Vertical coherency function model of spatial ground motion

Many studies have focused on horizontal ground motion, resulting in many coherency functions for horizontal ground motion while neglecting related problems arising from vertical ground motion. However, seismic events have demonstrated that the vertical components of ground motion sometimes govern the ultimate failure of structures. In this paper, a vertical coherency function model of spatial ground motion is proposed based on the Hao model and SMART 1 array records, and the validity of the model is demonstrated. The vertical coherency function model of spatial ground motion is also compared with the horizontal coherency function model, indicating that neither model exhibits isotropic characteristics. The value of the vertical coherency function has little correlation with that of the horizontal coherency function. However, the coherence of the vertical ground motion between a pair of stations decreases with their projection distance and the frequency of the ground motion. When the projection distance in the wave direction is greater than 800 meters, the coherency between the two points can be neglected.

Engineering characteristics of near-fault vertical ground motions and their effect on the seismic response of bridges

A wide variety of near-fault strong ground motion records were collected from various tectonic environments worldwide and were used to study the peak value ratio and response spectrum ratio of the vertical to horizontal component of ground motion, focusing on the effect of earthquake magnitude, site conditions, pulse duration, and statistical component. The results show that both the peak value ratio and response spectrum ratio are larger than the 2/3 value prescribed in existing seismic codes, and the relationship between the vertical and horizontal ground motions is comparatively intricate. In addition, the effect of the near-fault ground motions on bridge performance is analyzed, considering both the material nonlinear characteristics and the P-A effect.

Vertical-to-horizontal response spectral ratio for offshore ground motions:Analysis and simplified design equation

In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.

Vertical Observations and Analysis of PM_(2.5),O_3,and NO_x at Beijing and Tianjin from Towers during Summer and Autumn 2006

During the period between 18 August and 22 September 2006, an ultraviolet photometric O3 analyzer, a NO-NO2-NOx chemiluminescence analyzer, and a quartz micro-oscillating-scale particle concentration analyzer were simultaneously used for monitoring at three different heights each at Beijing （325-m tower） and Tianjin （255-m tower）. These towers belong to the Institute of Atmospheric Physics （IAP） of the Chinese Academy of Sciences （CAS） and to the Tianjin Municipal Meteorological Bureau, respectively. These measurements were used to continuously measure the atmospheric O3 and NOx volume-by-volume concentrations and the PM2.5 mass concentration within a vertical gradient. When combined with meteorological data and information on the variation of vertical characteristics of the various atmospheric pollutants in the two cities, analysis shows that these two cities were seriously polluted by both PM2.5 and O3 during summer and autumn. The highest daily-average concentrations of PM2.5 near the ground in Beijing and Tianjin reached 183 μgm a and 165 μg m^-3, respectively, while the 03 concentrations reached 52 ppb and 77 ppb, and NOx concentrations reached 48 ppb and 62 ppb for these two cities, respectively. The variations in the daily-average concentrations of PM2.5 between Beijing and Tianjin were demonstrated to be consistent over time. The concentrations of PM2.5 measured in Beijing were found to be higher than those in Tianjin. However, the overall O3 concentrations near the ground in Tianjin were higher than in Beijing. NOx concentrations in Tianjin were consistently lower than in Beijing. It was also found that PMz5 pollution in Beijing＇s atmosphere may also be affected by the pollutants originating in and delivered from Tianjin, and that Tianjin was impacted by Beijing＇s pollutants at a significantly reduced level.

