Direct observation of frictional contacts: New insights for state-dependent properties   总被引：9，自引：0，他引：9  

James H. Dieterich  Brian D. Kilgore 《Pure and Applied Geophysics》1994,143(1-3):283-302

Rocks and many other materials display a rather complicated, but characteristic, dependence of friction on sliding history. These effects are well-described by empirical rate- and state-dependent constitutive formulations which have been utilized for analysis of fault slip and earthquake processes. We present a procedure for direct quantitative microscopic observation of frictional contacts during slip. The observations reveal that frictional state dependence represents an increase of contact area with contact age. Transient changes of sliding resistance correlate with changes in contact area and arise from shifts of contact population age. Displacement-dependent replacement of contact populations is shown to cause the diagnostic evolution of friction over a characteristic sliding distance that occurs whenever slip begins or sliding conditions change.  相似文献   

A computerized method to estimate friction coefficient from orientation distribution of meso-scale faults     

《Journal of Structural Geology》2016

The friction coefficient controls the brittle strength of the Earth’s crust for deformation recorded by faults. This study proposes a computerized method to determine the friction coefficient of meso-scale faults. The method is based on the analysis of orientation distribution of faults, and the principal stress axes and the stress ratio calculated by a stress tensor inversion technique. The method assumes that faults are activated according to the cohesionless Coulomb’s failure criterion, where the fluctuations of fluid pressure and the magnitude of differential stress are assumed to induce faulting. In this case, the orientation distribution of fault planes is described by a probability density function that is visualized as linear contours on a Mohr diagram. The parametric optimization of the function for an observed fault population yields the friction coefficient. A test using an artificial fault-slip dataset successfully determines the internal friction angle (the arctangent of the friction coefficient) with its confidence interval of several degrees estimated by the bootstrap resampling technique. An application to natural faults cutting a Pleistocene forearc basin fill yields a friction coefficient around 0.7 which is experimentally predicted by the Byerlee’s law.  相似文献   

Benchmarking analogue models of brittle thrust wedges     

《Journal of Structural Geology》2016

We performed a quantitative comparison of brittle thrust wedge experiments to evaluate the variability among analogue models and to appraise the reproducibility and limits of model interpretation. Fifteen analogue modeling laboratories participated in this benchmark initiative. Each laboratory received a shipment of the same type of quartz and corundum sand and all laboratories adhered to a stringent model building protocol and used the same type of foil to cover base and sidewalls of the sandbox. Sieve structure, sifting height, filling rate, and details on off-scraping of excess sand followed prescribed procedures.Our analogue benchmark shows that even for simple plane-strain experiments with prescribed stringent model construction techniques, quantitative model results show variability, most notably for surface slope, thrust spacing and number of forward and backthrusts. One of the sources of the variability in model results is related to slight variations in how sand is deposited in the sandbox. Small changes in sifting height, sifting rate, and scraping will result in slightly heterogeneous material bulk densities, which will affect the mechanical properties of the sand, and will result in lateral and vertical differences in peak and boundary friction angles, as well as cohesion values once the model is constructed. Initial variations in basal friction are inferred to play the most important role in causing model variability.Our comparison shows that the human factor plays a decisive role, and even when one modeler repeats the same experiment, quantitative model results still show variability. Our observations highlight the limits of up-scaling quantitative analogue model results to nature or for making comparisons with numerical models. The frictional behavior of sand is highly sensitive to small variations in material state or experimental set-up, and hence, it will remain difficult to scale quantitative results such as number of thrusts, thrust spacing, and pop-up width from model to nature.  相似文献   

Characteristic friction coefficient and scale effects in oscillatory porous flow     

Dulce María Pérez-Romero  Miguel Ortega-Sánchez  Antonio Moñino  Miguel A. Losada 《Coastal Engineering》2009

This work presents a simple method to evaluate the performance of a porous breakwater when it is impinged with normal incidence by a non-breaking monochromatic wave train. It is based on: 1) a potential flow model for wave interaction with permeable structures and 2) a set of experimental tests on a rectangular porous structure with uniform granular distribution. A characteristic friction diagram is obtained considering wave energy balance in a control volume, minimising the error between the numerical model and the experimental results for the wave transmission coefficient. Results show that, for large breakwater widths, the reflection process reaches a saturation regime before the waves exit the structure at a distance from the seaside between the interval 0.2 < x/L < 0.45. For larger breakwater widths, the reflection coefficient is almost constant (except for “resonant” conditions) and wave transmission decreases exponentially. Under such conditions, the wave propagation through the porous medium depends on the relative diameter D/L and the porosity of the material; the dependence on the relative breakwater width B/L and the ratio diameter wave height D/H is weak. This diagram intends to be useful for preliminary engineering studies of breakwater's efficiency and performance and as an adequate selection criteria of the experimental stone diameter to minimize scale effects in laboratory studies.  相似文献   

