3D-DDM Simulation of Crack Propagation of Non-Linear Deformation Structural Plane

2011 ◽  
Vol 368-373 ◽  
pp. 2673-2678
Author(s):  
Ke Li ◽  
Ying Yi Wang ◽  
Xing Chun Huang
Keyword(s):  
Strength Criterion ◽  
Maximum Energy ◽  
Least Square ◽  
Displacement Discontinuity ◽  
Deformation Model ◽  
Linear Deformation ◽  
Structural Plane ◽  
Non Linear ◽  
Coulomb Criterion ◽  
Energy Release Rate Criterion

Structural plane is different from common crack, as it is often under pressure and has non-linear normal and tangential deformation behavior. This paper simulates the propagation of non-linear deformation structural plane by 3D displacement discontinuity method (DDM). Through least square regression of the elements near the tip, the stress intensity factor (SIF) of the tip is obtained. Maximum energy release rate criterion is adopted to be the fracture criterion in this paper, assuming the propagation occurred in the normal plane of the front edge, KI is modified to consider the effect of mode Ⅲ crack. The structural plane model is considered as a hyperbolic non-linear model, the Barton-Bandis model is adopted as the normal deformation model, the Kulhaway model is adopted as the tangential deformation model, and the Mohr-Coulomb criterion is adopted as the shear strength criterion. The result shows that the propagation direction is along the direction of the load, DDM could efficiently trace this process.

DDM Analysis of the Effect of Non-Linear Structural Plane on In Situ Stress Field

2011 ◽  
Vol 368-373 ◽  
pp. 2667-2672
Author(s):  
Ke Li ◽  
Ying Yi Wang ◽  
Xing Chun Huang
Keyword(s):  
Stress Concentration ◽  
Stress Field ◽  
Friction Angle ◽  
In Situ Stress ◽  
Displacement Discontinuity ◽  
Linear Deformation ◽  
Structural Plane ◽  
Non Linear ◽  
In Situ Stress Field

Based on the Barton-Bandis non-linear deformation structural plane model, displacement discontinuity method (DDM) is used to iteratively calculate the distribution of in-situ stress field around the structural plane, and then the parameter sensitivity analysis of the structural plane and rock is carried out. The results show that near the structural plane, especially near the tips, stress concentration is quite significant, the closer to the tips, the greater the principal stress difference is; the stress concentration around the structural plane decreases as the stiffness of structural plane grows; with the growth of the ratio of structural plane thickness to length, the stress concentration around the structural plane increases, but when reaching a certain level, the increasing slows down; as the friction angle of the structural plane grows, the stress concentration decreases.

scholarly journals Deformation of rockfill in bodies of rockfill dams

2019 ◽  
pp. 5-5
Author(s):  
Mikhail Sainov
Keyword(s):  
Reinforced Concrete ◽  
Deformation Modulus ◽  
Deformation Model ◽  
Observation Data ◽  
Linear Deformation ◽  
Laboratory Test Results ◽  
Wide Range ◽  
Deformation Properties ◽  
Non Linear ◽  
The Impact

Introduction. The main factor determining the stress-strain state (SSS) of rockfill dam with reinforced concrete faces is deformability of the dam body material, mostly rockfill. However, the deformation properties of rockfill have not been sufficiently studied yet for the time being due to technical complexity of the matter, Materials and methods. To determine the deformation parameters of rockfill, scientific and technical information on the results of rockfill laboratory tests in stabilometers were collected and analyzed, as well as field data on deformations in the existing rockfill dams. After that, the values of rockfill linear deformation modulus obtained in the laboratory and in the field were compared. The laboratory test results were processed and analyzed to determine the parameters of the non-linear rockfill deformation model. Results. Analyses of the field observation data demonstrates that the deformation of the rockfill in the existing dams varies in a wide range: its linear deformation modulus may vary from 30 to 500 МPа. It was found out that the results of the most rockfill tests conducted in the laboratory, as a rule, approximately correspond to the lower limit of the rockfill deformation modulus variation range in the bodies of the existing dams. This can be explained by the discrepancy in density and particle sizes of model and natural soils. Only recently, results of rockfill experimental tests were obtained which were comparable with the results of the field measurements. They demonstrate that depending on the stress state the rockfill linear deformation modulus may reach 700 МPа. The processing of the results of those experiments made it possible to determine the parameters on the non-linear model describing the deformation of rockfill in the dam body. Conclusions. The obtained data allows for enhancement of the validity of rockfill dams SSS analyses, as well as for studying of the impact of the non-linear character of the rockfill deformation on the SSS of reinforced concrete faces of rockfill dams.

