Experimental observation and realistic modeling of initiation and propagation of the rock fracture by acoustic emission

Shuhong Wang,Chung-in Lee,Seok-won Jeon,Heekwang Lee,Chun-an Tang 한국암반공학회 2006 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

It is well known that acoustic emission (AE) is indicator of rock fracturing or damage as rock is brought to failure under the uniaxial compressive loads. In this paper, an experimental study on the source location of acoustic emission on the cylindrical specimens of granite under uniaxial compression test was made. The AE source location was made by measuring the six channel AE data. Comparing to this experiment, the numerical method is applied to model the initiation and propagation of fracture by AE using a numerical code, RFPA (Realistic Failure Process Analysis). This code incorporates the mesoscopic heterogeneity in Young's modulus and rock strength characteristic of rock masses. In the numerical models, values of Young's modulus and rock strength are realized according to a Weibull distribution in which the distribution parameters represent the level of heterogeneity of the medium. The results of the simulations show that RFPA can be used not only to produce acoustic emission similar to those measurements in our experiments, but also to predict fracturing patterns under uniaxial loading condition.

Preservation Property of NBU<SUB>Mg</SUB> under Shock Models

Shuhong Zhang,Xiaohu Li 한국신뢰성학회 2003 International Journal of Reliability and Applicati Vol.4 No.2

UAV Photogrammetry and AFSA-Elman Neural Network in Slopes Vertical Displacement Monitoring and Forecasting

Shuhong Wang,Zishan Zhang,Yipeng Ren,Chengjin Zhu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.1

The monitoring and prediction of slope displacement plays a vital role in slope stability analysis. The displacement changes influences the stability of the slope. This paper described an approach to monitoring and predicting the variation of slope displacement. Firstly, The target slope was photographed from multiple angles by unmanned aerial vehicle (UAV) gimbal controller. Then an image algorithm of visual motion is applied to reconstruct the point cloud of the slope, and to get the digital elevation model (DEM) of the slope. The DEM model was used to calculate the displacement of the monitoring area. The Displacement information measured by UAV photogrammetry will be divided into training sample set and the prediction sample set. Using the AFSA-Elman algorithm neural network, the displacement sequences were trained and predict the variation of the displacement sequence. Compared with the on-site measurement results and existing Elman network, the result demonstrated that the UAV measurement technique have a high efficiency in monitoring the displacement at each measured point of the slope. And the AFSA-Elman network was proved a higher precision and better convergence comparing with the traditional Elman network, which was suitable for the predict the displacement of the key measuring point in the slope.

Analysis of the shear failure process of masonry by means of a meso-scopic mechanical modeling approach

Wang, Shuhong,Tang, Chun'an,Jia, Peng Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.2

The masonry is a complex heterogeneous material and its shear deformation and fracture is associated with very complicated progressive failures in masonry structure, and is investigated in this paper using a mesoscopic mechanical modelling, Considering the heterogeneity of masonry material, based on the damage mechanics and elastic-brittle theory, the newly developed Material Failure Process Analysis (MFPA) system was brought out to simulate the cracking process of masonry, which was considered as a three-phase composite of the block phase, the mortar phase and the block-mortar interfaces. The crack propagation processes simulated with this model shows good agreement with those of experimental observations by other researchers. This finding indicates that the shear fracture of masonry observed at the macroscopic level is predominantly caused by tensile damage at the mesoscopic level. Some brittle materials are so weak in tension relative to shear that tensile rather than shear fractures are generated in pure shear loading.

Feature-based fuzzy control adaptive finite-element mesh generation for electromagnetic fields

Wang, Shuhong,Yuan, Liang,Qiu, Jie,Wang, Semyung IEEE 2005 IEEE transactions on magnetics Vol.41 No.5

Considering the feature-based initial mesh generation and the a posteriori error estimator, a fuzzy control adaptive finite-element mesh generation method is presented. The error of potential derivative of each element is regarded as the input of fuzzy controller. Fuzzy rules and reasoning mechanism are constructed. Consequently, the size of the elements and refinement of mesh can be controlled. Applications suggest that this method has advantages such as fast convergence and reasonable element distribution, with strong adaptation.

