Modeling walking behavior of pedestrian groups with floor field cellular automaton approach

Walking in groups is very common in a realistic walking environment. An extended floor field cellular automaton （CA） model is therefore proposed to describe the walking behavior of pedestrian groups, This model represents the motion of pedestrian groups in a realistic way. The simulation results reveal that the walking behavior of groups has an important but negative influence on pedestrian flow dynamics, especially when the density is at a high level. The presence of pedestrian groups retards the emergence of lane formation and increases the instability of operation of pedestrian flow. Moreover, the average velocity and volume of pedestrian flow are significantly reduced due to the group motion. Meanwhile, the parameter-sensitive analysis suggests that pedestrian groups should make a compromise between efficient movement and staying coherent with a certain spatial structure when walking in a dense crowd.

An extended cellular automata model with modified floor field for evacuation

The floor field model has been widely used in evacuation simulation research based on cellular automata model. However, conventional methods of setting floor field will lead to highly insufficient utilization of the exit area when people gather on one side of the exit. In this study, an extended cellular automata model with modified floor field is proposed to solve this problem. Additionally, a congestion judgment mechanism is integrated in our model, whereby people can synthetically judge the degree of congestion and distance in front of them to determine whether they need to change another exit to evacuate or not. We contrasted the simulation results of the conventional floor field model, the extended model proposed in this paper, and Pathfinder software in a same scenario. It is demonstrated that this extended model can ameliorate the problem of insufficient utilization of the exit area and the trajectory of pedestrian movement and the crowd shape of pedestrians in front of exit in this new model are more realistic than those of the other two models. The findings have implications for modeling pedestrian evacuation.

Efficient Dynamic Floor Field Methods for Microscopic Pedestrian Crowd Simulations

Floor field methods are one of the most popular medium-scale navigation concepts in microscopic pedestrian simulators.Recently introduced dynamic floor field methods have significantly increased the realism of such simulations,i.e.agreement of spatio-temporal patterns of pedestrian densities in simulations with real world observations.These methods update floor fields continuously taking other pedestrians into account.This implies that computational times are mainly determined by the calculation of floor fields.In this work,we propose a new computational approach for the construction of dynamic floor fields.The approach is based on the one hand on adaptive grid concepts and on the other hand on a directed calculation of floor fields,i.e.the calculation is restricted to the domain of interest.Combining both techniques the computational complexity can be reduced by a factor of 10 as demonstrated by several realistic scenarios.Thus on-line simulations,a requirement of many applications,are possible for moderate realistic scenarios.

Comparative Analysis of the Distribution Characteristics of Floor Stress Field between Gob-Side Entry Retaining with Roof Cutting and Conventional Mining

All coal fields in North China are affected by floor confined water to varying degrees, floor failure and water inrush risk have always been a major problem to baffle coal mining activities. Roof cutting and pressure relief and the lack of protective coal pillar can cause the change of floor stress field, leading to the change of the floor failure depth, stress field of floor is the key to determine the depth of floor failure. In order to deeply study the distribution characteristics of floor stress field in gob-side entry retaining mining with roof cutting, taking the 50107 and 50109 working faces of Dongdong Coal Mine in Chenghe as the research objects, the numerical simulation software is used to simulate the floor stress field distribution of gob-side entry retaining mining with roof cutting and conventional mining. The distribution characteristics of the floor stress field of the working face are compared and analyzed under the three modes of conventional mining of reserved coal pillar, the first mining face of gob-side entry retaining with roof cutting and gob-side entry retaining with roof cutting. The results show that the peak stress concentration in front of the working face all occurs at 10 m under the three mining modes. The stress concentration area in front of conventional working face of reserved coal pillar is mainly in the middle of the working face. The stress concentration area in front of the first working face of gob-side entry retaining with roof cutting (50107) is located in the middle of the working face and the side of the working face of the retaining roadway. The stress concentration area of the working face (50109) is mainly in the middle and the two ends of the working face. The order of the peak value of the maximum concentrated stress in front of the working face is conventional working face of reserved coal pillar > the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109). There is a stress reduction zone behind the working face, but there is a stress concentration phenomenon extending to the outside of the roadway, and the stress distribution is obviously different. Conventional working face of reserved coal pillar and the first working face of gob-side retaining with roof cutting (50107) show a double peak form of stress concentration on the outside of the two ends of the roadway, and the peak value of the concentrated stress at the rear of the working face is in the following order: On the side close to the transportation roadway, conventional working face of reserved coal pillar = the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109);on the side close to the return airway, conventional working face of reserved coal pillar > the first working face of gob-side entry retaining with roof cutting (50107) > working face of gob-side entry retaining with roof cutting (50109).

