本文選題：加卸荷　切入點：屈服函數　出處：《青島理工大學》2013年碩士論文

【摘要】：地下工程開挖是一個極其復雜的加卸荷受力過程，而巖體在加卸荷不同應力路徑條件下的變形特征、強度特性及破壞機制存在明顯差異。對不同應力路徑下巖石變形破壞性質的研究，對補充完善巖石力學理論和指導工程設計、施工有著重要的理論和工程意義。本文開展了不同應力路徑條件下的大理巖加卸荷破壞試驗研究，從能量變化角度分析了不同應力路徑下大理巖的破壞機制，給出了大理巖變性破壞過程的能量非線性演化模型。論文主要取得了下列研究成果： (1)通過完整大理巖巖樣加卸荷試驗，揭示了加卸荷條件下巖石變形、破壞特征與強度參數變化規(guī)律。巖樣加荷破壞彈性階段軸向變形起主導作用，屈服開始后環(huán)向變形快速增加；加荷破壞大理巖起裂應力隨圍壓升高向峰值強度逐漸靠近，圍壓延遲了巖石的破壞；卸荷破壞巖樣的峰值強度隨著卸荷速率的增加逐漸減小，隨著卸荷初始圍壓的升高逐漸增大，環(huán)向變形和體積變形對慢速卸荷比快速卸荷更敏感。 (2)根據廣義塑性力學理論，利用試驗數據構建了大理巖加卸荷變形過程的屈服面，，保證了屈服函數的唯一性和準確性。大理巖加荷破壞過程的剪切屈服面為直線形式，卸荷破壞剪切屈服面分為卸荷前的直線形式和卸圍壓過程的二次拋物線形式，加荷破壞體積屈服面分為壓縮和剪脹兩段直線形式，卸荷破壞體積屈服面分為卸荷前的直線形式和卸荷后的二次拋物線形式。 (3)根據大理巖變形破壞過程的能量演化曲線，可以將大理巖卸荷破壞分為四個階段：壓密階段、彈性階段、裂紋擴展階段和峰后破壞階段。到達屈服點前，巖樣吸收的能量大部分以彈性能形式存儲于巖樣內部；屈服點后到峰前的非線性變形階段，彈性能增速緩慢，而耗散能的增速變大；到達峰值強度時，巖樣內部存儲的彈性能達到儲能極限，彈性能瞬間釋放，耗散能快速升高。常規(guī)三軸的儲能極限高于單軸壓縮，而峰前卸圍壓的儲能極限低于常規(guī)三軸壓縮；隨著卸荷速率增快，大理巖吸收總能量變化率、彈性能變化率和耗散能變化率都呈減小趨勢；卸荷速率越快，卸荷破壞需要的能量增量越小，在較小的能量增加下就會發(fā)生破壞；巖石破壞的驅動能量（存儲的可釋放彈性能）主要是在卸荷之前的加荷過程積聚的，加荷過程存儲的能量對巖石卸荷破壞起到決定作用。 (4)根據大理巖變形破壞過程的能量演化特征，結合生態(tài)學的競爭機制，構建了大理巖破壞過程的能量積聚演化模型。根據能量模型中的能量迭代增長因子與軸向應變的變化關系，提出了不同應力路徑下巖石破壞的起裂預警應變值，單軸壓縮為峰值應變的77%左右，常規(guī)三軸為峰值應變的72%~76%之間，卸荷試驗為峰值應變的72%~81%之間。
[Abstract]:The excavation of underground engineering is an extremely complicated process of loading and unloading, but the deformation characteristics, strength characteristics and failure mechanism of rock mass under different stress paths are obviously different.The study of rock deformation and failure properties under different stress paths is of great theoretical and engineering significance for supplementing and perfecting rock mechanics theory and guiding engineering design and construction.In this paper, the experimental study of marble unloading failure under different stress paths is carried out, the failure mechanism of marble under different stress paths is analyzed from the angle of energy variation, and the energy nonlinear evolution model of marble denaturing failure process is given.The main achievements of this thesis are as follows:1) through the loading and unloading test of complete marble samples, the variation law of rock deformation, failure characteristics and strength parameters under loading and unloading conditions is revealed.The axial deformation plays a leading role in the elastic stage of specimen loading failure, and the circumferential deformation increases rapidly after the beginning of yield, and the initial crack stress of loaded failure marble approaches to the peak strength with the increase of confining pressure, and the confining pressure delays the failure of rock.The peak strength of unloading failure rock samples decreases gradually with the increase of unloading rate and increases with the increase of initial confining pressure of unloading. The toroidal deformation and volume deformation are more sensitive to slow unloading than fast unloading.2) according to the generalized plastic mechanics theory, the yield surface of marble loading and unloading deformation process is constructed by using the test data, which ensures the uniqueness and accuracy of the yield function.The shear yield surface of marble loading failure process is linear. The unloading failure shear yield surface can be divided into straight line form before unloading and quadratic parabola form of confining pressure process.The yield surface of loading failure volume can be divided into two straight forms: compression and shear expansion. The yield surface of unloading failure volume can be divided into linear form before unloading and quadratic parabola form after unloading.According to the energy evolution curve of marble deformation and failure process, the unloading failure of marble can be divided into four stages: compaction stage, elastic stage, crack propagation stage and post-peak failure stage.Before reaching the yield point, most of the energy absorbed by the rock sample is stored in the form of elastic energy inside the rock sample. At the stage of nonlinear deformation from the yield point to the peak, the growth rate of elastic energy is slow, but the growth rate of dissipative energy becomes larger.The elastic energy stored in rock samples reaches the limit of energy storage, the elastic energy is released instantly, and the dissipation energy increases rapidly.The energy storage limit of conventional triaxial is higher than that of uniaxial compression, while the energy storage limit of unloading confining pressure before peak is lower than that of conventional triaxial compression, and with the increase of unloading rate, the change rate of total energy, elastic energy and dissipation energy of marble decrease.The faster the unloading rate, the smaller the energy increment required for unloading failure, and the smaller the increase in energy, the smaller the damage will occur. The driving energy of rock failure (the released elastic energy stored) is mainly accumulated during the loading process before unloading.The energy stored in the loading process plays a decisive role in the unloading failure of rock.4) according to the energy evolution characteristics of marble deformation and failure process and the competition mechanism of ecology, the energy accumulation evolution model of marble failure process is constructed.According to the relationship between the energy iterative growth factor and the axial strain in the energy model, the pre-warning strain values of rock failure under different stress paths are proposed. The uniaxial compression is about 77% of the peak strain.The conventional triaxial is between 72% of the peak strain and the unloading test is between 72% and 81% of the peak strain.
【學位授予單位】：青島理工大學
【學位級別】：碩士
【學位授予年份】：2013
【分類號】：TU45

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