本文選題：應(yīng)力路徑 + 加、卸荷��； 參考：《青島理工大學(xué)》2013年碩士論文

【摘要】：隨著我國人口的增長和經(jīng)濟(jì)建設(shè)的持續(xù)發(fā)展，人們對空間的需求已經(jīng)不僅僅局限在地上部分，地下空間的開發(fā)和利用正在逐漸成為城市建設(shè)的核心。地下工程開挖是一個(gè)復(fù)雜的加、卸荷過程，，開挖過程中經(jīng)常會(huì)出現(xiàn)坍塌、變形劇烈、巖爆等災(zāi)害，不僅影響整個(gè)工程的進(jìn)度，更威脅施工人員的生命安全。因此對不同加、卸荷路徑下巖體破壞機(jī)制的研究日益受到理論界和工程界的廣泛重視。本文針對地下工程開挖特點(diǎn)，制定幾種不同應(yīng)力路徑進(jìn)行巖石加、卸荷試驗(yàn)研究，并在此基礎(chǔ)上對巖石力學(xué)性質(zhì)和失穩(wěn)破壞機(jī)理進(jìn)行探討，從而為實(shí)際工程中判斷巖體失穩(wěn)提供依據(jù)。本文主要研究內(nèi)容如下： （1）通過加、卸荷試驗(yàn)，研究不同應(yīng)力路徑下大理巖的力學(xué)特性。結(jié)果表明：巖石的力學(xué)性質(zhì)受圍壓、卸荷速率及應(yīng)力路徑的影響，加荷及加軸壓、卸圍壓路徑下，巖樣的峰值軸壓、軸向應(yīng)變及達(dá)到峰值點(diǎn)的時(shí)間均隨著圍壓的增加逐漸增大，與圍壓呈線性關(guān)系。加軸壓、卸圍壓路徑下，圍壓相同，卸荷速率高的巖樣最先發(fā)生破壞。巖樣的強(qiáng)度、應(yīng)變隨卸荷速率的升高而減小，圍壓越高，卸荷速率對巖石變形的影響越明顯。與加荷相比，卸荷能夠降低巖石的承載力。加軸壓、卸圍壓和恒軸壓、卸圍壓兩種卸荷路徑中，卸荷速率較低時(shí)，加軸壓卸圍壓路徑下巖石承載力更高；卸荷速率較高時(shí)，兩種卸荷路徑下，巖石的變形特征沒有顯著差別。 （2）通過巖石破壞后宏觀破壞面的分析得出：巖石的破壞形態(tài)受圍壓和卸荷速率的影響。常規(guī)三軸試驗(yàn)中，主要呈現(xiàn)剪切破壞（單軸壓縮為劈裂破壞），破壞角隨圍壓升高而減小。加軸壓、卸圍壓應(yīng)力路徑下，巖樣破壞形態(tài)包括主剪切破壞、剪切加劈裂破壞和共軛剪切破壞三種。圍壓較低時(shí)，巖樣破壞形式主要為剪切加劈裂型破壞，個(gè)別試樣出現(xiàn)共軛破壞；圍壓較高時(shí)，巖樣破壞以剪切為主，其中圍壓高且卸荷速率低時(shí)，巖樣中部出現(xiàn)剪脹。圍壓相同卸荷速率愈高巖樣破壞角愈大，卸荷速率相同圍壓愈高巖樣破壞角愈小。應(yīng)力控峰前恒軸壓、卸圍壓試驗(yàn)中，不同卸荷速率下巖樣均以剪切破壞為主，剪脹現(xiàn)象不明顯，卸荷速率越高剪切面越小。 （3）通過對破裂面的分形研究發(fā)現(xiàn)，用改進(jìn)的立方體覆蓋法進(jìn)行破裂面分形維數(shù)計(jì)算時(shí)只有觀測尺度小于4.2mm時(shí)，破裂面才表現(xiàn)出分形性質(zhì)。單軸壓縮路徑下破裂面分形維數(shù)比常規(guī)三軸加荷大；加軸壓、卸圍壓路徑下圍壓較低時(shí)，破裂面的分形維數(shù)值在三種應(yīng)力路徑中最大，巖樣破壞形態(tài)最為復(fù)雜；加軸壓、卸圍壓路徑下，大理巖破裂面分形維數(shù)值與大理巖的峰值強(qiáng)度、破壞強(qiáng)度呈相關(guān)關(guān)系。
[Abstract]:With the growth of China's population and the continuous development of economic construction, the demand for space is not confined to the upper part of the earth. The development and utilization of underground space is gradually becoming the core of urban construction. Underground engineering excavation is a complex addition and unloading process, and the collapse, severe deformation and rock burst often occur during the opening and excavation process. Such disasters not only affect the progress of the whole project, but also threaten the safety of the construction personnel. Therefore, the research on the failure mechanism of rock mass under different loading and unloading paths has been paid more and more attention by the theorists and engineering circles. On this basis, the mechanical properties of rock and the failure mechanism of instability are discussed, which provides a basis for judging the instability of rock mass in practical engineering. The main contents of this paper are as follows:
(1) the mechanical properties of marble under different stress paths are studied by adding and unloading tests. The results show that the mechanical properties of rock are affected by confining pressure, unloading rate and stress path. Under loading and loading, the peak pressure of rock samples, axial strain and the time to peak point are gradually increased with the increase of confining pressure under loading and loading and unloading confining pressure path. There is a linear relationship with the confining pressure. Under the unloading confining pressure path, the confining pressure is the same, and the rock samples with high unloading rate are the first to destroy. The strength and strain of rock samples decrease with the increase of unloading rate, the higher the confining pressure, the more obvious the effect of unloading rate on rock deformation. In the two unloading paths with constant axial pressure and unloading confining pressure, the rock carrying capacity is higher under the load unloading path with the lower unloading rate, and the rock deformation characteristics are not significantly different when the unloading rate is high, while the unloading rate is high.
(2) through the analysis of the macroscopic failure surface after rock failure, it is concluded that the failure form of rock is affected by confining pressure and unloading rate. In the conventional three axis test, the shear failure (uniaxial compression is split fracture), and the failure angle decreases with the increase of confining pressure. Under the axial compression and unloading confining pressure path, the rock specimen failure form includes the main shear failure, There are three kinds of shear fracture failure and conjugate shear failure. When the confining pressure is low, the form of rock specimen failure is mainly shear plus split type failure, and a few specimens have conjugate destruction. When the confining pressure is high, the rock sample is destroyed mainly by shear. In the case of high confining pressure and low unloading rate, the shear bulging is found in the middle of the rock sample. The higher the confining pressure is, the higher the rock sample failure is, the higher the rock sample failure. The larger the angle is, the smaller the rock specimen failure angle is, the higher the unloading rate is, the less the rock sample is under the constant pressure. In the unloading confining pressure test, the rock samples are mainly shear failure at different unloading rates, and the shear dilatancy is not obvious, the higher the unloading rate is, the smaller the shear surface is.
(3) through the fractal study of fracture surface, it is found that only when the fractal dimension of the fracture surface is less than 4.2mm when the fractal dimension of fracture surface is calculated by the improved cube covering method, the fractal dimension of the fracture surface is larger than that of the conventional three axis under the uniaxial compression path, and the fracture surface is lower when the confining pressure is lower in the unloading confining pressure path. The fractal dimension value of the three stress paths is the largest and the most complex of the rock specimen failure. Under the axial compression and unloading confining pressure path, the fractal dimension of marble fracture surface is related to the peak strength and failure strength of marble.
【學(xué)位授予單位】：青島理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU45

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