Creep Fracture Characteristics of Fractured Rock Mass Strengthened with Toughened Epoxy Resin

For improving the toughness and long-term strength of the fractured rock mass reinforced with epoxy resin and reducing the opening displacement of the crack tip, three types of converging cracks are established according to the deformation and failure characteristics of the rock mass, structural planes, and epoxy resin composite structure. The stress intensity factor of the type II compound crack and the analytical formula of the crack surface tip opening displacement are obtained. An improved Kelvin nonlinear creep model is proposed. Through the creep isochronous curve, the time and long-term strength of accelerated creep failure are obtained, as well as creep rupture coupling characteristics. The ductile plastic deformation is used to characterize the toughness, and the toughness of epoxy resin is enhanced by adding mud powder, and the relationship between toughness and long-term strength is established. Combined with experimental verification, when the drying mud powder content is 20%, the toughness of the epoxy resin has a good correlation with the long-term strength; when the mud powder content exceeds 30%, its ductility and long-term strength decrease, and at the same time the toughness effect is significantly weakened. The research results can provide a useful reference for toughened epoxy resin to strengthen fractured rock mass engineering.

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Seepage Evolution Model of the Fractured Rock Mass under High Seepage Pressure in Dam Foundation

Advances in Civil Engineering ◽

10.1155/2021/8832774 ◽

2021 ◽

Vol 2021 ◽

pp. 1-18

Author(s):

Erfeng Zhao ◽

Yufeng Jiang

Keyword(s):

Rock Mass ◽

Fractured Rock ◽

Constitutive Models ◽

Storage Period ◽

Creep Damage ◽

Fractured Rock Mass ◽

Dam Foundation ◽

Compression Creep ◽

Seepage Characteristics

The seepage of the fractured rock mass in dam foundations involves complex fluid-structure coupling behavior, due to practical hydrogeological conditions. In this work, the seepage characteristics of the fractured rock mass and their correlations with the structural permeable mediums are experimentally explored to reveal the cracking effect on the hydromechanical properties firstly. Subsequently, the tangential and the compression creep damage constitutive models are, respectively, established by introducing a nonlinear viscoplastic body to improve the Nishihara model. Afterwards, an innovative evolution equation of the permeability coefficient considering the creep damage is proposed. It can indicate the time effect of the porosity, the permeability, and damage variables of the fractured rock mass under the long-term infiltration action of the hydraulic pressures. Ultimately, the proposed methods are applied to the seepage simulation on the dam foundation of the Longyangxia hydropower station and the significantly increased leakage is in good agreement with the measured values during the storage period. It was further confirmed that the crack expansion and penetration in the rock masses can be constantly intensified by the seepage pressures. The research results can provide a reference for engineering repair and supervision through controlling the permeability performance for long-term operations.

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Study on Creep Characteristics and Constitutive Relation of Fractured Rock Mass

Shock and Vibration ◽

10.1155/2020/8833512 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Maotong Li ◽

Kesheng Li ◽

Deng Zhang ◽

Chuanxiao Liu ◽

Depeng Ma

Keyword(s):

Rock Mass ◽

Creep Curve ◽

Fractured Rock ◽

Damage Variable ◽

Creep Model ◽

Creep Process ◽

Fractured Rock Mass ◽

Creep Equation ◽

Creep Characteristics ◽

Fractured Coal

In order to effectively describe the whole creep process of fractured rock mass, triaxial unloading creep tests were carried out on prefractured coal samples using constant axial pressure and graded unloading confining pressure, and the axial and lateral creep laws of fractured coal samples with different dip angles were studied. Combined with the characteristics of creep curve and based on Kachanov’s creep damage theory, the damage variable is introduced into the constitutive relation and creep equation, and the evolution equation of damage variable with time in the whole creep process is derived. At the same time, a new method to calculate the initial damage is proposed. The elastoplastic body with damage variable is connected with the Burgers model in series. Meanwhile, lade criterion and switch element are introduced into the creep model to establish a new fracture damage creep model. The one-dimensional and three-dimensional damage creep equations are derived. The damage creep equation is obtained according to the superposition principle. A simple and feasible method for parameter identification of the model is given based on the characteristics of creep curve. The applicability of the model is verified by comparing the creep test curve of fractured coal sample with the theoretical curve. The results show that the two models are in good agreement. The model can not only accurately reflect the nonlinear characteristics of creep curves in the attenuation and isokinetic stages but also describe the accelerated creep characteristics of fractured rocks.

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