Advanced discretization of rock slope using block theory within the framework of discontinuous deformation analysis

Wang, Shuhong,Huang, Runqiu,Ni, Pengpeng,Jeon, Seokwon Techno-Press 2017 Geomechanics & engineering Vol.12 No.4

Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at $60^{\circ}$ using combined GeoSMA-3D and DDA calculation.

Preservation Property of $NBU_{Mg}$ under Shock Models

Zhang, Shuhong,Li, Xiaohu The Korean Reliability Society 2003 International Journal of Reliability and Applicati Vol.4 No.2

We propose, in this paper, the discrete version of NBU$_{Mg}$and show that the NBU$_{Mg}$ class is preserved under both the non-homo geneous poisson shock model and the general shock model.

Three-dimensional flow simulation of transient power interruption process of a prototype pump-turbine at pump mode

Jintao Liu,Shuhong Liu,Yuekun Sun,Lei Jiao,Yulin Wu,Leqin Wang 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

The transient power failure process of a prototype pump-turbine was studied numerically by three-dimensional (3-D) simulations. Fluid coupling and dynamic mesh (DM) method were used to calculate the rotational speed of the runner. Simulations were performed based on turbulence model. Specific transient characteristics, such as the flow rate, head, rotational speed, were analyzed. The pumpturbine had a minimum head and a maximum axial force when the flow rate was 0 during the transient process. Pressure fluctuations increased when the pump-turbine ran at pump braking mode. Reverse flow in the casing as well as stall phenomenon in the runner had a great effect on the change of head. Pressure in the runner was greatly reduced when the pump-turbine ran at pump braking mode. The computational method could be used to interpret the abnormal phenomenon by the analysis of flow mechanism during a transient process.

An Outlook on the Draft-Tube-Surge Study

Michihiro Nishi,Shuhong Liu 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.1

If large pressure fluctuation is observed in the draft tube of a Francis turbine at part-load operation, we have generally called it draft-tube-surge. As occurrence of this phenomenon seriously affects the limit of turbine operating range, extensive studies on the surge have been made since proposal of surge-frequency criterion given by Rheingans. According to the literature survey of related topics in recent IAHR symposiums on hydraulic machinery and systems, in which state-of-the-art contributions were mainly presented, a certain review of them may be desirable for an outlook on the future studies in this research field. Thus, in this review paper, the authors' previous attempts for the last three decades to challenge the following topics: a rational method for component test of a draft tube, nature of spiral vortex rope and its behavior in a draft tube and cavitation characteristics of pressure fluctuations, are introduced together with other related contributions, expecting that more useful and significant studies will be accomplished in the future.

Hydraulic and Mechanical Coupling Analysis of Rough Fracture Network under Normal Stress and Shear Stress

Tianjiao Yang,Shuhong Wang,Pengyu Wang,Ze Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2

The hydraulic and mechanical coupling characteristics of fracture networks under normal stress and shear stress were studied in this paper. The hydraulic and mechanical coupling model of the fracture network comprehensively considers the normal stress, shear stress, seepage pressure and roughness characteristics. Based on the boundary conditions and reasonable assumptions, COMSOL Multiphysics software was used to develop the hydraulic and mechanical coupling finite element model of the fracture network with different intersection points under normal stress and shear stress, focusing on the study of the effect of normal stress and shear stress on the fracture permeability. The degree of permeability change caused by the normal stress and shear stress is different. The shear stress has a significant influence on the fracture permeability, and when the normal stress is low, the relationship between the fracture permeability and shear stress can be described by a linear relationship. Then, the influence of the number of intersection points in the fracture network on the average fracture width, average water pressure, average seepage velocity and seepage passage of the fractured rock mass was analyzed. The number of intersections in the fracture network has little influence on the average fracture gap width and average water pressure but has a great influence on the flow velocity. The analysis in this paper is very helpful to understand the seepage characteristics in rough fractures under normal stress and shear stress.