Response models of weakly consolidated soft rock roadway under different interior pressures considering dilatancy effect

Surrounding rocks of weakly consolidated soft rock roadway show obvious strain softening and dilatancy effects after excavation. A damage coefficient concerning modulus attenuation was defined. Response models of stress and displacement of surrounding rock of soft rock roadway and analytical expressions to calculate plastic zones under different interior pressures and non-uniform original rock stresses were derived based on damage theories and a triple linear elastic-plastic strain softening model. Influence laws of dilatancy gradient on damage development, distributions of stresses and displacement in plastic region were analyzed. Interior pressure conditions to develop plastic region under different origin rock stresses were established and their influences on plastic region distribution were also discussed. The results show that the order of maximum principle stress is exchanged between ~0 and trr with the increase of interior pressure P0, which causes distributions of plastic zone and stress shift. Dilatancy effect which has great influences on the damage propagation and displacements in plastic region has little effect on the size of plastic region and stress responses. The conclusions provide a theoretical basis for a reasonable evaluation of stability and effective supporting of weakly consolidated soft rock roadway.

基于灰色关联法的北京山区水土保持生态安全评价

北京山区是调节首都生态环境的重要保护带,水土保持是北京山区改善生态环境的迫切需要,建立北京山区水土保持生态安全评价体系具有特殊意义。以北京的7个山区、县为研究对象,参考现有生态安全评价体系与方法,应用压力-状态-响应模型,选取影响水土保持生态安全的13项指标,建立了水土保持生态安全评价指标体系。依据指标体系选取2007,2009,2012这3a的数据运用熵权法确定指标权重,利用灰色关联法分析2007-2012年北京山区水土保持生态安全状况。结果表明：2007-2009年北京山区7区县水土保持生态安全指数由0.2008~0.2753上升至0.2205~0.3268,水土保持生态安全状态整体呈现好转趋势;2009-2012年其状态受自然灾害影响明显,状态呈现下降趋势,水土保持生态安全指数下降至0.2001~0.2825。水土保持生态安全指数与水土保持治理力度呈显著正相关,自然灾害引起的指标变化成为影响水土保持生态安全的主要因子。

基于高温人体热反应模型的生理参数预测

为有效评估人员在高温环境的安全性,建立人体热反应模型模拟高温环境人体皮肤温度、核心温度等生理参数。计算人体-服装-环境之间的热交换,并考虑高温对人体代谢产热、血流量、换热系数的影响,建立适用于高温环境的人体热反应模型。通过人体实验测量值及Fiala模型模拟值验证所建模型的有效性,验证结果表明高温人体热反应模型和实验结果吻合得很好。在48℃环境中所建立模型模拟平均皮肤温度值与实验测量值最大差值小于0.3℃,而Fiala模型与测量值最大差值接近1℃。所建立的模型可用于高温环境人体皮肤温度和核心温度等生理参数预测,为公共安全领域的应急救援、人员安全性评估、防护服研发等提供参考。

GVC中贸易超调波动的传导机制研究——基于我国经验的观察视角

全球金融危机后国际贸易出现了快速萎缩、快速复苏的剧烈波动,已成为世界经济波动的突出现象。本文从全球价值链理论出发,对贸易波动在全球扩散的传导机制及效应进行分析,发现存在订单调整机制、存货调整机制、贸易叠加机制以及合成的“甩鞭”效应。通过选取2005~2013年我国流通企业消费品订单指数和存货指数的月度数据,建立VAR和脉冲响应模型,发现在全球价值链分工背景下,存货调整机制和订单调整机制的共同作用对我国贸易剧烈波动产生了长期显著的影响,且其脉冲结果与现实吻合。因此,建立完善有效的国际贸易价值链传导机制,对世界各国尤其是发展中国家实现互惠互利、共同发展十分必要。