循環(huán)動荷載作用下脆性巖石疲勞損傷力學(xué)特性研究
發(fā)布時間：2018-09-01 08:32
【摘要】：近年來,隨著國民經(jīng)濟的高速發(fā)展,各類基礎(chǔ)設(shè)施建設(shè)和大型巖土工程越來越多,例如,高陡巖質(zhì)邊坡工程、鐵路和公路隧道工程、城市地鐵工程、大型核電站工程、大型水電站工程、大型地下深埋長隧洞群及礦山深部開采等工程。機械沖擊和爆破憑借其高效、經(jīng)濟、快捷的技術(shù)特點,廣泛應(yīng)用于工程巖體開挖中,可帶來巨大的社會、經(jīng)濟效益。不管用何種方式進行巖體開挖時,其產(chǎn)生的沖擊應(yīng)力波在傳播過程中,不可避免會對遠離作業(yè)點的巖體造成一定程度的損傷和破壞,從而威脅工程巖體的穩(wěn)定性。因此,為合理指導(dǎo)工程實踐,以及根據(jù)圍巖的疲勞損傷特性充分利用圍巖的承載能力,減少不必要的工程浪費,研究巖石在循環(huán)動載荷作用下的疲勞損傷力學(xué)特性、損傷累積演化規(guī)律及破壞模式具有重要的實際意義。 巖石是在漫長的地質(zhì)歷史發(fā)展過程中,經(jīng)受各種復(fù)雜地質(zhì)構(gòu)造作用形成的產(chǎn)物,是由多種礦物晶粒、膠結(jié)物等組成的復(fù)雜混合體,而且其結(jié)構(gòu)一般都存在大量的地質(zhì)缺陷。作為一種天然材料,廣泛存在于自然界中,是天然的工程材料,對人類的經(jīng)濟活動起著非常重要的作用。巖石在靜態(tài)或準(zhǔn)靜態(tài)循環(huán)荷載作用下的力學(xué)特性研究已取得了豐富的研究成果,理論體系較完善。然而,對巖石在動態(tài)循環(huán)載荷作用下的疲勞損傷力學(xué)特性研究明顯不足,其理論研究明顯落后于工程實際。 論文針對脆性巖石在循環(huán)荷載作用下疲勞損傷力學(xué)特性研究的不足,通過SHPB試驗裝置對勞倫斯花崗巖進行循環(huán)沖擊壓縮試驗,根據(jù)試驗結(jié)果分析應(yīng)力—應(yīng)變曲線的變化規(guī)律及巖石強度和變形的動態(tài)特性；揭示試驗條件和試樣本身等因素對巖石疲勞力學(xué)特性的影響規(guī)律；分析巖石的損傷累積演化規(guī)律及破壞模式,為指導(dǎo)工程實踐提供理論基礎(chǔ)。 論文的主要研究工作及結(jié)論如下： 1.為便于研究巖石試樣在循環(huán)動荷載下的力學(xué)特性,通過改進試驗技術(shù),主要通過對巖石試樣施加套筒,控制試樣應(yīng)變與軸向變形。 2.巖石試樣在單次沖擊過程中的應(yīng)力-應(yīng)變變化過程,主要分為以下五個階段：壓密階段、彈性階段、加速變形階段、第一卸載階段、第二卸載階段；巖石試樣在循環(huán)動荷載下,彈性模量不斷減小,試樣抵抗變形的能力不斷減弱,力學(xué)性能不斷損傷,但是在累積損傷的過程中,具有突變性,即沖擊前期損傷緩慢,到即將破壞時力學(xué)性能劇減；試樣在循環(huán)動荷載下,其內(nèi)部裂紋不斷萌生、擴展,變形具有突變性,沖擊前期以彈性變形為主,無殘余變形,沖擊后期應(yīng)變劇增,巖石試樣急劇破壞。 3.沖擊氣壓和孔隙率不會影響巖石疲勞力學(xué)性能的整體變化規(guī)律,但會影響局部階段的損傷劣化過程,以及影響巖石宏觀力學(xué)性能與細觀結(jié)構(gòu)的損傷程度與速度。沖擊氣壓相對巖石孔隙率,對巖石疲勞力學(xué)特性的損傷較大,即巖石疲勞力學(xué)特性對沖擊氣壓較敏感。 4.巖石在循環(huán)動荷載下,聲波速度變化規(guī)律與峰值應(yīng)變變化規(guī)律大致對應(yīng)。波速整體變化趨勢不斷減小,沖擊前期波速緩慢遞減,后期快速減小。波速變化規(guī)律體現(xiàn)試樣細觀結(jié)構(gòu)的累積損傷過程,沖擊氣壓和孔隙率不影響波速的整體變化趨勢,但會影響局部階段波速的遞減幅度和速度。沖擊期間沖擊波速不變的可能原因是沖擊后的裂紋較小或者沖擊后試樣裂紋方向與P波的傳播方向一致。 5.巖石在循環(huán)動荷載作用下的損傷累積過程一般可分為三個階段：損傷初始階段、損傷低速發(fā)展階段和損傷加速發(fā)展破壞階段。沖擊氣壓和孔隙率不影響損傷累積演化的整體規(guī)律,但會影響局部階段的疲勞壽命、損傷程度與速度,與巖石宏觀應(yīng)力應(yīng)變隨循環(huán)沖擊次數(shù)的變化規(guī)律基本一致。 6.在一定范圍的沖擊氣壓下,試樣在較小的尺寸范圍內(nèi),巖石在循環(huán)動荷載下的破壞模式為劈裂破壞。其破壞機理為：在沖擊載荷作用下,試樣在發(fā)生軸向壓縮變形時,由于泊松效應(yīng)必然發(fā)生橫向擴展變形,即橫向伸長線應(yīng)變。由于巖石抵抗伸長變形的能力很弱,當(dāng)此應(yīng)變達到一定值時,巖石即發(fā)生破壞。
[Abstract]:In recent years, with the rapid development of the national economy, more and more infrastructures and large-scale geotechnical projects have been built, such as high and steep rock slope engineering, railway and highway tunnel engineering, urban subway engineering, large-scale nuclear power station engineering, large-scale hydropower station engineering, large underground deep-buried long tunnel group and deep mining engineering. And blasting with its high efficiency, economy, fast technical characteristics, widely used in engineering rock excavation, can bring enormous social and economic benefits. Therefore, in order to guide the engineering practice reasonably and make full use of the bearing capacity of surrounding rock according to the fatigue damage characteristics of surrounding rock, reduce unnecessary engineering waste, it is important to study the fatigue damage mechanics characteristics of rock under cyclic dynamic loading, the damage accumulation and evolution law and the failure mode. Practical significance.
