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Observer-Based Path Tracking Controller Design for Autonomous Ground Vehicles With Input Saturation 被引量:1
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作者 Heng Wang Tengfei Zhang +1 位作者 Xiaoyu Zhang Qing Li 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2023年第3期749-761,共13页
This paper investigates the problem of path tracking control for autonomous ground vehicles(AGVs),where the input saturation,system nonlinearities and uncertainties are considered.Firstly,the nonlinear path tracking s... This paper investigates the problem of path tracking control for autonomous ground vehicles(AGVs),where the input saturation,system nonlinearities and uncertainties are considered.Firstly,the nonlinear path tracking system is formulated as a linear parameter varying(LPV)model where the variation of vehicle velocity is taken into account.Secondly,considering the noise effects on the measurement of lateral offset and heading angle,an observer-based control strategy is proposed,and by analyzing the frequency domain characteristics of the derivative of desired heading angle,a finite frequency H_∞index is proposed to attenuate the effects of the derivative of desired heading angle on path tracking error.Thirdly,sufficient conditions are derived to guarantee robust H_∞performance of the path tracking system,and the calculation of observer and controller gains is converted into solving a convex optimization problem.Finally,simulation examples verify the advantages of the control method proposed in this paper. 展开更多
关键词 Autonomous ground vehicles(AGVs) H_∞index input saturation observer-based controller path tracking control
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Amplification of in-plane seismic ground motion by group cavities in layered half-space (Ⅱ): with saturated poroelastic soil layers 被引量:3
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作者 Jianwen Liang Ji Zhang Zhenning Ba 《Earthquake Science》 CSCD 2012年第4期287-298,共12页
As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and satur... As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and saturated poroelastic soil layers. The influence of poroelastic layers on the amplification of seismic ground motion is studied both in frequency domain and time domain using indirect boundary element method (IBEM). It is shown that for the example of a saturated poroelastic site in Tianjin under the excitation of Taft wave and E1 Centro wave, the amplification of seismic ground motion in poroelastic case is slightly smaller than that in the elastic case, and the amplification of PGA (peak ground acceleration) and its PRS (peak response spectrum).. can be increased up to 38.8% and 64.6%; the predominant period of response spectra in poroelastic case becomes shorter to some extent compared with that in the elastic case. It is suggested that the effect of underground group cavities in poroelastic half-space on design seismic ground motion should be considered. 展开更多
关键词 underground group cavity dry poroelastic saturated poroelastlc AMPLIFICATION IN-PLANE seismic ground motion indirect boundary element method (IBEM)
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Non-axisymmetrical vibration of elastic circular plate on layered transversely isotropic saturated ground 被引量:2