Numerical analysis of the destruction of water-resisting strata in a coal seam floor in mining above aquifers

With the increase in mining depth many mining areas in China have entered a period necessitating mining above aquifers. Production safety in coal mines in northern China is under serious threat from Ordovician karst water on coal seam floors, in order to analyze the destruction of water-resisting strata in floors of coal seams being mined and to achieve safe mining above deep aquifers, we established a numerical model of water-resisting strata, considering the structural characteristics and mechanical properties of a floor layered with hard and soft rock. We simulated the distribution characteristics of deformation, failure and seepage using the analytical module of fluid-structure interaction of FLAt：. We also obtained the corresponding stress distribution, deformation and flow vectors. Our results indi- cate that： （1） the advance of the working face causes water-resisting strata in goaf floors to form a deep double-clamped beam, subject to homogeneous loading at the bottom; （2） the two sides of the rock beam are subject 1~0 shear failure; （3） both sides of the rock seam at the bottom of the water-resisting strata are subject to tension and the greater the working face advance, the more serious the failure; C4） the original balance of the stress and seepage fields are broken and redistributed due to mining activities, especially the interaction of the abutment pressure in both sides of the goal; the lateral pressure on the goal floor and the water pressure on the floor of the aquifer promote floor heave and shear failure on both sides of the floor, forming a water-inrush passage. Our study results can provide references for the mechanism of water-inrush on mine floors.

考虑恐慌情绪和信息传递的行人疏散模拟

为分析应急疏散过程中恐慌情绪和信息传递对行人疏散效率的影响,提出基于热传递原理的情绪感染模型和元胞自动机场域模型相结合的疏散模拟方法。该方法通过量化的恐慌值影响行人决策偏好,并引入信息扩散模型,修正成功接收到出口信息的人群的疏散路径,模拟研究恐慌情绪作用下行人受到信息引导后疏散行为的变化。研究结果表明:恐慌情绪感染主要出现在人群聚集时期,伴随恐慌的蔓延,整体疏散效率降低,且对小规模行人疏散影响效果更显著;随着危险源向出口靠近,恐慌情绪使行人做出非理性决策的可能性更大,导致出口处人群出现分散再聚集现象;有效的信息传递可以降低恐慌情绪影响、提高疏散出口利用率,且信息传递影响效果随疏散人数的减少和危险源向出口的靠近而有所增强。研究结果可为提升应急疏散效率提供理论支持。

考虑折返行为的元胞自动机人员疏散模型

为研究行人折返行为对疏散的影响,考虑多出口对行人的吸引力、人员相互作用力、火源蔓延威胁以及折返场吸引力的共同影响,在元胞自动机模型的基础上提出基于静态场、动态场、火源场以及折返场共同作用的行人疏散场域模型,研究不同折返比例、折返区域、人员密度、出口数量和位置情况下折返行为对疏散进程的影响。研究结果表明:少量折返行为对总疏散时间影响较小,而群体性折返行为的存在会增加总体疏散时间,随着折返比例的增加,疏散时间随之增加。折返区域离出口越近,对总体疏散效率的影响越小。折返行为对疏散进程的影响效果,随着人员密度的增加不断增强。在双出口条件下,对侧设置出口位置能有效减少折返行为对疏散进程的负面影响。研究结果可为提高紧急情况下的疏散效率提供参考。

基于实测数据和灰度模型的船闸底板混凝土温度变化预测

船闸底板冬季施工时环境温度较低,大体积混凝土内外温差较大,在底板冬季温升过程中,温差超限的问题突出,养护不当极易出现开裂,有效预测底板温升变化尤为重要。基于实测数据,利用灰色模型分别按不同监测频次、不同原始序列分时段对温度变化进行预测,并对该模型进行了修正,用修正模型分时段预测了底板浇筑后3 d内的温升变化。根据精度及残差对比,监测时隔2 h结合数值原始序列、监测间隔3~6 h结合3数值原始序列的两种灰色模型预测方法合理有效,修正后的模型可有效提高精度及延长预测时长,用于指导温控,降低大体积混凝土开裂风险,为保障船闸底板结构安全提供科学支撑。

考虑换乘通道利用的地铁换乘站行人疏散引导策略研究

换乘地铁站的安全管理因其结构更为复杂、客流交织更为严重而备受关注。以某T形换乘地铁站为例,基于元胞自动机场域模型构建了考虑换乘通道利用程度的行人紧急疏散模型,并分别设计了面向站台层和站厅层的行人引导策略,对比分析了不同疏散策略组合对换乘地铁站行人疏散的影响。结果表明:T形换乘地铁站中等规模(约3000人)疏散场景下,与无引导策略相比,同时考虑站台引导和站厅引导的疏散用时更短,且疏散人员分布更均衡;针对换乘通道利用程度调配的疏散分区设计,存在最优分隔间距,总疏散人数的变化对最优分隔间距没有影响,但疏散人员在各个站台的分布比例对最优分隔间距有一定的影响。研究有助于T形换乘地铁站内的密集人群安全管理。

