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1.
Caving-induced fault reactivation and its effects on caving process are widely recognized as serious safety issues in mining and tunnelling industry. In this study, the effects of a variety of factors (i.e. friction coefficient, stick–slip instability, geological structure, pre-mining status, mining and its induced effects) that might exert an influence on fault dynamic behaviour of a 5-seam coal mine are investigated using practical mine-wide finite element numerical models with a normal fault. Based on the research outcomes on R-minimum-based finite element modelling of earthquake dynamics, the node-to-point contact strategy and the nonlinear friction contact law have been used here to simulate and analyse the caving-induced stick–slip frictional instability along the fault and related effects. The simulation results show that: (1) stress distribution before mining is relatively uniform around the fault for a homogenous rock material case, while stress concentration appears around the fault for the model with contrasting rock material properties; (2) the multiple-layered models are in favour of fault reactivation than models with only one material for whole strata; (3) the fault reactivation scale (i.e. dynamic relative motion and fault slip) induced by caving activity is significantly affected by rock mass strength, caving depth and its relative position to the fault. As caving progresses deeper and closer to the fault, the fault reactivation scale increases. Meanwhile, the fault in low strength strata is much more sensitive to fault slip behaviour; (4) seismic source parameters, namely seismic moment and moment magnitude, are adopted to evaluate the magnitude of caving-induced seismicity based on numerical results and fault slip risk and magnitude increase as fault reactivation scale expands; (5) during the caving stage, the failure zone initiates, develops and eventually connects the reactivated fault to the working area, presenting asymmetric failure pattern around the caving zone. The failure zone is obviously larger for the side closer to the fault than the other side due to caving-induced fault reactivation effects. This could help in better understanding fault reactivation and rock failure behaviours towards an optimised design of caving in a faulted region.
相似文献2.
We present an extended finite element (FE) approach for the simulation of slow‐rate frictional faulting in geologic media incorporating bulk plasticity and variable friction. The method allows the fault to pass through the interior of FEs without remeshing. The extended FE algorithm for frictional faulting, advocated in two recent articles, emanates from a variational equation formulated in terms of the relative displacement on the fault. In the present paper we consider the combined effects of bulk plasticity and variable friction in a two‐dimensional plane strain setting. Bulk plasticity is localized to the fault tip and could potentially be used as a predictor for the initiation and propagation of new faults. We utilize a variable velocity‐ and state‐dependent friction, known as the Dieterich–Ruina or ‘slowness’ law, formulated in a slip‐weakening format. The slip‐weakening/variable friction model is then time‐integrated according to the generalized trapezoidal rule. We present numerical examples demonstrating the convergence properties of a global Newton‐based iterative scheme, as well as illustrate some interesting properties of the variable friction model. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
The slip rate predicted from geodetic and geomorphological measurements is quite uniform on ~800–1,000 km length of the Altyn Tagh and the Kunlun faults. GPS velocity field documents that tectonic loading on the two active faults changes greatly along their strikes. To explore the mechanical relationship between far‐field tectonic loading and fault slip‐rate accumulation, we built a 3D viscoelastic finite‐element model with fault motion governed by frictional strength of contact interfaces. Based on numerical experiments, it is found that the observed uniform slip rate could reflect lateral variation of frictional strength along fault strike. Variation of predicted frictional coefficient ranges from ~0.13 to ~0.02, verifying that the two active faults must be weak for their mechanical strength. In addition, the good fitness between the relatively weak segment of faults and the location of strong earthquakes suggests that seismic activity along the two faults could be related to their frictional strength. 相似文献
4.
We use three‐dimensional mechanical modelling with fault as Coulomb‐type frictional surface to explore the active deformation of the Xianshuihe–Xiaojiang fault system in south‐eastern Tibet. Crustal rheology is simplified as an elastoplastic upper crust and a viscoelastic lower crust. Far‐field GPS velocities and Quaternary fault slip rates are used to constrain the model results. Numerical experiments show that effective fault friction lower than ∼0.1–0.08 leads to a high slip rate that fits well with geological estimates of the slip rate on the fault system. Associating with the modelled fault slip rate, strain in the surrounding crust distributes broadly, and is partitioned into strike–slip and thrust senses. This means that in the Indian‐Eurasia convergence, accommodation of the large fraction of sinistral motion on the fault system is achieved mainly due to its lower fault friction. This in turn affects crustal deformation around the south‐eastern Tibetan margin, resulting in negligible compression across the Longmen Shan. 相似文献
5.