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作者 王小岗 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2007年第10期1383-1396,共14页
The non-axisymmetrical vibration of elastic circular plate resting on a layered transversely isotropic saturated ground was studied. First, the 3-d dynamic equations in cylindrical coordinate for transversely isotropi... The non-axisymmetrical vibration of elastic circular plate resting on a layered transversely isotropic saturated ground was studied. First, the 3-d dynamic equations in cylindrical coordinate for transversely isotropic saturated soils were transformed into a group of governing differential equations with 1-order by the technique of Fourier expanding with respect to azimuth, and the state equation is established by Hankel integral transform method, furthermore the transfer matrixes within layered media are derived based on the solutions of the state equation. Secondly, by the transfer matrixes, the general solutions of dynamic response for layered transversely isotropic saturated ground excited by an arbitrary harmonic force were established under the boundary conditions, drainage conditions on the surface of ground as well as the contact conditions. Thirdly, the problem was led to a pair of dual integral equations describing the mixed boundaryvalue problem which can be reduced to the Fredholm integral equations of the second kind solved by numerical procedure easily. At the end of this paper, a numerical result concerning vertical and radical displacements both the surface of saturated ground and plate is evaluated. 展开更多
关键词 transversely isotropic layered saturated ground Blot's motion equations elastic circular plate Fredholm integral equation
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Consolidation of partially saturated ground improved by impervious column inclusion:Governing equations and semi-analytical solutions 被引量:2
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作者 Lei Wang Annan Zhou +1 位作者 Yongfu Xu Xiaohe Xia 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2022年第3期837-850,共14页
This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore wat... This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore water for partially saturated soils are proposed in the context of partially-saturated ground improved by impervious column inclusion.Settlement equation and dissipation equations of excess pore air/water pressures for a partially saturated improved ground are then derived.The semi-analytical solutions for ground settlement and pore pressure dissipation are then obtained through the Laplace transform and validated by the existing solutions for two special cases in the literature and the numerical results obtained from the finite difference method.A series of parametric studies is finally conducted to investigate the influence of some key factors on consolidation of partially saturated ground improved by impervious column inclusion.Based on the parametric study,it can be found that a higher value of the area replacement ratio or modulus of the pile results in a longer dissipation time of excess pore air pressure(PAP),a shorter dissipation time of excess pore water pressure(PWP),and a lower normalized settlement. 展开更多
关键词 Semi-analytical solution CONSOLIDATION Partially saturated soil ground improvement Impervious column inclusion
