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| Study on the effect of heterogeneity on the macro and mesoscopic failure characteristics of sandstone samples
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| WANG Kangyu1，2，LIU Guangjian1，2，LUO Zhanyou3，GAO Junqiang1，2，XU Yudong1，2，LI Shanlin1，2
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| (1. School of Civil Engineering，Shaoxing University，Shaoxing，Zhejiang 312000，China；2. Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province，Shaoxing University，Shaoxing，Zhejiang 312000，China；3. School of Civil and Environmental Engineering and Geography Science，Ningbo University，Ningbo，Zhejiang 315000，China)
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Abstract The mesoscopic heterogeneity of sandstone works as the fundamental cause of its stress-strain curve and variances in failure characteristics. In this paper，to investigate the macroscopic and mesoscopic failure characteristics of heterogenous sandstone，diffraction of x-rays(XRD) was employed for the precise characterization of mineral components and contents of sandstone，fish language was utilized to establish the UDEC-Tri heterogeneous normal distribution model of minerals and joint mechanical parameters. Indicators to identify damage of heterogenous rock samples were proposed，and the influence rules of heterogeneity in modulus of elasticity，spatial distribution of mineral particles and joint cohesion of minerals on the macroscopic failure and mesoscopic damage of rock samples were studied. The results show that with the increase of heterogeneous level( )，the nonlinear characteristics of stress-strain curves of rock samples are enhanced，the tangent modulus and compressive strength decreasing linearly，and macroscopic failure changes from the mode of shear failure to splitting failure. The increased value results in a non-synchronized yield of adjacent mineral particles，a higher proportion of tension crack，and decreased crack initiation stress and damage stress of rock samples；when embodying the identical value，the variance distribution in minerals of rock samples leads to the presence of “weak contact surfaces”，as measured by mechanic parameters，between adjacent particles，which shows good consistency with the extension path of macroscopic crack and serves as the basic cause of the discreteness of crack characteristics in low-strength rock samples. Compared with the mineral ，joint heterogeneity( )embodies a more conspicuous weakening effect on the mechanical properties of sandstone. As increases，the length of tension crack grows to more than that of shear crack，with an enlarged proportion of small-scale crack；and with the increase of joint cohesion ，the failure mode of rock changes from “shear failure on single slopes” to “X-shaped shear failure on conjugated slopes”. In general，the research findings explain the mechanism of variances in failure characteristics of sandstone samples collected of the identical origin and the same size，as references for building the mapping relation between heterogeneity and sample strength，and between heterogeneity and failure characteristics.
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2023, Vol. 42 