边坡岩体结构的三维失稳形式及稳定性分析研究   总被引：2，自引：0，他引：2  

张菊明  王思敬 《工程地质学报》1997,5(3):242-250

由两组结构面控制的四面体块体是岩体中最基本的结构体, 其稳定性取决于块体所受荷载及结构面上的摩阻力。正确判定边界面上摩阻力分布是评价块体稳定性的关键。本文提出的块体稳定性分析适用于岩体所受荷载为三维非共点力系。在不同外力作用下块体可产生平动、转动、翘扭及倾倒等各种三维失稳组合形式, 从而得到更为合理的块体稳定性评价。  相似文献   

Behaviour of the double concave Friction Pendulum bearing     

Daniel M. Fenz  Michael C. Constantinou 《地震工程与结构动力学》2006,35(11):1403-1424

The double concave Friction Pendulum (DCFP) bearing is an adaptation of the well‐known single concave Friction Pendulum bearing. The principal benefit of the DCFP bearing is its capacity to accommodate substantially larger displacements compared to a traditional FP bearing of identical plan dimensions. Moreover, there is the capability to use sliding surfaces with varying radii of curvature and coefficients of friction, offering the designer greater flexibility to optimize performance. This paper describes the principles of operation of the bearing and presents the development of the force–displacement relationship based on considerations of equilibrium. The theoretical force–displacement relationship is then verified through characterization testing of bearings with sliding surfaces having the same and then different radii of curvature and coefficients of friction. Lastly, some practical considerations for analysis and design of DCFP bearings are presented. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

ON THE THEORIES OF HYDRAULIC GEOMETRY     

Vijay P. SINGH 《国际泥沙研究》2003,18(3)

Hydraulic geometry is of fundamental importance in planning, design, and management of river engineering and training works. Although some concepts of hydraulic geometry were proposed toward the end of the nineteenth century, the real impetus toward formulating a theory of hydraulic geometry was provided by the work of Leopold and Maddock (1953). A number of theories have since been proposed. Some of the theories are interrelated but others are based on quite different principles. All theories, however, assume that the river flow is steady and uniform and the river tends to attain a state of equilibrium or quasi-equilibrium. The differences are due to the differences in hydraulic mechanisms that the theories employ to explain the attainment of equilibrium by the river.  相似文献   

土工织物与土的直剪摩擦试验研究     

崔伟  穆乃敏等 《地质与勘探》2002,38(5):94-96

土工织物作为一种新型的建筑材料，因经济和技术及过滤、排水、隔离、加筋、防护作用的优势，国外自20世纪50年代后期，我国自70年代后期广泛应用于岩土工程的各个方面。土与织物界面相互作用的机理十分复杂，室内测试目前还处于探索和完善阶段。主要介绍土工织物与土的直剪摩擦试验方面的研究。  相似文献   

Friction of rocks   总被引：76，自引：0，他引：76  

J. Byerlee 《Pure and Applied Geophysics》1978,116(4-5):615-626

Experimental results in the published literature show that at low normal stress the shear stress required to slide one rock over another varies widely between experiments. This is because at low stress rock friction is strongly dependent on surface roughness. At high normal stress that effect is diminished and the friction is nearly independent of rock type. If the sliding surfaces are separated by gouge composed of Montmorillonite or vermiculite the friction can be very low.  相似文献   

Rupture and particle velocity during frictional sliding     

Tracy L. Johnson 《Pure and Applied Geophysics》1978,116(4-5):954-963

Summary Laboratory measurements of rupture and particle velocity are in surprisingly good agreement with seismic values, providing further evidence that stick-slip friction is a suitable mechanism for shallow earthquakes. A simple theory is developed to explain the linear relationship observed between average particle velocity and stress drop for stick-slip events. Both stick-slip ruptures and cracks in brittle material commonly propagate at velocities roughly comparable to theS wave velocity of the material. Rupture normally begins relatively slowly and accelerates to a steady velocity in a few centimeters. Observations suggest that stick-slip ruptures can propagate atS wave speeds or occasionally greater and that cracks in pre-stressed glass can also propagate faster than theS waves. Fracture and thus rupture velocity of intact rock specimens is greatly influenced by the inhomogeneous structure of rock. Fracture may be modeled by coalescence of many cracks rather than growth of a single crack.Lamont-Doherty Geological Observatory Contribution No. 2627.  相似文献