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Axisymmetric alternating direction explicit scheme for efficient coupled simulation of hydro-mechanical interaction in geotechnical engineering-Application to circular footing and deep tunnel in saturated ground
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作者 Simon Heru Prassetyo Marte Gutierrez 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2018年第2期259-279,共21页
Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under sat... Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit(ADE)scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in nonuniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourthorder finite difference(FD) approximation to the spatial derivatives of the axisymmetric fluid-diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps,giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua(FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%-50% that of FLAC’s basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%-1.8%. 展开更多
关键词 Hydro-mechanical(H-M) interaction Explicit coupling technique Alternating direction explicit(ADE) scheme High-order finite difference(FD) Non-uniform grid Axisymmetric consolidation Circular footing Deep tunnel in saturated ground
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河流冲积平原饱和砂土区地下管线渗漏诱发地面塌陷机制研究
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作者 李云峰 张庆 +4 位作者 陆远志 葛伟亚 周小平 侯莉莉 郭纪祥 《地质与勘探》 CAS CSCD 北大核心 2024年第1期105-112,共8页
河流冲积平原区是我国城市建设的主要区域,地层以松散冲洪积物为主,该地区地下管网破损带走松散地层极易形成隐蔽性很高的地下空洞,进而诱发地面塌陷,威胁人身财产和基础设施安全。以安庆市长风路地面塌陷为例,建立渗流、应力多场可控... 河流冲积平原区是我国城市建设的主要区域,地层以松散冲洪积物为主,该地区地下管网破损带走松散地层极易形成隐蔽性很高的地下空洞,进而诱发地面塌陷,威胁人身财产和基础设施安全。以安庆市长风路地面塌陷为例,建立渗流、应力多场可控的等比实体模型箱,开展城市地面塌陷仿真实验,分析带水管线破损后地层中孔洞发育过程及孔洞周边各个方向应力变化特征,旨在揭示地面塌陷形成机制。结果表明:(1)安庆市长风路地面塌陷从孕育到塌陷,经历了小孔、竖直孔洞、塌陷坑三种形态,可将地下异常孔洞当作前兆进行预警;(2)河流冲积平原区城市地面塌陷的孕灾环境是地层的高渗透性地层和地下水位,诱发因子是管道的破损,尤其是污水排水管道破损;(3)城市地面塌陷危害大小主要受控于管道及地下水位相对埋深,且可以根据地层性质对塌陷坑的大小进行计算评估。该成果可为城市地面塌陷风险评价、防治区划等提供理论基础。 展开更多
关键词 城市地面塌陷 饱和砂土 致灾机制 冲积平原 长风路 安庆市
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P波入射下饱和冻土自由场地地震地面运动分析
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作者 焦豪 马强 周凤玺 《冰川冻土》 CSCD 2024年第1期137-151,共15页
地震波的放大或衰减受场地条件的影响,因而选择符合实际情况的场地模型来分析地震地面运动极为重要。为了研究西部高寒地区冻土场地的地震地面运动特征,基于弹性波在单相弹性介质与冻结饱和多孔介质中的传播理论,建立了P波入射下基岩上... 地震波的放大或衰减受场地条件的影响,因而选择符合实际情况的场地模型来分析地震地面运动极为重要。为了研究西部高寒地区冻土场地的地震地面运动特征,基于弹性波在单相弹性介质与冻结饱和多孔介质中的传播理论,建立了P波入射下基岩上覆饱和冻土自由场地模型,求得了平面P波入射情况下基岩上覆饱和冻土自由场地地震地面运动的解析解答。通过数值计算,分析了平面P波在不同入射角度下,入射频率、孔隙率、介质温度、胶结参数和接触参数等物理力学参数对饱和冻土自由场地地震地面运动的影响规律。分析结果表明:平面P波的入射频率对基岩上覆饱和冻土自由场地地表位移有显著影响。基岩上覆饱和冻土自由场地的水平位移随着平面P波入射频率增大而减小,竖向位移随入射频率增大而增大;孔隙率的增大也会导致饱和冻土自由场地水平位移增大,但其增幅随着平面P波入射角度的增加先增大后减小,竖向位移也增大,但增幅随入射角度增加逐渐减小;冻土场地中介质温度的降低会导致饱和冻土自由场地的水平位移和竖向位移减小。这表明冰相对于冻土场地中地震波传播具有重要影响;此外,泊松比也会对自由场地的位移产生一定影响,水平位移随泊松比增大而减小,增幅随平面P波入射角度增加先增大后减小。随着泊松比增大,饱和冻土自由场地的竖向位移显著增大,增幅随平面P波入射角度增加逐渐减小;接触参数的增加会导致自由场地的水平位移增大,增幅先增大后逐渐减小。同时,地表竖向位移也会增大,但增幅逐渐减小。 展开更多
关键词 饱和冻土 平面P波 反射与透射 地面运动 解析解
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自重湿陷性黄土场地地裂缝地铁暗挖隧道涌泥灾害处理与风险控制
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作者 胡自全 沙鸣 胡银林 《城市轨道交通研究》 北大核心 2024年第9期249-254,259,共7页
[目的]黄土饱和湿陷可能出现地下空洞。暗挖隧道穿过自重湿陷性黄土场地地裂缝设防段时,若遇到地下空洞,易引发涌泥灾害,需采取有效的处理措施,以控制施工风险。[方法]以我国某穿越地裂缝的浅埋暗挖法地铁隧道为例,介绍了该工程的概况... [目的]黄土饱和湿陷可能出现地下空洞。暗挖隧道穿过自重湿陷性黄土场地地裂缝设防段时,若遇到地下空洞,易引发涌泥灾害,需采取有效的处理措施,以控制施工风险。[方法]以我国某穿越地裂缝的浅埋暗挖法地铁隧道为例,介绍了该工程的概况及地质情况,以及发生涌泥灾害的概要。地质勘探查明地铁右线隧道上方地裂缝破碎带存在黄土空洞,根据该空洞的地层特性及涌泥风险特征,采取了挂网喷射混凝土、小导管注浆固结、型钢及支撑加固、注浆回填空洞等施工措施。在此基础上,进一步阐述了隧道涌泥体清理、隧道二次开挖过程的风险控制措施。[结果及结论]案例工程涌泥灾害的处理措施,以及隧道涌泥体清理、隧道二次开挖过程的风险控制措施是可行、安全的。措施实施后,快速控制了险情,确保了周边建筑物安全。 展开更多
