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Numerical Method for Hydraulic Fracturing
In this chapter, a new finite element technique was presented for the judgment and the simulation of the hydraulic fracturing in earth‐rock fill dams. The technique utilized the theoretical formulations to calculate the energy release rate using the virtual crack extension method proposed by Hellen (1975). The main differences from the published studies exist in the finite element model of the crack and in the element mesh around the crack especially near the crack tip. The present technique can simulate the same structure with different crack depths using only one element mesh. The recreation of the element mesh is not necessary. This can conveniently simulate the propagation of the crack if the phenomenon of the hydraulic fracturing occurs. The influence factors on the convergence of the calculated J integral were investigated. In order to obtain a convergent J integral, the ratio of the width to length of the crack element should be from 0.30 to 0.90, the number of the crack elements should be greater than 4, and the numbers of the layers of the elements similar to the crack element both beside and ahead of the crack should also be greater than 4. In addition, the proportion of the virtual crack depth Δa to the length of the crack element between 0.02% and 10%, and the Young's modulus of the crack material less than 0.1% of the modulus of the specimen material are needed for the convergent calculated J integral. The accuracy of the calculated J integral was verified by analyzing three typical problems in Fracture Mechanics, in which the propagation of the crack may follow the mode I, the mode II and the mixed mode I‐II, respectively.
Numerical Method for Hydraulic Fracturing
In this chapter, a new finite element technique was presented for the judgment and the simulation of the hydraulic fracturing in earth‐rock fill dams. The technique utilized the theoretical formulations to calculate the energy release rate using the virtual crack extension method proposed by Hellen (1975). The main differences from the published studies exist in the finite element model of the crack and in the element mesh around the crack especially near the crack tip. The present technique can simulate the same structure with different crack depths using only one element mesh. The recreation of the element mesh is not necessary. This can conveniently simulate the propagation of the crack if the phenomenon of the hydraulic fracturing occurs. The influence factors on the convergence of the calculated J integral were investigated. In order to obtain a convergent J integral, the ratio of the width to length of the crack element should be from 0.30 to 0.90, the number of the crack elements should be greater than 4, and the numbers of the layers of the elements similar to the crack element both beside and ahead of the crack should also be greater than 4. In addition, the proportion of the virtual crack depth Δa to the length of the crack element between 0.02% and 10%, and the Young's modulus of the crack material less than 0.1% of the modulus of the specimen material are needed for the convergent calculated J integral. The accuracy of the calculated J integral was verified by analyzing three typical problems in Fracture Mechanics, in which the propagation of the crack may follow the mode I, the mode II and the mixed mode I‐II, respectively.
Numerical Method for Hydraulic Fracturing
Wang, Jun‐Jie (author)
2014-03-10
20 pages
Article/Chapter (Book)
Electronic Resource
English
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