Abstract
In this study, a data analysis method for the relaxation test was proposed under step loading by conducting creep and stress relaxation tests of dentate discontinuity poured by cement mortar using biaxial creep machine under step loading and single-stage loading. First, a superposition method for the stress relaxation curve was deduced based on the data processing method of creep test by considering the effect of loading history on the relaxation curve and the characteristic of relaxation was analyzed. Second, this superposition method was verified by testing data under step loading and single-stage loading. Finally, this paper indicate the accurate way for the processing of relaxation test data under step loading. The results show that under the same stress level, the values of relaxation curve after the superposition are different from that under the single-stage loading test. Furthermore, the relaxation curves in the step loading test under different stress levels are similar to those in single-stage loading under the same stress level. Furthermore, creep deformation increase monotonically during the creep, but stress do not exhibit such a trend during relaxation, which is inconsistent with the Boltzmann superposition principle. The relaxation curve in the step loading test under different shear stress could reflect the relaxation properties of the single-stage loading test under the same shear stress, and unlike the data processing method of step loading creep test, superimposition is not needed.
Highlights
Rock mass is a complex geological body, and the existence of structural planes such as fractures and joints is the source of discontinuities, anisotropy, and heterogeneity in rock engineering [1]
Several engineering studies have shown that the failure and instability of rock mass does not occur immediately after the excavation is completed. e deformation characteristic of rock mass is affected by the stressstrain state, and the deformation occurs and adjusts with time continuously for a long period of time [2]. e timevarying nature of the stress-strain state of a rock mass is defined as the rheology of the rock mass. e indoor rheological test is a vital method for studying the rheological mechanical properties of rocks, which includes two commonly used test methods. e first method is the single-stage loading method, where the sample is directly loaded to a certain stress level during the test, which avoids the impact of loading history
By analyzing the effect of Advances in Civil Engineering loading history on the deformation of rock specimens based on the data obtained from shale multi-stage cyclic singlepump compression creep tests, Xia et al [13] proposed a method for collating the creep test data. e “Chen’s loading method” proposed by Chen and Kang can be used to infer the creep curve of the load under one-step loading through a mapping method [14, 15]. is method can establish the superposition relationship of the true deformation process, and it has been widely accepted and used in geotechnical rheology research globally
Summary
Rock mass is a complex geological body, and the existence of structural planes such as fractures and joints is the source of discontinuities, anisotropy, and heterogeneity in rock engineering [1]. E existence of structural planes significantly affects the mechanical properties of rock masses Many researchers such as Xu et al [8], Shen et al [9], Zhang et al [10], Wang et al [11], and Lin et al [12] used the step loading method to study the creep characteristics of structural planes. Regular toothed discontinuity can be found in practical engineering, such as the headscarp of the Aishihik River Landslide [38] To address this issue, cement mortar is used to artificially cast the samples with regular toothed structural surfaces at different angles to reduce the dispersion of test results. First, the creep test and stress relaxation test under step loading are performed on samples with regular toothed structural surface. A data processing method for the relaxation test under step loading is deduced from a theoretical perspective considering the influence of loading history, and the results are verified based on the test data. en, the similarities and differences between the creep curve and relaxation curve according to the superposition principle are analyzed, and an appropriate method for the relaxation test under step loading is proposed. is knowledge resolves the outstanding issues of creep and relaxation equivalence, thereby enriching the theoretical understanding of rock mechanics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