关键词 地铁暗挖隧道 湿陷性黄土 地裂缝 涌泥灾害 风险控制
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考虑指数渗流的砂井地基弹黏塑性固结分析
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作者 杨强 《力学与实践》 2024年第3期593-601,共9页
为深入探究饱和黏土地区砂井地基的固结机制,在Barron自由应变假定下,引入考虑时间效应的统一硬化(unified hardening,UH)模型描述土骨架的变形非线性关系,同时引入指数渗流方程代替Darcy定律,并考虑渗透系数变化及涂抹效应的影响,研究... 为深入探究饱和黏土地区砂井地基的固结机制,在Barron自由应变假定下,引入考虑时间效应的统一硬化(unified hardening,UH)模型描述土骨架的变形非线性关系,同时引入指数渗流方程代替Darcy定律,并考虑渗透系数变化及涂抹效应的影响,研究了土体非线性、施工扰动及外载荷等因素对砂井地基非线性固结过程的影响规律。结果表明:由于土体的黏滞效应,在加载前期,砂井地基不排水边界附近孔压出现升高现象,且考虑非Darcy渗流时上述现象更加明显,砂井地基固结速率也愈加缓慢。此外,涂抹区渗透系数的减小显著降低了砂井地基整体孔压消散速率,而外载荷的增大却加快了地基的固结进程。 展开更多
关键词 饱和黏土 砂井地基 流变固结 指数渗流 统一硬化模型 涂抹效应
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Preliminary research on the method for determination of ground motion parameters of diffuse earthquakes 被引量:2
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作者 Jian Wu Yanxiang Yu 《Earthquake Science》 CSCD 2010年第1期87-93,共7页
This paper proposes that on the basis of near-source saturation characteristic of ground motion, the peak ground motion acceleration and the acceleration response spectra of diffuse earthquakes affecting the nuclear f... This paper proposes that on the basis of near-source saturation characteristic of ground motion, the peak ground motion acceleration and the acceleration response spectra of diffuse earthquakes affecting the nuclear facility site can be determined by the statistic method. In view of the problem of insufficient statistic samples due to fewer qualified strong earth- quake records on the bedrock site, it also proposes that according to the features of ground motion response of the soil, the acceleration records on the soil site can be transformed into the equivalent acceleration records on rock site for a simultane- ous statistic analysis together with the records on rock site. Consequently, we have obtained by this method the near-source peak acceleration and the acceleration response spectra of small and moderate earthquakes on the site that could meet the need of nuclear facility and made a comparative analysis to the results from relevant researches. This new method for deter- mining diffuse earthquakes is only preliminarily verified in the paper and further research is needed for practical application. 展开更多
关键词 diffuse earthquake near-source ground motion saturATION record transformation
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饱和地基中骨架非流动黏性对体波传播特性的影响分析
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作者 任圆圆 《兰州理工大学学报》 CAS 北大核心 2023年第3期140-146,共7页
基于饱和多孔介质的研究成果,考虑天然土体中骨架的非流动黏性和孔隙流体的流动黏性的影响,研究了黏弹性饱和地基中体波的传播特性.利用Biot波动理论,引入Kelvin-Voigt线性黏弹性模型,建立了饱和土体的黏弹性动力耦合模型.通过引入位移... 基于饱和多孔介质的研究成果,考虑天然土体中骨架的非流动黏性和孔隙流体的流动黏性的影响,研究了黏弹性饱和地基中体波的传播特性.利用Biot波动理论,引入Kelvin-Voigt线性黏弹性模型,建立了饱和土体的黏弹性动力耦合模型.通过引入位移势函数,根据Helmholtz势函数分解定理推导给出了黏弹性饱和地基中体波的特征方程.利用数值算例,结合参数分析讨论了各类体波的波速和衰减系数随土体非流动黏性松弛时间、频率和渗透系数等物理力学参数的变化规律.结果表明:土体非流动黏性松弛时间的增大将引起P_(1)波、P_(2)波和S波的波速和衰减系数的增大;频率和渗透系数的不同区间对P_(1)波、P_(2)波和S波的波速和衰减系数的影响不同. 展开更多
关键词 黏弹性 饱和地基 体波 波速 衰减系数
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2.5维有限元分析高铁荷载下准饱和横观各向同性地基振动特性
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作者 高广运 耿建龙 +2 位作者 张其唯 张璐璐 司志鹏 《振动与冲击》 EI CSCD 北大核心 2023年第15期298-308,共11页
