动静组合加载下刀具破岩的力学模型

基于初始弹性和动静荷分工的假设,将动静复合加载下坚硬完整的脆性岩石的破碎过程分为弹性、损伤和断裂3阶段,综合运用弹性力学、岩石力学、损伤力学和断裂力学进行分析。由集中力作用下弹性半空间的应力场和单元体的剪切破坏,得出了岩石损伤的裂纹源和其曲线扩展路径;选定Ⅰ型、Ⅱ型裂纹作为动载冲击作用下压剪裂纹的扩展模式。提出了以冲击能（次数）来定义损伤度的方法。以相邻破碎坑的侧向裂纹扩展贯通作为岩石破碎的终点。本力学模型可以用于动静复合加载破碎岩石的系统仿真、数值模拟和机具设计。     

Propagation and Control of Crack in Rock Material under Dynamic Loading

Fracture mechanism, initiation and propagation of cracks, and the control method of cracks in rock like brittle material under dynamic load are described in this paper.     

动载作用下岩石断裂裂纹的扩展与控制

本文主要论述了动荷载作用下岩石等脆性材料的断裂破坏机理、裂纹形成与扩展以及裂纹的止裂与控制等内容。     

岩石在循环荷载作用下的强度及变形特征

本文着重研究了岩石在循环荷载作用下的强度及变形特征。实验结果表明,岩石在循环荷载作用下的强度低于其静力强度,而这个循环疲劳强度极限与振幅、频率有关;岩石在循环荷载作用下的变形特征类似于静力蠕变特征。     

Analysis of the Dynamic Performance of an Underground Excavation in Jointed Rock under Repeated Seismic Loading

Results from field observations of dynamic behaviour of an underground excavation have been compared with numerical studies of the rock deformation history. The field behaviour shows progressive accumulation of rock displacement and excavation deformation under successive episodes of dynamic loading. It is possible to reproduce the modes of rock response quite well using a Distinct Element model of the rock mass, but the way displacements develop is dependent on the joint model used in the analysis. It is suggested that, in rock masses subject to repeated dynamic loading, excavation design may need to take account of the prospect of repeated episodes of transient loading at the excavation site.     

Effects of Frequency on the Dynamic Properties of Intact Rock Samples Subjected to Cyclic Loading under Confining Pressure Conditions

A series of laboratory tests was performed to assess the effects of frequency on the dynamic properties of sandstone samples subjected to cyclic loading in the confining stress state. Three levels of confining pressure (2.0, 10.0, and 40.0 MPa) and three sets of frequencies (0.1, 1.0, and 3.0 Hz) were applied for the axial cyclic loading tests by the MTS-815 Rock and Concrete Test System. The results from the cyclic loading tests indicate that frequency has a strong influence on the dynamic deformation, the dynamic stiffness, and the failure mode at the same confining pressure. With an increase in the frequency, the axial strain and the number of cycles at failure increased at the same confining pressure, the residual volumetric strain increased when dilatancy occurred at the same confining pressure, and the number of cycles at failure increased. A new damage variable D was defined that describes the degradation process of sandstone samples upon dynamic cyclic loading. The larger the frequency, the wider the localized band. Sandstone samples subjected to dynamic cyclic loading responded with a significantly higher initial stiffness. The higher the initial stiffness, the greater the frequency.     

An Approach for Modeling Rock Discontinuous Mechanical Behavior Under Multiphase Fluid Flow Conditions

In this paper, the two computer codes TOUGH2 and RDCA (for “rock discontinuous cellular automaton”) are integrated for coupled hydromechanical analysis of multiphase fluid flow and discontinuous mechanical behavior in heterogeneous rock. TOUGH2 is a well-established code for geohydrological analysis involving multiphase, multicomponent fluid flow and heat transport; RDCA is a numerical model developed for simulating the nonlinear and discontinuous geomechanical behavior of rock. The RDCA incorporates the discontinuity of a fracture independently of the mesh, such that the fracture can be arbitrarily located within an element, while the fluid pressure calculated by TOUGH2 can be conveniently applied to fracture surfaces. We verify and demonstrate the coupled TOUGH–RDCA simulator by modeling a number of simulation examples related to coupled multiphase flow and geomechanical processes associated with the deep geological storage of carbon dioxide—including modeling of ground surface uplift, stress-dependent permeability, and the coupled multiphase flow and geomechanical behavior of fractures intersecting the caprock.     

Numerical Analysis of Himalayan Rock Tunnels under Static and Blast Loading

Geotechnical and Geological Engineering - Tunnels have been the necessary element of the modern construction industry. Due to their importance for the infrastructural and economic point of view,...     

Study on Deformation and Strength Behavior of the Large-sized Triaxial Rock Samples under Cyclic Loading

When in Institute of Soil and Rock Mechanics, Karlsruhe University, Federal Germany, the author of this paper performed some cyclic loading tests on the large-sized triaxial testing machine developed in this institute. The rock sample used were 60cm in diameter and 120cm in height. The work mainly included the study of deformation and strength behavior of the samples and was based on the viewpoint of analyzing the irreversible deformation. Under cyclic loading, although the irreversible deformation generally increased with the n umber of cycles, the deformation trends obtained at various stress levels distinctly differed from each other. At low stress levels a comparatively large irreversible deformation arouse from the first few cycles of loading. With the increase of the number of cycles its growth decayed gradually and tended finally to a stable constant value. When the stress level reached a certain “threshold” value, the situation became entirely different. The increase of the number of cycles caused an acclecrated growth of the irreversible deformation till a complete failure of the whole sample. The test results also illustrated that this characteristic stress value was slightly lower than the so-called “yield” value. The study of such a characteristic value is of great importance for under-standing the mechanical properties of rock masses under cyclic loading. The experimental curves of irreversible deformation vs. the number of cycles show a remarkable resemblance to corresponding rheological curves, which, perhaps, may not be accidental. It is propose in this paper that the relation of the strength obtained in conventional tests, the long-term strength in rheological tests and the strength under cyclic loading should be studied. Undoubtedly, it is significant for evaluating the strength and safety factor in rock engineering problems.     

