地基模拟空间碎片速度测试技术

碎片速度测试技术是地基空间碎片模拟设备系统中的一项关键技术。文章对于毫米级尺寸碎片的测速技术,介绍了电探针方法、激光遮断法、X闪光照相以及激光干涉测速技术(VISAR)等;对于微米级碎片,介绍了压电传感器方法、超高速条纹摄影法及散射光法等测速方法。通过介绍这些测速方法的基本原理片的地基驱动设备及其技术参数也进行了介绍。及应用范围,并对相应的系统性能进行评价,可以为相关研究提供参考。另外。

空间连续流电泳电流体力学过程的地基模拟

通过相似性分析得到了空间连续流电泳电流体力学过程地基模拟的相似性准则．数值模拟表明，所得相似性准则是有效（近似）的．基于此，建立了空间连续流电泳电流体力学过程地基模拟实验系统，并进行了生物样品分离实验．当然，相似准则的最终检验有待于空间实验．

各向异性模拟的复合地基分析方法

本文将工程上常用的复合地基（水泥搅拌桩，粉喷桩等）模拟成各向异性弹性体，选取了样条位移函数来表征复合地基的位移，用半解析无限元来表征外部土体位移，并对圆板－成层复合地基系统进行了分析。

复合地基褥垫层作用的模拟与模型试验的对比

应用ANSYS数值模拟、物理模型试验相结合的方法,对复合地基褥垫层的作用随厚度变化的规律进行了研究,在数值模拟结果的基础上,以物理模型试验对数值模拟的结论加以验证。

深水防波堤软土地基数值模拟

某深水防波堤为斜坡式结构,水深18~30 m,软土层厚度超过30 m,基础采用部分开挖换填方式,基底保留了10余米原状软土层,地基沉降较大。为准确预计竣工后地基沉降,预留堤顶沉降以满足堤顶高程的设计要求,采用数值方法研究深水防波堤深厚软土地基沉降变形和稳定性。在利用施工期水下地基监测获得的大量实测数据验证数值模型真实可信的基础上,模拟防波堤的开挖和抛填施工及长期沉降全过程,得到各典型断面的最终沉降、施工期沉降和竣工后沉降,可为堤顶预留竣工后沉降及后期防波堤维护提供参考。同时,利用该模型进一步复核了防波堤地基的安全稳定性。

CFG桩复合地基的室外模拟试验研究

简述了CFG桩的应用优势,研究了CFG桩复合地基的室外模拟试验,通过分析试验结果,得出了所加荷载与桩最终沉降、桩端承载力、桩侧摩阻力的关系,对CFG桩复合地基的处理具有参考作用。

用于晶体生长的地基无容器悬浮技术

空间微重力环境下几乎无对流和沉降,可为晶体生长提供一个相对稳定和均一的理想环境,易于得到尺寸较大的高质量单晶。但是,空间结晶实验成功率低,费用昂贵,实验机会受限。因此,研发各种空间微重力环境地基模拟技术具有重要意义。目前可用于晶体生长的地基无容器悬浮技术主要有空气动力悬浮、静电悬浮、电磁悬浮、液体界面悬浮、超声悬浮和磁场悬浮技术等。这些地基模拟技术可实现晶体的无容器悬浮生长,避免器壁对晶体生长的不良影响,提高晶体质量,为解决X射线单晶衍射技术中的瓶颈问题提供新途径,还可为在地基进行结晶动力学和机理研究提供简单易行的方法。从技术原理、优势、缺陷及在结晶(特别是蛋白质结晶)中的应用4个方面对这些技术逐一进行了介绍和评述。重点介绍了液体界面悬浮、超声悬浮和磁场悬浮技术这3种用于蛋白质晶体生长的较为成熟的地基无容器悬浮技术。

材料空间环境效应研究方法与展望

空间环境是多因素交叉耦合作用的复杂、动态系统,是影响空间装备正常服役的重要因素,深入开展空间特殊环境效应研究已成为世界各国降低航天器在轨故障率、保证空间装备长期可靠运行的重要手段。总结近30年来世界各国进行空间环境效应研究的主要方法,即空间飞行试验、地基模拟试验和数值仿真计算,分析各种研究方法的优点与不足;综述各主要航天大国材料空间环境效应的研究现状,指出今后可以从基础理论和技术设备两方面对空间环境效应进行深入研究,通过开发新型的模拟试验设备和先进的数值仿真技术,未来将有望大大减少空间环境效应研究的周期和成本,从而加速推进相关空间材料和技术的研究与应用。