为分析高铁荷载下准饱和横观各向同性地基振动特性,推导了准饱和横观各向同性地基2.5维有限元控制方程,建立了列车-轨道-准饱和横观各向同性地基2.5维有限元模型,对比研究了不同车速下饱和与准饱和横观各向同性地基的振动特性,分析了准... 为分析高铁荷载下准饱和横观各向同性地基振动特性,推导了准饱和横观各向同性地基2.5维有限元控制方程,建立了列车-轨道-准饱和横观各向同性地基2.5维有限元模型,对比研究了不同车速下饱和与准饱和横观各向同性地基的振动特性,分析了准饱和横观各向同性地基土体参数对振动特性的影响。研究结果表明,准饱和横观各向同性地基表面产生的向上和向下位移均大于饱和地基。不同车速下准饱和地基振动位移均大于饱和地基,但超静孔压远小于饱和地基;车速越高,饱和与准饱和地基表面振动位移越大而衰减越慢,超静孔压越大且衰减越快,轨道中心处准饱和与饱和地基位移相差越大。准饱和地基竖向振动位移和超静孔压随水平弹性模量和垂直弹性模量的增加而减小,随水平泊松比增加而增大,随垂直泊松比增加而减小,随垂直剪切模量增加而减小。垂直弹性模量较水平弹性模量对地面竖向振动位移影响更大。与水平泊松比相比,垂直泊松比对准饱和横观各向同性地基竖向振动位移峰值和超静孔压影响更大。 展开更多
关键词 高铁 准饱和横观各向同性地基 2.5维有限元模型 地面振动 土体参数
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Ultrafast Laser Energy Density and Retinal Absorption Cross-Section Determination by Saturable Absorption Measurements
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作者 Alfons Penzkofer Meike Luck +1 位作者 Tilo Mathes Peter Hegemann 《Journal of Analytical Sciences, Methods and Instrumentation》 2014年第1期19-26,共8页
Laser pulse nonlinear transmission measurements through saturable absorbers of known absorption parameters allow the measurement of their energy density. On the other hand, nonlinear transmission measurements of laser... Laser pulse nonlinear transmission measurements through saturable absorbers of known absorption parameters allow the measurement of their energy density. On the other hand, nonlinear transmission measurements of laser pulses of known energy density through absorbing media allow their absorption parameter determination. The peak energy density w0P of second harmonic pulses of a mode-locked titanium sapphire laser at wavelength λP = 400 nm is determined by nonlinear energy transmission measurement TE through the dye ADS084BE (1,4-bis(9-ethyl-3-car-bazovinylene)-2-methoxy-5-(2’-ethyl-hexyloxy)-benzene) in tetrahydrofuran. TE(w0P) calibration curves are calculated for laser pulse peak energy density reading w0P from measured pulse energy transmissions TE. The ground-state absorption cross-section σP and the excited-state absorption cross-section σex at λP, and the number density N0 of the retinal Schiff base isoform RetA in pH 7.4 buffer of the blue-light adapted recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from Chlamydomonas reinhardtii were determined by picosecond titanium sapphire second harmonic laser pulse energy transmission measurement TE through RetA as a function of laser input peak energy density w0P. The complete absorption cross-section spectrum 展开更多
关键词 Laser Pulse Peak Energy DENSITY DETERMINATION ground-State ABSORPTION CROSS-SECTION DETERMINATION Excited-State ABSORPTION CROSS-SECTION DETERMINATION saturable ABSORPTION ADS084BE Dye Histidine Kinase RHODOPSIN HKR1 RETINAL Schiff Base RetA Cofactor Number DENSITY DETERMINATION
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矩形管波阻板对饱和地基中列车振动的隔振性能研究 被引量:3
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作者 王滢 赵彩清 +1 位作者 高盟 李丹阳 《地震工程与工程振动》 CSCD 北大核心 2023年第1期229-238,共10页
高铁列车运行产生的环境振动对人体健康、沿线建筑物安全、精密设备正常使用等产生不可忽视的影响。提出一种“矩形管波阻板”新型隔振屏障,用于减少环境振动污染。根据饱和地基2.5D有限元理论,建立轨道-地基-屏障-建筑结构模型,计算分... 高铁列车运行产生的环境振动对人体健康、沿线建筑物安全、精密设备正常使用等产生不可忽视的影响。提出一种“矩形管波阻板”新型隔振屏障,用于减少环境振动污染。根据饱和地基2.5D有限元理论,建立轨道-地基-屏障-建筑结构模型,计算分析空沟、填充沟和矩形管波阻板3种不同屏障的隔振效果。计算表明:列车速度较低时,空沟隔振效应并不显著,而当列车运行速度较高时,空沟有一定的隔振效应,可在沟前出现震荡放大的现象。而填充沟和矩形管波阻板不论列车运行速度高低都有较好的隔振作用,但列车在高速运行时的隔振效应超过了低速性能运行时的隔振效应。填充沟和矩形管波阻板2种屏障隔振效果相近,但矩形管波阻板可减少混凝土用量,降低成本,隔振效率更高。 展开更多
关键词 饱和地基 2.5D有限元 矩形管波阻板 邻近建筑 振动控制
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饱和砂砾土未冻水含量预测模型的适应性分析 被引量:1