Role of equal-strain assumption in unit-cell theory for consolidation with vertical drains

In the development of unit-cell theory for the analytical analysis of consolidation with vertical drains, the equal-strain assumption is often made with the intention of modelling consolidation under uniform settlement conditions. In contrast, the free-strain assumption for modelling consolidation under uniform load conditions is seldom employed, mainly because of the complexities involved in the analysis. This study derives a rigorous analytical solution to the generalised governing equations of free-strain consolidation with a vertical drain subjected to an instantaneous load. Calculated results from the newly proposed solution are compared with those from three available solutions derived based on the equal-strain assumption. Surprisingly good agreement is obtained in terms of excess pore-water pressure, degree of consolidation, and settlement. Horizontal profiles of settlement were not uniform before the end of consolidation. This indicates that the uniform settlement condition is not actually reproduced by the analytical solutions derived based on the equal-strain assumption. The equal-strain assumption is a sufficient but not necessary condition for deriving an analytical solution to unit-cell consolidation theory. The assumption plays no role in modelling consolidation under uniform settlement conditions but simplifies the analytical analysis of free-strain consolidation and results in an approximate solution of high accuracy for consolidation under uniform load conditions. Moreover, drain resistance and smear effects not only retard the consolidation rate, but also importantly shape the vertical and horizontal profiles of excess pore-water pressure, respectively.

Analytical solution for vertical site response analysis and its validation

Existing studies for site response analysis in geotechnical earthquake engineering have widely concentrated on the horizontal component of the ground motion. However, strong vertical ground motions have been repeatedly observed, resulting in significant vertical compression damage of engineering structures. Furthermore, for the seismic design of critical structures(e.g. large-scale dams and nuclear power plants), the ground motions in all three directions should be considered. Therefore, there is a need to investigate the site response subjected to the vertical component of the ground motion, especially for the seismic design of critical structures. Consequently, in this study, a numerical program for vertical site response analysis is proposed based on the commonly used analytical transfer function method. The proposed program is then validated against well-documented case studies obtained from the Japanese KiK-net(Kiban Kyoshin network) downhole array monitoring system. Results show that the response spectra at the ground surface are well predicted in the low frequency range(<5 Hz), while discrepancies are observed in the high frequency range. However, the high frequency discrepancies do not significantly affect the overall prediction accuracy, as the overall seismic response of geotechnical structures are usually dominated by low frequency vibrations. Furthermore, the limitations in the analysis are also discussed.

Vertical deformation and tectonic activity in Tianjin area

Vertical deformation in Tianjin area during 1992 -2008 was calculated from leveling data. The effect of large surface subsidence caused by extensive groundwater pumping was removed by fitting the data along each survey line with a polynomial function. The results are fitted with crustal blocks individually in this area. Vertical deformation rates are mapped, vertical rates of the main fault zones were calculated, and the activities of the blocks and fault zones were investigated. The observed vertical deformation shows that some of the blocks tilted and some blocks rose or subsided as a whole. The vertical rates at fault zones in the area vary within the range of 0. 13-0. 48 mm/a,with an average value of 0.29 mm/a.

Effect of seawater on incident plane P and SV waves at ocean bottom and engineering characteristics of offshore ground motion records off the coast of southern California, USA

The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of seawater on incident plane P and SV waves at ocean bottom indicate that on one hand, the affected frequency range of vertical ground motions is prominent due to P wave resonance in the water layer if the impedance ratio between the seawater and the underlying medium is large, but it is greatly suppressed if the impedance ratio is small; on the other hand, for the ocean bottom interface model selected herein, vertical ground motions consisting of mostly P waves are more easily affected by seawater than those dominated by SV waves. The statistical analysis of engineering parameters of offshore ground motion records indicate that:(1) Under the infl uence of softer surface soil at the seafl oor, both horizontal and vertical spectral accelerations of offshore motions are exaggerated at long period components, which leads to the peak spectral values moving to a longer period.(2) The spectral ratios(V/H) of offshore ground motions are much smaller than onshore ground motions near the P wave resonant frequencies in the water layer; and as the period becomes larger, the effect of seawater becomes smaller, which leads to a similar V/H at intermediate periods(near 2 s). These results are consistent with the conclusions of Boore and Smith(1999), but the V/H of offshore motion may be smaller than the onshore ground motions at longer periods(more than 5 s).

