钙质砂单颗粒破碎强度和模式的试验研究

Experimental study on single particle crushing strength and patterns of calcareous sand

通过自动单轴加载系统对不同粒径和形状的钙质砂颗粒进行了单颗粒压碎试验,同时借助于显微探头观测记录钙质砂颗粒的压碎过程和破碎模式,并利用统计方法分析粒径、形状和干湿条件等因素对钙质砂颗粒破碎强度和破碎模式的影响。此外,通过原位X射线μCT扫描支持下的微型单轴加载装置分别对两个钙质砂颗粒的压碎过程进行了高精度扫描,利用图像处理和分析技术对内孔隙结构的影响进行了深入研究。结果表明:形状类似时,钙质砂颗粒的粒径越大,特征强度越低;粒径相当时,块状颗粒的特征强度最大,片状颗粒次之,刃状颗粒再次之,条状颗粒最小;钙质砂颗粒的破碎过程可以归纳为3种裂纹形式和3种破碎模式,分别为单裂纹、交叉裂纹、拱裂纹和模式Ⅰ、Ⅱ、Ⅲ。μCT图像分析结果表明,颗粒破碎产生的裂纹主要集中于内孔隙较密集处。这说明内孔隙结构对于钙质砂颗粒的破碎行为具有重要的影响。

Analysis of the effects of sizes,shapes and wetting condition on crushing strength and modes of calcareous sand can be accomplished using a statistical method by subjecting particles with different sizes and shapes to single particle crushing tests through automatically uniaxial loading system and the crushing process,and modes of particles were observed and recorded with the help of microscopic probe.In addition,the micro-uniaxial loading device supported by in-situ X-rayμCT scan was used to scan the crushing process of two calcareous sand particles with high precision,and the effects of internal pore structure were deeply investigated by image processing and analysis technology.The results show that the characteristic strength of calcareous sand particles is decreased with increasing sizes.While for the particles with similar sizes,the characteristic strength of compact particles is the largest,followed by platy particles and bladed particles,and elongated particles are the least.The crushing process of calcareous sand particles can be summarized as three crack forms and three fracture patterns,which are single crack,cross crack,arch crack and patterns I,II,III,respectively.Finally,analysis results ofμCT images show that the cracks caused by particle crushing concentrated mainly in the dense internal pores,which indicated that internal pore structure has an important influence on the crushing behavior of calcareous sand particle.