1、巖體三維裂隙拉伸斷裂機理的試驗與數值模擬研究        【中文摘要】裂隙巖體是各種巖體工程和環境工程中經常碰到的一種復雜工程介質。在承受工程荷載時,巖體中大量的裂隙開始萌生、擴展和貫通,導致巖體介質力學性能的劣化以致終極破壞。因此,巖體中原生裂隙的擴展演化特征、破裂模式以及對巖體力學特性的影響一直為學術界和工程界所重視。鑒于三維題目在數學處理和現象觀測上的復雜性,人們對裂隙題目的研究往往簡化為二維情況來處理,但裂隙大都處于三維應力狀態(表面裂隙或深埋裂隙),把三維裂隙簡化為二維裂隙會引起較大差距。因此,近年來有

2、關三維裂隙擴展演化機制及其對巖體材料力學特性影響的研究成為巖土工程重要研究課題。目前壓縮條件下巖體中三維裂隙擴展演化機制的試驗研究已有一些,但由于試驗設備和技術方面的制約,拉伸條件下相應的成果很少。巖石材料具有低抗拉性,在較低拉伸應力作用下內部裂隙就開始擴展、貫通導致材料破壞。巖體工程中不可避免的要碰到拉應力區,因此開展拉伸條件下三維裂隙擴展演化機制以及對巖體力學特性影響的研究具有重要的理論意義和工程價值。物理試驗方法和數值模擬方法是研究裂隙擴展題目的有效手段。本文結合這兩種方法開展了以下研究工作:1、通過閱讀大量文獻,分析比較了以往三維裂隙巖體斷裂機理試驗中所用各種材料的優缺點。結合本試驗情

3、況,研制了脆性砂漿材料,其物理力學參數與砂巖接近,代替真實巖石進行試驗可表現出類似的受力變形特征,并且該材料方便埋設三維裂隙。2、由于巖石材料直接拉伸試驗技術不成熟,故改進了目前采用較多的夾具法和黏結法,設計加工了適用于脆性材料單軸拉伸試驗的端部擴大型試件模具、與試件外形配套的夾具以及黏結拉伸軸向定位裝置。3、制作了含不同形式(不同角度、不同間距和不同數目)內置裂隙的試件,并對其進行了單軸拉伸試驗,得到了各試件的應力應變曲線,觀察分析了試件的受力變形過程,總結了內置裂隙角度、間距及數目對材料力學特性以及裂隙擴展演化過程的影響。4、制作了含不同傾角表面裂隙的試件,并對其進行了單軸拉伸試驗,得到相

4、應的應力應變曲線,觀察分析了試件的受力變形過程,總結了表面裂隙傾角對材料力學特性以及裂隙擴展演化過程的影響。5、用FRANC3D軟件計算了含不同形式(不同角度、不同間距和不同數目)內置裂隙和不同傾角表面裂隙的試件在單軸拉伸條件下,裂隙前緣應力應力強度因子分布,裂隙前緣應變能開釋率分布,模擬了所含三維裂隙的擴展演化過程。6、結合物理試驗和數值模擬的結果,得出若干有價值的結論,并對實際工程提出一些建議。');【Abstract】 Fractured rock mass is usually met in most of the rock mass engineering and envir

5、onmental engineering. Under different kinds of loads, the crack initiation, propagation, coalescence and interaction may induce the degradation of mechanical properties, even damage of the rock mass material. Therefore, the growth and evolvement features, fracture pattern, and the influence on rock

6、strength of flaws in the rock mass are always focused by the researchers of academic and engineering fields.Because of the difficulties of mathematical treatment and phenomena observation on 3-D problem, people usually simplify the 3-D crack problem to 2-D situation. But most cracks are under 3-D st

7、ress condition (internal crack or su*ce crack), such simplification would lead to error. So, the study of crack propagation mechanism and the influence on the material strength become important research subjects in Geotechnical Engineering.Up to now, there have been some experimental studies about c

8、rack propagation mechanism in rock mass under compressive stress. Because of the constraint of experimental equipment and technology, there are quite few studies on the crack propagation mechanism of rock mass under tensile stress. Compared to the compressive strength, the tensile strength of rock m

9、ass is very low. Under low tensile stress, the cracks in rock mass will initiate, grow and coalesce, resulting in the damage of rock mass. The tension stress zone is inevitable met in the geotechnical projects, so the study of crack propagation mechanism in rock mass under tensile stress and its inf

10、luence on the rock strength is full of theoretical meaning and application value.Both experimental test and the numerical simulation are effective methods to study the crack propagation problems. In this *, the two methods are combined to do the following research work:1. By reading lots of literatu

11、res, analyze and compare the advantages and disadvantages of the materials used in the similar researches. According to practical situation, develop a kind of mortar material with good brittleness, the physical and mechanical parameters of which are closed to the real rock material. So the mortar ma

12、terial is a good alternative of real rock material, with the advantage of * pre-exist flaws conveniently. 2. Improve the clamp method and bonding method used most frequently in the tensile test of brittle material. Design and make a sample die with the shape of end region enlargement, a clamp matchi

13、ng with the sample, and axial direction location device, which suit for the axial tensile experiment of brittle material.3. Make samples containing different kinds (different dip angle, different distance between two cracks, different amount of cracks) of internal cracks. Carry out axial tension exp

14、eriments with those samples, and obtain the stress-strain curves of all the samples, at the same time observe and analyze the loading and deformation course of samples. Finally, conclude the 3-D internal crack growth rules and the influence on the material strength.4. Make samples containing single

15、su*ce crack with different dip angle. Carry out axial tension experiments with those samples, and obtain the stress-strain curves, at the same time observe and analyze the loading and deformation course of samples. Finally, conclude the 3-D su*ce crack growth rules and the influence on the material strength.5. Using the FRANC3D numerical program, compute and analyze the distribution of stress intensity factor and energy release rate along the tips of different forms of internal and su*ce cracks under