Reduction in ground reaction force variables with instructed barefoot running

Backgound:Barefoot(BF) running has recently increased in popularity with claims that it is more natural and may result in fewer injuries due to a reduction in impact loading.However,novice BF runners do not necessarily immediately switch to a forefoot strike pattern.This may increase mechanical parameters such as loading rate,which has heen associated with certain running-related injuries,specifically,tibial stress fractures.patellofemoral pain,and plantar iasciitis.The purpose of this study was to examine changes in loading parameters between typical shod running and instructed BF running with real-time force feedback.Methods:Forty-nine patients seeking treatment for a lower extremity injury ran on a force-sensing treadmill in their typical shod condition and then BF at the same speed.While BF they received verbal instruction and real-time feedback of vertical ground reaction forces.Results:While 92%of subjects(n = 45) demonstrated a rearfoot strike pattern when shod,only 2%(n = 1) did during the instructed BF run.Additionally,while BF 47%(n = 23) eliminated the vertical impact transient in all eight steps analyzed.All loading variables of interest were significantly reduced from the shod to instructed BF condition.These included maximum instantaneous and average vertical loading rates of the ground reaction force(p 【 0.0001),stiffness during initial loading(p 【 0.0001).and peak medial(p = 0.001) and lateral(p 【 0.0001) ground reaction forces and impulses in the vertical(p 【 0.0001).medial(p = 0.047),and lateral(p 【 0.0001) directions.Conclusion:As impact loading has been associated with certain running-related injuries,instruction and feedback on the proper forefoot strike pattern may help reduce the injury risk associated with transitioning to BF running.

Measured Performance and Analysis of the Residual Settlement of a PVD-Improved Marine Soft Ground

Prefabricated vertical drains(PVDs)are commonly used to shorten the drainage path for consolidation as part of the improvement of marine soft ground.Many studies that focus on the primary consolidation settlement of PVD-improved soft ground have been conducted;however,residual settlement has been scarcely investigated.Residual settlement is the net effect of secondary compression and the remaining primary consolidation and generally occurs while the facilities are operating.In this study,residual settlement was investigated using the measured field settlement data obtained from the surface settlement plate and multilayer settlement gauges.This study determined that PVD still has some effect on residual settlement and can reduce the settlement times.Residual settlement is only related to the PVD-improved soil layer and only occurs significantly in the middle zone of that layer over a few months.The middle zone may be related to the time delay of excess pore water pressure dissipation.This study concluded that the remaining primary consolidation in the PVD-improved soil layer is the primary cause of residual settlement,whereas secondary compression in the PVD-improved soil layer is only a minor cause.

Turbulent Energy Budgets of a Ground Vortex Flow

Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.

Ground Magnetic, GPR, and Dipole-Dipole Resistivity for Landfill Investigation

Ground magnetic, ground penetrating radar (GPR), and dipole-dipole resistivity were carried out to environmentally investigate a landfill. In this context, these geophysical techniques were conducted to identify the subsurface contents of the landfill, furthermore, specify any possible leakage and/or contamination in the study area. The ground-magnetic survey carried out in the study area comprised 31 profiles each 120 m in length. Different wavelength filters were applied to the measured data. Vertical derivative, downward continuation, apparent susceptibility, band-pass, and analytical signal filters separated successfully the shallow sources. Whereas, upward continuation and low-pass Gaussian filters isolated significantly the deep magnetic sources. 3D Euler deconvolution (SI = 3) remarkably estimated the depths of the shallow sources (0 - 10 m) of the landfill contents. The conducted GPR and dipole-dipole resistivity allocated tangibly the locations and depths of the near surface anomalies. Both techniques didn’t reveal any possible leakage and/or contamination. Noteworthy, integration among magnetic, GPR, and dipole-dipole resistivity confirmed positively the results of each method. Nevertheless, some anomalies were recognized successfully by one technique and not by the others.