浅海孤立子内波作用下的三维声场空间特性

针对浅海环境下孤立子内波对声场空间特性的影响,以三维抛物方程理论及高精度根式算子近似方法为基础,建立了适应孤立子内波环境的三维声场计算方法。充分考虑孤立子内波传播特点与浅海中点源柱扩散形式的声场结构特征,形成以直角坐标系−柱坐标系的联合环境处理的声场计算形式,通过改变环境参数输入形式,提升了计算效率,并研究了孤立子内波影响下的三维声场分布特性。结果表明,平坦海底情况下,内波影响下的三维声场垂直和水平分布结构均发生变化,且随频率增加而增大,尤其是声源深度在跃层附近时变化更为明显;非平坦海底环境下,三维声场受到非水平海底和内波的双重调制作用,导致孤立子内波影响下的声场水平分布变化进一步加剧,从而在一定程度上反映出海底地形这一大尺度非均匀性对声场产生的水平折射效应以及对声传播特性的影响。

超化煤矿“三软”煤层采动底板变形破坏的实测研究

通过现场应变实测系统研究了郑州矿区超化煤矿"三软"煤层底板采动变形破坏的深度及其受采动煤壁前方影响的范围。得出了在正常采动情况下厚的软煤和软底对应力和变形的传播具有一定的缓冲作用,受超前应力集中的影响,竖直应力的变化比水平应力大。揭示了中段灰岩组对应力分布和变形破坏的重要控制作用,为豫西煤炭资源向深部开采所引起的底板水防治提供了部分参考的依据。

考虑环境熟悉度的行人疏散模型研究

为研究不同环境熟悉度下行人疏散时的特性,将熟悉度参数引入到传统地场模型中,修正模型的转移概率,并将模型中原有动态场改进为基于距离选择的动态场,建立扩展的行人疏散模型。以无障碍物建筑物及教室为例,分析熟悉度不变、可变时各参数对行人疏散的影响。数值模拟结果表明,扩展模型在给定静态参数条件下,疏散时间随熟悉程度的增加而减少;熟悉度较低时,陌生概率下的跟随移动策略优于其他策略;同时模型能够避免自身及后方行人的干扰。该模型可为建筑物设计、疏散性能评估和突发事件下的疏散引导等提供一定指导。

基于教室人群疏散实验的行人流建模和模拟

基于教室人群疏散实验,从中归纳出疏散过程中行人的基本运动特征.将桌椅分别视为不可穿越和可穿越的静态障碍物,而行人则被当成可移动的障碍物,这将导致背景场随人群的运动而动态更新,因此可以更好地反映前方拥挤程度对后面人群路径选择行为的影响.采用基于动态背景场的元胞自动机模型研究了不同桌椅排列和出口宽度的教室人群疏散过程,给出了疏散时间的空间分布以及平均和最大疏散时间,再现了实验中人群疏散的基本特征.数值模拟结果表明,疏散时间取决于桌椅的排列方式和教室出口的宽度.对于同一种排列,出口越小则疏散时间越长;对于给定的出口宽度,通常随着过道数的增加,疏散时间随之减少;当过道数增加且过道宽度不足以两人并行,从两侧进入过道的行人会发生冲突,使疏散效率有所降低;靠近出口一侧墙壁设置过道有利于人群的疏散.文中进一步分析了模拟与实验结果存在差异的原因.

基于元胞自动机的火源威胁下人员疏散模型

为研究火源对人员疏散的影响,在现有场域模型的基础上进行扩展,结合元胞自动机提出1种考虑多出口吸引、人员从众行为与火源威胁3者耦合作用的场域疏散模型。此模型综合考虑心理和环境等因素,定量描述人员之间、人与环境之间的相互影响,将出口吸引、从众心理与火源威胁3个影响行人疏散决策的元素归一化,以静态场和动态场耦合作用确定的转移概率作为行人移动的准则。采用此模型,分别对火源位置、火源威胁范围扩散速度在疏散中的影响进行模拟研究。结果表明:模型在一定程度上能够反映火源威胁下行人的疏散过程,再现了行人躲避和趋众行为,能为火源威胁下行人疏散提供理论借鉴。