地铁近接施工时通道桥的变形计算及分析

对于城市市区常见的地铁近接现况通道桥、地下通道施工,合理评估地基沉降对现况结构内力的影响,进而检验相应控制指标的精度,有着十分重要的意义。结合北京市地铁9号线侧穿白石新桥的设计咨询工程,对其地基沉降工况进行了数值模拟计算,而后用计算结果对结构强度进行校核,验证了设计咨询报告中相关沉降控制指标的合理性。由此,为解决类似工程问题提供一种可资借鉴的思路及方法。

Analysis of tunnel face stability with advanced pipes support

To keep the tunnel face stable is very important for tunnel construction.In this paper,the tunnel face stability under the advanced pipe was analyzed using the Winkler foundation model and rigid limit equilibrium.The tunnel face deformation characteristics were also analyzed using the numerical simulation.The influence of parameters on the deflection of the pipe roof and the stability of the tunnel face were discussed.The results show that the tunnel face stability can be improved through increasing the pipe diameter,decreasing the initial displacement at the beginning of the pipe seat,and adopting the short round length and small excavation height.With the increase of tunnel burial depth,the safety factor of tunnel face stability first decreases,then increases,and then remains unchanged.The deformation at the center of the tunnel face is larger than the deformation at the surround sides and at the corner.The horizontal displacement varies little with the increasing of the pipe length.The horizontal displacement at the center of the tunnel face increases with the increase of the pipe ring spacing and the pipe longitudinal spacing.There is an optimum external angle.

Gas emission quantity prediction and drainage technology of steeply inclined and extremely thick coal seams

Gas emissions of workfaces in steeply inclined and extremely thick coal seams differ from those under normal geological conditions, which usually feature a high gas concentration and a large emission quantity. This study took the Wudong coal mine in Xinjiang province of China as a typical case. The gas occurrence of the coal seam and the pressure-relief range of the surrounding rock(coal) were studied by experiments and numerical simulations. Then, a new method to calculate the gas emission quantity for this special geological condition was provided. Based on the calculated quantity, a further gas drainage plan, as well as the evaluation of it with field drainage data, was finally given. The results are important for engineers to reasonably plan the gas drainage boreholes of steeply inclined and extremely thick coal seams.

基础下浅埋洞室安全顶板厚度研究

在参考已有资料的基础上 ,分析了山区城市浅埋地下洞室安全顶板厚度的影响因素。采用有限单元数值模拟法研究了基础与洞室相互作用下的破坏机制 ,以及各影响因素对浅埋地下洞室安全顶板厚度的影响及相关变化规律。并运用逐步线性回归的方法得出了一个能综合考虑各影响因素的安全顶板厚度的预测模型。

Longitudinal dynamic response of pile in layered soil based on virtual soil pile model

Taking the effect of finite soil layers below pile end into account,the longitudinal dynamic response of pile undergoing dynamic loading in layered soil was theoretically investigated.Firstly,finite soil layers below pile end are modeled as virtual soil pile whose cross-section area is the same as that of the pile and the soil layers surrounding the pile are described by the plane strain model.Then,by virtue of Laplace transform and impedance function transfer method,the analytical solution of longitudinal dynamic response at the pile head in frequency domain is yielded.Also,the semi-analytical solution in time domain undergoing half-cycle sine pulse at the pile head is obtained by means of inverse Laplace transform.Based on these solutions,a parametric study is conducted to analyze emphatically the effects of parameters of soil below pile end on velocity admittance and reflected wave signals at the pile head.Additionally,a comparison with other models with different supporting conditions from soil below pile end is performed to verify the model presented.

Seismic Centrifuge Modelling of Offshore Wind Turbine with Tripod Foundation

The development of offshore wind energy is fast as it is clean, safe and of high efficiency. The harsh marine environment raises high demand on the foundation design of offshore wind turbine. Earthquake loading is one of the most significant factors which should be considered in the design phase. In this paper, a group of earthquake centrifuge tests were conducted on a physical wind turbine model with tripod foundation. The seismic responses of both wind turbine model and foundation soil were analyzed in terms of the recorded accelerations, pore water pressures, lateral displacements and settlements. The results were also compared with those measured in the previous research on mono-pile foundation. It is demonstrated that the tripod foundation can provide better resistance in the lateral displacement and structural settlement under earthquake loading.