《Journal of Structural Geology》2003,25(10):1569-1574
High-velocity friction experiments on gabbro and monzodiorite, using a rotary-shear high-velocity friction apparatus, have revealed that frictional melting and progressive growth of a molten layer along a fault cause slip weakening, eventually reaching a nearly steady-state. The melting surface at the host rock/molten layer interface is initially very flat, but it becomes more complex and rounded in shape towards the steady state owing to the selective melting of minerals with lower melting points and the Gibbs–Thomson effect. This change in the melting-surface topography can be quantitatively expressed by the fractal dimension D, as determined by the divider method, from about 1.0 near the peak friction to around 1.1 near the steady-state friction. The ultimate fractal dimension at steady-state friction tends to decrease with increasing heat production rate presumably due to more rapid and uniform melting. A systematic correlation of D with mechanical behavior of the fault during frictional melting may provide a way of estimating slip-weakening distance and heat production rate at steady-state friction by measuring D for natural pseudotachylytes on slip surfaces with different displacements. The weakening distance is of vital significance in relation to fault instability and the heat production rate is related to the fault strength. The experimental studies point to ways to estimate these difficult quantities for natural faults. 相似文献
6.
断层作用热模型及其对烃源岩热演化的影响 总被引：1，自引：0，他引：1
从盆地的应力状态分析入手,从断层摩擦生热的角度,建立了断层作用生热的定量模型。在此基础上,确定了断层摩擦产生的热量与断层的性质、深度、构造应力和流体压力等之间的定量关系,定量分析了断层摩擦生热对烃源岩热演化的影响。结果表明:断层作用的生热量主要决定于断层的深度,构造应力的大小、流体压力、断层的位移量、断面摩擦系数等;断层的活动速率对断层摩擦的生热量没有影响,但对断层带内产生的温度却起决定性的作用;在断层快速活动的条件下(地震型),断层摩擦生热虽然可以产生很高的温度,可以造成断层面附近岩石的局部熔融,但其影响范围和影响持续的时间是十分有限的。 相似文献
7.
A new model for three-dimensional non-linear contact problems with irreversible friction is presented here for the interaction between the rock foundation and an arch dam structure. Based on the finite element method and load incremental theory, a constraint contact element with displacements and contact stresses as node parameters is developed. In this approach, four contact conditions are considered, i.e. fixed, slip, free and mixed. This model can simulate frictional slippage, decoupling and re-bonding of two bodies initially mating at a common interface or with any initial gaps. Furthermore boundary conditions for this element are discussed and treatment measures proposed. This method is shown to be effective and to have the advantage of being easily implemented into standard finite element programs. Solutions are obtained for a centrally loaded, simply supported composite beam and for an end-loaded elastica with initial gaps in regional contact with a rigid surface. The results obtained for these examples are compared to the plane stress solutions by contact friction analysis. As an application example, Quanshui arch dam located in Ruyuan County of Guangdong Province in southern China is simulated with the new element. 相似文献
8.
A new finite element model based on a large strain formulation has been developed to study cone penetration in normally consolidated sand. An auto‐adaptive remeshing technique was utilized for handling the very large distortion of sand surrounding the cone tip. A frictional contact interface utilizing Mohr–Coulomb's theory was chosen to represent interactions between the surface of the cone and sand. To model the sand behaviour, the non‐associated Drucker–Prager constitutive model was selected. ABAQUS, a commercial finite element software package, was used to implement the model. The explicit solution algorithm was chosen due to its effectiveness for complicated contact problems. Analysis results proved that the model successfully captured the cone penetration behavior in sand. In addition, a chart to predict internal friction angles based on cone tip resistance for different vertical effective stresses was provided. This paper also shows a typical distribution of sleeve resistance, tip resistance—penetration relationship, and typical contours of vertical, horizontal, and shear stresses in normally consolidated sand. Finally, a non‐uniform resistance was found along the length of the friction sleeve. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
针对常规摩擦阻尼器的起滑力难以确定的问题,提出了复合摩擦阻尼系统（CFDS）,它由非线性硬弹簧和摩擦阻尼器串联而成。当地震较小时,摩擦阻尼器处于附着状态,非线性硬弹簧发挥作用,防止隔震层位移过大;当地震较大时,非线性硬弹簧的变形则保持不变,摩擦阻尼器处于滑动状态,通过摩擦阻尼耗散能量。建立了带有复合摩擦阻尼系统的基础隔震结构的运动方程,指出摩擦阻尼器处于附着和滑移2种状态下边界条件。据此研究了常规强震和近断层脉冲型地震动作用下复合摩擦阻尼装置对橡胶隔震结构的减震效果。仿真分析表明：安装复合摩擦阻尼系统,在显著降低隔震层位移的同时,对上部结构的层间位移和加速度均有一定的减震效果;并且,在整个运动过程中,摩擦阻尼器会在附着和滑移2种状态之间来回切换。详细研究了复合摩擦阻尼系统的３个参数对隔震结构的减震效果。结果表明：在不同地震波作用下,由于摩擦阻尼系统参数的变化导致隔震结构地震响应的变化趋势是不同的,因此最优参数的取值与输入地震波类型和地面加速度峰值有关,并且不存在使隔震层位移和上部结构加速度同时达到最小的最优参数,因此需要设定合适的控制目标以确定适当的阻尼系统参数。 相似文献
10.
