静动载下共面非贯通裂隙贯通机制分析

共面非贯通裂隙的贯通机制对于确定外载下岩质边坡的滑动面位置及滑动面综合抗剪强度至关重要。采用预制共面非贯通裂隙石膏模型试样单轴静动载对比试验,对不同裂隙倾角共面排列裂隙的扩展、贯通过程进行了观测,研究显示：共面非贯通裂隙不同倾角下的贯通模式存在较大差异,裂隙倾角为0o～35o时以裂隙面发生闭合变形为主;45o～65o时裂隙间较易出现剪切型破坏模式;75o～90o预制裂隙面较难产生滑动,裂隙试样主要产生劈裂形式的破坏。动载下预制裂隙试样裂尖翼裂纹及次生共面裂纹起裂后易朝原起裂方向快速发展;易在两预制裂隙内端部产生直接贯通,这与静载下岩桥处的贯通常通过分支裂纹拐折扩展、相连不同。含共面非贯通裂隙试样在裂隙倾角为35o左右时强度呈现最小值,这与贯通性裂隙试样裂隙倾角为60o左右呈现最小值相差较大,这是因为裂隙面摩擦强度没来得及发挥作用所致。因此,含非贯通节理裂隙岩体的综合抗剪强度公式应引入强度发挥系数,以充分考虑岩桥胶结强度与裂隙面摩擦强度不能同步发挥作用的破坏本质。     

共面闭合断续节理岩体强度特性直剪试验研究

为了揭示不同裂纹贯通模式的细观演化机理,采用颗粒流程序(PFC)模拟含平行双裂隙石膏试样的单轴压缩试验。对双预制裂隙在不同相对位置时试样内出现的裂纹贯通模式进行分类,并对不同贯通模式形成过程中预制裂隙周围的力链和颗粒位移场进行分析。研究发现预制裂隙的相对位置会改变压缩过程中其周围的接触力分布以及颗粒位移趋势,进而影响预制裂隙端部以及岩桥区域裂纹的扩展路径。当两预制裂隙几乎共面时,在岩桥区域存在接触力集中情况,岩桥区域首先出现微张拉裂纹,随着加载,这些微张拉裂纹逐渐演化为宏观剪切带并连接两个预制裂隙端点,形成Ⅰ型贯通。当岩桥倾角较大且两个预制裂隙不重叠时,岩桥区域的接触力集中程度增大,岩桥区域首先出现竖向的微张拉裂纹并演化为竖向的宏观裂纹连接两个预制裂隙端点,导致Ⅱ或Ⅶb型贯通。当两个预制裂隙的端部部分重叠时,由于应力屏蔽效应,重叠端部的压缩接触力集中程度小于未重叠端部,导致翼裂纹成为主导贯通的裂纹。当两个预制裂隙在竖直方向完全重叠时,两预制裂隙同侧端点之间的接触力集中导致出现由压致拉的张拉裂纹连接预制裂隙同侧端点,形成Ⅴ型贯通。出现Ⅱ、Ⅴ和Ⅶb型贯通试样的微裂纹数量曲线呈现阶梯状增长的趋势,表明这3类贯通中宏观裂纹的扩展是由应变能的突然释放导致的。     

PROGRESSIVE COALESCENCE MODEL FOR BRITTLE FAULT FORMATION AND ITS MECHANISM

In shallow crust, faults often consist of a series of secondary fractures. Based on experimental micro-features in rock mechanics and macro-structures in field, the progressive coalescence model, in which a brittle fault evolved from micro-crack, stylolitic fracture, large fault to super-large fault, is founded, and its forming mechanism is discussed by variation of stress field. At last the undulation,branches of faults and the phenomenon that the angle between fractures and the principal stress axis decreases gradually are explained by the G. C. Sih model.     

多节理岩体裂纹扩展及变形破坏试验研究

为了研究不同倾角下多节理岩体力学行为,采用10 MN微机控制电液伺服大型多功能动静力三轴仪,开展包含较多预制非贯通节理类岩石试件的单轴压缩试验,研究了多节理岩体裂纹的特征、贯通模式、破坏模式、应力-应变特征等与节理倾角之间的关系。试验结果表明,（1）多节理岩体的裂纹类型主要有翼裂纹和次生共面裂纹,翼裂纹的扩展路径与单个节理情况下的扩展路径差异较大,翼裂纹起裂后沿起裂方向存在较长的扩展长度,直接与相邻节理或翼裂纹形成贯通,并且裂纹的贯通表现出四种不同的模式;（2）多节理岩体的破坏模式归纳为3种类型：平面破坏、块体转动式破坏和台阶式破坏;（3）根据多节理岩体的应力-应变曲线在应变软化阶段所表现出的不同非线性变形行为特征,可以将曲线归纳为4种类型;（4）多节理岩体的强度和变形各向异性特征非常显著,强度和弹性模量均在节理倾角30°时最小,90°时最大。     

含共面结构面岩体的岩桥贯通准则研究

块体理论是一种比较常用的岩土工程稳定性分析方法,但缺乏对非贯通结构面的研究,导致搜索出的关键块体不够精准和全面。如何处理非贯通结构面,判断其是否应该连通成为块体理论研究至关重要的一个问题。采用数值模拟的方法计算含两共面结构面岩体试样在不同岩桥倾角、结构面摩擦系数、围压和连通率情况下的贯通强度与峰值强度。引入贯通系数变量,定量描述贯通强度与峰值强度之间的关系。将贯通强度作为判断岩桥贯通与否的一个衡量指标,建立起贯通强度与岩桥倾角、结构面摩擦系数、围压和连通率之间的函数,即含两条共面结构面岩体的岩桥贯通准则。该准则可准确判断含两条共面结构面岩体的岩桥是否应该连通。基于岩桥贯通准则的块体理论能够准确搜索出因岩桥贯通而滑移的关键块体。     

Strength failure behavior and crack evolution mechanism of granite containing pre-existing non-coplanar holes: Experimental study and particle flow modeling

In this study, uniaxial compression tests were conducted on granite specimens containing three non-coplanar holes. The relationships between the stress, acoustic emission (AE) and crack evolution process were analyzed using AE measuring and photographic monitoring techniques. Particle flow code (PFC) was then used to simulate the strength failure behaviors of the specimens with three non-coplanar holes under uniaxially loading. Four typical crack coalescence patterns were identified, i.e., shear, mixed tensile and shear, and tensile. The crack evolution mechanisms around the pre-existing holes in the granite specimens were revealed by an analysis of the force and displacement fields.     

