不同截面形状砂岩试样的力学特性试验研究

人们通常采用实心圆柱试样进行静态及动态加载试验分析岩石的力学特性,然而实际工程岩体中方形和空心圆柱体试样也很常见。为了研究不同横截面形状对岩石力学特征的影响,本文对相同高度和横截面面积的完整圆柱试样、方形试样和厚壁圆筒试样进行单轴压缩试验和声发射检测。试验结果表明,方形截面菱角、厚壁圆筒试样孔道自由面有利于岩石的局部变形,方形试样强度比实心圆柱体试样偏低6.2%而比厚壁圆筒试样偏高10.0%,方形试样弹性模量分别比实心圆柱体试样和厚壁圆筒试样偏低4.7%、2.8%。实心圆柱试样和厚壁圆筒试样在单轴压缩过程中峰值强度之前可释放弹性能占吸收总能量比值比方形试样大,耗散能所占比值比其小。实心圆柱试样和厚壁圆筒试样破坏以张拉复合破坏为主,方形试样出现了“沙漏”状的破坏形式,试样菱角处都出现明显的剪切面。研究结果为理解岩石的失稳破坏提供了参考。

Experimental Study on Mechanical Properties of Sandstone with Different Cross-sectional Shapes

The solid cylindrical rock samples are always used to investigate the mechanical properties of rocks in static and dynamic tests. However, the prism and hollow cylindrical samples are also common in practical engineering. To study the mechanical behavior of rocks induced by shapes, the uniaxial compression and acoustic emission (AE) testing were carried out considering the solid cylindrical, prism, hollow cylindrical shaped samples with the same height and the cross-sectional area. Results show that corners of square cross-section and free surface of hollow cylinder are beneficial to the local deformation of rock. The strength for prism sample is 6.2% lower than that of solid cylindrical sample but is 10% higher than that of hollow cylindrical sample, while the elastic modulus is 4.8% lower than that of solid cylindrical sample and is 2.8% lower than that of hollow cylindrical sample. As for solid and hollow cylindrical samples, the ratio of the releasable elastic energy to the total absorbed energy is larger than that of prism samples under uniaxial compression, while the dissipated energy of the total absorbed energy is smaller than that of the prism ones. Failure modes of solid and hollow cylindrical samples are mainly tensile-shear failure, while the prism specimen is an hour-glass failure mode. The results provide a reference to study the rock failure.