Rock is the product of various complex geological structures in the long process of geological history. Rock is a complex mixture of many mineral grains and cements, and its structure generally has a large number of geological defects. The research on the mechanical properties of rock under static or quasi-static cyclic loading has made abundant achievements, and the theoretical system is perfect. However, the research on the mechanical properties of rock under dynamic cyclic loading is obviously insufficient, and the theoretical research lags behind the engineering. Actual.
Aiming at the insufficiency of fatigue damage mechanics research on brittle rock under cyclic loading, the cyclic impact compression test of Lawrence granite is carried out by means of SHPB test equipment. According to the test results, the variation law of stress-strain curve and the dynamic characteristics of rock strength and deformation are analyzed. The influence of some factors on the fatigue mechanical properties of rock is analyzed, and the cumulative damage evolution law and failure mode of rock are analyzed.
The main research work and conclusions are as follows:
1. In order to study the mechanical properties of rock specimens under cyclic dynamic loads, the strain and axial deformation of rock specimens are controlled by applying sleeves to the rock specimens through improving the test techniques.
2. The stress-strain change process of rock specimen during single impact is divided into the following five stages: compaction stage, elastic stage, accelerated deformation stage, first unloading stage and second unloading stage; under cyclic dynamic load, the elastic modulus of rock specimen decreases continuously, the ability of resisting deformation of specimen decreases continuously, and the mechanical properties are not. Fracture damage, but in the process of cumulative damage, has catastrophe, that is, the damage in the early stage of impact is slow, and the mechanical properties of the specimen will be reduced sharply when it is about to be destroyed; under cyclic dynamic load, the internal cracks of the specimen are continuously germinated, propagated, and the deformation has catastrophe, the elastic deformation is dominant in the early stage of impact, without residual deformation, the strain increases sharply in the late stage of Rapid destruction.
3. The impact pressure and porosity will not affect the overall variation of the fatigue mechanical properties of rocks, but will affect the damage deterioration process in the local stage and the damage degree and velocity of the macro-mechanical properties and micro-structure of rocks. Mechanical properties are sensitive to impact pressure.
4. Under cyclic dynamic loading, the variation law of acoustic wave velocity corresponds to the variation law of peak strain roughly. The overall variation trend of acoustic wave velocity decreases continuously, and the wave velocity decreases slowly at the early stage of impact, and decreases rapidly at the later stage. The trend, however, will affect the amplitude and velocity of the wave velocity in the local stage.