安徽省姑山铁矿床中赤铁矿微晶的聚合

安徽省姑山铁矿床的矿石产在中生代辉长闪长岩与以三叠纪页岩，粉砂岩和砂岩为主的围岩的接触带上，矿石成分主要是微晶赤铁矿，其粒径为０．０１－０．０５ｍｍ，并与玉髓和细粒石英相交生，粒径达１－２ｍｍ的赤铁矿斑晶呈板状自形晶浸染于块状矿石中，显微镜观察表明，赤铁矿自形斑晶是在成矿期后由赤铁矿微晶聚合而成的。整个聚合过程包括微晶颗粒的相互靠近，颗粒旋转，结晶方位的定向以及最终的焊结，从而形成光性均一的变斑晶     

Failure mechanisms of post-earthquake bedrock landslides in response to rainfall infiltration

Among the triggering factors of post-earthquake bedrock landslides,rainfall plays an important role.However,with slope variation,the mechanism of its effects on the failure of rock landslides is not clear.Here,from the viewpoint of fracture mechanics,and based on post-earthquake conditions,the mechanisms of crack propagation,water infiltration and development of the sliding surface were investigated.Then,according to the upper boundary theorem,the effects of water infiltrated into fractures on the stability of rock slopes were analyzed quantitatively.Finally,an example is presented to verify the theory.The results show that the propagation and coalescence of cracks and the lubrication of incipient sliding surfaces are the main causes of the failure of post-earthquake rock landslides in response to rainfall.     

三轴压缩条件下冻融单裂隙岩样裂缝贯通机制

采用岩石力学伺服试验机,对预制单裂隙模型试样进行冻融循环后的三轴压缩试验,基于冻融循环试验对裂隙岩体的冻融损伤劣化模式进行研究,探讨经历不同冻融循环次数后的裂隙岩样在三轴压缩条件下裂缝的贯通机制。试验发现：裂隙岩体的冻融损伤劣化模式有颗粒散落模式、龟裂模式和沿预制裂隙断裂模式3种;在三轴加载条件下,冻融裂隙岩样的贯通模式呈现拉贯通、剪贯通、压贯通和混合贯通4种;贯通模式和冻融循环次数、围压的大小以及裂隙倾角有关,随着冻融循环次数的增加和围压的升高,岩样表面的破裂线越来越多,导致裂纹的贯通模式由单一贯通转换为混合贯通,在围压为2、6 MPa时,岩样的破坏模式为拉-压贯通,而围压为4 MPa时,岩样主要呈现拉贯通,裂隙倾角为30°的岩样主要贯通模式为拉贯通,裂隙倾角为60°的岩样主要贯通模式为剪贯通。     

The coalescence of water drops I. A theoretical model of approaching drops

The approach of two water drops in the absence of air flow around them is theoretically investigated. By assuming deformation criteria it is possible to solve the equation of motion of the drops under the influence of a variety of forces. These forces include the viscous force exerted by the air between the two deformed surfaces, the London-Van Der Waals forces and the force of gravity. It is found that the viscous forces dominate over the whole distance of the interaction. The equations have analytical solutions when a head-on approach is considered and when the deformation of the drops is assumed constant during the interaction. The equations were solved numerically for other deformation criteria and for non head-on approaches.The results of the present model are used in the following paper to compute the coalescence efficiencies of water drops. The model is primarily applicable to situations in which the large drop is stationary and the small one approaches it from below. However, it could also be used for interaction between freely falling drops as long as their relative velocities exceed about 13 cm/sec.Appendix: List of symbols C constant of the motion - D distance between the deformed surfaces of the drops - D _o initial value ofD - D _m the value at which the viscous force is maximum - D _N normalized distance - D _s the distance at which the velocity of approach vanishes - F _c centrifugal force - F _g force due to gravity - F _N normalized viscous force - F _LV force due to London-Van der Waals effect - F _R radial component of the force - F _V viscous force - F _t tangential component of the force - g acceleration due to gravity - M _L mass of large drop - m _s mass of small drop - p ratio of radii of interacting drops - R radius of an arbitrary drop - r distance between the centers of mass of the two drops - R _D radius of deformation - R _L radius of larger drop - R _s radius of smaller drop - t time - u defined in equation 20 — has the meaning of kinetic energy - v relative velocity of the deformed surfaces - v ₀ initial value ofv - V ₀ initial relative velocity of the centers of the drops - V _c critical impact velocity - V _i impact velocity - V _N ,v _n normalized velocity - V _t tangential component of the velocity - W _i velocity of the small drop at infinity for it to reach the pointD ₀ at velocityV ₀ - x instantaneous impact distance -  average critical impact distance for coalescence - x ₀ initial value of the impact distance - x _c critical impact distance for coalescence - coefficient of deformation - _i impact angle according toWhelpdale andList (1971) - coefficient of deformation - viscosity - surface tension - F _s sum of forces acting on the small drop - F _L sum of forces acting on the large drop - time constant - _R Rayleigh's oscillation period On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation.