Comprehensive Investigation of Submarine Slide Zones and Mass Movements at the Northern Continental Slope of South China Sea

Multi-beam bathymetry and seismic sequence surveys in the northern slope of the South China Sea reveal detailed geomorphology and seismic stratigraphy characteristics of canyons, gullies, and mass movements. Modern canyons and gullies are roughly elongated NNW–SSW with U-shaped cross sections at water depths of 400–1000 m. Mass movements include slide complexes, slide scars, and debris/turbidity flows. Slide complexes and slide scars are oriented in the NE–SW direction and cover an area of about 1790 and 926 km^2, respectively. The debris/turbidity flows developed along the lower slope. A detailed facies analysis suggests that four seismic facies exist, and the late Cenozoic stratigraphy above the acoustic basement can be roughly subdivided into three sequences separated by regional unconformities in the study area. The occurrence of gas hydrates is marked by seismic velocity anomalies, bottom-simulating reflectors, gas chimneys, and pockmarks in the study area. Seismic observations suggest that modern canyons and mass movements formed around the transition between the last glacial period and the current interglacial period. The possible existence and dissociation of gas hydrates and the regional tectonic setting may trigger instability and mass movements on the seafloor. Canyons may be the final result of gas hydrate dissociation. Our study aims to contribute new information that is applicable to engineering construction required for deep-water petroleum exploration and gas hydrate surveys along any marginal sea.

考虑滑块动态特性的变质心四旋翼无人机双回路控制

针对滑块动态特性引入的附加干扰力矩造成系统姿态抖动强烈的问题,开展变质心四旋翼无人机滑块参数设计与姿态/伺服双回路控制研究。通过建立双滑块变质心四旋翼无人机八自由度运动模型,明确了滑块的引入对系统的影响,给出了与滑块动态特性相关的各项附加干扰力矩;分析并设计了滑块的安装位置、质量以及行程等参数,降低滑块对系统的耦合与干扰;最后以滑块驱动力作为控制量,设计了姿态/伺服双回路动态滑模控制器,同时利用非线性扰动观测器对复合扰动进行估计和补偿,并进行了仿真试验。仿真结果表明,在考虑滑块动态特性的情况下,所设计的控制器能够实现对变质心四旋翼无人机的姿态控制,并具有良好的抗干扰性能与鲁棒性。

桥式起重机分布式质量吊重系统双摆滑模控制

随着吊装作业的多元化发展,起重机吊装对象也从传统的质点式吊重向分布式质量吊重方向发展。针对桥式起重机在吊装分布式质量吊重时吊重的大摆角抑制和小车定位控制问题,提出了两种基于滑模控制理论的、用于吊重消摆和小车快速定位的方法。首先,综合考虑了桥式起重机吊装对象的结构特征、小车电机的驱动特性、摩擦阻力以及环境中的随机扰动对吊装作业的影响,建立了桥式起重机分布式质量吊重系统的非线性双摆动力学模型;然后,设计了桥式起重机分布式质量吊重系统的非线性双摆动力学普通滑模控制器(OSMC)和分层滑模控制器(HSMC),采用Lyapunov函数和Barbalat引理证明了闭环系统的稳定性;最后,利用数值仿真研究了OSMC和HSMC在分布式质量吊重减摆控制方面的性能差异。仿真及研究结果表明:与OSMC相比,采用HSMC不仅可以在12 s内实现小车精确定位目的,而且可以实现对分布式质量吊重在5°~9°摆动范围下的快速抑制目的,完成了对系统状态变量的有效控制;同时,对比结果表明HSMC对起重机系统内部和外部扰动变化有很强的鲁棒性和抗干扰性。

滑坡-抗滑桩相互作用下滑坡推力的研究

为了研究滑坡-抗滑桩相互作用下的滑坡推力,通过模拟滑坡试验,分析了初期变形阶段、均匀变形阶段、加速变形阶段以及破坏阶段土压力变化。研究结果表明:在土体初始变形阶段,随着荷载的增大,土压力随之增大,其中桩3桩后土压力最大,最大土压力为3.85 kPa,在此阶段土体开始出现裂缝。在土体均匀变形阶段,随着荷载的增大,最大土压力出现深度增大,其中桩2桩后土压力最大,最大土压力为6.74 kPa,在此阶段土体裂缝扩大,微小裂缝增加。在土体加速变形阶段,随着荷载的增大,桩2桩后土体和桩间土体最先被破坏。在土体破坏阶段,土体压力快速下降,表面位移增大,桩中间部位土压力小于两端,土体完全被破坏。

Up-Sliding Slantwise Vorticity Development and the Complete Vorticity Equation with Mass Forcing

The moist potential vorticity (MPV) equation is derived from complete atmospheric equations including the effect of mass forcing, with which the theory of Up-sliding Slantwise Vorticity Development, (USVD) is proposed based on the theory of Slantwise Vorticity Development (SVD). When an air parcel slides up along a slantwise isentropic surface, its vertical component of relative vorticity will develop, and the steeper the isentropic surface is, the more violent the development will he. From the definition of MPV and the MPV equation produced here in, a complete vorticity equation is then put forward with mass forcing, which explicitly includes the effects of both internal forcings, such as variations of stability, baroclinicity, and vertical shear of horizontal wind, arid external forcings, such as diabatic heating, friction, and mass forcing. When isentropic surfaces are flat, the complete vorticity equation matches its traditional counterpart. The physical interpretations of some of the items which are included in the complete- vorticity equation but not in the traditional one are studied with a simplified model of the Changjiang-Huaihe Meiyu front. A 60-h simulation is then performed to reproduce a torrential rain event in the Changjiang-Huaihe region and the output of the model is studied qualitatively based on the theory of USVD. The result shows that the conditions of the theory of USVD are easily satisfied immediately in front of mesoscale rainstorms in the downwind direction, that is, the theory of USVD is important to the development and movement of these kinds of systems.

Numerical solutions for point masses sliding over analytical surfaces: Part 1

In this study, we introduce a system of differential equations describing the motion of a single point mass or of two interacting point masses on a surface, that is solved by a fourth-order explicit Runge–Kutta(RK4) scheme. The forces acting on the masses are gravity, the reaction force of the surface, friction, and, in case of two masses, their mutual interaction force. This latter is introduced by imposing that the geometrical distance between the coupled masses is constant. The solution is computed under the assumption that the point masses strictly slide on the surface, without leaping or rolling. To avoid complications stemming from numerical errors related to real topographies that are only known over discrete grids, we restrict our attention to simulations on analytical continuous surfaces. This study sets the basis for a generalization to more complex systems of masses, such as chains or matrices of blocks that are often used to model complex processes such as landslides and rockfalls. The results shown in this paper provide a background for a companion paper in which the system of equations is generalized, and different geometries are presented.

Mass transport deposits and processes in the north slope of the Xisha Trough,northern South China Sea

Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length （from headwall to termination）. Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and three- dimensional structure model diagram af the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.

Second order sliding mode control with back stepping approach for moving mass spinning missiles

An attitude controller using the second order sliding mode control methodology with a backstepping approach（SOSMCB）is designed and implemented for a spinning missile with two internal moving mass blocks.The system consists of a rigid body and two radial internal moving mass blocks and its mathematical model is established based on Newtonian mechanics.The control scheme integrates a second order sliding mode control algorithm into the last step of the backstepping approach,and its stability is proved by means of a Lyapunov function.The performance of the controller is demonstrated by numerical simulations,the results show that the attitude controller is stable and effective.

