新建地铁车站超近接既有区间隧道影响分析

为探明地铁车站深基坑开挖对超近接并行既有地铁隧道的影响,该文以成都地铁18号线倪家桥站为研究对象,采用有限元计算方法,分析不同围护桩桩径、内支撑层数下,基坑开挖对既有地铁隧道的影响。研究结果表明：支撑层数对隧道位移的影响最大,增大围护桩桩径、支撑层数可以使既有车站、隧道和基坑变形逐渐减少,但一味地增大地连墙厚度和支撑层数,控制变形效果并不明显,还会增加施工成本和施工难度。研究成果为类似地铁车站结构设计提拱理论依据。     

基于倒频谱解析法的近接型相似微地震对研究

为查明水力压裂实验所产生的人工裂隙网络区域的地应力场和局部构造特征,分析了1995～1996年在Soultz 干热岩(HDR)地热田水力压裂实验中获得的声发射数据,通过倒频谱解析法,检出近接型相似微地震对,对其进行时间-倒频率分析,结合时间-倒频率-倒频谱表示图,判断出了P波的到达时间间隔,最后标定出近接型相似微地震对的相对震源坐标,判断出人工裂隙网局部的裂隙进展方向.     

交叉隧道盾构施工参数与交叉角度对既有隧道的沉降影响研究

隧道开挖施工引起地层的位移可能会引起附近建筑物或其他各类结构的变形,甚至造成灾害。运用三维有限元方法,采用变刚度等效法来模拟注浆材料的硬化,同时采用等效均布注浆压力来模拟盾尾同步注浆,计算分析了不同的盾构顶进力、盾尾注浆、千斤顶推力等施工参数下及不同的隧道交叉角度下,交叉隧道盾构施工对既有隧道沉降的影响。结果表明：注浆压力和注浆材料的硬化对既有隧道沉降产生直接影响;既有隧道沉降值随着盾构推进力和注浆层参数的增大而减小;盾构千斤顶推力变化引起的既有隧道沉降值大于正常推进时的沉降值;当隧道交叉角度小于90°时,既有隧道沉降随着交叉角度的减小而增大。     

系梁对哑铃型高桩承台基础抗震性能影响

针对我国大跨度桥梁目前常用的哑铃型高桩承台基础,分析了系梁对其地震反应的影响因素,采用反应谱分析方法重点讨论了在工程可行的几何尺寸范围内,系梁轴向刚度和抗弯刚度对哑铃型高桩承台基础的地震反应影响规律,进一步讨论了系梁底桩基对系梁刚度的影响。结果表明：设置系梁后,系梁轴向刚度和抗弯刚度会对哑铃型高桩承台基础的地震反应产生较大影响,但在工程可行几何尺寸范围内,系梁轴向刚度的变化对其影响不大,而抗弯刚度的变化对其影响较大,且抗弯刚度越大对基础抗震越有利。在系梁底布置桩基可有效提高系梁的刚度。     

Influence of pile shape and pile interaction on the crushable behavior of granular materials around driven piles: DEM analyses

This study presents an analysis and a visualization of the effect that the pile shape has on the penetration resistance of driven piles in crushable granular materials. Discrete Element Method (DEM) simulations of single piles with different shapes (flat tip, open pile, triangular tip) being driven into a previously compacted uniform crushable soil are presented. The results from the DEM simulations showed that the shape of the driven piles has a significant influence on the development of penetration resistance and particle crushing. This study also presents the penetration resistance and particle crushing results when a second flat tip pile was driven in a region near a pre-existing single flat tip pile. It was found that considerable high crushing was induced by the second pile. The second pile induced crushing not only on the particles surrounding itself but also on the particles surrounding the pre-existing pile, showing that particle crushing around a driven pile not only takes place when the pre-existing pile is being driven, but it also occurs during the installation of a second pile, in a region closely located to the first one.     

钢包回转台与基础共同作用的研究

对钢包回转台各种工况的荷载及地脚螺栓的预紧力和工作应力进行分析。在上部结构和基础共同作用下,钢筋混凝土基础的不同截面和部位处于复杂的应力状态;地脚螺栓承受反复张拉荷载,可导致地脚螺栓的疲劳破坏、界面破坏和松动。按荷载效应的基本组合进行承载能力极限状态分析,按荷载效应的标准组合进行抗拉疲劳分析,采用许用应力设计法进行地脚螺栓的设计。考虑欠荷载系数的影响,对栓杆的变幅疲劳按常幅疲劳验算,通过分析栓杆与混凝土界面的粘聚力和摩擦力,提出按混凝土的局部受压进行锚板及基础混凝土设计。     

Application of beam on elastic foundation to the interaction between a corrugated box and pallet deckboard

Corrugated boxes are ubiquitous in shipping and warehousing logistics. In physical distribution, corrugated boxes are often shipped in a unit load form where the interaction between the components determines the effectiveness and safety of the overall system. When lower stiffness pallets are used to support the corrugated boxes, the compression strength of boxes is reduced due to the uneven support conditions caused by the deforming top deckboards of the pallet. In this study, a modification of the principle of beam on elastic foundation was used to predict the effect of pallet deck stiffness on the performance of a corrugated box. In the model, the corrugated box acts as the elastic foundation, and the deckboard is represented as the beam. Pallet deck stiffness, pallet connection stiffness, and package stiffness are required model inputs. The resulting model was capable of predicting the normalized distribution of forces along the boxes' length sidewall but was not capable of predicting the compression strength of the box at failure.     

