李可,余伟健,廖泽,等. 不同应力加载速率下深埋泥岩力学特性与扩容特征试验研究[J]. 煤炭学报,2023,48(9):3360−3371. doi: 10.13225/j.cnki.jccs.2022.1501
引用本文: 李可,余伟健,廖泽,等. 不同应力加载速率下深埋泥岩力学特性与扩容特征试验研究[J]. 煤炭学报,2023,48(9):3360−3371. doi: 10.13225/j.cnki.jccs.2022.1501
LI Ke,YU Weijian,LIAO Ze,et al. A laboratory-testing-based study on mechanical properties and dilatancy characteristics of deeply buried mudstone under different stress loading rates[J]. Journal of China Coal Society,2023,48(9):3360−3371. doi: 10.13225/j.cnki.jccs.2022.1501
Citation: LI Ke,YU Weijian,LIAO Ze,et al. A laboratory-testing-based study on mechanical properties and dilatancy characteristics of deeply buried mudstone under different stress loading rates[J]. Journal of China Coal Society,2023,48(9):3360−3371. doi: 10.13225/j.cnki.jccs.2022.1501

不同应力加载速率下深埋泥岩力学特性与扩容特征试验研究

A laboratory-testing-based study on mechanical properties and dilatancy characteristics of deeply buried mudstone under different stress loading rates

  • 摘要: 岩石工程的损伤破坏过程和其扩容现象密不可分,扩容是岩石在偏应力超过屈服极限后表现出的体积增大的现象。为了进一步研究深埋泥岩扩容现象,对矿山现场钻取的埋深近1 300 m的岩石试样做了系列试验,包括XRD衍射试验、SEM电镜扫描试验和不同加载速率下(0.1、0.5、2.0和5.0 kN/s)的单轴压缩变形试验等。结果表明:泥岩成分以长石为主,岩石内部各矿物成分分布不均匀,长石呈条带状分布,其间填充其他矿物,填充物以绿泥石为主。在不同的加载速率下,各试样轴向应力−应变曲线属典型的塑−弹−塑性曲线,有明显的压密过程,加载速率越小,压密过程越明显,即曲线越平缓。进入弹性阶段后,加载速率越大,曲线斜率越大,即平均弹性模量越大。采用单因素方差分析方法对各组数据进行了差异显著性检验,结果显示试验加载速率(Vload)和泥岩岩石单轴抗压强度(σc)、平均弹性模量(E)、最大轴向应变(εa,max)、最大径向应变(εd,max)、扩容起始应力(f*)、扩容起始应力与单轴抗压强度比值(f*/σc)有关联关系,和试样最大体积应变(εV,max)、扩容起始体积应变与最大体积应变比值(εV,d/εV,max)无关联关系。加载速率越大,测试得到的泥岩岩石单轴抗压强度、平均弹性模量越大,加载速率由0.1 kN/s增大50倍至5.0 kN/s时,测得单轴抗压强度均值由26.8 MPa增大至36.5 MPa,平均弹性模量均值由3.5 GPa增大至5.9 GPa。加载速率越大,最大轴向应变和最大径向应变均越小,轴向和径向应变率均越大,即加载速率越大,泥岩岩石在未充分变形的情况下发生破坏的可能性越大。加载速率越大,试样扩容起始应力、试样扩容起始应力与单轴抗压强度比值越小,即试样加载荷载速率越大,越容易进入体积扩容阶段。认为泥岩强度参数、变形与扩容参数有显著的应力加载速率依赖性。

     

    Abstract: The damage and failure process of rock engineering is inseparable from rock dilatancy. Dilatancy is the phenomenon of rock volume increase after the differential stress exceeds the yield limit. X-ray diffraction, scanning electron microscope, and uniaxial compression tests under different stress loading rates (0.1, 0.5, 2.0, 5.0 kN/s) were carried out on mudstone specimens from drill holes in the mine site with a depth of nearly 1300 m. The results demonstrate that the mudstone is mainly composed of plagioclase. The distribution of various minerals in the rock is not uniform. The main component plagioclase is distributed in strips, filled with other minerals, the filling material is mainly chlorite. Under different stress loading rates, the axial strain curves are typical plastic-elastic-plastic curves, and each specimen has an obvious micro-crack compaction process. The lower the stress loading rate, the more pronounced the compaction process, that is, the smoother the curve. In the elastic stage, the slope of the curve increases as the stress loading rate increases, indicating that the rock’s elastic modulus rises. The one-way analysis of variance method was used to test the significance of the differences in each analysis item’s data. The results indicate that the stress loading rate (Vload) is related to the uniaxial compressive strength (σc), elastic modulus(E), maximum axial strain(εa,max), maximum radial strain(εd,max), the initial dilatancy strength(f*), and the ratio of the initial dilatancy stress to the uniaxial compressive strength(f*/σc) of mudstone. It does not correlate with the maximum volumetric strain value (εV,max), and the ratio of the initial dilatancy volumetric strain to the maximum volumetric strain (εV,d/εV,max). As the Vload increases, σc and E increase, when Vload increases 50 times from 0.1 kN/s to 5.0 kN/s, the measured σc increases from 26.8 MPa to 36.5 MPa, and E increases from 3.5 GPa to 5.9 GPa. The εa,max and εd,max decrease with increasing Vload while axial and radial strain rates increase. Hence, the likelihood of failure of mudstone rock under insufficient deformation increases with increasing Vload. The f* and f*/σc decrease as Vload increases, meaning that it is easier to enter the dilatancy stage with higher Vload. It is considered that the strength parameters, deformation and dilatancy parameters of mudstone are significantly dependent on Vload.

     

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