Management of the Water Slide Brought and Saline Flow in Irrigated Onion (<i>Allium cepa</i>L.) Cultivation in the Senegal River Delta

The find for the optimal slide of water to bring to the plot during the irrigated onion crop was important in order to limit the recharge of the water table close to the soil surface. The quantities of water supplied during onion irrigation were estimated from measurements made with a metal crest to the plot positioned at the tertiary canal. The flow rates at the tertiary canal directly irrigating the plot were recorded during irrigation. From this flow rate, the quantity of water supplied to each plot was determined. From then, the performance of the irrigated system in onion cultivation should pass on the management of this water slide at the level of the hydroagricultural facilities. The integrated soil water mass, salinity and water table dynamics monitoring system was used to assess the water requirements of onion following the irrigation. The daily water requirement of onion in the holland soil of the delta was estimated to average 0.45 g/m3. These requirements were varied according to the development stage of the crop. The water level between the ridges was between 6 and 9 mm during irrigation. This was not permanent, it infiltrated between 12 and 18 hours. This type to the stingray irrigation did not favour the arrival of the water table on the surface. The only fluctuations in the water table were observed during the bulb maturation phase. During this phase, the soil water masses were important. The electrical conductivity recorded varied during the campaign. At the beginning of irrigation, it was 3.62 mS/cm on a 30 cm profile, it decreased towards the end of the irrigations to reach 2.06 mS/cm. The quantities of salt recorded on a 30 cm profile varied from one month to the next;they were 0.468 t/ha at the beginning of irrigation (January) and 0.275 t/ha at the end of the campaign (April). From these results we can say that land degradation in the Senegal river delta would be linked to the arrival of salty groundwater on the surface.

长江下游侧滑型窝崩成因及其力学机制

为全面认识长江下游各类窝崩的形成原因和力学机制,以和畅洲头窝崩为例进行全面分析,进而借鉴土力学方面成果,提出相应的失稳模式和估算方法。结果表明:和畅洲头窝崩属于侧滑型窝崩,其成因主要是岸滩土体中存在易液化的粉砂层,当外界出现一定的振动扰动因素,粉砂层液化条件成熟时则成为滑动层,液化层和上覆土层分多次发生大幅度侧向滑移,土体滑出窝塘口门进入河道深槽,随后被河道主流迅速分散搬运至下游。采用数理统计方法,得到土体滑移距离与液化层厚度和滑移层倾角之间幂函数形式的经验公式。研究结果可为长江下游此类窝崩的预警和治理提供参考。

动态扰动下顶板块体失稳冒落研究综述

巷道、采场等地下开挖空间周边围岩的次生结构面发育,岩体极易被切割成多个独立岩块,并在准静态地应力或外界动力扰动作用下发生滑动冒落.针对准静态条件下的顶板失稳冒落问题,研究的重点在于结构面的扩展分析以及块体系统的受力平衡条件分析.对于动态扰动条件下的顶板岩块滑动失稳问题,不仅涉及到应力波促进下的裂隙扩展问题,还与块体系统中应力波的传播规律和应力波影响下岩块动态受力条件有关.本文分别从静态条件下与动态扰动条件下两个方面总结了顶板岩块稳定性相关研究.目前针对静态条件下的顶板块体稳定性研究已经形成了诸多较为成熟的理论体系;而对于动态扰动条件下的块体稳定性的研究主要还是集中于块体系统内部应力波传播过程的分析,忽略了对顶板岩体受扰过程中裂隙扩展和应力失衡的分析.因此,针对顶板岩块动态失稳问题的研究尚不能揭示冒落机理,而该研究的难点在于“揭示动态扰动诱发块体失稳的本质机理”.最后,介绍了课题组针对动态扰动下顶板块体滑动失稳问题开展的一系列实验与数值模拟研究,揭示了不同方向动态扰动作用诱发顶板块体滑动失稳的机理,为地下矿山冒顶灾害的防控提供一定的理论参考.

