Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shear...Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shearing dislocation.Using digital image techno-logy and three-dimensional(3D)laser morphology scanning techniques,a set of 3D models with rough joint surfaces was established.Further,the mechanical behavior of rock–backfill shearing dislocation was investigated using a direct shear test.The effects of interface roughness on the shear–displacement curve and failure characteristics of rock–backfill specimens were considered.The 3D fractal dimen-sion,profile line joint roughness coefficient(JRC),profile line two-dimensional fractal dimension,and the surface curvature of the frac-tures were obtained.The correlation characterization of surface roughness was then analyzed,and the shear strength could be measured and calculated using JRC.The results showed the following:there were three failure threshold value points in rock–backfill shearing dis-location:30%–50%displacement before the peak,70%–90%displacement before the peak,and 100%displacement before the peak to post-peak,which could be a sign for rock–backfill shearing dislocation failure.The surface JRC could be used to judge the rock–backfill shearing dislocation failure,including post-peak sliding,uniform variations,and gradient change,corresponding to rock–backfill disloca-tion failure on the field site.The research reveals the damage mechanism for rock–backfill complexes based on the free joint surface,fills the gap of existing shearing theoretical systems for isomerism complexes,and provides a theoretical basis for the prevention and control of possible disasters in backfill mining.展开更多
目的:研究不同真空冷冻干燥工艺条件下天麻干燥特性和活性成分的变化规律;评价不同干燥条件下冻干天麻样品的质量。方法:分别以干燥速率、单位时间生产率及面积收缩率为干燥特性指标;以天麻素、天麻多糖、对羟基苯甲醇、醇溶性浸出物含...目的:研究不同真空冷冻干燥工艺条件下天麻干燥特性和活性成分的变化规律;评价不同干燥条件下冻干天麻样品的质量。方法:分别以干燥速率、单位时间生产率及面积收缩率为干燥特性指标;以天麻素、天麻多糖、对羟基苯甲醇、醇溶性浸出物含量为指标成分,考察真空压强、隔板温度和切片厚度对天麻干燥特性和活性成分的影响;采用多层次分析结合正交设计优化干燥工艺;并从红外光谱、扫描电镜(Scanning electron microscope,SEM)及色度三个方面对天麻冻干样品的质量进行评价。结果:天麻的干燥特性与真空压强、隔板温度和切片厚度均呈现显著变化规律;天麻的活性成分则无显著变化规律。在优化的工艺条件(真空压强45 Pa,隔板温度55℃,切片厚度5 mm)下,天麻素、天麻多糖、对羟基苯甲醇和醇溶性浸出物含量分别为0.472%、22.54%、0.292%和31.98%,且质量优于其他干燥样品。结论:天麻的干燥特性参数与真空冷冻干燥工艺密切相关;成分指标随工艺参数改变无明显趋势;采用真空冷冻干燥工艺制备的天麻样品质量良好。展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFC3001302)the National Natural Science Foundation of China(No.52274072).
文摘Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shearing dislocation.Using digital image techno-logy and three-dimensional(3D)laser morphology scanning techniques,a set of 3D models with rough joint surfaces was established.Further,the mechanical behavior of rock–backfill shearing dislocation was investigated using a direct shear test.The effects of interface roughness on the shear–displacement curve and failure characteristics of rock–backfill specimens were considered.The 3D fractal dimen-sion,profile line joint roughness coefficient(JRC),profile line two-dimensional fractal dimension,and the surface curvature of the frac-tures were obtained.The correlation characterization of surface roughness was then analyzed,and the shear strength could be measured and calculated using JRC.The results showed the following:there were three failure threshold value points in rock–backfill shearing dis-location:30%–50%displacement before the peak,70%–90%displacement before the peak,and 100%displacement before the peak to post-peak,which could be a sign for rock–backfill shearing dislocation failure.The surface JRC could be used to judge the rock–backfill shearing dislocation failure,including post-peak sliding,uniform variations,and gradient change,corresponding to rock–backfill disloca-tion failure on the field site.The research reveals the damage mechanism for rock–backfill complexes based on the free joint surface,fills the gap of existing shearing theoretical systems for isomerism complexes,and provides a theoretical basis for the prevention and control of possible disasters in backfill mining.
文摘目的:研究不同真空冷冻干燥工艺条件下天麻干燥特性和活性成分的变化规律;评价不同干燥条件下冻干天麻样品的质量。方法:分别以干燥速率、单位时间生产率及面积收缩率为干燥特性指标;以天麻素、天麻多糖、对羟基苯甲醇、醇溶性浸出物含量为指标成分,考察真空压强、隔板温度和切片厚度对天麻干燥特性和活性成分的影响;采用多层次分析结合正交设计优化干燥工艺;并从红外光谱、扫描电镜(Scanning electron microscope,SEM)及色度三个方面对天麻冻干样品的质量进行评价。结果:天麻的干燥特性与真空压强、隔板温度和切片厚度均呈现显著变化规律;天麻的活性成分则无显著变化规律。在优化的工艺条件(真空压强45 Pa,隔板温度55℃,切片厚度5 mm)下,天麻素、天麻多糖、对羟基苯甲醇和醇溶性浸出物含量分别为0.472%、22.54%、0.292%和31.98%,且质量优于其他干燥样品。结论:天麻的干燥特性参数与真空冷冻干燥工艺密切相关;成分指标随工艺参数改变无明显趋势;采用真空冷冻干燥工艺制备的天麻样品质量良好。
