岩石力学与工程学报
巖石力學與工程學報
암석역학여공정학보
CHINESE JOURNAL OF ROCK MECHANICS AND ENGINEERING
2013年
3期
474-482
,共9页
包春燕%唐春安%唐世斌%蔡明%于群
包春燕%唐春安%唐世斌%蔡明%于群
포춘연%당춘안%당세빈%채명%우군
岩石力学%表面裂纹%材料非均质%裂纹扩展过程%数值模拟%层状材料
巖石力學%錶麵裂紋%材料非均質%裂紋擴展過程%數值模擬%層狀材料
암석역학%표면렬문%재료비균질%렬문확전과정%수치모의%층상재료
rock mechanics%surface fracture%heterogeneity of material%propagation process of crack%numerical modelling%layered materials
层状岩石的表面裂纹发端于表面自由边界,而后向着层与层之间的交界面扩展,最后止于交界面或沿着交界面继续扩展.为更深入地理解这一表面裂纹扩展现象的机制,采用数值模拟方法,再现微裂纹从萌生、扩展、贯通、成核、填充到饱和的全过程,以及层间剥离现象.首先以表面预制裂纹的模型为例,对其进行单轴拉伸加载,发现不同预制裂纹间距的情况下两裂纹间的应力分布不同,这将直接影响到新裂纹的产生模式,即裂纹是插入到表层(与已有裂纹平行),还是不再有新裂纹插入(裂纹饱和),而是产生层间剥离,或已有裂纹向下扩展,导致模型破坏.其次,对比分析模型均质和非均质情况下不同裂纹间距时的应力分布,结果表明非均质材料情况下产生相同间距的裂纹所需的荷载较均质材料情况下更小,裂纹饱和对应的裂纹间距与层厚比值的临界值基本一致.最后,提取等间距裂纹形成过程中若干具有代表性的截面应力,通过分析其应力转化机制,解释裂纹饱和现象的力学机制.数值计算得到的应变与裂纹间距之间的关系拟合结果良好.研究结果还表明:产生层间开裂的裂纹间距比没有层间开裂的裂纹间距大.通过对层间的应力传递过程随着裂纹间距变化规律的探讨,研究此过程的应力传递模式.
層狀巖石的錶麵裂紋髮耑于錶麵自由邊界,而後嚮著層與層之間的交界麵擴展,最後止于交界麵或沿著交界麵繼續擴展.為更深入地理解這一錶麵裂紋擴展現象的機製,採用數值模擬方法,再現微裂紋從萌生、擴展、貫通、成覈、填充到飽和的全過程,以及層間剝離現象.首先以錶麵預製裂紋的模型為例,對其進行單軸拉伸加載,髮現不同預製裂紋間距的情況下兩裂紋間的應力分佈不同,這將直接影響到新裂紋的產生模式,即裂紋是插入到錶層(與已有裂紋平行),還是不再有新裂紋插入(裂紋飽和),而是產生層間剝離,或已有裂紋嚮下擴展,導緻模型破壞.其次,對比分析模型均質和非均質情況下不同裂紋間距時的應力分佈,結果錶明非均質材料情況下產生相同間距的裂紋所需的荷載較均質材料情況下更小,裂紋飽和對應的裂紋間距與層厚比值的臨界值基本一緻.最後,提取等間距裂紋形成過程中若榦具有代錶性的截麵應力,通過分析其應力轉化機製,解釋裂紋飽和現象的力學機製.數值計算得到的應變與裂紋間距之間的關繫擬閤結果良好.研究結果還錶明:產生層間開裂的裂紋間距比沒有層間開裂的裂紋間距大.通過對層間的應力傳遞過程隨著裂紋間距變化規律的探討,研究此過程的應力傳遞模式.
층상암석적표면렬문발단우표면자유변계,이후향착층여층지간적교계면확전,최후지우교계면혹연착교계면계속확전.위경심입지리해저일표면렬문확전현상적궤제,채용수치모의방법,재현미렬문종맹생、확전、관통、성핵、전충도포화적전과정,이급층간박리현상.수선이표면예제렬문적모형위례,대기진행단축랍신가재,발현불동예제렬문간거적정황하량렬문간적응력분포불동,저장직접영향도신렬문적산생모식,즉렬문시삽입도표층(여이유렬문평행),환시불재유신렬문삽입(렬문포화),이시산생층간박리,혹이유렬문향하확전,도치모형파배.기차,대비분석모형균질화비균질정황하불동렬문간거시적응력분포,결과표명비균질재료정황하산생상동간거적렬문소수적하재교균질재료정황하경소,렬문포화대응적렬문간거여층후비치적림계치기본일치.최후,제취등간거렬문형성과정중약간구유대표성적절면응력,통과분석기응력전화궤제,해석렬문포화현상적역학궤제.수치계산득도적응변여렬문간거지간적관계의합결과량호.연구결과환표명:산생층간개렬적렬문간거비몰유층간개렬적렬문간거대.통과대층간적응력전체과정수착렬문간거변화규률적탐토,연구차과정적응력전체모식.
@@@@Fractures initiated from free surface of layered rocks,which are called surface cracks,often terminate at the interface which divides the fractured layer and the matrix layer,but can continue to propagate along the interface. A numerical simulation is carried out to study the mechanism of surface fracturing process including micro-fracture formation,propagation,coalescence,nucleation,fracture infilling,fracture saturation,termination, and interface delamination. A model with a fractured surface subjected to uniaxial tension is simulated firstly. It is found that the stress distribution between fractures depends on the fracture spacing;and the stress distribution will directly affect the fracture mode. New fractures can either appear in the surface layer(parallel to existing fractures),or appear between the layers(interface peeling). Furthermore,an existing fracture can propagate to the underlying layer with no fracture inserting(fracture saturation). Secondly,material homogeneity is considered in the simulation;and the results show that the stress distributions in homogeneous and heterogeneous models are different. A smaller stress is required to produce the same fracture spacing in the heterogeneous model;and the critical values of the spacing to layer thickness ratio at fracture saturation are almost the same. Lastly,stresses in a few sections during fracture formation are analyzed;and it is found that stress transformation can be used to explain the mechanism of fracture saturation. A fitting curve of the relationship between strain and spacing to layer thickness ratio is obtained. It is found that fracture spacing in the case of interface delamination is greater than that without interface delamination. Stress transition between the two layers on fracture spacing in the fracture process is also investigated,with a focus on stress transfer mode.