一种滑移型危岩体的力学判识方法

边坡岩体在地震、长期降雨或施工扰动等影响因素的强烈作用下,稳定岩体逐渐演化成危岩体,基岩开始分离而导致稳定性不断下降,随之发生下滑破坏,是威胁工程施工运维安全的主要隐患之一.单一的稳定性系数只能判断破坏是否发生,而无法识别岩体由稳定阶段至分离阶段这一变化,也就难以实现危岩体的定量力学判识.通过引入黏结稳定性系数,对潜在滑动面黏聚力及其抗滑占比进行了分析,以期实现滑移型危岩体稳定阶段、分离阶段和破坏阶段的动态考量.当黏结稳定性系数小于1,黏聚力抗滑占比小于结构面长期强度与破坏强度的比值时,即可判定为危岩体.实验结果得出,单一的稳定性系数无法有效识别A8危岩体,而黏结稳定性系数的引入则从力学角度实现了A8危岩体的定量评价.此外现场案例研究表明,基于双力学指标的滑移型危岩体判识方法可以提供相对客观统一的判识结果,有效区分了重庆三峡等地区稳定性系数在1.2附近的滑移型危岩体,提高了传统力学识别方法的准确率与科学性,为我国地质灾害高风险地区更好地应对滑移型崩塌灾害提供新的技术支持.

甘肃灵台县南店子滑坡活动特征及成因分析

2021年10月3日甘肃灵台南店子发生大型推移式黄土—泥岩接触面滑坡,因成功预警而未造成人员伤亡。为探明南店子滑坡发生机理,对滑体地形地貌、地层岩性、水文地质条件以及人类工程活动等进行了基础调查,根据滑坡裂缝发育特征和差异,将该滑坡体分为5个滑块,并对每个滑体特征进行深入研究,定性定量分析了不同滑坡部位的具体滑动情况,并为滑坡分级分块的客观合理性和滑坡机理分析进一步提供证据。最终分析得出滑坡灾害的发生主要是:(1)斜坡中下部和坡脚抗滑段不合理的大规模挖坡取土等人为活动使斜坡变陡、抗滑力减小;(2)坡面洼坑,导致排水不畅,长期大量入渗软化了岩层接触面,降低了斜坡的稳定性;(3)长时间的强降雨。研究成果对于相似区域监测预警、风险评价和工程治理工作具有很好的借鉴意义。

基于零力矩点滑模预测控制的电动前移式叉车稳定性研究

考虑了在电动前移式叉车装载货物转向行驶的情况下,其门架受载变形和货物升降共同引起叉车合成质心位置的变化,进而结合叉车合成质心变化模型和叉车三自由度模型建立了叉车动力学模型。针对叉车合成质心位置变化导致其转向稳定性不足的问题,根据零力矩点(Zero Moment Point,ZMP)理论分析了叉车行驶的稳定条件并得到了侧倾指标来判断车辆的稳定性。通过理想跟踪模型得到理想的叉车横摆角速度、质心侧偏角、车身侧倾角和侧倾角速度,以理想值与由叉车动力学模型仿真得到的实际值的差值为输入,设计了一种基于零力矩点的滑模预测控制(Sliding Mode Predictive Control,SMPC)算法,以调节叉车后轮转角的大小。仿真研究表明,在阶跃工况和双移线工况下,当货物升降速度不同时,与滑模控制(Sliding Mode Control,SMC)和无控制相比,基于ZMP滑模预测控制实现了对理想叉车横摆角速度和质心侧偏角的实时快速跟踪,提高了叉车的稳定性。

双异步电机驱动双质体振动系统同步滑模控制

针对2个异步电机安装在2个不同质体上的振动系统在部分参数条件下不能同步运转或同步相位差不满足设计要求的问题,提出采用主从控制结构和滑模控制算法对异步电机进行矢量控制,以使振动系统实现0或π相位差的同步运转。首先,基于拉格朗日方程建立了振动系统的运动微分方程,并推导了其固有频率的表达式。然后,设计了振动系统异步电机的控制器,并分别证明了其稳定性。最后,在MATLAB/Simulink环境中建立了振动系统的机电-控制仿真模型,开展了自同步和控制同步仿真并进行了对比。结果表明:所设计的控制器可使振动系统实现0或π相位差的同步运转。研究结果可为双异步电机驱动双质体振动系统的研制提供参考。

