Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the s...Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.展开更多
智能网联车辆队列行驶面临复杂的交通环境,所引发的时延、丢包等信息传输问题将导致队列车辆行驶稳定性降低而亟待解决.针对复杂交通环境,引入信息新鲜度(age of information, AoI)并提出了一种适应时变时延的智能网联车辆队列行驶稳定...智能网联车辆队列行驶面临复杂的交通环境,所引发的时延、丢包等信息传输问题将导致队列车辆行驶稳定性降低而亟待解决.针对复杂交通环境,引入信息新鲜度(age of information, AoI)并提出了一种适应时变时延的智能网联车辆队列行驶稳定性控制算法.该控制算法根据队列中多前车信息新鲜度来调整其对队列车辆车头间距影响的权重,同时依据时变时延信息预测队列中跟驰车辆与前车的车头间距,队列车辆按照请求周期向路侧单元(road side unit, RSU)实时发送请求,RSU依据车辆间距从小到大依次回应请求队列中的各个车辆,以控制其因时变时延可能造成的碰撞.数值仿真结果显示,相对智能驾驶员模型(intelligent driver model, IDM)而言,所提出的队列纵向稳定性控制算法具有更好的控制效果.针对时变时延发生概率20%的车车通信,队列车辆车头间距偏差的降低比例达6.4%,平均峰值信息新鲜度的降低比例达8.7%.同时,分析了队列车辆请求周期和回应请求车辆数量对队列纵向稳定性的影响,随着两者数值增加,控制算法给出的队列纵向稳定性分别呈现降低和增加的趋势.最后,实车测试了队列切出场景下车辆行驶数据和车辆接收信息的时延数据,将其引入数值仿真实验中.结果表明,车头间距偏差降低比例达15%.展开更多
针对网联车队列系统易受到干扰和拒绝服务(Denial of service, DoS)攻击问题,提出一种外部干扰和随机DoS攻击作用下的网联车安全H∞队列控制方法.首先,采用马尔科夫随机过程,将网联车随机DoS攻击特性建模为一个随机通信拓扑切换模型,据...针对网联车队列系统易受到干扰和拒绝服务(Denial of service, DoS)攻击问题,提出一种外部干扰和随机DoS攻击作用下的网联车安全H∞队列控制方法.首先,采用马尔科夫随机过程,将网联车随机DoS攻击特性建模为一个随机通信拓扑切换模型,据此设计网联车安全队列控制协议.然后,采用线性矩阵不等式(Linear matrix inequality, LMI)技术计算安全队列控制器参数,并应用Lyapunov-Krasovskii稳定性理论,建立在外部扰动和随机DoS攻击下队列系统稳定性充分条件.在此基础上,分析得到该队列闭环系统的弦稳定性充分条件.最后,通过7辆车组成的队列系统对比仿真实验,验证该方法的优越性.展开更多
基金Financial support for this work was provided by the General Program and Youth Fund Program of the National Natural Science Foundation of China(Grant Nos.42377175 and 42002292).
文摘Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling(HLSCB)mining method.At the design stage,it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars(i.e.cohesion and internal friction angle)when they are supported by cemented backfilling.In this study,a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine.A new method of estimating the shear strength of such pillars was then proposed based on the Hoek eBrown failure criterion.Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value.A reasonable and effective value for σ3max can then be determined.The value of s3max predicted using the proposed method is generally less than 3 MPa.Within this range,the shear strength of the high-level pillar is accurately calculated using the equivalent MohreCoulomb theory.The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original HoekeBrown criterion is used in the presence of large confining pressures,i.e.the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided.The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method.The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations.The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.
文摘智能网联车辆队列行驶面临复杂的交通环境,所引发的时延、丢包等信息传输问题将导致队列车辆行驶稳定性降低而亟待解决.针对复杂交通环境,引入信息新鲜度(age of information, AoI)并提出了一种适应时变时延的智能网联车辆队列行驶稳定性控制算法.该控制算法根据队列中多前车信息新鲜度来调整其对队列车辆车头间距影响的权重,同时依据时变时延信息预测队列中跟驰车辆与前车的车头间距,队列车辆按照请求周期向路侧单元(road side unit, RSU)实时发送请求,RSU依据车辆间距从小到大依次回应请求队列中的各个车辆,以控制其因时变时延可能造成的碰撞.数值仿真结果显示,相对智能驾驶员模型(intelligent driver model, IDM)而言,所提出的队列纵向稳定性控制算法具有更好的控制效果.针对时变时延发生概率20%的车车通信,队列车辆车头间距偏差的降低比例达6.4%,平均峰值信息新鲜度的降低比例达8.7%.同时,分析了队列车辆请求周期和回应请求车辆数量对队列纵向稳定性的影响,随着两者数值增加,控制算法给出的队列纵向稳定性分别呈现降低和增加的趋势.最后,实车测试了队列切出场景下车辆行驶数据和车辆接收信息的时延数据,将其引入数值仿真实验中.结果表明,车头间距偏差降低比例达15%.
