超聲波振動下花崗巖裂紋變化特性的研究
發(fā)布時間：2018-08-09 19:22
【摘要】：世界經(jīng)濟的迅猛發(fā)展使得人類對礦產(chǎn)資源的需求量越來越大,礦產(chǎn)資源的勘探深度越來越大,勘探地層越來越硬。硬巖具有致密、研磨性強、強度高、破碎功大等特點,使得其很難被破壞。為解決硬巖鉆進的基本問題,應(yīng)進行碎巖新方法及碎巖機理的研究,降低巖石的破碎強度,實現(xiàn)大體積破碎。完整致密硬巖的固有頻率一般為20KHz~40KHz,在巖石受到合理地共振時,內(nèi)部會快速產(chǎn)生裂紋,導致其強度急劇下降,這種情況下,巖石會很容易被破壞,進而提高了鉆頭使用壽命與鉆進速度。因此,采用超聲波振動配合切削鉆進的方法來解決硬巖鉆進的難題,具有一定的可行性。巖石是一種含有多種細觀缺陷的混合物質(zhì),巖石的破壞過程受控于這些細觀結(jié)構(gòu),在載荷作用下,這些細觀缺陷會產(chǎn)生不可逆的演化,從而導致巖石強度的降低。研究巖石在超聲波振動下其內(nèi)部細觀裂紋的變化特性,能夠從根本上揭示超聲波作用下巖石強度下降規(guī)律的內(nèi)在機理,為超聲波振動輔助鉆進技術(shù)提供理論指導,這對解決硬巖鉆進的技術(shù)難題具有非常重要的戰(zhàn)略性意義。本文從超聲波振動下花崗巖裂紋的開裂條件、擴展特性及靜載荷對花崗巖損傷的影響規(guī)律三個方面,采用有限單元法與室內(nèi)實驗相結(jié)合的方法,對超聲波振動下花崗巖裂紋的變化特性進行了研究。介紹了花崗巖的物理力學參數(shù),并以此為基礎(chǔ),通過聯(lián)合強度理論推導出了超聲波振動下花崗巖裂紋起裂的數(shù)學模型,應(yīng)用巖石損傷力學,獲取了以推導出的聯(lián)合強度準則為基礎(chǔ)的超聲波振動下花崗巖的損傷模型。利用ANSYS軟件與MATLAB軟件建立了可以體現(xiàn)花崗巖非均勻程度的數(shù)值模擬模型,并以此模型為基礎(chǔ),對超聲波振動下花崗巖裂紋的變化過程進行了數(shù)值模擬計算,得到以下結(jié)論:花崗巖固有頻率隨靜載荷的增大而逐漸增大,靜載荷-固有頻率曲線近似呈對數(shù)型,固有頻率的增加幅度隨靜載荷的增大逐漸減緩;當振動頻率與花崗巖一階固有頻率相近時,花崗巖內(nèi)應(yīng)力、應(yīng)變遠遠高于其他振動頻率下花崗巖內(nèi)部應(yīng)力、應(yīng)變值,振動頻率對應(yīng)力、應(yīng)變變化速率的影響作用十分明顯,當振動頻率與花崗巖一階固有頻率相同時,應(yīng)力、應(yīng)變達到最大值;只有當花崗巖裂紋尖端處局部微單元體滿足強度準則時,花崗巖裂紋開始擴展,其擴展過程分為萌生、擴展、貫通3個階段,在萌生階段,巖石內(nèi)某些節(jié)點上產(chǎn)生應(yīng)力集中,這些節(jié)點開裂形成微孔隙,緩和了應(yīng)力集中并使得巖石內(nèi)部應(yīng)力重新分布,在擴展階段,微孔隙不斷向四周緩慢擴展,最終沿某一方向形成主裂紋,主裂紋繼續(xù)延伸,在主裂紋上出現(xiàn)隨機分布的次裂紋,在貫通階段,微孔隙、微裂紋之間開始相互貫通,形成新的裂紋。設(shè)計了超聲波動靜組合加載裝置,對超聲波振動下花崗巖裂紋變化特性進行實驗研究,實驗結(jié)果與數(shù)值模擬結(jié)果基本一致。對比實驗結(jié)果與數(shù)值模擬結(jié)果,發(fā)現(xiàn)采用以聯(lián)合強度理論為基礎(chǔ)的花崗巖裂紋起裂條件的數(shù)學模型進行數(shù)值模擬得到的結(jié)果要比單獨采用第二或者第三強度理論進行數(shù)值模擬更加接近實驗結(jié)果。對超聲波振動實驗數(shù)據(jù)進行整理,研究靜載荷對花崗巖損傷程度的影響規(guī)律,得到以下結(jié)論:超聲波振動過程中,靜載荷存在閾值,當施加的靜載荷小于閾值時,靜載荷的變化并不引起花崗巖彈性模量的變化,靜載荷的變化對花崗巖損傷沒有影響,當施加的靜載荷大于閾值時,改變靜載荷值將直接影響對花崗巖造成的損傷程度;在施加的靜載荷大于閾值的前提下,靜載荷對花崗巖造成損傷的過程可分為緩沖階段和損傷階段,在緩沖階段,花崗巖彈性模量下降不明顯,在損傷階段,花崗巖彈性模量急劇下降;在其他條件不變的情況下,超聲波振動下存在最優(yōu)的靜載荷值使得花崗巖損傷程度最大,本實驗中最優(yōu)靜載荷值為400N。進行CT掃描實驗,獲取了不同振動條件下花崗巖的CT圖像,根據(jù)CT圖像對超聲波振動下花崗巖裂紋擴展過程進行分析,將花崗巖裂紋擴展過程分為萌生、擴展、貫通三個階段,與數(shù)值模擬結(jié)果基本一致。振動過程中,隨著振動時間的增加,裂紋逐漸向軸心處匯聚。
[Abstract]:With the rapid development of the world economy, the demand for mineral resources is becoming more and more large, the exploration depth of mineral resources is increasing, and the exploration strata are becoming harder and harder. Hard rock has the characteristics of tight, strong abrasive, high strength and great crushing work, which makes it difficult to destroy. In order to solve the basic problem of hard rock drilling, a new method of rock breaking and a new method of rock breaking should be carried out. The study of rock breaking mechanism reduces the crushing strength of rock and realizes large volume crushing. The natural frequency of the complete and dense hard rock is generally 20KHz~40KHz. When the rock is reasonably resonant, it will quickly produce cracks and