Random failure mechanism method for assessment of working platform bearing capacity with a linear trend in undrained shear strength

A bearing capacity evaluation for the surface strip foundation on a working platform modelled on a twolayered substrate is considered in the study.The upper layer is assumed as man-made and wellcontrolled and thus non-variable.The lower layer modelling natural cohesive soil is subjected to spatial variability of undrained shear strength.The random failure mechanism method(RFMM)is used to evaluate the bearing capacity.This approach employs a kinematic assessment of the critical load and incorporates the averaging of three-dimensional(3 D)random field along dissipation surfaces that result from the failure mechanism geometry.A novel version of the approach considering an additional linear trend of undrained shear strength in the spatially variable layer is proposed.The high efficiency of the RFMM algorithm is preserved.The influences of foundation length,trend slope in the spatially variable layer,fluctuation scales,and thickness of the homogenous sand layer on the resulting bearing capacity evaluations are analysed.Moreover,for selected cases,verification of the RFMM based assessment obtained using random finite difference method(RFDM)based on 3 D analysis is provided.Two types of analyses are performed using RFDM based on associated and non-associated flow rules.For associated flow rule which corresponds to RFMM,the RFMM is conservative and efficient and thus it seems preferable.However,if RFDM employs non-associated flow rule(much lower dilation angle for sand layer),the efficient RFMM is no longer conservative.For this situation,a combined approach that improves the efficiency of the numerical method is suggested.

Rb-Sr Isotopic Chronology of the Au-Bearing Quartz Veins in Gold Deposits in the Eastern Part of North China Platform

In the eastern part of China there had occurred large\|scale gold mineralization during the Mesozoic, resulting in a large number of important gold ore\|concentrated areas. In this paper we have selected some isotope data (including four gold deposits previously studied and two gold deposits in this work) of Au\|bearing quartz veins of the representative gold deposits in six important gold ore\|concentrated areas in the periphery of the North China Platform and calculated their metallogenic ages using the method of Ludwig (2.90 version). The results show that the representative gold deposits in the six gold ore\|concentrated areas were formed during the Mesozoic.

Pit Bearing Capacity Effect on Status of Soil Plug During Pile Driving in Ocean Engineering

Foundation piles of the offshore oil platforms in the Bohai Bay are usually longer than 100 m with a diameter larger than 2 m. Driving such long and large-sized piles into the ground is a difficult task. It needs a comprehensive consider ation of the pile dimensions, soil properties and the hammer energy. Thoughtful drivability analysis has to be performed in the design stage. It has been shown that judging whether the soil column inside the pile is fully plugged, which makes the pile behave as close-ended, strongly influences the accuracy of drivability analysis. Engineering practice repeatedly indicates that the current methods widely used for soil plug judgment often give incorrect results, leading the designers to make a wrong decision. It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile. Based on the Terzaghi＇s bearing capacity calculation method for deep foundation, a new approach for judging soil plug status is put forward, in which the surcharge effect has been considered and the dynamic effect coefficient is included. This approach has been applied to some practical engineering projects successfully, which may give more reasonable results than the currently used method does.

Occurrence and conceptual sedimentary model of Cambrian gypsum-bearing evaporites in the Sichuan Basin, SW China

During the Cambrian, gypsum-bearing evaporites formed in the Sichuan Basin, SW China. These rocks are important for oil and gas sealing, but details of their distribution and origin are not well established. This study examines the regional distribution and origin of the gypsum-bearing evaporites using a comprehensive analysis of drilling data from 34 wells, 5 measured cross-sections in the basin and surrounding area, and 96 maps of area-survey data. Results show that in the stratigraphic succession, the gypsum-bearing evaporites occur mainly in the Lower Cambrian Longwangmiao Formation, the Middle Cambrian Douposi Formation, and the Middle-Upper Cambrian Xixiangchi Group. Geographically, the rocks are found mainly in the southeastern part of the basin, and the distribution of deposits shows an overall SW-NE trend. The sedimentary environments for evaporite formation were evaporative lagoon and inter-platform basin in a platform setting. Gypsum was generated by the underwater concentration of sea water in a strongly evaporative environment. Both an evaporative restricted platform and a mixeddeposition restricted platform model appear to be applicable to the development of gypsum in the Sichuan Basin. The gypsum-bearing evaporites with the best sealing capacity are located mostly in the southeastern part of the basin. These constraints can be applied directly to regional exploration, and have implications for the regional paleogeography and paleoclimate.

