scholarly journals Distribution of Cracks in an Anchored Cavern Under Blast Load Based on Cohesive Elements

2021 ◽  
Author(s):  
Yi Luo ◽  
Chenhao Pei ◽  
Dengxing Qu ◽  
Xinping Li ◽  
Ruiqiu Ma ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Side Wall ◽  
Blast Load ◽  
Shear Cracks ◽  
Cohesive Elements ◽  
Peak Displacement ◽  
Tensile Cracks ◽  
Crack Propagation Process ◽  
The Difference ◽  
Dip Angle

Abstract To explore the distribution of cracks in anchored caverns under the blast load, cohesive elements with zero thickness were employed to simulate crack propagation through numerical analysis based on a similar model test. Furthermore, the crack propagation process in anchored caverns under top explosion was analysed and the distribution and mode of propagation of cracks in anchored caverns when a fracture with different dip angles was present in the vault were discussed. With the propagation of the explosive stress waves, cracks successively occur at the boundary of the anchored zone of the vault, arch foot, and floor of the anchored caverns. Tensile cracks are preliminarily found in rocks surrounding the caverns. In the case that a pre-fabricated fracture is present in the upper part of the vault, the number of cracks at the boundary of the anchored zone of the vault decreases, then increases with increasing dip angle of the pre-fabricated fracture. The fewest cracks at the boundary of the anchored zone occur if the dip angle of the pre-fabricated fracture is 45º. The wing cracks deflected to the vault are formed at the tip of the pre-fabricated fracture, around which tensile and shear cracks are synchronously present. Under top explosion, both the peak displacement and peak particle velocity in surrounding rocks of anchored caverns reach their maximum values at the vault, successively followed by the side wall and the floor. In addition, they show asymmetry with the difference of the dip angle of the pre-fabricated fracture; the vault displacement of anchored caverns is mainly attributed to the formation of tensile cracks at the boundary of the anchored zone generated due to tensile waves reflected from the free face of the vault. When a fracture is present in the vault, the peak displacement of the vault decreases while the residual displacement increases.

scholarly journals Biaxial Shear Crack Propagation Modes of Rock-Like Specimens with Prefabricated Fissures and Their Strength Characteristics

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Nai-Zhong Xu ◽  
Chang-Qing Liu ◽  
You-Jian Wang ◽  
Hong-Bin Dang
Keyword(s):  
Shear Strength ◽  
Crack Propagation ◽  
Shear Crack ◽  
Crack Coalescence ◽  
Strength Characteristics ◽  
Propagation Mode ◽  
Peak Shear Strength ◽  
Shear Cracks ◽  
Tensile Shear ◽  
Dip Angle

A biaxial shear test is performed on prefabricated, single-fissure type, cubic rock-like specimens by using the TZW-500 rock direct shear apparatus to study the shear strength characteristics, crack coalescence, and propagation modes of the specimens with different geometric parameters. Results show that the crack coalescence and propagation modes of the rock-like specimens with prefabricated fissures can be divided into four types, namely, single main shear crack coalescence mode, main shear crack coalescence and secondary tensile-shear crack propagation mode, main shear crack coalescence and secondary shear crack propagation mode, and main shear crack coalescence and secondary tensile crack propagation mode. All modes are affected by the dip angle α and length l of the prefabricated fissure. When the dip angle of the prefabricated fissure is α∈[0°, 20°) or (70°, 90°], the cracks center on shear failure, and most shear cracks propagate along one end of the prefabricated fissure. At α∈(30°, 50°), the cracks bear the tensile-shear combined action, and the shear cracks propagate along the two ends of the prefabricated fissure. The peak shear strength of the rock-like specimens with prefabricated fissures is also closely related to the dip angle α and length l of the fissure. With the increase in dip angle α of the prefabricated fissure, the peak shear strength of each rock-like specimen decreases initially then increases, and the peak shear strength curve presents a similar “U” shape. At α∈[30°, 60°], the peak shear strength is within the peak-valley interval. When the length l of the prefabricated fissure is increased, the peak shear strength experiences a gradual reduction. When l > 20 mm, the peak shear strength is greatly influenced by l, but the influence is minimal when l ≥ 20 mm. At the same dip angle α and fissure length of l ≥ 20 mm, the correlation between peak shear strength and fissure width b is low.

Numerical Simulation on Mixed Mode I-II Crack Propagation Process in Concrete

2008 ◽  
Vol 385-387 ◽  
pp. 233-236 ◽  
Author(s):  
Qing Xu ◽  
Wei Dong ◽  
Zhi Min Wu
Keyword(s):  
Crack Propagation ◽  
Mixed Mode ◽  
Uniaxial Tensile ◽  
Mode I ◽  
Displacement Curve ◽  
Uniaxial Tensile Strength ◽  
Unstable Failure ◽  
Crack Propagation Process ◽  
The Difference ◽  
The One

A crack propagation criteria is proposed for mixed mode I-II fracture in concrete based on the initial cracking KⅠ-KⅡ curve obtained from experiment. Once the difference between the stress intensity factor at the crack tip caused by the external load and the one caused by the cohesive force attains the above KI-KII curve, the crack begins to propagate. Based on this criteria, the finite element method was used to simulate the mixed mode I-II crack initiation, stable propagation and unstable failure in concrete. For the four-point shear concrete specimens, the crack propagation trajectory and P-CMSD (Crack Mouth Sliding Displacement) curve were obtained. Upon the comparison with the experimental results, the calculated results show good agreement. It is concluded that, if the elastic modulus E, the uniaxial tensile strength ft and the initial cracking KI-KII curve of concrete are measured from experiment, the complete process of mixed mode I-II crack propagation can be simulated using the proposed criterion.