多障碍情境下矿工紧急疏散建模及仿真

为克服基于最短距离方法构建的地面场在指引元胞移动时由于路径上存在障碍物而不可行的弊端,提出了一种用元胞格点到出口的最短路径构建地面场的新方法。在此基础上,以多障碍情景下的矿工疏散问题为例,假设矿工以无后退移动方式疏散,建立了矿工紧急疏散模型,并用Matlab进行了仿真模拟。结果表明,构建的模型能够真实地模拟矿工的疏散行为,平均疏散时间随位置保持概率增大而迅速增大的模拟结果与实际情况相符。

双出口房间人群疏散的出口选择行为

采用基于背景场的元胞自动机模型研究双出口房间的人群疏散.为了刻画行人的出口选择行为,引入了衰减背景场,其中考虑了出口处拥堵的影响.出口区域内人数的变化导致衰减背景场随之动态改变.在疏散过程中,行人根据变化的背景场来选择出口.数值模拟结果显示,在衰减背景场的作用下,多数行人选择大出口,少数行人选择小出口.从两个出口离开的人群几乎同时完成疏散,因此疏散时间明显缩短,两个出口都得到了有效利用.背景场衰减系数可以作为衡量行人对出口拥堵状况变化敏感程度的标志,但衰减系数并非越大越好.当衰减系数较大时,会出现振荡流并导致疏散时间变长.确定了临界衰减系数,当衰减系数取临界值时,疏散时间最短,出口利用率最大.模拟结果表明,采用衰减背景场可以很好地描述多出口人群疏散的出口选择行为.

底板采动破坏深度实测与模拟

针对煤矿底板突水问题,确定底板采动破坏深度是评价底板是否突水的重要因素之一.以山东东山矿业王楼煤矿11 301工作面为工程背景,采用钻孔双端堵水设备对工作面底板破坏深度进行了现场实测.基于FLAC3D数值模拟软件,根据王楼煤矿11 301工作面地质条件建立了数值模型,对该工作面底板应力场变化及底板变形破坏规律进行了数值仿真.研究结果表明:现场实测工作面开采后底板采动破坏深度为12.9 m,模拟结果显示底板破坏深度在12~15 m.实测结果与数值模拟结果相吻合,说明所建模型可以为相似条件下工作面开采底板破坏深度进行预测,为底板承压水上安全开采提供基础资料,对预防底板水害有一定的指导意义.

高承压水上采煤底板突水通道形成的监测与数值模拟

底板采动破坏及导水通道的形成是底板突水发生的必要条件,也是进行矿井突水的监测预报基础。以新义矿为例,采用现场监测及数值模拟等手段,研究高承压水上采煤底板采动破坏及突水通道的形成及演化过程,分析该过程中的底板电阻率、应力及孔隙水压力的变化规律。结果表明:高承压水上采煤底板受工作面超前支撑压力破坏严重,11011工作面底板破坏深度达到25 m,大于一般经验计算值;建立的基于流-固耦合底板采动破坏数值模拟模型更能准确、客观地反映底板破坏的影响因素,模拟的最大破坏深度为23.75 m,与现场监测结果接近;采动过程中的底板电阻率、应力以及孔隙水压力变化较好地反映底板破坏及突水通道形成、演化以及充水的整个过程,可作为矿井突水临突监测预报的重要信息源。

基于ANSYS的火灾下楼板的温度场研究

利用有限元分析软件ANSYS对火灾情况下楼板的温度场进行分析,获得了楼板截面温度场的分布规律,计算结果与试验结果吻合良好,为进一步研究钢筋混凝土楼板高温下的力学性能创造了条件。

元谋干热河谷辣木人工林地灌水后不同覆盖措施对土壤水分及辣木物候的影响

根据元谋干热河谷气候特点,2010年初步研究了旱坡地辣木人工林地灌溉后地表盖草和覆膜的土壤水分及其变化状况,研究结果得出:(1)在地面覆盖物作用下,无论是沙土、沙壤土还是黏土样地,耕作层0-20cm、20-40cm土壤水分高于未覆盖样株的土壤水分,辣木生育期比未覆盖提前。总体表明,盖膜土壤水分增加最多,在0-20cm土层,2龄辣木树10d的土壤水分高于对照1.2%～4.6%,幼龄辣木树(栽植8个月)10d的土壤水分高于对照1.8%～4.7%。其次是草覆盖,在0-20cm土层,2龄辣木树10d的土壤水分高于对照2.6%～3.4%,幼龄辣木树(栽植8个月)10d的土壤水分高于对照1.8%～4.6%。土层20-40cm下土壤水分变化较小。(2)由于土壤质地差异,无论是灌水量的多少与处理的不同,沙土蒸发均高于沙壤土,而且变化较大,沙壤土变化均匀,黏土较保水。深层土壤水分总体趋势是随土壤深度增加而增加,增加幅度随之减少。