The greatest portion of the fatigue life is spent nucleating and growing a fatigue crack to a length at which it can be detected the range. When stress exceeds the strength of the rock the rock will bend or fold 3. Analysis and monitoring of roadway deformation mechanisms. The existence of vug waves would also imply that in many geologic environments the strain. Strain is the relative internal change in shape of an infinitesimally small cube of material and can be expressed as a nondimensional change in. Pdf a study of the large deformation mechanism and. Deflection is the relative change in external displacements on an object. This paper deeply analyzes the geological characteristics, rock mechanics characteristics, and surrounding rock failure characteristics of muzhailing tunnel. Pdf the kinetics of rock deformation by pressure solution. Nonlinear large deformation mechanism and stability. A study of the large deformation mechanism and control techniques for deep soft rock roadways article pdf available in sustainability 104. The stressstrain curve can be divided into three parts, each representing a different dominant deformational process.
Movement then depends on rock rheology or ability to flow and occurs along planar structures. Deformation mechanisms is commonly characterized as brittle, ductile and brittleductile. Surrounding rock deformation mechanism and control. During the brittle state the maximum strain is below 3%, while in a ductile state it is over 5%. The interaction between fluid infiltration, mineral reactions and rock deformation has been the subject of much debate and raises fundamental issues such as the mechanism of fluid transport in nominally impermeable rocks, the role of deformation in initiating and driving fluid flow and the relationship between mineral reaction, the strength of. Surrounding rock deformation mechanism and control technology for gobside entry retaining with fully. Overprinting faulting mechanisms during the development of. Mechanisms of fatiguecrack propagation in ductile and brittle solids 59 in general, ductile materials are toughened intrinsically, e. Take fenghuang mountain tunnel in suzhou city as an example, the main work and funding are as follow. Mount everest is the highest peak on earth at 29,028 feet above sea level.
By investigating how deformation mechanisms at different rates and strain magnitudes are related namely by combining laboratory and theoretical analyses. These mechanisms produce a range of microstructures studied in rocks to constrain the conditions. Rock mechanics 5 the original and modified griffith theories, when expressed in terms of the stresses at fracture5, contribute little to the understanding of rock fracture under dynamic stress conditions, the energy changes associated with fracture or the deformation process of. A case study in china dong wang 1,2, yujing jiang 1,3, xiaoming sun 2, hengjie luan 1 and hui zhang 2 1 state key laboratory of mining disaster prevention and control cofounded by shandong province and the ministry of science and technology, shandong. The determination of the deformation mechanism of rock was accomplished by the examination of the volumetric differences of the rock sample. Many naturally deformed crustal rocks contain mineralfilled extension veins. Overpressured fluids are attributed to one or more of several mechanisms. The essential driving power for the rock deformation is the strain energy released from the rockmass after excavation. This work is intended to study the postfailure characteristic behaviour of rocks and the techniques of controlling the postfailure regime based on the mechanism of rocks deformation process. Results are reported for sixtynine triaxial compression tests run on a marble, a lithographic limestone, a very finegrained sandstone, and a siltstone at room temperature, dry, confining pressures of 1,000 and 2,000 bars, and at strain rates of,, and second. The formation mechanism of island arc is constituted by the factors of dehydration of subducted oceanic crust, substrate melting underplating of backarc basin, temperature rise of rocks, rock expansion, deformation of the long axis of backarc basin and etc. Dependence of strainrate effects on deformation mechanism. In addition to sedimentary structures that are normally associated with bedding.
The crystals making up the vein filling often show a fibrous habit and seem to be built up by a succession of crack. Vug is a cornish word for a hole within the earth oxford english dictionary. The deformation mechanism of a high rock ll dam during the. Deformation of rock mount everest is the highest peak on earth at 29,028 feet above sea level. Strain is the change in shape, or nonrigid body deformation of a rock caused by. A case study on large deformation failure mechanism and control techniques for soft rock roadways in tectonic stress areas guangzhe xue 1, chao gu 1,2, xinqiu fang 1, and tao wei 1 1 state key laboratory of coal resources and safe mining, china university of mining and technology, xuzhou 221116, china. Study on deformation mechanism and support measures of. Localized deformation due to shearing of the wnwstriking regional joints formed wnwstriking mapscale normal faults. The rock at the top of the peak is a marine limestone, deposited on the sea floor about 450 million years ago. The deformation of muzhailing deep tunnel is about 2. Flow or coherent change in the rock in the solid crystalline state. Strain is the change in shape, or nonrigid body deformation of a rock caused by stresses. We did some investigations and monitoring works in jinchuan mine 2. Introduction to high pressure rock deformation techniques.
Plastic deformation occurs when the strain rate is low, and leads to microscale foliation and large. A case study on large deformation failure mechanism and. In this paper, based on field investigation, roadway deformation was summarized three features. In engineering, deformation refers to the change in size or shape of an object. The greater part of the released strain energy is dissipated in rock fracturing, which in turn brings about rock. Flow is a change in deformation that continues as long as the force is applied. The relationship between the deformation mechanism and. The greater part of the released strain energy is dissipated in rock fracturing, which in turn brings about rock deformation. Request pdf deformation mechanism of soft rock the deformation mechanism of soft rocks can be divided into three categories. Plastic deformation might increase effective compressibility of the rock several orders of magnitude with increasing effective pressure fig.