Experimental and Numerical Study on Mode I-II Crack Propagation for Small Size Specimens of Concrete

2010 ◽  
Vol 163-167 ◽  
pp. 908-912
Author(s):  
Wei Dong ◽  
Hua Nan He ◽  
Zhi Min Wu
Keyword(s):  
Crack Propagation ◽  
Numerical Study ◽  
Initial Crack ◽  
Mode I ◽  
Propagation Process ◽  
Crack Propagation Process ◽  
Series Of Experiments ◽  
The Difference ◽  
The One ◽  
Good Agreement

The crack criterion is important to determine the crack propagation for mode I-II fracture in concrete. The paper aims to obtain the initial crack criterion of four-point shearing beams experimentally, which can be applied in the numerical simulation for crack propagation process. A series of experiments of four-point shearing notched beams of concrete with five different heights of 80mm, 100mm, 120mm, 140mm and 160mm respectively were carried out to measure the initial loading Pini. The different combinations of KiniI and KiniII corresponding to Pini were obtained according to different positions of pre-cracks in the specimens, and the initial crack criterion was fitted using the combinations of KiniI and KiniII. With the assumption that the crack will extend when the difference between the stress intensity factor at the crack tip caused by the load P and the one caused by the cohesive force attained the above KiniI- KiniII curve, the criterion was applied to simulate the crack propagation process in the paper. It was found that the numerical analysis showed a good agreement with the experimental results and that the size effect is not remarkable for the KiniI-KiniII curves of different heights specimens in the test.

scholarly journals Delamination Buckling and Crack Propagation Simulations in Fiber-Metal Laminates Using xFEM and Cohesive Elements

2018 ◽  
Vol 8 (12) ◽  
pp. 2440 ◽  
Author(s):  
Davide De Cicco ◽  
Farid Taheri
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Hybrid Composites ◽  
Cohesive Elements ◽  
Zone Method ◽  
Fiber Metal Laminates ◽  
Finite Element Software ◽  
Numerical Predictions ◽  
Delamination Buckling ◽  
Fiber Metal

Simulation of fracture in fiber-reinforced plastics (FRP) and hybrid composites is a challenging task. This paper investigates the potential of combining the extended finite element method (xFEM) and cohesive zone method (CZM), available through LS-DYNA commercial finite element software, for effectively modeling delamination buckling and crack propagation in fiber metal laminates (FML). The investigation includes modeling the response of the standard double cantilever beam test specimen, and delamination-buckling of a 3D-FML under axial impact loading. It is shown that the adopted approach could effectively simulate the complex state of crack propagation in such materials, which involves crack propagation within the adhesive layer along the interface, and its diversion from one interface to the other. The corroboration of the numerical predictions and actual experimental observations is also demonstrated. In addition, the limitations of these numerical methodologies are discussed.

Dynamic Error Analysis of Measurement While Drilling Using Variable Geomagnetic In-Field Referencing

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2327-2338 ◽  
Author(s):  
Hojjat Kabirzadeh ◽  
Elena Rangelova ◽  
Gyoo Ho Lee ◽  
Jaehoon Jeong ◽  
Ik Woo ◽  
...  
Keyword(s):  
Reference Values ◽  
Dynamic Error ◽  
Directional Drilling ◽  
Average Reference ◽  
Marquardt Algorithm ◽  
Measurement While Drilling ◽  
The Difference ◽  
Dip Angle ◽  
Forward And Inverse Modeling

Summary The safe and economical determination of a wellbore trajectory in directional drilling is traditionally achieved by measurement-while-drilling (MWD) methods, which implement magnetic north-seeking sensor packages. Inaccuracies in the determination of well path arise because of random and systematic errors in the measurements of the sensors. Multistation analysis (MSA) and magnetic in-field referencing (IFR) have already demonstrated the potential to decrease the effects of errors because of magnetization of drillstring components along with variable errors caused by irregularities in the magnetization of crustal rocks in the vicinity of wells. Advanced MSA methodologies divide a borehole into several sections and use the average reference values of the total magnetic field, declination, and dip angle for analysis of errors in each section. Our investigations indicate that the variable-reference MSA (VR-MSA) can lead to a better determination of errors, specifically in areas of high magnetization. In this methodology, magnetic reference values are estimated at each station using forward and inverse modeling of surface-magnetic observations from IFR surveys. The fixed errors in magnetometer components are then calculated by minimizing the variance of the difference between the measured and unique estimated reference values at each station. A Levenberg-Marquardt algorithm (LMA) is adopted to solve the nonlinear optimization problem. Examination of this methodology using MWD data confirms more than 20% improvement in well-path-determination accuracy by comparing the results with the corrected path from the conventional MSA method and gyro surveys.

The Comparison of Self-Compacting Rock-Filled Concrete with Large-Size Natural and Recycled Aggregate

2014 ◽  
Vol 513-517 ◽  
pp. 20-23
Author(s):  
Hai Chao Wang ◽  
Xue Hua Wang ◽  
Xue Hui An
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Fracture Energy ◽  
Fracture Mechanism ◽  
Recycled Aggregate ◽  
Propagation Process ◽  
Fracture Characteristics ◽  
Three Point Bending ◽  
Large Size ◽  
Crack Propagation Process

The different fracture characteristics of self-compacting rock-filled concrete with large-size natural and recycled aggregate are analyzed by three-point bending experiment. According to the analysis of the crack propagation process, the fracture mechanism differences of self-compacting rock-filled concrete with large-size natural and recycled aggregate are discussed. The further analysis of the differences of fracture toughness, fracture energy, and are gain

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