scholarly journals A Macroscopic Strength Criterion for Isotropic Metals Based on the Concept of Fracture Plane

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 634 ◽  
Author(s):  
Jiefei Gu ◽  
Puhui Chen ◽  
Ke Li ◽  
Lei Su
Keyword(s):  
Predictive Ability ◽  
Strength Criterion ◽  
Strength Parameter ◽  
Fracture Plane ◽  
Compression Tests ◽  
Failure Function ◽  
Linear Behavior ◽  
Non Linear ◽  
Tension And Compression ◽  
Coulomb Criterion

Although the linear Mohr–Coulomb criterion is frequently applied to predict the failure of brittle materials such as cast iron, it can be used for ductile metals too. However, the criterion has some significant deficiencies which limit its predictive ability. In the present study, the underlying failure hypotheses of the linear Mohr–Coulomb criterion were thoroughly discussed. Based on Mohr’s physically meaningful concept of fracture plane, a macroscopic strength criterion was developed to explain the failure mechanism of isotropic metals. The failure function was expressed as a polynomial expansion in terms of the stresses acting on the fracture plane, and the quadratic approximation was employed to describe the non-linear behavior of the failure envelope. With an in-depth understanding of Mohr’s fracture plane concept, the failure angle was regarded as a generalized strength parameter in addition to the failure stress (i.e., the conventional basic strength). The undetermined coefficients of the non-linear failure function were calibrated by the strength parameters obtained from the common uniaxial tension and compression tests. Theoretical and experimental assessment for different types of isotropic metals validated the effectiveness of the proposed criterion in predicting material failure.

scholarly journals Constructing Adaptive Deformation Models for Estimating DEM Error in SBAS-InSAR Based on Hypothesis Testing

2021 ◽  
Vol 13 (10) ◽  
pp. 2006
Author(s):  
Jun Hu ◽  
Qiaoqiao Ge ◽  
Jihong Liu ◽  
Wenyan Yang ◽  
Zhigui Du ◽  
...  
Keyword(s):  
Time Series ◽  
Hypothesis Testing ◽  
Surface Deformation ◽  
A Priori ◽  
Least Square ◽  
Deformation Model ◽  
Phase Time ◽  
Testing Theory ◽  
Sbas Insar ◽  
Deformation Models

The Interferometric Synthetic Aperture Radar (InSAR) technique has been widely used to obtain the ground surface deformation of geohazards (e.g., mining subsidence and landslides). As one of the inherent errors in the interferometric phase, the digital elevation model (DEM) error is usually estimated with the help of an a priori deformation model. However, it is difficult to determine an a priori deformation model that can fit the deformation time series well, leading to possible bias in the estimation of DEM error and the deformation time series. In this paper, we propose a method that can construct an adaptive deformation model, based on a set of predefined functions and the hypothesis testing theory in the framework of the small baseline subset InSAR (SBAS-InSAR) method. Since it is difficult to fit the deformation time series over a long time span by using only one function, the phase time series is first divided into several groups with overlapping regions. In each group, the hypothesis testing theory is employed to adaptively select the optimal deformation model from the predefined functions. The parameters of adaptive deformation models and the DEM error can be modeled with the phase time series and solved by a least square method. Simulations and real data experiments in the Pingchuan mining area, Gaunsu Province, China, demonstrate that, compared to the state-of-the-art deformation modeling strategy (e.g., the linear deformation model and the function group deformation model), the proposed method can significantly improve the accuracy of DEM error estimation and can benefit the estimation of deformation time series.

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