A numerical simulation of kinetic friction function in the fracture process of rocks in the framework of General Particle Dynamics (GPD) is performed in this paper. The frictional algorithm is implemented into the General Particle Dynamics code (GPD) to describe frictional behavior of particles, where frictional forces among discrete particles are formulated using the principle of balance of two forces based on ideal plastic contact between two surfaces of solids. In General Particle Dynamics code (GPD), interaction among discrete particles is formulated using the virtual-bond method. Fractures of virtual bonds among particles are determined through the Hoek-Brown damage evolution law of rock materials. Three numerical cases are to verify the stability and accuracy of the numerical algorithm. Then, the numerical results are compared with analytical solutions and experimental results. It is found that the numerical results are in good agreement with the experimental ones. 相似文献
11.
Contact between stiff structural elements and soil is encountered in many applications in geotechnical engineering. Modelling of such contact is challenging as it often involves impact that would lead to large deformation and failure of the soil. The Material Point Method (MPM) is a mesh‐free method that has been applied to simulate such phenomena. However, the frictional contact algorithm commonly used in MPM only supports Coulomb friction and cannot model fully or partially rough contact conditions in terms of geotechnical engineering. Moreover, because of very different stiffness of contacting materials, the contact force predicted by the previous frictional contact algorithms usually suffers from severe oscillation when applied in structure–soil interaction. This paper presents a new contact algorithm, termed Geo‐contact, designed for geotechnical engineering. In Geo‐contact, a penalty function is incorporated to reduce the oscillation in contact computation, and a limited shear stress is specified along the contact interface. The proposed Geo‐contact algorithm has been implemented to simulate smooth, partially rough and rough contact in typical large deformation penetration problems. The resistance–displacement curves obtained using the Geo‐contact are compared with analytical solutions of limit analysis and large deformation finite element results to verify the accuracy and robustness of the proposed contact algorithm. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
QIN Xianghui CHEN Qunce FENG Chengjun DU Jianjun WU Manlu MENG Wen and SUN Dongsheng 《《地质学报》英文版》2016,90(2):567-577
The present-day stress state of the Yingxiu-Beichuan fault after the Wenchuan earthquake was re-estimated using measured in-situ stress data obtained after the Wenchuan earthquake. The results reveal that the gradient coefficients of principal stresses versus depth decrease from south to north along the Yingxiu-Beichuan fault, revealing that the stress level decreases from south to north. The consistency between the present-day stress levels and surface ruptures generated during the earthquake indicates that the accumulated tectonic stress beneath the Yingxiu-Beichuan fault before the Wenchuan earthquake was relieved in form of surface ruptures. This resulted in the stress remaining high in the southern section of the Yingxiu-Beichuan fault but relatively low in the northern section. Abnormal high pore pressure conditions and an extremely low frictional coefficient play important role in the interpretation of the stress field adjustment and seismic events observed after the Wenchuan earthquake along this fault, according to the estimation results using the Coulomb frictional-failure theory incorporating frictional coefficients ranging from 0.4 to 1.0. To accurately estimate the seismological hazard of the Yingxiu-Beichuan fault by analyzing fault instability using the Coulomb frictional-failure theory, much attention should be focused on the pore pressure conditions and the evolution state of the frictional coefficient under the present-day stress state. 相似文献
13.