lead to a sharp decline in its strength. In this case, the rock will be easily destroyed, thus improving the service life and drilling of the drill. Therefore, it is feasible to use the method of ultrasonic vibration and cutting drilling to solve the difficult problem of hard rock drilling. The rock is a kind of mixture containing a variety of mesoscopic defects. The failure process of the rock is controlled by these mesoscopic structures. Under the load, these fine defects will produce irreversible evolution and thus lead to the irreversible evolution. The reduction of rock strength. The study of the change characteristics of the meso crack in the rock under ultrasonic vibration can reveal the inherent mechanism of the law of rock strength decreasing under ultrasonic wave, and provide theoretical guidance for the ultrasonic vibration assisted drilling technology. It has a very important strategy to solve the technical problems of hard rock drilling. In this paper, the characteristics of granite crack under ultrasonic vibration, the propagation characteristics and the effect of static load on the damage of granite are three aspects. The method of combining the finite element method with the laboratory experiment is used to study the change characteristics of the granite crack under ultrasonic vibration. The physical and mechanical parameters of the granite are introduced. On the basis of this, the mathematical model of granite crack initiation under ultrasonic vibration is derived through the joint strength theory, and the damage model of granite under ultrasonic vibration is obtained by using the rock damage mechanics, which is based on the combined strength criterion derived from the ultrasonic vibration. The ANSYS soft parts and the MATLAB software can be used to reflect the granitoid. The numerical simulation model of uniform degree is used to simulate the change process of granite crack under ultrasonic vibration. The following conclusion is obtained: the inherent frequency of granite increases gradually with the increase of static load, and the static load natural frequency curve is approximate to logarithmic type, and the increase of natural frequency is with static load. When the vibration frequency is similar to the first natural frequency of granite, the internal stress of granite is much higher than that of the internal stress of granite under other vibration frequencies, the strain value, the vibration frequency correspond to the force, the change rate of strain change is very obvious, when the frequency of the vibration is the same as the first natural frequency of the granite, the stress is the same. The strain reaches the maximum. Only when the local microelement meets the strength criterion at the tip of the granite crack, the granite crack begins to expand, and its expansion process is