Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock

Advances in Civil Engineering, Jul 2016

The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals.

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Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock

Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock Weichao Wang,1,2 Mengmeng Wang,1 and Xiliang Liu1 1School of Civil Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China 2Henan Colleges and Universities Deep Mine Construction Key Discipline Open Laboratory, Jiaozuo, Henan 454000, China Received 12 January 2016; Revised 24 March 2016; Accepted 26 May 2016 Academic Editor: Serji N. Amirkhanian Copyright © 2016 Weichao Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals. 1. Introduction Geotechnical engineering is often subjected to cyclic loading. The mechanical characteristic of the surrounding rock under cyclic loading is one of the important factors that affect fatigue life of geotechnical engineering. Therefore, the fatigue failure mechanism of the rock is of great significance to the long-term stability and safety of rock mass, which has been widely given concern for domestic and foreign scholars. Lots of material fatigue failure tests for rocks were carried out by the domestic and foreign scholars [1–6]. They found that the fatigue life is related to the maximum stress limit, loading waveforms, and stress amplitudes. Investigation on fatigue failure process of white sandstone under cyclic loading indicates that the maximum stress limit and amplitude are the main factors affecting the fatigue failure process [1]; the strain rate is in negative correlation with the fatigue life and showing a rule of exponential curve. Zhu et al. carried out uniaxial cyclic impact compression test for granite through using the improved large diameter of Higginson (SHPB) test system and analyzed the mechanical properties under cyclic impact load and the law of energy absorption [2]. Su et al. carried out splitting fatigue failure tests on the sandstone. The results show that the fatigue limit load ratio and tensile fatigue strength are in negative correlation with cyclic number [3]. Erarslan and Williams had studied splitting test on rocks of preexisting crack and analyzed the fracture mode of the fatigue damage [4]. Salt rock can be used as underground storage medium of oil, gas, and other strategic energy with its advantages of low permeability and damage self-repairing [7]. At present, our country is gradually increasing the construction of salt dome energy storage. Domestic scholars also have carried out many research projects. Li et al. had studied the fatigue strength, deformation, and damage characteristics of salt rock under uniaxial cyclic loading [8]. The results show that the cyclic fatigue failure process of rock salt is also controlled by static full curve. Yang et al. found that, in the uniaxial cyclic loading tests of rock salt, deformation modulus of linear portion displayed a general ascending trend with the increase of load level, whether it is unloaded or loaded [9]. Ma et al. considered that the upper limit stress threshold of three-axis cyclic deformation failure is 89%~80%, which is inferred through experiments indirectly [10]. They also found that the strain hardening characteristics in secondary compression of salt rock are more remarkable than that of the first compression. The stress field of surrounding rock is changing constantly in the operation of salt cavern storage due to the injection-production cycle load. However, the study of the above scholars mostly concerned the uniaxial and triaxial fatigue tests of the salt rock and lack of research on mechanical properties of (...truncated)


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Weichao Wang, Mengmeng Wang, Xiliang Liu. Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock, Advances in Civil Engineering, 2016, 2016, DOI: 10.1155/2016/5436240