【摘要】：在地下工程的建設(shè)當(dāng)中,巖體的開挖則會(huì)導(dǎo)致在一個(gè)或多個(gè)方向的卸荷,在高地應(yīng)力區(qū)域,由于巖體內(nèi)儲(chǔ)存的能量較高,開挖導(dǎo)致巖體內(nèi)部能量突然釋放,多余的能量以動(dòng)能形式釋放,導(dǎo)致巖體爆裂并彈射,對(duì)人員生命安全、設(shè)備以及工程的安全造成巨大威脅。本文通過單軸循環(huán)加卸載試驗(yàn)、三軸卸荷試驗(yàn)以及數(shù)值軟件RFpA2D,研究了大理巖在不同加卸荷條件下的變形、破壞等特性,分析不同應(yīng)力環(huán)境下巖石內(nèi)部裂紋發(fā)育過程以及聲發(fā)射分布規(guī)律。本文主要取得下列研究成果:(1)通過不同路徑的單軸循環(huán)加卸載試驗(yàn),分析了循環(huán)荷載作用下巖石的力學(xué)特性以及破壞特征。結(jié)果表明:循環(huán)荷載作用下巖石不同循環(huán)階段的彈模和泊松比隨著循環(huán)次數(shù)的增加而提高,小幅度微擾動(dòng)荷載對(duì)巖石彈性模量的強(qiáng)化作用明顯,巖石泊松比則出現(xiàn)降低;循環(huán)加卸載作用下巖石最終以縱向劈裂破壞為主,不同應(yīng)力路徑下巖石破壞差別體現(xiàn)在巖石碎屑長(zhǎng)厚比上。(2)通過恒軸向位移卸圍壓試驗(yàn)分析了卸荷過程中初始圍壓和卸荷速率對(duì)巖石力學(xué)特征、聲發(fā)射、破壞形態(tài)等的影響。結(jié)果表明:(a)在卸荷破壞過程中,初始圍壓對(duì)巖石力學(xué)性質(zhì)強(qiáng)化作用明顯。(b)巖石破壞以及發(fā)生損傷時(shí)對(duì)應(yīng)的應(yīng)力值以及聲發(fā)射平均振鈴計(jì)數(shù)值隨著卸荷速率的提高,先增大后減小;巖石破裂角隨著卸荷速率的提高先減小后增大。(c)隨初始圍壓的增大,卸荷速率的提高,巖石破裂宏觀破裂面小裂紋數(shù)目減少,微觀破裂面逐漸趨于光滑,巖石逐漸由漸進(jìn)式破壞向突發(fā)式破壞轉(zhuǎn)變,巖石更容易發(fā)生巖爆。(3)通過RFPA數(shù)值軟件,對(duì)恒軸向位移卸圍壓試驗(yàn)進(jìn)行了模擬,結(jié)果表明:(a)隨著圍壓的降低,巖石內(nèi)部失穩(wěn)單元逐漸從無序向有序發(fā)展,最終微裂紋匯集貫通形成大尺度宏觀裂紋。(b)卸荷速率一定時(shí),不同初始圍壓下巖石破壞力學(xué)特性模擬結(jié)果同室內(nèi)力學(xué)試驗(yàn)結(jié)果較為接近。(c)不同卸荷速率下,數(shù)值模擬所得結(jié)果同室內(nèi)試驗(yàn)的差異主要體現(xiàn)在巖石破壞時(shí)軸壓以及巖石殘余強(qiáng)度。本文采用單軸循環(huán)加卸荷,三軸加卸荷試驗(yàn)和數(shù)值模擬方法,對(duì)深部巖體開挖加卸荷條件下力學(xué)特性進(jìn)行研究,再現(xiàn)了卸荷誘發(fā)巖體破壞的過程,分析了加卸荷誘發(fā)巖爆的機(jī)理。巖石加卸荷力學(xué)特性的研究,不僅可以揭示巖體在開挖卸荷作用下的破壞機(jī)理,促進(jìn)巖爆機(jī)理研究,而且對(duì)實(shí)際工程有很好的參考和應(yīng)用價(jià)值。
[Abstract]:In the construction of underground engineering, the excavation of rock mass will lead to unloading in one or more directions. In the area of high ground stress, because of the high energy stored in the rock body, the excavation results in the sudden release of energy inside the rock mass. The excess energy is released in the form of kinetic energy, resulting in rock burst and ejection, which poses a great threat to the safety of personnel, equipment and engineering. In this paper, uniaxial cyclic loading and unloading tests, triaxial unloading tests and numerical software RFpA2D, are used to study the deformation and failure characteristics of marble under different loading and unloading conditions. The process of crack development and the distribution of acoustic emission in rock under different stress conditions are analyzed. The main achievements of this paper are as follows: (1) the mechanical properties and failure characteristics of rock under cyclic loading are analyzed by uniaxial cyclic loading and unloading tests with different paths. The results show that the modulus of elasticity and Poisson's ratio increase with the increase of cycle times under cyclic loading, and the elastic modulus of rock is strengthened obviously by small amplitude micro-disturbance load, and the Poisson's ratio of rock decreases. Under cyclic loading and unloading, the main failure of rock is longitudinal splitting failure. The difference of rock failure under different stress paths is reflected in the ratio of length to thickness of rock debris. (2) the initial confining pressure and unloading rate during unloading process are analyzed by means of constant axial displacement confining pressure test to analyze the mechanical characteristics and acoustic emission of rock. The effect of damage patterns, etc. The results show that during the unloading failure of: (a), the initial confining pressure strengthens the mechanical properties of rock obviously. The stress values corresponding to the damage of. (b) rock and the average acoustic emission ringer are increased with the increase of unloading rate. First increase and then decrease; With the increase of unloading rate, the fracture angle of rock decreases first and then increases with the increase of initial confining pressure. With the increase of unloading rate, the number of small cracks on the macroscopic fracture surface of rock decreases, and the micro-fracture surface tends to smooth. Rock gradually changes from progressive failure to sudden failure, and rock burst is more likely to occur. (3) through RFPA numerical software, the constant axial displacement confining pressure relief test is simulated. The results show that: (a) decreases with confining pressure. The internal instability unit of rock gradually develops from disorder to order, and finally microcrack aggregates through to form large scale macroscopic crack. (b) unloading rate is fixed. Under different initial confining pressures, the simulation results of rock failure characteristics are similar to those of laboratory mechanical tests under different unloading rates of. (c). The difference between the results of numerical simulation and that of laboratory tests is mainly reflected in the axial compression and residual strength of rock during rock failure. In this paper, uniaxial cyclic loading and unloading, triaxial loading and unloading tests and numerical simulation are used to study the mechanical properties of deep rock mass under the condition of loading and unloading, and the process of rock mass failure induced by unloading is reappeared. The mechanism of rockburst induced by loading and unloading is analyzed. The study on the mechanical properties of rock loading and unloading can not only reveal the failure mechanism of rock mass under excavation and unloading, but also promote the study of rock burst mechanism, and have a good reference and application value for practical engineering.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TD313

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