Molecular-Based Simulation of Feedstock Properties for Complex Reaction System

The kinetics of complex reaction systems were studied on molecular level with the combined method of Monte Carlo simulation and Structural Oriented Lumping by focusing on deep catalytic cracking （DCC） process, the model parameters were optimized by means of routine analytic data of a DCC unit. A model was established to transform the feedstock of the complex reaction systems such as DCC to 1000-10000 pseudo-molecules with the Monte Carlo simulation and every molecule was expressed by 19 attributes. The results of model simulation showed that these pseudo-molecules reflected the characteristics of feedstock very well and their average properties gave a good agreement with the plant data.

Mitigation of floor heave in West Kentucky Coal Mine

A West Kentucky mine operation in No. 11 seam encountered floor heave, due to the localized increase in the thickness of the fireclay mine floor. Floor heave has overridden seals installed in two mined out panels. The third seal's location was planned for isolating that area from the Mains. A plan of support has been developed to prevent repetition of the floor heave and related problems outby the seals. The applied ground control measures were successful. An attempt of a 3D numerical modeling was made; thus, it would match the observed behavior of the mine floor and could be used as a design tool in similar conditions. The paper describes sequence of events, an applied mitigation ground control system, and the first stage of numerical modeling.

Centrifugal model test and numerical simulation of vertical earth pressure on soft foundation box culvert

To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and the comparisons with the current methods to determine the load on a culvert were completed. The results of the model test and numerical analysis are in satisfactory agreement, which shows that the direction of the shear stress between the culvert and the adjacent embankment depends on the differential settlement between them. A vertical earth pressure concentration appears on the culvert with a rigid piles foundation because of a downward shear stress. The ratio of the load on a soft foundation culvert and the overburden pressure above the culvert raises first and then decreases as the backfill height increases. In order to reduce the load on a culvert, it is suggested to limit the stiffness difference of the foundations under the culvert and embankment and to use a light backfill over the culvert.

如何在地球表面模拟空间微重力环境或效应：从空间细胞生长对微重力响应谈起

当前,人们对空间微重力环境影响生命、化学、物理等过程的认识仍较为粗浅,在地球表面是否可以且如何模拟空间微重力环境或效应尚不清楚.本文拟从空间细胞生长对微重力响应这一基本问题入手,从力学/物理基本原理出发,讨论什么是重力变化、如何模拟微重力环境或效应、怎样模拟微重力环境所致的生物学响应等问题,以期澄清空间生命科学与空间生物技术、乃至空间生理学与医学研究中的相关基本概念,为地基相关研究提供科学参考.

Evaluation of Dynamic Behavior of Bedrock Foundation Based on FEM and DEM Simulations

The seismic behavior of the bedrock foundation during earthquakes concerns the stability and safety of nuclear power plants. Discontinuities like joints and faults existing in rock masses affect significantly the dynamic behavior of bedrock. The dynamic FEM （finite element method） has been commonly utilized to analyze the seismic responses of bedrock, however, it cannot well represent the large deformation behavior of discontinuities. The DEM （distinct element method） has a better capability of simulating the sliding and separation of discontinuities existing in the bedrock, which influence the propagation of seismic waves. In this study, the dynamic FEM and DEM simulations were carried out to investigate the seismic behavior of the bedrock foundation under a nuclear power plant, and the differences between those two methods were illuminated. Numerical simulation results indicate that the FEM underestimates the attenuation effect of faults on the propagation of seismic waves. With the capability of simulating large deformation behavior of discontinuities, the DEM can be regarded as a better method for studying the seismic responses of bedrock foundation which contains discontinuities.

Verification of Seismic Performance of Pile Foundation in Composite Ground through Experimental and Numerical Methods

A new construction method of pile foundation in composite ground, in which, prior to installing piles, the ground is improved around the heads of the piles in soft ground or ground subject to liquefaction, which is introduced in this paper. This construction method uses a combination of pile foundation construction together with common ground improvement methods, including deep mixing, preloading and sand compaction piling, and it is referred to as the composite ground pile method. Since an artificial ground with relatively high rigidity comparing with that of the original ground was formed around the pile in this method, and the seismic performance has not been made clear, thus the seismic performance of piles in composite ground was systematically analyzed through a series of centrifuge model tests and numerical analyses by using dynamic nonlinear finite element method, and a verification method for the seismic performance of piles in composite ground was proposed on the basis of the experimental and numerical results.