The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in nu...The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical forms.This study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy model.The developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical significance.The overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed granite.The applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,e.g.deep rock mass.The PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical solutions.The sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock dilatancy.Tunnel deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior.展开更多
为探究气候温和地区高校教室内的热舒适性,且修正预测热感觉和不满意度模型(predicted mean vote-predicted percentage of dissatisfaction,PMV-PPD模型)与实际热感觉投票值存在偏差情况,本文以昆明某高校大学生受试者为试验对象,分别...为探究气候温和地区高校教室内的热舒适性,且修正预测热感觉和不满意度模型(predicted mean vote-predicted percentage of dissatisfaction,PMV-PPD模型)与实际热感觉投票值存在偏差情况,本文以昆明某高校大学生受试者为试验对象,分别测试室内环境参数、人员评估环境温度(t_(1))以及受试者主观评价等,共获得2229份有效数据。结果表明:在自然通风教室中,超过80%的大学生可以接受当前的热湿环境,PMV与实际平均热感觉投票(mean thermal sensation,MTS)模型相关较弱,PMV模型高估了受试者的实际热感觉,实测人员不满意百分比普遍大于预测不满意百分比。鉴于PMV模型预测准确性较低,综合考虑温度变化、主观反应等影响因素,提出人员评估环境温度(t_(1))作为修正性指标。人员评估环境温度与实际环境温度存在较强相关性,且在不同场景中两者温差值小于1.5℃。将t_(1)与热感觉投票进行回归分析,该参数与热感觉投票高度相关。在PMV计算中使用t_(1)代替空气温度对PMV模型进行修正得到tPMV,修正后的tPMV更接近于MTS模型,对PMV起到显著有效的修正作用。展开更多
基于三维k-ε湍流模型,利用Fluent软件模拟了高温高湿回采工作面中的热环境.并根据热舒适性的评价指标PMV-PPD(Predicted mean vote-predicted percentage of dissatisfied)对巷道中热环境进行预测和评价,给出了高温高湿回采工作面中的...基于三维k-ε湍流模型,利用Fluent软件模拟了高温高湿回采工作面中的热环境.并根据热舒适性的评价指标PMV-PPD(Predicted mean vote-predicted percentage of dissatisfied)对巷道中热环境进行预测和评价,给出了高温高湿回采工作面中的速度场、温度场、热舒适性指标PMV、PPD分布图.结果表明:当入口空气速度0.5≤v≤1.0m/s时,送风温度在18≤t≤22℃比较合适.当入口空气速度1.0<v<4m/s时,以22℃送风时人体有吹风感,但是人体处于-1≤PMV≤+1舒适范围,能满足矿工的热舒适要求.高温高湿回采工作面通过优化送风速度和送风温度,可满足井下作业人员的热舒适性要求,同时达到节约能源目的.展开更多
近年来,随着变频恒温技术的发展,变频空调给需求响应(demand response,DR)控制策略带来了新的机遇与挑战。文章引入PMV-PPD(predicted mean vote-predicted percentage of dissatisfied)用户舒适度量化评估模型,提出了一种考虑热舒适度...近年来,随着变频恒温技术的发展,变频空调给需求响应(demand response,DR)控制策略带来了新的机遇与挑战。文章引入PMV-PPD(predicted mean vote-predicted percentage of dissatisfied)用户舒适度量化评估模型,提出了一种考虑热舒适度的多家庭变频空调群组恒温控制策略,综合考虑用户舒适体验和负荷削减容量最大化。首先,以用户热舒适度与空调负荷最大削减为目标,确定变频空调单机恒温控制的最优设定温度,建立了空调群组非分组恒温控制策略。然后,针对不同调度周期,分析评估空调群组非分组控制的可削减容量及机会响应损失;提出当调度周期在一定范围内时可以通过分组控制减少机会响应损失,建立了动态分组轮控策略模型,更加充分地挖掘了家庭空调负荷的需求响应潜力,并获得了可削减容量稳定的需求响应资源。最后,算例验证表明该策略的可行性和有效性。展开更多
基金funded by a Special Fund for Basic Research on Scientific Instruments of the National Natural Science Foundation of China(Grant No.41827807)the Study on Intelligent Technology for Tunnels Construction of Sichuan-Tibet Railway(Grant No.19-21-1).
文摘The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical forms.This study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy model.The developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical significance.The overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed granite.The applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,e.g.deep rock mass.The PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical solutions.The sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock dilatancy.Tunnel deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior.
文摘为探究气候温和地区高校教室内的热舒适性,且修正预测热感觉和不满意度模型(predicted mean vote-predicted percentage of dissatisfaction,PMV-PPD模型)与实际热感觉投票值存在偏差情况,本文以昆明某高校大学生受试者为试验对象,分别测试室内环境参数、人员评估环境温度(t_(1))以及受试者主观评价等,共获得2229份有效数据。结果表明:在自然通风教室中,超过80%的大学生可以接受当前的热湿环境,PMV与实际平均热感觉投票(mean thermal sensation,MTS)模型相关较弱,PMV模型高估了受试者的实际热感觉,实测人员不满意百分比普遍大于预测不满意百分比。鉴于PMV模型预测准确性较低,综合考虑温度变化、主观反应等影响因素,提出人员评估环境温度(t_(1))作为修正性指标。人员评估环境温度与实际环境温度存在较强相关性,且在不同场景中两者温差值小于1.5℃。将t_(1)与热感觉投票进行回归分析,该参数与热感觉投票高度相关。在PMV计算中使用t_(1)代替空气温度对PMV模型进行修正得到tPMV,修正后的tPMV更接近于MTS模型,对PMV起到显著有效的修正作用。
文摘基于三维k-ε湍流模型,利用Fluent软件模拟了高温高湿回采工作面中的热环境.并根据热舒适性的评价指标PMV-PPD(Predicted mean vote-predicted percentage of dissatisfied)对巷道中热环境进行预测和评价,给出了高温高湿回采工作面中的速度场、温度场、热舒适性指标PMV、PPD分布图.结果表明:当入口空气速度0.5≤v≤1.0m/s时,送风温度在18≤t≤22℃比较合适.当入口空气速度1.0<v<4m/s时,以22℃送风时人体有吹风感,但是人体处于-1≤PMV≤+1舒适范围,能满足矿工的热舒适要求.高温高湿回采工作面通过优化送风速度和送风温度,可满足井下作业人员的热舒适性要求,同时达到节约能源目的.
文摘近年来,随着变频恒温技术的发展,变频空调给需求响应(demand response,DR)控制策略带来了新的机遇与挑战。文章引入PMV-PPD(predicted mean vote-predicted percentage of dissatisfied)用户舒适度量化评估模型,提出了一种考虑热舒适度的多家庭变频空调群组恒温控制策略,综合考虑用户舒适体验和负荷削减容量最大化。首先,以用户热舒适度与空调负荷最大削减为目标,确定变频空调单机恒温控制的最优设定温度,建立了空调群组非分组恒温控制策略。然后,针对不同调度周期,分析评估空调群组非分组控制的可削减容量及机会响应损失;提出当调度周期在一定范围内时可以通过分组控制减少机会响应损失,建立了动态分组轮控策略模型,更加充分地挖掘了家庭空调负荷的需求响应潜力,并获得了可削减容量稳定的需求响应资源。最后,算例验证表明该策略的可行性和有效性。
