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基于巷道开挖过程中围岩应力转移分布特点,着重探究非均匀荷载下岩体变形规律。提出了新的岩石力学试验方法,该方法根据岩石应力–应变曲线,加工出特定的梯形截面试件及相应的刚性垫片,以实现单轴压缩时的轴向荷载非均匀分布。计算了梯形截面试件压缩时荷载分布与截面高度的关系,并对试验条件下的试件应力分布与岩石状态分区进行讨论,在右侧面高度为75 mm时试件破坏前左侧面处于塑性变形阶段,在右侧面高度为85 mm时试件破坏前左侧面仍处于弹性变形阶段。得到了非均匀荷载压缩条件下单一完整岩体的变形特性;梯形截面砂岩破坏前有明显的分区,各点位塑性硬化程度不一致,S85试件点位3右侧处塑性硬化程度最大,S75试件点位2右侧处塑性硬化程度最大。试验结果表明,非均匀荷载压缩条件下的岩石呈非线性变形特征;同时,岩石局部的损伤会加快附近岩石的塑性软化。提出了非均匀荷载条件下不同竖向截面内轴向应变差会引起附加切应力,附加切应力在中性面上、下方向相反,大小与应变变化率成正相关。在附加切应力作用下,岩石单元最大剪应力平面角度增大,试件破坏形态由原本对“核”形态转变为沿着斜面倾向拉长的相对棱台状。
Abstract：Based on the characteristics of stress transfer distribution in surrounding rock during roadway excavation, this study focuses on exploring the deformation law of rock mass under non-uniform loading. A new rock mechanics testing method has been proposed, in which rock specimens of the specific trapezoidal cross section were prepared and corresponding rigid pads were fabricated based on the stress-strain curve of rocks to achieve non-uniform distribution of axial loads during uniaxial compression. The relationship between load distribution and the height of cross section during compression of trapezoidal section specimens was calculated, and the stress distribution of specimens under test conditions and rock state zoning were discussed. When the height of the right side is 75 mm, the left side of the specimen was in the plastic deformation stage before failure, while the of height of right side reaches 85 mm, the specimen was still in the elastic deformation stage before failure. From the tests,the deformation characteristics of a single intact rock mass under non-uniform load compression conditions was obtained. Obvious zoneing phenomenon was observed before the failure of trapezoid-sectional sandstone, wherethe degree of plastic hardening at each point is inconsistent. The plastic hardening degree reached its maximum at point 3 on the right side of S85 specimen, and it reaches its maximum at point 2 on the right side of S75 specimen. The results indicate that rocks under non-uniform load compression exhibit nonlinear deformation characteristics, and the local damage accelerated the plastic softening of rocks nearby. It is proposed that under non-uniform loading conditions, the difference in axial strain within different vertical cross sections caused additional shear stress.The induced shear stresses are positively correlated with the rate of strain change,but there directions opposite in the upper and lower directions of the neutral plane. Under the action of additional shear stress, the plane angle of the maximum shear stress of the rock element increased, and the specimen failure mode changed from the original ''core''shape to a relatively elongated pyramid shape along the inclined plane.
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基本信息:
DOI：10.13532/j.jmsce.cn10-1638/td.2024.03.001
中图分类号:TD315
引用信息:
[1]余伟健,潘豹,吴根水,等.等效非均匀荷载条件下梯形截面岩石力学特性试验研究[J].采矿与岩层控制工程学报,2024,6(03):108-117.DOI:10.13532/j.jmsce.cn10-1638/td.2024.03.001.
基金信息:
国家自然科学基金资助项目(52174076);; 湖南省自然科学基金资助项目(2023JJ30261)