摘要
粮仓中粮堆在装卸时存在着复杂的应力路径,为了得出复杂应力路径对粮堆模量和临界状态特性的影响规律,以及粮堆应力应变关系模型,该文在侧向应力50~300 k Pa下,进行了常规三轴压缩(conventional triaxial compression,CTC)、等p压缩(constant mean normal stress compression,CMS)、三轴主动压缩(reduced triaxial compression,RTC)三轴应力路径试验,分析了应力路径和侧向压力对模量的影响和粮堆临界状态特性;修正岩土体三次曲线模型,建立了适于描述仓内小麦粮堆应力应变的模型,并通过应力路径试验结果和文献试验结果对模型的适用性进行验证。研究结果表明:各应力路径下初始模量、割线模量E50均随着侧向应力呈幂函数增长;CTC、CMS试验的割线模量E50比初始模量发生较大的降低,而RTC试验没有明显降低。在参考压力(大气压力)下,对于初始模量,CTC试验的结果最大,RTC试验的结果最小;对于割线模量E50,CTC试验的结果最小,RTC试验的结果最大。CTC试验的初始模量、割线模量均随着侧向应力增长最慢,而RTC试验的结果均随着侧向应力增长最快。不同应力路径和侧向应力下,试验的破坏点均落于同一临界状态线上,小麦粮堆临界状态应力比为0.976。修正三次曲线模型反映了粮堆强度、峰度系数和峰值应变等特性,并通过8个参数进行计算;通过应力路径试验结果和文献试验结果对该模型进行了验证。研究结果可为粮仓装卸料压力、变形的计算提供更符合实际应力路径条件的参量,建立的修正三次曲线模型可用于粮堆应力和变形的数值模拟,为粮仓的设计提供参考。
Total amount of stored grain in China is about 200 million tons,which is of great importance to ensure the quality and safety of grain during storage period,and to modernization of agriculture engineering.When a storage cycle is ended,grain will be discharged from bins,and then loaded in for another storage cycle.Vertical stress increases in loading process,while decreases in discharging process,and different stress path will be generated in the bulk grain,resulting in complicated pressure and frictional force on bin wall,which will cause crack,failure or even overturn of bin structures.It is vital to study stress strain relation and strength properties of bulk grain under different stress paths.Geotechnical constitutive models have been used in grain bin simulation,however,the feasibility of these models for bulk grain has not been validated.In this study,stress path triaxial test was utilized to simulate complicated load path in grain bins.Wheat purchased from grain depot in Zhengzhou City,Henan Province was used in this study.Specimen had water content of 10.9%,bulk density of 0.85 g/cm3,diameter of 61.8 mm and height of 125 mm,the average axial length of wheat kernel was 4.5 mm,and the ratio of specimen diameter to kernel axial length was 13.7,which was larger than the minimum specified ratio for triaxial test.Three types of stress paths were investigated in this study:conventional triaxial compression(CTC),constant mean normal stress compression(CMS),and reduced triaxial compression(RTC).In CTC test,radial stress was set as constant,while axial stress increased simultaneously;in CMS test,radial stress decreased,while axial stress increased simultaneously to keep mean normal stress constant;in RTC test,axial stress was set as constant,and radial stress decreased simultaneously.Stress path triaxial test procedure was as follows:After bulk wheat specimen was mounted on triaxial apparatus,isotropic stress was applied from 0 to prescribed value(50,100,150,200,250,300 kPa);then CTC,CMS or RTC stress path was appli
作者
蒋敏敏
陈桂香
Jiang Minmin;Chen Guixiang(School of Civil Engineering and Architecture,Henan University of Technology,Zhengzhou 450001,China;National Engineering Laboratory for Grain Storage and Transportation,Zhengzhou 450001,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2018年第7期280-287,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(51408197)
粮食公益性行业科研专项(201513001)
河南省科技攻关项目(162102210188)
河南省属高校基本科研业务费专项资金(2015RCJH16)