Simulation of frictional contact between soils and rigid or deformable structure in the framework of smoothed particle hydrodynamics (SPH) is presented in this study. Two algorithms are implemented into the SPH code to describe contact behavior, where the contact forces are calculated using the law of conservation of momentum based on ideal plastic collision or using the criteria of partial penetrating. In both algorithms, the problem of boundary deficiency inherited from SPH is properly handled so that the particles located at contact boundary can have precise acceleration, which is critical for contact detection. And the movement and rotation of the rigid structure are taken into account so that it is easy to simulate the process of pile driving or movement of a retaining wall in geotechnical engineering analysis. Furthermore, the capability of modeling deformability of a structure during frictional contact simulations broadens the fields of SPH application. In contrast to previous work dealing with contact in SPH, which usually use particle‐to‐particle contact or ignoring sliding between particles and solid structure, the method proposed here is more efficient and accurate, and it is suitable to simulate interaction between soft materials and rigid or deformable structures, which are very common in geotechnical engineering. A number of numerical tests are carried out to verify the accuracy and stability of the proposed algorithms, and their results are compared with analytical solutions or results from finite element method analysis. Good agreement obtained from these comparisons suggests that the proposed algorithms are robust and can be applied to extend the capability of SPH in solving geotechnical problems. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
14.
Michael G. Katona 《国际地质力学数值与分析法杂志》1983,7(3):371-384
A simple friction–contact interface element is introduced which simulates frictional slippage, separation, and re-bonding of two bodies initially mating at a common interface and subsequently deforming with an arbitrary static loading schedule. Constraint equations between initially mating node pairs and the general principle of virtual work are used to formulate the interface element for a finite element solution procedure. Some advantages of the interface element include; easy implementation intostandard finite element programs, direct determination of interface forces without round-off problems, and the generality afforded by the virtual work formulation to include other non-conservative models in the system. The application of the interface element to an idealized buried culvert problem illustrates that the model behaves properly. A second application, for a long-span culvert installation with incremental soil loading, demonstrates the importance of modelling slippage at the culvert–soil interface in order to conform with experimental observations. 相似文献
15.
Three‐dimensional numerical analysis of concrete‐faced rockfill dam using dual‐mortar finite element method with mixed tangential contact constraints 
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下载免费PDF全文 Concrete‐faced rockfill dam (CFRD) is a popular alternative to traditional dam types in the last two decades. The modelling of CFRD involves complex multi‐body contact and strong geometry and material nonlinearities. We present a numerical approach for the modelling of CFRDs in this paper. Based on the dual‐mortar finite element method, the presented approach considers different parts of rockfill and all concrete slabs as independent deformable continuum. The multi‐body contacts are modelled using Lagrange multipliers with a weak form segment‐to‐segment contact strategy. To alleviate instability induced by strong geometry nonlinearity in the slab–slab contact, we propose a mixed type of constraints for the tangential contact. A general transformation scheme is introduced to simplify the implementation of contact constraints. Three‐dimensional analysis of Tianshengqiao‐1 CFRD is performed. The nonlinear and time‐dependent deformation of the rockfill is considered. We study the influence of the rockfill deformation on the reliability of the concrete face. Three major concerns of the face, that is, the axial compression, the slab–slab separation and the face‐rockfill separation, are discussed in detail. The numerical results are compared with data from in‐situ observation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
16.
深部岩体具有块状层次结构,深部动载造成岩块发生相互间的振动脱离产生低摩擦效应,从而极易诱发原先处于平衡状态的岩体的动力变形破坏。在前人研究基础上,将块系岩体振动简化为等效质量-黏弹性模型,引入岩石摩擦滑移速率弱化模式,最终得到块系岩体滑移失稳计算模型。通过计算分析块系岩体自身特性及外荷载特性对岩块间低摩擦效应的影响。理论计算表明：水平静力及外扰动保持不变,增大岩块间弹性系数或者减小黏性系数,更容易引发岩体低摩擦滑移。随着冲击扰动、水平拉力幅值的增加,岩块的水平残余位移量值增加,当它们幅值超过一临界值时,岩块发生自持续滑移失稳运动。冲击扰动诱发岩块间不可逆位移、动力滑移失稳的临界能量与剪切力水平密切相关,在较大的剪切内力条件下,极其微弱的动力扰动即可诱发较大的岩块间不可逆位移甚至岩块的动力滑移失稳,随着剪切内力的减小,诱发岩块滑移失稳的能量阈值不断增大,当剪切内力低于岩块动摩擦强度时,单次冲击扰动只能诱发岩块间的不可逆位移。初步开展扰动诱发含初应力紫砂岩块体滑移试验,试验结果与理论计算基本符合,证明该模型的可行性。 相似文献
17.