滚动轴承热处理虚拟仿真实验探索

轴承热处理是提高轴承品质的关键工艺之一,培养具有轴承热处理专业知识、实践和创新能力的人才对我国轴承行业发展具有重要意义。针对传统实体轴承热处理实验模式受限于设备要求高、成本高等因素,以及在课程实验中应用困难的问题,以《轴承热处理技术》课程为典型案例,构建“四层次双模块”的滚动轴承热处理虚拟仿真实验平台,并对比三年来全教学过程中实验指标的变化情况。数据显示本试验获得了良好的实验成效。

广西公路承灾体自然灾害风险信息化普查技术研究

针对为全国公路运营管理提供灾害风险信息和科学决策依据,开展了自然灾害综合风险公路承灾体信息化普查技术研究工作,形成了一套科学规范、便于操作的普查技术标准。创新性地引入“信息化普查仿真”理念,将自动化检测车与无人机结合起来,提出了一种基于信息化三维实景普查的全新思路,并研发了相应的数字信息化SOA架构普查平台分析和管理数据库。研究成果可广泛应用于公路承灾体自然灾害风险普查,可有效提高公路普查的效率、缩短普查周期、节省普查费用,并可向其他领域拓展。

近邻铁路桥梁转体施工防护技术

新建津石高速公路与既有铁路线路交汇,采用2×65 m T形刚构大节段现浇转体上跨既有铁路。考虑桥墩下部承台桩基距离既有铁路较近,通过施作防护桩、拉森钢板桩、回灌井及调整施工顺序等手段最大限度的减小对既有铁路的影响;采用水泥搅拌桩加固地基,满足现浇梁支架地基承载要求;转体施工加强防护与监测。采用PLAXIS完成相关模拟运算,顺利完成上跨铁路转体施工,对后续类似工程有较大的参考价值。

一种应用于精密隔振平台的双曲线磁通磁轴承设计

针对精密隔振系统磁轴承存在悬浮力密度小、波动大以及耦合力大问题,设计了一种双曲线磁通结构的磁轴承(MBHFM)。首先利用等效电流法和永磁体镜像法推导了带有磁轭的双曲线磁通的磁轴承的气隙磁场和悬浮力的表达式,并分析了磁轴承悬浮力波动对隔振性能的影响。其次根据双曲线磁通的磁轴承悬浮力线性分布特点,采用电流前馈补偿方法使磁轴承获取更低悬浮力波动的恒定悬浮力。最后,对双曲线磁通的磁轴承与常见的双边Halbach结构磁轴承(MBBH)进行了仿真分析与测试。仿真结果表明所设计双曲线磁通的磁轴承样机静态悬浮力平均值为153.75 N,静态耦合力系数为0.42%,电流前馈补偿后合成悬浮力波动系数为0.15%,较双边Halbach结构磁轴承静态悬浮力密度提高了20%,静态耦合力系数减小了72.2%,合成悬浮力波动系数减小了89.3%。测试结果进一步验证了所设计样机的高性能。

排水方式及加载条件对三筒型基础水平承载的影响

以三筒型基础为研究对象,分析吸力筒筒高、加载角度、加载速度以及排水条件对其承载性能的影响。研究表明,在其他3种影响因素不变的情况下,随着筒裙高度的增大,三筒基础的水平承载力提高;不排水条件下,加载速度明显影响筒型基础水平承载力和筒内孔隙水压力,排水条件下加载速度对筒型基础的水平承载力影响有限;加载角度不同,筒型基础的水平承载力最大增加1倍;不排水条件较排水条件可致使水平极限承载力最大增幅达149%。因此,实际工程中,沉放三筒型基础后,宜关闭筒顶阀门,有助于筒型基础保持较好的水平承载能力。

基于物联网技术的推力滑动轴承综合试验系统设计

设计了一种基于物联网技术的多功能推力滑动轴承综合试验系统,从试验台硬件部分和物联网平台软件设计两方面具体阐述方案的整体设计,结合物联网技术,开发数据采集、传输、存储与显示系统和终端设备,搭建云平台,实时展示轴瓦工作状态、油膜压力和摩擦系数。该系统可用于大型装备中推力滑动轴承运行状态的智能监控。

双缓动平台时延下的纯方位定位测角误差分析

水下双缓动平台协同探测可实现对水声目标纯方位定位和跟踪。针对双探测平台接收目标信号因传播时延导致探测时间未配准、方位测量偏差的问题,根据缓动平台的实际应用场景,建立目标运动模型和二维探测空间几何分布,构建一种基于不同时延条件的方位测量误差分析模型,并详细分析得出目标和双平台不同分布场景下的最大测角误差结果,该模型物理意义明确、直观简单,仿真和实测实验结果验证测角误差模型的准确性,并得出双平台探测时延下目标方位测角的误差分布规律。

桥梁门式墩不平衡转体承台施工技术

转体结构的施工是桥梁转体施工至关重要的环节,尤其对于门式墩不平衡结构的转体施工。为保证桥梁门式墩不平衡转体结构的施工质量及施工安全,通过下转盘及滑道采用定位骨架结合可调定位板粗调,结合专用自制微调装置精调,实现转体系统精细安装;上承台采用水密砂基础及砂浆垫层作为承台支撑体系及底模,解决狭窄空间及密集预埋件条件下模板体系支撑难题。

钢板桩围堰在桥梁施工中的应用分析

本文以某高速公路特大桥桥墩承台钢板的围堰的施工为研究基础,分析如何选择承台施工围堰方案,并从多方面介绍钢板围堰技术的要点,主要包括围堰结构形式选用、材料及设备进场要求、桩板桩插打及合拢注意事项、内撑系统施工要求、承台封底砼施工方案,从而为钢板桩围堰在桥梁施工中的应用提供理论指导。