Implications for deformation mechanism and rock strength hiroki mukai1y, hkon austrheim2, christine v. Relatively low t and p, large forces or rapid imposed deformation ductile. The deformation mechanism of soft rock roadway in mines is usually complex, often a combination of three or more types. Determination of class i and class ii rocks from conventional method based on the mechanism of rock deformation process. The driving mechanism responsible is a subject of interplay between internal e. The microdamage to the rock during the propagation of the main fracture may significantly reduce the strength of the rock and lead to substantial elastoplastic deformation during the leakoff stage. In this discussion we will try to answer that question. Acousticmechanical responses of intact and flawcontained. Deformation mechanism map activity reading lecture presentation plastic regime 2019 8. Mechanical properties and failure mechanism of intact rock were investigated. Geology and setting the unstable rock slope is located 500 m upstream of the laxiwa hydropower dam, along the east bank of the yellow river. This is an amazing fact that begs the question how did that rock get there. Pressure has a profound impact on the deformation behavior of rocks. In the transition state the maximum strain varies between 3% and 5%.
The cyclic deformation of metals is fundamentally different from the monotonic deformation. There is little, if any, evidence for constantvolume plastic deformation at any level of uniaxial stress. These mechanisms produce a range of microstructures studied in rocks to constrain the. Limestone mechanical deformation behavior and failure. Original paper complex rock slope deformation at laxiwa hydropower station, china. Fracture of rock with possible slip along the fracture surface fault. It is impossible to determine the postfailure regime of rocks using conventional laboratory testing equipment. In general the deformation of a single crystal in tension or compression consists of shear strain in which sheets of the crystal parallel to a crystal plane slip over one. The deformation mechanism of a high rock ll dam during the construction and rst impounding a. Pdf deformation mechanisms and evolution of the microstructure. In order to study the relationship between the deformation mechanism and permeability on brittle rock, the curves of stressstrain and permeabilitystrain of brittle rock were analyzed, the results indicated that the permeability of brittle rock increased rapidly at the critical failure point due to the microstructure changed seriously during the compaction, elastic. Rock deformation can be significantly large in tunnels excavated in highly stressed soft and weak rock because of vast rock failure. Deformation and flow, in physics, alteration in shape or size of a body under the influence of mechanical forces. Displacements are the absolute change in position of a point on the object.
Shear stress, which result in slippage and translation. Rigid materials such as metals, concrete, or rocks sustain large forces while undergoing little deformation, but if sufficiently large forces are applied, the materials can no longer sustain. Determination of postfailure characteristic behaviour of. There are five words used to describe rock deformation that are frequently misused. An orogen or orogenic belt develops when a continental plate crumples and is pushed upwards to form one or more mountain ranges. In plastic material, specific point of failure difficult to identify because deformation continues indefinitely at a constant level of stress. Research on deformation mechanism of surrounding rock. Other articles where elastic deformation is discussed. Deformation of p olycrystalline materials, suc hasroc k and ice, b y dislo cation glide giv es rise to a nonrandom orien tation distribution of the constituen t crystals r ib e and y u, 1991 due to in tracrystalline deformation. Deformation mechanism an overview sciencedirect topics. Up to now, a lot of studies have been performed on strength, deformation, and cracking behaviors of rock material under axial compression.
Salari department of civil engineering, faculty of engineering, ferdowsi university of mashhad, mashhad, p. Deformation mechanisms and evolution of the microstructure of gouge in the main fault in opalinus clay in the mont terri rock laboratory ch. The formation mechanism of these faults can be characterized by the shearing of joints that produces splay joints, breccia, and eventually a core of fault rock deformation mechanism 2. Plastic strain ductile deformation permanent strain. Therefore, better understanding of the mechanical properties and failure mechanism of jointed rock mass is pressing. Chapter 7 deformation mechanisms dislocation creep. Causes of rock deformation stress pressure placed on rocks strain deformation of the rock strength rock resistance to deformation brittle deformation the rocks break or fracture. Mechanics deals with the effects of forces on bodies. When stress exceeds the strength of the rock the rock will break or fracture 29. Rock mechanics an introduction for the practical engineer. Ice i h crystals deform mainly b y dislo cation glide on the basal plane, other systems b eing at least.
Experiments on the plastic deformation of single crystals, of metals and of rock salt have given results which differ in detail but possess certain common characteristics. Disaggregation band shearrelated disaggregation of grains by grain rolling, grain boundary sliding and. Complex rock slope deformation at laxiwa hydropower. Textural evolution of plagioclase feldspar across a shear zone. These are compared with rates of deformation by crystal plastic and high temperature diffusive flow processes, by using deformation mechanism. The crackseal mechanism of rock deformation nature. The deformation mechanism of surrounding rock during excavation is difficult to stability evaluation for largespan shallowburied doublearch tunnel. Mechanisms of fatiguecrack propagation in ductile and. The mechanism of deformation and fracture in potash rock. Mechanism of brittle fracture of rock in compression showing stages in the failure process 21. Textural evolution of plagioclase feldspar across a shear. The measured data in the middle of the tunnel, including settlement on the top of the tunnel and deformation between. A decrease in strain rate from to second at 2,000 bars confining pressure caused a decrease in strength at 2.