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作者 王炳禄 刘欣 +3 位作者 沈宇鹏 刘志坚 陈贤波 寇鼎涛 《铁道建筑》 北大核心 2023年第11期116-121,共6页
依托北京地铁19号线草桥站—景风门站联络通道人工地层冻结工程,采用频域反射法得到了不同含泥量饱和砂砾土的冻结特征曲线,分析含泥量对未冻水含量的影响。讨论拟合参数对六种典型未冻水含量预测模型的影响,基于未冻水含量测试结果,开... 依托北京地铁19号线草桥站—景风门站联络通道人工地层冻结工程,采用频域反射法得到了不同含泥量饱和砂砾土的冻结特征曲线,分析含泥量对未冻水含量的影响。讨论拟合参数对六种典型未冻水含量预测模型的影响,基于未冻水含量测试结果,开展饱和砂砾土未冻水含量预测模型的适应性分析。结果表明:饱和砂砾土冻结特征曲线随温度降低主要经历快速下降、缓慢下降和稳定三个阶段,含泥量提高引起剧烈相变区间增大,残余含水量明显提高;VG-Clapeyron模型对含泥量0、10%和20%饱和砂砾土均具有较好的适应性,且形式简单,推荐使用VG-Clapeyron模型预测饱和砂砾土未冻水含量随温度的变化规律。 展开更多
关键词 人工地层冻结 饱和砂砾土 未冻水含量 冻结特征曲线 适应性分析
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Centrifuge tests for seismic response of single pile foundation supported wind turbines in sand influenced by earthquake history 被引量:2
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作者 Wang Yubing Zhang Zhongchang +1 位作者 Wu Xiaofeng Zhu Bin 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2023年第3期623-636,共14页
This paper reports on two sets of centrifuge model tests of wind turbines in dry sand and saturated sand subjected to earthquake sequences.The wind turbine system is composed of a single pile foundation and a wind tur... This paper reports on two sets of centrifuge model tests of wind turbines in dry sand and saturated sand subjected to earthquake sequences.The wind turbine system is composed of a single pile foundation and a wind turbine.All tests were applied with liquefaction experiments and analysis projects(LEAP)waves to simplify the analysis.The objectives of the tests are to investigate:(1)the influence of earthquake history on the seismic response of wind turbines;(2)the influence of earthquake history on the dynamic pile-soil interaction;and(3)the influence of two different foundation types on the seismic response of wind turbines.The tests indicated that earthquake history has a significant influence on the natural frequency of the pile and the soil around the pile in the saturated sand,but has no obvious influence on the dry sand.The shear modulus of the soil and the acceleration amplification factor of the pile top in both tests increased and the maximum bending moment envelope of the single pile foundation shrunk.The stiffness of the p-y curve in saturated sand was increased by the earthquake history,while that in dry sand was not significantly affected. 展开更多
关键词 earthquake history effect wind turbine pile bending moment dry and saturated sand ground dynamic p-y curves
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具有落角约束的全局复合滑模制导律 被引量:1
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作者 赵子恒 包长春 《控制工程》 CSCD 北大核心 2023年第2期339-344,共6页
为实现对运动目标的精确打击,以脱靶量与终端落角为约束条件,提出了一种全局复合滑模制导律。首先,建立俯仰平面的一体化模型,讨论视线角速率与弹道倾角间的变化关系,为保证系统的全程鲁棒性,采用全局滑模控制器设计切换函数。接着,为... 为实现对运动目标的精确打击,以脱靶量与终端落角为约束条件,提出了一种全局复合滑模制导律。首先,建立俯仰平面的一体化模型,讨论视线角速率与弹道倾角间的变化关系,为保证系统的全程鲁棒性,采用全局滑模控制器设计切换函数。接着,为提升制导过程中系统的动态特性,采用幂次趋近律并对其改进以提升系统的自适应能力。然后,采用李雅普诺夫函数验证系统的稳定性,并添加白噪声验证系统的抗干扰能力。最后,为解决滑模控制中广泛产生的抖振问题,运用饱和函数代替趋近律中的开关函数,抖振现象得到了有效抑制。结果表明,该制导律可实现在不同落角约束下对运动目标的精确打击,并具备一定的抗干扰能力。 展开更多
关键词 滑模控制 空地导弹 落角约束 幂次趋近律 饱和函数法
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基于有限差分法的非饱和砂土层地震反应研究
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作者 邬俊杰 咸甘玲 +1 位作者 刘娟 兰景岩 《洛阳理工学院学报(自然科学版)》 2023年第3期17-21,25,共6页
