本文選題：卸荷破壞 + 能量��； 參考：《青島理工大學》2014年博士論文

【摘要】：本論文包含兩個部分：一是針對地下工程開挖的復雜加、卸荷過程，尤其是卸荷過程，弄清卸荷路徑下的巖石破壞機理，重點研究不同卸荷路徑下巖石宏細觀破壞機理，包括：不同卸荷條件破壞過程中能量演化規(guī)律；巖石卸荷破壞過程中聲發(fā)射特征演化規(guī)律與量化分析；基于顆粒流方法巖石卸荷破壞過程數值模擬等。二是針對巖石地鐵工程設計計算的實際問題，應用數值極限分析方法，開展對巖石地鐵工程的圍巖分級與設計計算方法的研究，包括：改進巖石地鐵工程圍巖分級的基本質量指標；考慮跨度對圍巖分級的影響；初襯混凝土的抗剪強度；巖石地鐵工程設計計算方法等。 論文的研究成果如下： （1）采用能量原理自編程序，研究不同卸荷條件下大理巖卸荷破壞過程中的能量演化規(guī)律，取得以下主要研究成果：巖樣卸荷破壞過程的軸向吸收能量曲線非線性變化，經歷了緩慢增長-快速增長-緩慢增長-釋放的演化過程�？偰芰壳�經歷了緩慢增長-快速增長-緩慢減小-釋放等階段。不同卸荷應力路徑對破壞過程中能量演化規(guī)律的影響主要表現在屈服弱化階段。圍壓高的巖樣消耗更多的能量，軸向能量曲線增長速率增加；卸荷速率越低，軸向能量增長速率升高，卸荷點處軸向能量曲線轉折更明顯；卸荷水平接近巖樣承載能力峰值時，軸向能量增長速率增大，總能量曲線負向增長速率高，巖樣破壞越劇烈。 （2）研究不同卸荷條件下巖樣破壞過程中的聲發(fā)射特征演化規(guī)律，采用分形的方法自編程序進一步量化聲發(fā)射特征，取得以下主要研究成果：不同卸荷路徑試驗過程中，聲發(fā)射事件計數率最大值都出現在巖樣破壞處，達到最大值前，巖樣均會出現一段聲發(fā)射相對平靜期。圍壓越高，巖樣的聲發(fā)射活動水平越高，聲發(fā)射相對平靜期會縮短，聲發(fā)射事件最大值也增加；卸荷速率越高，相對平靜期的振鈴計數率越高，持續(xù)時間越短；越接近巖樣承載力峰值卸荷，巖樣破壞前的聲發(fā)射事件相對平靜期持續(xù)時間越短。巖樣破壞前存在聲發(fā)射分維值較低區(qū)域，破壞處附近的分維值，加軸壓、卸圍壓路徑＞恒軸壓、卸圍壓路徑＞常規(guī)三軸路徑。 （3）基于顆粒流方法，利用FISH語言實現大理巖加、卸荷破壞過程數值模擬，從細觀角度有利地補充宏觀的室內試驗分析，其創(chuàng)新點為：通過FISH語言設計不同的卸荷應力路徑方案，有效實現巖樣復雜卸荷試驗的數值模擬，研究卸荷破壞過程中摩擦能、動能、黏結能與應變能等細觀能量與應力路徑之間的聯(lián)系，，破壞過程中細觀裂紋數與巖石破壞前兆的關系，以及巖石微觀裂紋產生、發(fā)展與貫通的過程。通過不同卸荷應力路徑試驗模擬分析，給出細觀參數與巖樣宏觀強度參數之間的非線性關系；圍壓主要影響顆粒間摩擦滑動引起的摩擦能，進而改變試樣的破壞形式。卸荷速率越高，試樣內部裂紋發(fā)展越不充分，黏結能越少；試樣破壞時顆粒運動引起的動能越大。卸荷破壞過程是由壓破壞形成貫通剪切面，與拉剪破壞共同作用引起試樣破壞。壓破壞剪切面都是由破壞面兩端向中間發(fā)展，逐漸貫通，試樣內部主要破壞形式都表征為壓力引起的損傷破壞，拉剪破壞伴隨壓破壞，在壓破壞裂紋尖端有集中的趨勢。 （4）從細觀角度分析卸荷破壞過程，并通過實例驗證圍巖卸荷分析的可行性，其主要結論：經典強度準則中Mogi-Coulomb準則相對適合加軸壓、卸圍壓路徑下的試驗分析；將裂紋考慮成橢圓形，從細觀力學和單連通域的解析函數出發(fā)分析卸荷路徑下的強度準則；從單元體裂紋生成的復合應力狀態(tài)出發(fā)，建立卸荷過程中的應力-應變關系。 （5）在國標《工程巖體分級標準》和《地下工程圍巖穩(wěn)定分析與設計理論》一書對國標改進意見的基礎上，提出巖石地鐵工程圍巖分級設想，其主要結論：一是對圍巖分級表中圍巖定性特征進行了改進和調整，改進了各級圍巖基本質量BQ值，使定性分級和定量分級協(xié)調一致，發(fā)展與完善了圍巖巖體基本質量標準。二是在圍巖分級中反映了地下工程跨度對圍巖穩(wěn)定性的影響，提出按巖體質量和工程跨度為基準的圍巖分級思想，結合地鐵工程特點，給出區(qū)間隧道與車站隧道的亞級分級，量化了亞級的基本質量指標。采用了由安全系數反映圍巖自穩(wěn)性的量化指標和通過反算得到各級圍巖物理力學參數。對重慶軌道1#、6#線的巖體物理力學參數和圍巖分級進行了調研，采用本文提出的分級方法與國標相比：區(qū)間隧道砂巖由III、IV級圍巖提升為II、III級圍巖；區(qū)間隧道砂質泥巖有1/3的Ⅳ級圍巖提升為Ⅲ級圍巖；車站隧道砂巖約有80%的IV級圍巖提升為III級圍巖。 （6）采用數值極限分析新方法發(fā)展與完善了地鐵隧道的設計計算方法，提出了合理的設計計算參數和初襯二襯的計算方法。其主要結論是：一是依據現有試驗設備條件，提出了將直剪試驗與單軸抗壓試驗相結合的混凝土剪切試驗方法，從而確定不同強度等級混凝土剪切強度指標c、φ值；二是依據摩爾庫倫公式和數值方法，提出混凝土剪切強度和抗壓強度之間的關系，驗證了混凝土剪切強度試驗結果的可靠性，并將混凝土強度的標準值與設計值換算成剪切強度的標準值與設計值。結合實例，討論了荷載釋放量的確定、不同深淺埋分界標準的適用范圍、應力釋放后的圍巖安全系數、初襯圍巖與二襯結構的安全系數計算過程。最后對重慶地鐵、青島地鐵車站進行的計算分析表明，Ⅲ級圍巖以上可比現行襯砌厚度約減少30%，而Ⅳ、Ⅴ級圍巖初襯厚度或強度尚需適當增加，以確保施工安全。
[Abstract]:This paper consists of two parts : one is the complex loading and unloading process for the underground engineering excavation , especially the unloading process , the rock failure mechanism under the unloading path is clarified , and the damage mechanism of the rock macro - meso - view under different unloading paths is emphatically studied , including : the energy evolution law during the destruction of different unloading conditions ;
Evolution law and quantitative analysis of acoustic emission characteristics during rock unloading and destruction
Based on the numerical simulation of the rock unloading damage process in rock metro engineering , the study on the calculation methods of surrounding rock classification and design of rock metro engineering is carried out by using numerical limit analysis method , including the improvement of the basic quality index of rock classification of rock metro engineering .
Considering the influence of span on the grading of surrounding rock ;
Shear strength of initial lining concrete
Calculation methods of rock subway engineering design and so on .