基坑开挖爆破作用邻近压力燃气管道动力响应特性研究

确保复杂城市环境基坑爆破开挖工程中邻近压力燃气管道的安全性是关键性问题。依托武汉地铁8号线二期竖井基坑爆破开挖工程,利用现场监测数据建立ANSYS/LS-DYNA三维有限元数值计算模型,分析计算了不同运行压力条件下埋地燃气管道的动力响应特性。研究结果表明:实际工况下管道截面峰值合振速为0.453 cm/s,单元峰值von-Mises应力4.95 MPa,压力燃气管道处于安全运行状态;管道截面峰值合振速大于其正上方地表振速,且两者存在线性关系,由此建立管道爆破振动速度的预测模型;管道截面峰值合振速、峰值von-Mises应力均位于迎爆侧,且随管道内压的增加而增加,内压为零时为最佳运行状态,由此建立了管道峰值von-Mises应力与内压、爆破参数的数学计算模型,为实际爆破工程的安全作业提供指导。     

空分塔保冷箱基础结霜原因分析及处理

介绍了空分塔保冷箱基础结霜的现象 ,经过分析 ,得出液氮阀泄漏是保冷箱基础结霜的原因 ,并提出了相应的应急措施。     

Explicit analysis for the ground-support interaction of a circular tunnel excavation in anisotropic stress fields

ABSTRACT

The convergence-confinement method (CCM) applied to a circular tunnel drilled through the ground under, initially, an anisotropic stress condition is investigated in this paper by employing the explicit procedure for implementing the analytical solution for executable calculations that can be directly estimated using a simple computational spreadsheet. The solutions of ground-support interaction in the final equilibrium state are solved with, in the elastic state, the simultaneous equations between the support confining curve (SCC) and the ground reaction curve (GRC) and using the Newton recursion method for finding roots in the plastic state. The influence factor of ground reaction, the apparent shear modulus of the ground, the apparent stiffness of the support and the interaction curve (IC) were especially examined in this study to consider the influence of locations around the tunnel in anisotropic stress fields. The validity of the developed explicit procedure for analytical solution was verified by numerical analysis to study the effects of in-situ stress ratio on the stress path, SCC and GRC at the intrados of the tunnel. The comparison of results obtained between the proposed explicit analysis (EAM) and the numerical analysis (FEM) was found to be consistent in elastic and elastic-perfectly plastic media.     

我国工业设计发展存在的问题及对策研究

工业设计(Industrial Design)指以工学、美学、经济学为基础对工业产品进行设计,其起源于德国魏玛市"公立包豪斯学校"。工业设计作为一门刚发展起来的新兴学科,它对人们生活影响已越来越突出,对于一个国家的发展起着很重要的作用。但是综观工业设计在我国近年的发展,既有令人兴奋鼓舞的一面,又有一些不尽人意的方面。     

The effect of slip on the motion of a sphere close to a wall and of two adjacent spheres

Summary The motion of a sphere towards a plane or another sphere is opposed by the fluid between them with a force which is inversely proportional to the gap. In consequence, it is impossible for a constant force to produce contact in a finite time, unless the Stokes equations are modified. When the gap is of the same order as the mean free path of the air molecules, the Stokes theory for the motion of the air must be modified. The Maxwell slip flow approximation is used in this paper to show that, when the gap is small, the resisting force between the approaching surfaces becomes only logarithmically dependent on the gap, and contact can be achieved in a finite time. The difficulty in applying the Stokes theory to the problem of determining collision efficiencies for cloud droplets is thereby removed.The calculated values of the resistance to approach are used to determine the motion of a sphere falling towards a plane. If the motion is compared with the corresponding motion when no allowance is made for slip flow, the sphere without slip would still be at a distance of 1.3 times the mean free path from the plane, when the sphere with slip has made contact.Transverse motion must also be considered if the trajectory of a particle close to a collector is required. The forces and couples on the sphere in that situation have a logarithmic dependence on the gap without slip, but they tend to constant values when the effect of slip is included. Some calculations of collision efficiency of drops falling under gravity (Hocking and Jonas [1]) have been amended to include the effect of slip when the colliding drops are very close together, and show a significant increase in the collision efficiency.