周期荷载下岩石大型三轴试件的变形和强度特性研究

本文介绍了作者在联邦德国卡尔斯鲁厄大学土岩力学研究所利用该所研制的大型三轴试验机进行周期荷载下大型三轴试验的情况和结果。岩石为薄层灰岩,试件直径为60cm,高为120cm。整个研究工作是基于分析不可逆变形的观点来探讨变形和强度特性的。在周期荷载作用下,不可逆变形的总量随着循环次数的增加而增长;但在不同的应力水平下,不可逆变形的发展趋势具有显著的,甚至是质的差异。应力水平很低时,最初几次的循环荷载将导致产生较大的不可逆变形;随着循环次数之增加,其不可逆变形的增长率逐步衰减,最终趋向于一个比较稳定的常值。但是当应力水平达到某一“门槛”值后,情景则迥然不同;循环次数之增加将促使不可逆变形的加速增长,最终导致整个试件的破坏。试验结果表明,这一特征应力值略低于常规三轴试验中的所谓“屈服值”。研究结果表明,每一个加荷-卸荷循环过程中的不可逆变形主要发生在超过这一“门槛”值后的区段内。研究这样的特征值对于探讨周期荷载作用下岩体的力学性质是十分重要的。由试验获得的不可逆变形与循环次数的关系曲线在形态上与流变曲线十分相似。     

含软弱岩层反倾岩质边坡地震动力响应与破坏模式

以鲁甸地震诱发的红石岩崩塌滑坡为研究对象,通过大型振动台模型试验和3DEC数值模拟,研究了含软弱岩层的反倾岩质边坡的动力响应和破坏失稳模式.研究结果表明:水平加载下,随频率增大PGA放大系数先减小后增大,在接近坡体自振频率8Hz的波形加载下,坡体动力响应最为剧烈,软弱岩层对不同频率的横波具有放大和吸收作用,对5~10Hz的横波放大效应明显,对15~20Hz的横波则明显吸收;竖向加载下,随加载正弦波频率的增加,PGA放大系数先增大,25Hz时PGA放大系数减小,随后又继续增大,在频率为30Hz时PGA放大系数达到最大,在5~30Hz范围内软弱岩层对纵波均具有一定的放大效果;双向加载下,坡体水平和竖向PGA放大系数分布与单向加载一致,但双向加载下坡体部分位置动力响应加剧,部分位置动力响应则受到抑制.含软弱岩层的反倾岩质边坡破坏过程可以分为6个阶段:坡体内部轻微损伤-软岩挤出、软硬岩交界上方硬岩拉裂-硬岩裂纹向上延展-软弱岩层挤压滑动-层面和纵向节理贯通形成滑面-边坡破坏.在软弱岩层的反倾岩质边坡中,软弱岩层具有对地震波的放大吸收、折射反射作用,影响着边坡的动力响应特征,软弱岩层的挤出破坏导致上部岩体岩结构面松动开裂,是该类岩质边坡破坏发展的主要原因,对该类边坡需应注意对软弱岩层进行加固防护,减小边坡的动力破坏.      

Experimental Study of Mechanical Behaviour of Rock Joints Under Cyclic Loading

Summary Evaluation of the effects of small repetitive earthquakes on the strength parameters of rock joints in active seismic zones is of interest of the designers of underground constructions. In order to evaluate these effects, it is necessary to study the behaviour of rock joints under dynamic and cyclic loadings. This paper presents the results of a systematic study on the behaviour of artificial rock joints subjected to cyclic shearing. More than 30 identical replicas have been tested using triaxial compression devices under different conditions of monotonic and cyclic loading. At the first stage a few samples have been tested in monotonic loading modes under various confining pressures and rate of displacement. In the second series of tests, small cyclic loads were applied on the samples for increasing number of cycles, frequency levels and stress amplitudes. These were then followed by monotonic loading again. The variations of maximum and residual shear strengths for each test have been studied. The results show increase of shear strength as a result of the increase in confining pressure and they display decrease of shear strength due to the increase of rate of loading, number of cycles, frequency levels and stress amplitudes.     

动,静载作用下裂纹扩展的异同点

本文通过对具有不同分布裂纹模型实验的破裂过程的描述,分析了单轴动载荷、静裁荷作用下裂纹扩展的实验研究结果,揭示了它们之间的差异和共同遵循的规律。     

冻结砂土在动荷载下的蠕变特征

通过分析不同试验条件下的蠕变过程曲线,探讨了冻结砂土在动荷载下的蠕变模型,分析了最大加载应力,温度及加载频率对冻土蠕变破坏应变,破坏时间和最小蠕变速率的影响.结果表明,当最大加载应力变大时,破坏应变增加,破坏时间缩短,最小蠕变速率变快;加载条件相同时,温度越低,破坏应变越小,破坏时间越长,最小蠕变速率越小;加载频率变化时,最小蠕变速率的变化无明显规律,都在一个量级范围内,当频率变大时,最小蠕变速率略有变小的趋势.频率增加,破坏时间缩短,破坏应变减小.频率小于7Hz时,频率对破坏应变和破坏时间影响较大,而当频率大于7Hz时,随频率加快,破坏时间和破坏应变只略有减小.