The research results are as follows :

( 1 ) The energy evolution law in the process of unloading the marble under different loading conditions is studied by using the self - compiled program of energy principle , and the following main research results are obtained : the nonlinear change of the axial absorption energy curve of the rock sample unloading damage process , and the evolution process of slow growth - fast growth - slow growth - release is experienced .
The lower the unloading speed , the increasing rate of axial energy increase , the turning of the axial energy curve at the unloading point is more obvious ;
When the unloading level is close to the peak load carrying capacity , the increasing rate of axial energy increases , the negative growth rate of the total energy curve is high , and the more severe the rock sample damage .

( 2 ) To study the evolution of acoustic emission characteristics during rock sample destruction under different loading conditions , and further quantify the acoustic emission characteristics by fractal method .
The higher the unloading rate , the higher the ringing count rate of the relative calm period , the shorter the duration ;
The closer to the peak unloading of rock - like bearing capacity , the shorter the relative calm period of the acoustic emission events before the rock sample destruction . There is a lower area of the sound emission fractal dimension before the rock sample damage , the fractal dimension near the destruction point , the adding shaft pressure , the pressure relief path of the pressure relief , the constant axial pressure , the pressure relief path of the pressure relief and the conventional three - axis path .

( 3 ) Based on the particle flow method , the numerical simulation of loading and unloading damage process of marble is realized by FISH language .
The confining pressure mainly affects the friction energy caused by the friction sliding between the particles , and then changes the damage form of the sample . The higher the unloading rate , the less the internal crack development of the sample is , the less the binding energy is ;
The larger the kinetic energy caused by the movement of the particles , the more kinetic energy caused by the movement of the particles when the specimen is damaged . The damage of the specimen is caused by the failure of the breaking surface . The damage of the specimen is caused by the failure of the breaking surface to the middle . The main damage form inside the sample is characterized by the damage caused by the pressure , the shear failure is accompanied by the pressure damage , and there is a concentration trend in the crack tip .

( 4 ) To analyze the unloading damage process from the viewpoint of view angle , and verify the feasibility of surrounding rock unloading analysis by examples . The main conclusions are as follows : the Mogi - Coulomb criterion in the classical strength criterion is relatively suitable for the test analysis under the axial pressure and the pressure relief path ;
taking the crack into an ellipse , analyzing the strength criterion under the unloading path from the analytic function of the meso - mechanics and the single - connected domain ;
The stress - strain relationship in unloading process is established based on the composite stress state generated by unit crack .

( 5 ) Based on the improvement of the surrounding rock mass , the paper puts forward the improvement and adjustment of the surrounding rock stability in the rock mass classification table . The main conclusions are as follows : 1 . The influence of underground engineering span on the stability of surrounding rock is proposed .
Grade 鈪

本文編號：1899095