宜昌地基遥感垂直观测系统探测精度分析研究

宜昌地基遥感垂直观测系统能够实时监测本区域上空云、雾、弱降水、风速、风向、温度、相对湿度、液态含水量垂直廓线、气溶胶浓度等探测要素,增强突发性、灾害性天气监测能力.该文针对宜昌地基遥感垂直观测系统探测数据的准确性评估问题,提出了一种观测要素评估方法.方法使用了同址探空站的观测资料作为参考标准,通过对比时空匹配的垂直探测数据,分析宜昌垂直观测系统各类探测数据的准确性.通过该系统的垂直廓线产品联合观测2024年2月宜昌雨雪冰冻灾害天气过程,进行多条垂直廓线融合应用研究.定量分析结果表明:宜昌地基遥感垂直观测系统的数据质量全部满足评估指标要求,探测数据与探空资料相关性总体较好,可为气象监测提供精密的观测数据.

黄金矿山深井开采研究进展与发展趋势

详细阐述了黄金矿山深井开采国内外研究现状及所面临的技术难题,围绕采动岩石力学理论、岩体结构识别与岩体质量分级、矿山三维工程灾害建模、深部采矿设计方法研究、深部采场爆破落矿技术、采动地压调控、采动地压监测、自承载主动释压支护技术、深部采动对地表岩移影响、通风降温技术、智能开采技术、超深竖井建设等展开了详细的讨论与分析;对于黄金矿山非爆采矿机器人研制、采动岩石力学、深部采动地压灾害防控、深井降温技术、超深竖井建设、基于采动地压均衡的深部连续智能化开采技术等方面的未来发展趋势提出了展望,为黄金矿山深井开采的系统研究提供参考依据。

地基遥感垂直观测系统数据质量评估与产品融合分析

针对地基遥感垂直观测系统风向与风速、温度与相对湿度、云底高度与云顶高度、大气瑞利信号拟合误差与有效探测距离、大气可降水量与对流层总延迟等10种探测要素的数据准确性评估及融合产品有效性验证问题。以2024年1月1日至7月1日宜昌地基遥感垂直观测系统的实际探测资料为例,采用同址的L波段探空雷达观测数据作为参考标准,选取时空匹配的垂直廓线产品进行对比,评估地基遥感垂直观测系统探测数据的准确性,并综合运用系统高时空分辨率的融合产品,从大气动力结构、云雨结构等方面剖析宜昌地区2024年6月27—28日梅雨期降雨过程。研究结果表明:宜昌地基遥感垂直观测系统探测设备性能优良,运行较为稳定,能够在垂直方向上综合解析大气结构;运行评估期内,宜昌地基遥感垂直观测系统探测数据的准确性均满足评估指标,与探空观测资料的相关性总体较好;多条垂直廓线融合产品可以清晰展示降雨过程发生、发展、消散的垂直动态变化细节,证实了融合产品在天气分析中的有效性和实用性。

2022年四川泸定 M_(s)6.8地震强震动特性研究

北京时间2022年9月5日12时52分,四川省甘孜州泸定县发生M_(s)6.8级地震。国家强震动台网获得了133组三分量加速度记录,在对记录进行初步筛选和滤波后,研究了PGA和PGV衰减关系、竖向地震动特点、地震动速度脉冲,对比分析了反应谱和设计谱,着重对石棉挖角台站附近震害与地震动的相关性进行了分析,结论如下:1)三种台站强震动记录的PGA和PGV拟合曲线都比较相近,PGA、PGV拟合曲线与霍俊荣的预测模型较为接近;2)竖向地震动偏大,约38.2%的强震动记录V/H大于2/3,可能是屋顶塌落、柱子扭转和天花板坠落等震害现象出现的主要原因;3)识别出具有速度脉冲特性的记录11条,该类记录对长周期结构影响较大;4)所选记录反应谱大多超过了罕遇地震设计谱水平段,具有速度脉冲特性的051SMW台站周围房屋破坏较严重,人员伤亡较重。

基于深度强化学习的空天地一体化网络信息物理系统垂直切换策略

针对空天地一体化网络信息物理系统模型复杂、很难获得网络拓扑先验知识和模型化假设的特点,研究其基于深度强化学习的垂直切换策略。首先,综合考虑系统稳定性、切换开销和网络使用成本约束,将垂直切换策略问题建模为约束马尔可夫决策过程(CMDP),并给出保证可行解存在的充分条件;其次,提出约束-近端策略优化(CPPO)算法解决该问题,并在基站侧引入分布式强化学习机制加速训练收敛。相较于基准策略,仿真验证了所提垂直切换策略的优越性和有效性。