基于管冷系统的大体积承台水化热抗裂研究

为了研究管冷系统作用下大体积混凝土因水化热引起的开裂问题,以河沟大桥主墩承台为依托,实时采集温度场数据并进行分析,使用Midas FEA软件建立该承台三维有限元模型,分析了管冷系统对承台的冷却效果,研究表明:通过改变冷却水入管口温度和冷却管直径以优化系统设计可以有效减小结构里表温差,防止结构早期开裂。

基于带相移角双输入陷波器的磁悬浮转子转速估计方法

针对磁悬浮转子在主动振动抑制过程中需要获取转子的实时转速信息,而某些情况下存在转速传感器失效或无法安装转速传感器的问题,提出了一种带相移角双输入陷波器的磁悬浮转子转速估计方法。首先,对磁悬浮转子进行了动力学建模,建立了转子广义坐标系和传感器坐标系的变换关系;然后,经过理论推导验证了该算法可以利用转子径向两通道位移输出相互正交的特性,准确估计出转子的转速,并在调整相移角后于整个转速范围内实现了转速估计的目的;此外,为了提高转速估计的准确性,在转速估计中加入了一阶惯性环节;最后,在磁轴承平台上进行了实验验证,尤其是对于磁悬浮转子转速极低的情况进行了验证。研究结果表明:该算法在2400 r/min和3000 r/min转速下的收敛时间分别提升了0.21 s和4.01 s,精度提高了87.4%,当转速发生变化时最快仅需0.15 s即可响应变化,且在极低速时仍可完成对转速的估计;该算法能够实现对转子转速的快速高精度估计。

轻量型机载惯性稳定平台电磁轴承性能与温度场仿真分析

针对机载惯性稳定平台电磁轴承的体积、质量较大,电磁场和温度场同时运算的双向耦合法研究较少的问题,提出一种轻量化、大承载磁悬浮机载惯性稳定平台电磁轴承的总体方案,设计了三点式单导磁环电磁轴承支承方式,采用有限元法完成该系统电磁性能的仿真分析,并对结构强度进行校核,完成电磁场和温度场单向、双向耦合的温度场分析。结果表明,电磁轴承性能满足设计要求,磁热双向耦合分析得到的温度分布更符合实际情况,自然空冷的方式能保证系统安全运行。

某塔架回转平台力学特性仿真分析

为研究某塔架回转平台结构的安全性,按照实际尺寸和工况建立了回转平台的三维数值模型,仿真分析了结构的受力情况、不同风速下液压系统的压力裕度、升降平台数量的影响三方面与实际应用密切相关的问题。应用工况下,结构最大应力为223.98MPa,安全系数ns为1.58。按最不利的风载方向和迎风面积计算,许用风速下打开平台时,液压系统至少需要5.40MPa的压力,压力裕度为2.96。当升降平台数量达到理论最大值9层时,ns为1.35,满足要求。计算结果验证了回转平台主体结构的安全性,可以为回转平台的使用提供参考。

海生物对渤海导管架平台结构性能的影响

为分析附着海生物对渤海导管架平台结构性能的影响,以渤海某典型4腿平台为例,结合渤海油田导管架附着海生物现场实测数据,针对不同海生物厚度及密度对导管架结构的影响进行敏感性分析,结果表明,平台所受环境荷载随海生物厚度增加而增大,而海生物密度对环境荷载不产生影响;结构杆件UC值和桩头力随海生物厚度及密度的增加而增大,节点UC值随海生物厚度增加而增大,随海生物密度增加几乎没有变化;平台前三阶自振周期随海生物厚度及密度的增加而小幅增大;疲劳寿命随海生物厚度的增加逐渐降低,且几乎不受海生物密度的影响;平台极限承载力不受海生物的影响。

基于时间节点联合估计的多平台纯方位机动目标跟踪算法

针对水面及水下纯方位变速、变向目标机动检测跟踪问题,提出一种基于时间节点联合估计的多平台纯方位机动目标跟踪算法,该算法将目标的机动时刻等价于“时间未知节点”,基于Taylor级数运动要素估计方法直接对目标机动时刻、目标机动前后运动要素进行估计。机动检测特征是估计机动时刻以及估计机动时刻迭代分量的迭代过程,当迭代过程震荡发散,或机动时刻估计值不在观测时间范围内时,目标未发生机动。仿真结果表明,该算法在跟踪中远距离海上变向变速目标时,具有较低的机动检测虚警率和较高的跟踪精度。

平台法盘扣架模板支撑体系施工技术

为解决盘扣式模板支撑架在实际工程设计使用过程中承载力利用率低、立杆水平杆布置不灵活的问题,通过对某市新能源装备产业园生产车间层高、柱网间距、梁截面尺寸、梁底标高进行分析,研究平台法盘扣架模板支撑体系。结果表明,该体系可有效发挥盘扣架承载力高的特点,节约材料,提高效率,立杆水平杆布置相对更灵活,可为类似工程提供借鉴。