5. The damage accumulation process of rock under cyclic dynamic loading can be generally divided into three stages: the initial stage of damage, the stage of low-speed damage development and the stage of accelerated damage development and failure. The macroscopic stress-strain of rock is basically the same as that of cyclic impact.
6. In a certain range of impact pressure, the failure mode of rock under cyclic dynamic load is splitting failure in a smaller size range. The failure mechanism is that when the specimen is subjected to axial compression deformation under impact load, the transverse propagation deformation, i.e. the transverse elongation line strain, will inevitably occur due to Poisson effect. The ability to resist elongation deformation is very weak. When the strain reaches a certain value, the rock will be destroyed.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU45
本文編號：2216649
[Abstract]:In recent years, with the rapid development of the national economy, more and more infrastructures and large-scale geotechnical projects have been built, such as high and steep rock slope engineering, railway and highway tunnel engineering, urban subway engineering, large-scale nuclear power station engineering, large-scale hydropower station engineering, large underground deep-buried long tunnel group and deep mining engineering. And blasting with its high efficiency, economy, fast technical characteristics, widely used in engineering rock excavation, can bring enormous social and economic benefits. Therefore, in order to guide the engineering practice reasonably and make full use of the bearing capacity of surrounding rock according to the fatigue damage characteristics of surrounding rock, reduce unnecessary engineering waste, it is important to study the fatigue damage mechanics characteristics of rock under cyclic dynamic loading, the damage accumulation and evolution law and the failure mode. Practical significance.
Rock is the product of various complex geological structures in the long process of geological history. Rock is a complex mixture of many mineral grains and cements, and its structure generally has a large number of geological defects. The research on the mechanical properties of rock under static or quasi-static cyclic loading has made abundant achievements, and the theoretical system is perfect. However, the research on the mechanical properties of rock under dynamic cyclic loading is obviously insufficient, and the theoretical research lags behind the engineering. Actual.
Aiming at the insufficiency of fatigue damage mechanics research on brittle rock under cyclic loading, the cyclic impact compression test of Lawrence granite is carried out by means of SHPB test equipment. According to the test results, the variation law of stress-strain curve and the dynamic characteristics of rock strength and deformation are analyzed. The influence of some factors on the fatigue mechanical properties of rock is analyzed, and the cumulative damage evolution law and failure mode of rock are analyzed.
The main research work and conclusions are as follows:
1. In order to study the mechanical properties of rock specimens under cyclic dynamic loads, the strain and axial deformation of rock specimens are controlled by applying sleeves to the rock specimens through improving the test techniques.
2. The stress-strain change process of rock specimen during single impact is divided into the following five stages: compaction stage, elastic stage, accelerated deformation stage, first unloading stage and second unloading stage; under cyclic dynamic load, the elastic modulus of rock specimen decreases continuously, the ability of resisting deformation of specimen decreases continuously, and the mechanical properties are not. Fracture damage, but in the process of cumulative damage, has catastrophe, that is, the damage in the early stage of impact is slow, and the mechanical properties of the specimen will be reduced sharply when it is about to be destroyed; under cyclic dynamic load, the internal cracks of the specimen are continuously germinated, propagated, and the deformation has catastrophe, the elastic deformation is dominant in the early stage of impact, without residual deformation, the strain increases sharply in the late stage of Rapid destruction.
3. The impact pressure and porosity will not affect the overall variation of the fatigue mechanical properties of rocks, but will affect the damage deterioration process in the local stage and the damage degree and velocity of the macro-mechanical properties and micro-structure of rocks. Mechanical properties are sensitive to impact pressure.
4. Under cyclic dynamic loading, the variation law of acoustic wave velocity corresponds to the variation law of peak strain roughly. The overall variation trend of acoustic wave velocity decreases continuously, and the wave velocity decreases slowly at the early stage of impact, and decreases rapidly at the later stage. The trend, however, will affect the amplitude and velocity of the wave velocity in the local stage.
5. The damage accumulation process of rock under cyclic dynamic loading can be generally divided into three stages: the initial stage of damage, the stage of low-speed damage development and the stage of accelerated damage development and failure. The macroscopic stress-strain of rock is basically the same as that of cyclic impact.
6. In a certain range of impact pressure, the failure mode of rock under cyclic dynamic load is splitting failure in a smaller size range. The failure mechanism is that when the specimen is subjected to axial compression deformation under impact load, the transverse propagation deformation, i.e. the transverse elongation line strain, will inevitably occur due to Poisson effect. The ability to resist elongation deformation is very weak. When the strain reaches a certain value, the rock will be destroyed.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU45
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