divided into 3 stages: germination, expansion and penetration. In the initiation stage, the stress concentration is produced on some nodes in the rock, and these joints crack down to form micro pores and ease the stress concentration and make it possible. The internal stress of the rock is redistributed. In the expansion stage, the pore gap expands slowly around the surrounding area, and eventually forms the main crack along a certain direction. The main crack continues to extend, and the secondary crack is randomly distributed on the main crack. In the penetration stage, the micro pores and the micro cracks begin to interconnect with each other to form a new crack. The ultrasonic dynamic combination is designed. The experimental results are basically the same with the numerical simulation results. Compared with the results of the experimental and numerical simulation, it is found that the numerical simulation results of the cracking conditions of the granite crack based on the joint strength theory are compared with the results of the numerical simulation. The numerical simulation is closer to the experimental results with the second or third strength theory. The experimental data of ultrasonic vibration are arranged and the influence of static load on the damage degree of granite is studied. The following conclusion is drawn: the static load has a threshold in the process of ultrasonic vibration, and the static load changes when the applied static load is less than the threshold. It does not cause the change of the elastic modulus of granite, and the change of static load does not affect the damage of granite. When the static load is greater than the threshold, the change of static load will directly affect the damage degree of granite. Under the precondition that the static load is greater than the threshold, the process of damage caused by static load on granite can be divided into buffer. In the stage and the stage of damage, the modulus of granite's elastic modulus decreases not obviously in the buffer stage, and the elastic modulus of granite decreases sharply in the stage of damage. Under the condition of other conditions, the optimal static load value under ultrasonic vibration makes the maximum damage degree of granite. The optimal static load value in this experiment is 400N. CT scanning experiment. The CT images of granite under different vibration conditions are obtained. According to the CT image, the crack propagation process of granite under ultrasonic vibration is analyzed. The crack propagation process of the granite is divided into three stages: germination, expansion and penetration, which is basically consistent with the numerical simulation results. In the process of vibration, the crack gradually goes to the axis of the axis with the increase of vibration time Gather together.