The paper deals with constitutive modelling of contiguous rock located between rock joints. A fully explicit kinematically constrained microplane‐type constitutive model for hardening and softening non‐linear triaxial behaviour of isotropic porous rock is developed. The microplane framework, in which the constitutive relation is expressed in terms of stress and strain vectors rather than tensors, makes it possible to model various microstructural physical mechanisms associated with oriented internal surfaces, such as cracking, slip, friction and splitting of a particular orientation. Formulation of the constitutive relation is facilitated by the fact that it is decoupled from the tensorial invariance restrictions, which are satisfied automatically. In its basic features, the present model is similar to the recently developed microplane model M4 for concrete, but there are significant improvements and modifications. They include a realistic simulation of (1) the effects of pore collapse on the volume changes during triaxial loading and on the reduction of frictional strength, (2) recovery of frictional strength during shearing, and (3) the shear‐enhanced compaction in triaxial tests, manifested by a deviation from the hydrostatic stress–strain curve. The model is calibrated by optimal fitting of extensive triaxial test data for Salem limestone, and good fits are demonstrated. Although these data do not cover the entire range of behaviour, credence in broad capabilities of the model is lend by its similarity to model M4 for concrete—an artificial rock. The model is intended for large explicit finite‐element programs. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
18.
Serpentinite bodies within the Franciscan Complex, a Mesozoic accretionary prism located in California, USA, display a unique form of deformation that involves the recrystallization of chrysotile and the formation of a block‐in‐matrix structure. The phacoidal‐shaped blocks have a preferred orientation, and result from the local replacement of serpentine minerals by chrysotile grains that are aligned parallel to ductile shear planes such as S–C foliation; ultimately, some of the rocks evolved into chrysotile schist. The relic blocks are also fragmented into multiple parts, with the spaces between fragments being infilled by recrystallized chrysotile. The low coefficient of friction of chrysotile means that this deformation process acts to suppress the frictional properties of the entire serpentinite body within the forearc mantle. This phenomenon can be attributed to the slip style that occurs in aseismic regions of subduction zones in areas shallower than the stability field of antigorite. 相似文献
19.
Rock friction varies as a function of mainly four parameters that are waiting time and velocity of motion between two frictional surfaces, surface roughness and normal stress. In this paper, a study on former two aspects of rock frictional behaviour has been attempted for granitic rock surface. In one experiment, waiting time for which the two surfaces remain in contact is increased from 20 seconds to 18 hours. In the second experiment, waiting time is kept constant for a series of rock slip experiments where the velocity is increased from 10??m/sec to 350??m/sec. The value of critical velocity is obtained from transformation of the stick slip motion to steady motion occurs. The relation of coefficients of dynamic and static friction with increasing velocity of motion is studied and these are used to calculate the frictional constants, namely ??a?? and ??b?? specific to the chosen simulation type. 相似文献
20.
Naoyuki Kato Takashi Satoh Xinglin Lei Kiyohiko Yamamoto Tomowo Hirasawa 《Tectonophysics》1999,310(1-4):81-99
An experimental study of stick-slip is performed to examine the effect of a fault bend on the dynamic rupture propagation process. A granite sample used in the experiment has a pre-cut fault that is artificially bent by an angle of 5.6° at the center of the fault along strike, and accordingly the fault consists of two fault segments. The rupture propagation process during stick-slip instability is investigated by analyzing the records of shear strain and relative displacement measured with strain gauge sensors together with the hypocenters of AE (acoustic emission) events detected with piezoelectric transducers. The observed rupture propagation process of typical stick-slip events is as follows. (1) The dynamic rupture started on a fault segment is stopped near the fault bend. (2) The rupture propagation is restarted near the bend on the other fault segment 10.8 ms to 3.5 s after the stop of the first rupture. The delay time of the second rupture decreases with an increase in the slip amount of the first rupture or a decrease in the normal stress acting on the fault segment where the second rupture started. (3) The restarted rupture is not arrested by the presence of a fault bend, and slip occurs over the entire fault. We theoretically analyze the stress concentration near the fault bend to find that the normal stress produced by the preceding slip near the fault bend plays an important part in controlling the rupture propagation. A numerical simulation based on a rate- and state-dependent friction law is performed to interpret physically the retarded rupture in the experiment. The observed time interval of 10.8 ms to 3.5 s between the first rupture and the second is explained by the numerical simulation, suggesting that the rate- and state-dependence of rock friction is a possible mechanism for the retarded rupture on the fault. 相似文献