利用有限差分法建立非饱和砂土层-基岩的自由场模型,分别在水平向和竖直向天然地震动输入条件下,分析非饱和砂土层的饱和度对地震反应分析结果的影响,通过计算分析地震动峰值和反应谱等参数,初步揭示非饱和砂土层对地震动响应规律。饱... 利用有限差分法建立非饱和砂土层-基岩的自由场模型,分别在水平向和竖直向天然地震动输入条件下,分析非饱和砂土层的饱和度对地震反应分析结果的影响,通过计算分析地震动峰值和反应谱等参数,初步揭示非饱和砂土层对地震动响应规律。饱和度变化影响土体剪切模量和体积模量而导致场地地表峰值加速度出现差异;加速度反应谱方面,饱和度较大的工况加速度反应谱峰值到达周期会出现滞后现象;加速度反应谱峰值大小以及到达峰值周期时长受地震波输入方向和饱和度共同影响。 展开更多
关键词 非饱和砂 有限差分法 饱和度 场地效应
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地铁移动荷载作用下准饱和地基振动特性及隔振研究
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作者 王滢 姚真 +1 位作者 宋永山 赵礼治 《山东科技大学学报(自然科学版)》 CAS 北大核心 2023年第5期48-57,共10页
根据2.5维有限元理论,将地基假设为准饱和地基,建立地铁列车-轨道-隧道衬砌-分层准饱和地基2.5维有限元模型,研究准饱和地基饱和度变化对地铁列车运行产生的地面振动响应的影响规律,并分析了准饱和地基饱和度对波阻板隔振性能的影响。... 根据2.5维有限元理论,将地基假设为准饱和地基,建立地铁列车-轨道-隧道衬砌-分层准饱和地基2.5维有限元模型,研究准饱和地基饱和度变化对地铁列车运行产生的地面振动响应的影响规律,并分析了准饱和地基饱和度对波阻板隔振性能的影响。结果表明:准饱和地基饱和度减小使地面振动加速度、水平x方向、竖向z方向位移幅值有一定程度减小;随着距离轨道中心距离增加,饱和度对地面振动响应的影响越明显;准饱和地基饱和度减小,波阻板对x方向隔振性能增强,对z方向隔振系数减弱;波阻板对地铁移动荷载产生的低频振动有较好隔振性能。 展开更多
关键词 准饱和地基 饱和度 地面振动响应 波阻板 隔振性能
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Effect of surface loading on the hydro-mechanical response of a tunnel in saturated ground
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作者 Simon Heru Prassetyo Marte Gutierrez 《Underground Space》 SCIE EI 2016年第1期1-19,共19页
The design of underground spaces in urban areas must account not only for the current overburden load but also for future surface loads,such as from construction of high-rise buildings above underground structures.In ... The design of underground spaces in urban areas must account not only for the current overburden load but also for future surface loads,such as from construction of high-rise buildings above underground structures.In saturated ground,the surface load will generate an additional mechanical response through stress changes and ground displacement,as well as a hydraulic response through pore pressure changes.These hydro-mechanical(H-M)changes can severely influence tunnel stability.This paper examines the effect of surface loading on the H-M response of a typical horseshoe-shaped tunnel in saturated ground.Two tunnel models were created in the computer code Fast Lagrangian Analysis of Continua(FLAC).One model represented weak and low permeability ground(stiff clay),and the other represented strong and high permeability ground(weathered granite).Each of the models was run under two liner permeabilities:permeable and impermeable.Two main cases were compared.In Case 1,the surface load was applied 10 years after tunnel construction.In Case 2,the surface load was applied after the steady state pore pressure condition was achieved.The simulation results show that tunnels with impermeable liners experienced the most severe influence from the surface loading,with high pore pressures,large inward displacement around the tunnels,and high bending moments in the liner.In addition,the severity of the response increased toward steady state.This induced H-M response was worse for tunnels in clay than for those in granite.Furthermore,the long-term liner stabilities in Case 1 and Case 2 were similar,indicating that the influence of the length of time between when the tunnel was completed and when the surface load was applied was negligible.These findings suggest that under surface loading,in addition to the ground strength,tunnel stability in saturated ground is largely influenced by liner permeability and the long-term H-M response of the ground. 展开更多
关键词 Surface loading Hydro-mechanical response Urban tunnels saturated ground
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