【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P634.1
本文編號：2175070
[Abstract]:With the rapid development of the world economy, the demand for mineral resources is becoming more and more large, the exploration depth of mineral resources is increasing, and the exploration strata are becoming harder and harder. Hard rock has the characteristics of tight, strong abrasive, high strength and great crushing work, which makes it difficult to destroy. In order to solve the basic problem of hard rock drilling, a new method of rock breaking and a new method of rock breaking should be carried out. The study of rock breaking mechanism reduces the crushing strength of rock and realizes large volume crushing. The natural frequency of the complete and dense hard rock is generally 20KHz~40KHz. When the rock is reasonably resonant, it will quickly produce cracks and lead to a sharp decline in its strength. In this case, the rock will be easily destroyed, thus improving the service life and drilling of the drill. Therefore, it is feasible to use the method of ultrasonic vibration and cutting drilling to solve the difficult problem of hard rock drilling. The rock is a kind of mixture containing a variety of mesoscopic defects. The failure process of the rock is controlled by these mesoscopic structures. Under the load, these fine defects will produce irreversible evolution and thus lead to the irreversible evolution. The reduction of rock strength. The study of the change characteristics of the meso crack in the rock under ultrasonic vibration can reveal the inherent mechanism of the law of rock strength decreasing under ultrasonic wave, and provide theoretical guidance for the ultrasonic vibration assisted drilling technology. It has a very important strategy to solve the technical problems of hard rock drilling. In this paper, the characteristics of granite crack under ultrasonic vibration, the propagation characteristics and the effect of static load on the damage of granite are three aspects. The method of combining the finite element method with the laboratory experiment is used to study the change characteristics of the granite crack under ultrasonic vibration. The physical and mechanical parameters of the granite are introduced. On the basis of this, the mathematical model of granite crack initiation under ultrasonic vibration is derived through the joint strength theory, and the damage model of granite under ultrasonic vibration is obtained by using the rock damage mechanics, which is based on the combined strength criterion derived from the ultrasonic vibration. The ANSYS soft parts and the MATLAB software can be used to reflect the granitoid. The numerical simulation model of uniform degree is used to simulate the change process of granite crack under ultrasonic vibration. The following conclusion is obtained: the inherent frequency of granite increases gradually with the increase of static load, and the static load natural frequency curve is approximate to logarithmic type, and the increase of natural frequency is with static load. When the vibration frequency is similar to the first natural frequency of granite, the internal stress of granite is much higher than that of the internal stress of granite under other vibration frequencies, the strain value, the vibration frequency correspond to the force, the change rate of strain change is very obvious, when the frequency of the vibration is the same as the first natural frequency of the granite, the stress is the same. The strain reaches the maximum. Only when the local microelement meets the strength criterion at the tip of the granite crack, the granite crack begins to expand, and its expansion process is divided into 3 stages: germination, expansion and penetration. In the initiation stage, the stress concentration is produced on some nodes in the rock, and these joints crack down to form micro pores and ease the stress concentration and make it possible. The internal stress of the rock is redistributed. In the expansion stage, the pore gap expands slowly around the surrounding area, and eventually forms the main crack along a certain direction. The main crack continues to extend, and the secondary crack is randomly distributed on the main crack. In the penetration stage, the micro pores and the micro cracks begin to interconnect with each other to form a new crack. The ultrasonic dynamic combination is designed. The experimental results are basically the same with the numerical simulation results. Compared with the results of the experimental and numerical simulation, it is found that the numerical simulation results of the cracking conditions of the granite crack based on the joint strength theory are compared with the results of the numerical simulation. The numerical simulation is closer to the experimental results with the second or third strength theory. The experimental data of ultrasonic vibration are arranged and the influence of static load on the damage degree of granite is studied. The following conclusion is drawn: the static load has a threshold in the process of ultrasonic vibration, and the static load changes when the applied static load is less than the threshold. It does not cause the change of the elastic modulus of granite, and the change of static load does not affect the damage of granite. When the static load is greater than the threshold, the change of static load will directly affect the damage degree of granite. Under the precondition that the static load is greater than the threshold, the process of damage caused by static load on granite can be divided into buffer. In the stage and the stage of damage, the modulus of granite's elastic modulus decreases not obviously in the buffer stage, and the elastic modulus of granite decreases sharply in the stage of damage. Under the condition of other conditions, the optimal static load value under ultrasonic vibration makes the maximum damage degree of granite. The optimal static load value in this experiment is 400N. CT scanning experiment. The CT images of granite under different vibration conditions are obtained. According to the CT image, the crack propagation process of granite under ultrasonic vibration is analyzed. The crack propagation process of the granite is divided into three stages: germination, expansion and penetration, which is basically consistent with the numerical simulation results. In the process of vibration, the crack gradually goes to the axis of the axis with the increase of vibration time Gather together.
【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P634.1
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