试件及作者设计的试验方法,可以对内置裂隙试件施加不同的水压和侧压,开展多种工况下含预置裂隙试件的压缩试验和水压致裂试验。 (2)通过透明预置裂隙试件单轴压缩试验,研究了三维内置裂隙试件的新生裂纹的起裂、扩展和贯通破坏规律。研究表明,三维试件受压破裂过程大致经历四个阶段。其四个变形阶段与岩石试件完全相对应,并发现材料有非常明显的与岩石类似的扩容特性。试验过程中除了观测到常见的包裹状翼型裂纹,还出现了前人理论推测出的花瓣形裂纹。不饱和树脂材料制作的试件为均质材料试件,除预置裂隙外,不存在其他缺陷,因此可认为该均质材料试件压缩试验为无其他缺陷干扰的情况下此单一缺陷(预置裂隙)产生破坏的过程。同非均质材料试验比较,在裂隙新生裂纹萌生和扩展初期两种材料扩展方式相同,但由于受非均质缺陷的影响,最终破坏形式有所不同。 (3)进行了有水压条件下裂隙试件的压缩试验。根据试验结果,有水压作用下与无水压条件下裂隙试块的破坏过程和现象有相同和不同之处为：试验过程中均在椭圆状裂隙长轴端部产生包裹状翼型裂纹,但有水压作用下未出现花瓣状裂纹；有水压条件下,新生裂纹的萌生和试块达到完全劈裂状态时所需的压力更小,即在水压作用下,试块的承压能力降低,而且水压越大,新生裂纹的萌生和和试件破坏所需的轴向压力越小。 (4)使用FLAC3D计算程序,通过二次开发,采用弹脆性损伤模型模拟了单裂隙和双裂隙试块在单轴加载条件下裂纹扩展过程和破坏情况,计算结果与试验过程基本吻合。通过计算不同侧压工况下裂隙试件的破坏过程,随着围压的增加,新生裂纹的萌生应力、扩容点和峰值强度都随之增加,而且裂纹的扩展形态有所不同。 (5)采用流固耦合方法研究了不同水压作用下裂纹的起裂和扩展规律。水压的增加使得新生裂纹萌生的压力和峰值强度均有所降低,而且二者随着水压的增加而下降。水压致裂试验模拟计算表明,水压致裂的最终破坏裂纹始终垂直于最小主应力；如果垂直主应力小于水平主应力,则破坏方式为水平方向,如果垂直主应力大于水平主应力,则破坏方式为垂直方向。 (6)以大型地下洞室开挖为例,进行了准三维模型的洞室开挖数值模拟,计算结果基本能够反应洞室开挖围岩应力场、位移场的变化规律,特别是由于采用了模型细观计算方法,基本能够反应洞周原生裂隙的扩展规律和渗流对洞室开挖的影响。
[Abstract]:The characteristics of initiation, propagation and penetration evolution and failure law of primary fractures are the basis for studying the failure and instability of rock mass engineering, and the influence of seepage on rock mass strength is also paid attention by engineering circles. In recent years, it has become an important subject in the field of fractured rock mass to study the three-dimensional propagation form and failure mechanism of cracks. The research on the fracture process and mechanism of fractured rock mass under three-dimensional stress condition still needs to be further carried out. In addition, the instability of many rock mass engineering is often closely related to the action of groundwater. It is also very important to study the change of fracture law and new characteristics of fractured rock mass with pressurized water. In this paper, by means of experimental research, theoretical analysis and numerical simulation, the law and mechanism of crack propagation of rock-like materials with cracks are studied, and the crack propagation process and failure are revealed by means of microscopic theory. In this paper, the fracture process and strength law of fractured specimens with hydraulic pressure are analyzed, and the analysis method is applied to engineering practice. The following work is mainly completed and carried out:
(1) A resin material with a tensile-compressive ratio of 1/6.6 at low temperature was developed for making model specimens. The material has high brittleness and accords with the basic characteristics of rock. Its mechanical parameters, such as marble, are close to each other, which can simulate the mechanical properties of these rocks to a great extent; moreover, it has high transparency and can be clearly observed by naked eyes. At the same time, a specimen with a hollow crack is developed by the author, and the compression test of a built-in crack is carried out under the condition of water pressure. Water pressure and lateral pressure are used to carry out compression tests and hydraulic fracturing tests of preset fractured specimens under various conditions.
(2) Through uniaxial compression test of transparent pre-cracked specimens, the law of initiation, propagation and penetration failure of new cracks in three-dimensional specimens with internal cracks is studied. In addition to the common wrapped airfoil cracks, petal-shaped cracks were also observed during the test.
The specimen made of unsaturated resin material is homogeneous material, and there are no other defects except pre-cracks. Therefore, it can be considered that the compression test of the homogeneous material specimen is the failure process of the single defect (pre-crack) without interference of other defects. In the early stage of development, the two materials have the same propagation mode, but due to the influence of heterogeneous defects, the ultimate failure mode is different.
(3) Compression tests of fractured specimens under hydrostatic pressure are carried out. According to the test results, the failure process and phenomena of fractured specimens under hydrostatic pressure are the same and different as those under non-hydrostatic pressure: wrapped airfoil cracks occur at the end of the long axis of elliptical cracks, but no petal cracks appear under hydrostatic pressure. Under the condition of water pressure, the pressure required for the initiation of new cracks and the complete splitting of the specimen is smaller, that is, the bearing capacity of the specimen decreases under the action of water pressure, and the larger the water pressure, the smaller the axial pressure required for the initiation of new cracks and the failure of the specimen.
(4) By using FLAC3D program and secondary development, the crack propagation and failure of single crack and double crack specimens under uniaxial loading are simulated by using the elastic-brittle damage model. The calculated results are in good agreement with the experimental results. The initiation stress, dilatancy point and peak strength of the crack increase, and the crack propagation morphology is different.
(5) The initiation and propagation of cracks under different hydraulic pressures are studied by fluid-solid coupling method. The pressure and peak strength of the initiation of new cracks decrease with the increase of hydraulic pressure. The simulation results of hydraulic fracturing test show that the ultimate failure crack is perpendicular to the maximum. If the vertical principal stress is less than the horizontal principal stress, the failure mode is horizontal, and if the vertical principal stress is greater than the horizontal principal stress, the failure mode is vertical.
(6) Taking the excavation of a large underground cavern as an example, the quasi-three-dimensional numerical simulation of the excavation of the cavern is carried out. The calculated results can basically reflect the stress field and the displacement field of the surrounding rock of the cavern excavation. Especially, the micro-calculation method of the model can basically reflect the propagation law of the primary cracks around the cavern and the excavation of the cavern by seepage. Influence.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU452

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