Papers by Keyword: Rock Material

Abstract: The article considers the effectiveness of using bitumen emulsion in technologies for dedusting sections of the Vilyui A-331 federal highway. The sections allocated for the work have transitional coatings of sand and gravel (crushed stone), crushed stone sand and gravel mixtures. Their wear degree is up to 100% and they belong to dust-forming and highly dusting ones. The average traffic intensity on Vilyui A-331 highway is 937 units per day. The efficiency of technologies for dedusting coatings of transitional type has been evaluated and the prospects of using cationic bitumen emulsions for these purposes have been shown.

Abstract: Through introduction of meso-damage theory and application situation in recent years, the related categories and mechanism of meso-damage were analyzed. The previous research on the application of the meso-damage of various materials was discussed and various research results analyzed. The emphasis and advantages of meso-damage theory in material application were concluded.

Abstract: Acoustic emission (AE) is defined as a transient elastic wave generated by the rapid release of energy within a material. Crack initiation, phase transition and rupturing in rock materials are all detectable with the measurement of AE signals, and therefore such measurement helps to understand the underlying mechanism (s) of macroscopic deformation. In this study of the deformation mechanism (s) of rock samples, simultaneous measurements of the neutron diffraction pattern and AE signals were performed using the Engineering Materials Diffractometer TAKUMI at the Japan Proton Accelerator Research Complex (J-PARC). Two types of rock sample were tested in the experiments: sandstone and carbonate rock. A discrepancy was found between macroscopic strain (measured by strain gauge) and lattice strain (measured by neutron diffraction), and AE signals that would be generated by grain slip and pore collapse in rock samples were detected. Macroscopic strain in the rock samples was associated not only with lattice strain but also with mineral grain slip and pore collapse within the rock. The combination of AE signal measurements and neutron diffraction is an effective tool for investigating the deformation mechanisms of rock materials.

Abstract: In this paper, firstly we utilize the elastic model, which provides the simplest representation of material behavior in civil engineering. This model is valid for homogeneous, isotropic, continuous materials that exhibit linear stress-strain behavior with no hysteresis on unloading. The elastic models include both isotropic and anisotropic elastic models. Then the Mohr-Coulomb model is used which can represent shear failure in soils and rocks in civil engineering and geotechnical engineering. After that, the strain- softening model is founded, which allows representation of nonlinear material softening and hardening behavior based on prescribed variations of the Mohr-Coulomb model properties (cohesion, friction, dilation, tensile strength) as functions of the deviatoric plastic strain. Finally, a case study is done for the stratified rock mass, the elastic modulus of the rock sample for different surrounding compressive are obtained, to exhibit the anisotropy characteristic of this type of rock material

Abstract: All rock mass engineering projects are closely related to rock mass material property. The methods of obtaining these properties decides the project design’s safety and reasonable. The varied characteristics of rock mass under force are subjected by their texture, construction and tectonic history. The experimental results imply that the rock mass strength, deformation and failure modes are all effected by following aspects, including the test controlling method, machine stiffness and the sample size, etc,. In order to use the test results to guide the practice projects, we must first know the natural status and engineering propagation process of rock mass, then design suitable experimental scheme, subsequently, the more fit for the natural results of rock changed process will be appear. According to the analysis of previous research achievement and newly test results, we can investigate the rock mass stability and predict its failure.

Abstract: A digital image processing method based on partial differential equation(PDE) for rock’s heterogeneity is introduced. The actual microstructures of the rock sample was obtained by multiphase level set method. The main components of granite, quartz, feldspar and biotite, can be easily identified. The numerical results show that the method has advantage of self-adaptation and is benefit for grid generation in the following mechanical properties analyzing with Abaqus.

Abstract: Mechanical parameter analysis is a complicated issue since it is influenced by many factors. Closely related with the influencing factors of compressibility coefficients of rock material (sandstone), this article first introduces the way to process partial least square regression (PLSR) analysis. The process of carrying out PLSR is divided into six steps as for analysis and prediction of the regression model, which are data preparation, principle collection, regression model for first principle component, secondary principle analysis, establishment of final regression model and number determination of principal component l. And then introduces PLSR for application of analysis and prediction of compressibility coefficients with 30 experiment samples. Seven prediction samples are carried out by PLSR with the training process of 30 samples. The result shows PLSR has good accuracy in prediction under the condition that the model is properly deprived based on certain experimental samples. Finally, some conclusions are made for further study on both mechanical parameters and partial least square regression method.

Abstract: Based on the assumption of one-dimensional specimens and stress distribution hypothesis，SHPB experiment is used to analysis dynamic characteristics of materials. But it is impossible for the transverse inertia and the friction on the surfaces of specimen. A model is established in order to evaluate the degree of influence of horizontal specimen inertia and friction on the experimental results. Moreover, the model is applied to discuss the transverse inertia effect influence on elastic modulus of materials.

Abstract: A 3D anisotropic elastoplastic-damage model was presented based on continuum damage mechanics theory. In this model, the tensor decomposition technique is employed. Combined with the plastic yield rule and damage evolution, the stress tensor in incremental format is obtained. The derivate eigenmodes in the proposed model are assumed to be related with the uniaxial behavior of the rock material. Each eigenmode has a corresponding damage variable due to the fact that damage is a function of the magnitude of the eigenstrain. Within an eigenmodes, different damage evolution can be used for tensile and compressive loadings. This model was also developed into finite element code in explicit format, and the code was integrated into the well-known computational environment ABAQUS using the ABAQUS/Explicit Solver. Numerical simulation of an uniaxial compressive test for a rock sample is used to examine the performance of the proposed model, and the progressive failure process of the rock sample is unveiled.

Abstract: Manifold Method provides a unified framework for solving problems with both continuous and discontinuous media. In this paper, by introducing a criterion of crack initiation and propagation, the second order manifold method is used to simulate two-hole blasting and Hopkinson spalling of rock. In the study of two-hole blasting, two different initiation conditions are considered. One is simultaneous initiation, the other is 0.1 ms delay initiation. The whole blasting process including crack initiation, crack growth and fragment formation is simulated. In the study of Hopkinson spalling, the propagation and interaction of stress waves and the spalling process caused by a reflected tensile stress wave are reproduced. The simulation results including the thickness of the formed scab and its velocity are in good agreement with theoretical values. Manifold method proves to be an efficient method in the study of dynamic fracture of rock.