A nonlinear rheological model of backfill material for retaining roadways and the analysis of its stability

The long-term stability of backfill material is the key to retaining roadways successfully.In order to study the rheological deformation of backfill material and its long-term stability,given the visco-elastoplastic properties of this material,we introduced a softening and a hardening function for a new nonlinear rheological model with time-varying parameters.Based on this,we presented the instability condition of this model by using the principle of minimum potential energy.Combined with engineering practice,we calculated the unstable time period of backfill material.The results show that the time of instability of the backfill material relate to the initial parameters of the material,the coefficients decided by temperature and the ratio of the plastic zone of the backfill material.Based on the results of our analysis from the point of view of energy,we can quickly obtain the time of instability of this model from our graphical analysis.The time of instability of the backfill material obtained from our investigation coincides with an actual project.

乌鲁木齐城市和农村绝经后女性生活方式与维生素D水平的状况

目的调查乌鲁木齐城市和农村绝经后女性生活方式与维生素D状况。方法在乌鲁木齐市及周边农村招募年龄≥55岁,绝经时间≥1年,能够独立行动的城市和农村女性各120名,排除严重肾病、肿瘤、营养不良等疾病。问卷调查采集受试者的生活、饮食习惯情况。所有受试者完成血清25(OH)D检测。结果①农村女性整体年龄低于城市女性(P<0.01),城市女性绝经年限中位数(20年)高于农村女性(13年)(P<0.01)。城市女性受教育程度及年限均高于农村女性(P<0.01)。②城市女性的健康状况及对维生素D的认知状况均好于农村女性(P<0.01),农村女性每周接受日照时间中位数高于城市女性(P<0.01),2组比较差异均具有统计学意义。城市女性中常摄入牛奶、酸奶和蛋黄人数比例均高于农村女性,农村女性饮茶人数所占比例高于城市女性,2组比较差异具有统计学意义。③农村女性总体25(OH)D水平中位数低于城市(14 ng/mL和16.5 ng/mL,P=0.003)。农村女性中25(OH)D水平<30 ng/mL者所占比例高于城市女性(106/120和116/120,P=0.025)。乌鲁木齐绝经后女性维生素D缺乏程度与发生跌倒情况呈弱负相关(P=-0.133,P=0.04)。结论乌鲁木齐城市和农村绝经后女性普遍存在维生素D缺乏,且对于维生素D认知不足,缺少户外运动及日光照射,饮食摄入不均衡可能是导致维生素D缺乏的因素。