基于广义条件强度参数的水平和竖向地震动联合选取研究

为了合理地考虑竖向地震作用和实现水平和竖向地震动的联合选取,提出了基于广义条件强度参数的水平和竖向地震动联合选取方法:扩展广义条件强度参数的基本理论,提出水平和竖向地震动广义条件强度参数分布的构建方法,并与“无条件分布”对比,提出基于广义条件强度参数的水平和竖向地震动联合选取方法的基本理论,给出以水平强度参数作为条件的实际算例,利用现有水平-水平、水平-竖向强度参数相关系数模型构建水平和竖向地震动广义条件强度参数目标分布,对目标地震动数据库进行联合选取,将选取结果与传统选取方法进行对比,说明该方法的合理性。结果表明:构建出的水平和竖向广义条件强度参数分布与“无条件”分布之间存在一定差异;水平和竖向地震动联合选取结果与目标理论分布匹配良好;与仅考虑水平向广义条件强度参数地震动选取方法相比,联合选取方法能够考虑竖向地震动特性,并且不会对水平向造成影响,提出的水平和竖向地震动联合选取方法能够更加合理地、全面地考虑水平和竖向地震动特性,为工程结构在水平和竖向地震动作用下的抗震性能研究提供地震动输入基础。

竖向地震动对地铁车站共构结构体系地震响应的影响研究

[目的]地铁车站共构结构体系(以下简称“共构结构体系”)通过厚板实现箱形结构与箱形框架结构的连接转换。因共构结构体系的结构形式独特,其地震响应规律目前尚不明确,需进一步研究其地震响应特征。[方法]以某综合管廊与地铁车站共构结构体系为例,建立了土-共构结构体系相互作用的有限元仿真模型。考虑单向地震波和双向地震波(含水平向、竖向)作为输入,选取了3种工况,分析了共构结构体系在地震作用下的加速度响应特征、位移响应特征、受压受拉损伤情况及演变过程,并以共构结构体系左侧柱端为例,讨论了部分结构部位的内力响应特征。[结果及结论]双向耦合地震动对共构结构体系竖向加速度的影响较大,在侧墙与负一层底板连接处加速度的最大增幅达158%(与竖向地震动作用相比)。竖向地震动会加大共构结构体系顶底板的相对水平位移和相对竖向位移,加大柱子的内力响应。柱端、侧墙下部、底板两端、构件连接处、腋角等位置为共构结构体系地震损伤薄弱部位,应对这些部位进行加强处理。

河西走廊东部西北气流型沙尘暴的大气物理特征

利用2006-2022年河西走廊东部常规高空地面观测资料、民勤探空站8时和20时间隔50 m高空加密观测资料,分析冬季和春季西北气流型沙尘暴气象要素时间、垂直结构变化及大气层结特征。结果表明:(1)研究区西北气流型沙尘暴出现在地气温度和温差最大、相对湿度最小、地面气压和风速陡增时,春季,沙尘暴发生时,风速大、地表干且近地层热力对流最强。(2)垂直结构特征是早干晚湿、风速随高度递增,风向先顺转后逆转,低层暖高层冷;春季低层气温较高,垂直温度梯度增幅大,温度露点差大,冷暖空气强度强且交汇高度较低(1 km附近),层结不稳定,易发生沙尘暴。(3)春季8时和冬季20时位温随不稳定层结高度变化梯度较大,即沙尘暴春季出现早于冬季。春季20时和冬季8时不稳定高度厚而低,因而春季下午到夜间和冬季中午沙尘暴较强。(4)500 hPa冷平流中心强度(≥-34℃)和西北急流(≥26 m/s)越强,对应700 hPa河西风速>20 m/s及低层暖区范围越大,沙尘暴强度越强,持续时间越长。