滑坡体预应力锚索抗滑桩参数优化设计研究

依托青峪口水库上游草池滑坡体,采用有限差分法分析不同状态下的滑坡体变形和受力分布,进行预应力锚索抗滑桩参数优化设计。结果表明:桩位对滑坡体稳定性的影响较大,随着桩位与坡脚距离的增大,滑坡体安全系数先增大后减小;同一桩位下,抗滑桩锚固段存在临界长度,为30 m;抗滑桩桩距对滑坡体稳定性的影响比桩截面尺寸的影响大;在26°~35°范围内的锚索角度对滑坡体稳定性的影响较小。建议抗滑桩截面尺寸、桩距、锚索角度分别取2.5 m×3.5 m、7 m和27°。

基于液液非均相的离散相润湿性能影响分析

多层斜板重力沉降分离器分离液液非均相物系过程中,离散相与接触壁面的润湿特性对分离效率有明显的影响。利用可视化与图像后处理技术,实验研究了水下环境中配比不同碘质量分数的CCl4油滴与3种常用板材的润湿性能。结果表明:聚甲基丙烯酸甲酯(PMMA)和不锈钢为水下亲油表面,玻璃为水下疏油表面。水下油滴含杂质质量分数相同的条件下,与玻璃表面的接触角较大,PMMA和不锈钢表面接触角接近。随着油滴含杂质质量分数的增加,水下油滴在PMMA表面的接触角增大,润湿时间增加;在玻璃表面接触角减小,润湿时间基本不变;3种材质表面滑动角均呈现减小趋势。该研究对液相环境下离散相油滴在壁面上润湿性能提供基础数据,为相关设备的选材和角度设计提供优化设计方案。

巨量转移装备核心轴自适应反步滑模控制

Micro-LED巨量转移装备核心轴具有多变量、强耦合、非线性以及容易受到参数摄动影响等特点,较难实现系统的高精度定位和快速响应。以基于永磁同步直线电机(PMSLM)的巨量转移装备X轴伺服系统为研究对象,提出了一种结合非线性函数和幂指数超螺旋切换控制律的自适应反步超螺旋滑模控制(ABSTASMC)算法,提高系统抗参数摄动能力,降低固有抖振,同时辅以前馈控制器,实现系统的快速响应。实验结果表明,相比传统的PID控制,ABSTASMC拥有更高的定位精度和更强的鲁棒性,调整时间更短,很好满足了巨量转移装备核心轴对高加速高精度运动性能的要求。

高速动车组分布式全局快速终端滑模控制策略

速度跟踪控制是高速动车组自动驾驶的关键技术之一。通过分析列车运行过程的动力学关系,将车钩系统描述为弹簧-阻尼器系统,并考虑列车受到的附加阻力,以及由于列车车钩形变产生的列车长度变化等,建立高速动车组纵向多质点动力学模型。在此模型基础上,设计分布式全局快速滑模控制器,此策略连续的控制率消除了传统滑模控制的抖振问题,控制器考虑动车与拖车的不同动力分配和牵引电机的输出功率上限,分别对动车与拖车的控制力进行不同的饱和限制。基于李雅普诺夫稳定性原理,证明了提出的控制算法的收敛与稳定。仿真结果表明,此高速动车组多质点模型能较为准确地反映列车运行中车钩的状态与受到的附加阻力,基于该模型的带有输出限制的分布式全局快速终端滑模控制器,使车钩纵向冲动更小,速度跟踪性能更优。

广西某高岭土露天矿最终边坡稳定性分析

以广西某高岭土露天矿为工程实例,通过室内岩石力学实验和现场工程地质调查相结合,采用RQD和RMR法对边坡岩体进行岩体质量评价,基于广义Hoek-Brown准则利用RocLab软件计算边坡岩体力学参数,基于极限平衡法利用Slide软件对最终边坡三种工况的稳定性进行分析。结果表明:最终边坡稳定性较好,采场边坡参数选取可行,可为同类矿山提供参考。计算结果为矿山的边坡防护与治理提供依据。