苏通大桥二期试桩后压浆的施工及效果检测

随着高层建筑和大型桥梁的兴建,钻孔灌注桩在工程中已得到了极为广泛的应用。但是,钻孔灌注桩的固有缺陷,例如孔底沉渣、孔壁泥浆、端阻力、侧阻力发挥不同步等,限制了其承载力的发挥并且沉降较大。由此,钻孔灌注桩压力注浆技术应运而生,并被逐渐应用于工程实践中。所以,对桩的后压浆施工工艺、受力机理等技术问题进行研究是非常重要的。在国内外现有的理论研究和工程应用基础上,通过对苏通大桥Ⅱ期的试桩工程施工,详细阐述了桩端后压浆技术的具体应用。同时,利用钻孔取心及CT检测技术分析后压浆的施工效果。     

冻融循环作用下含水率对粗颗粒填料水分迁移影响的宏细观试验研究北大核心CSCD

冻融循环作用和初始含水率是影响粗颗粒填料水分迁移特征和冻胀融沉变形的两个主要因素。为明确冻融循环作用下,不同初始含水率粗颗粒填料的水分迁移特征及细观机制,采用荧光素为追踪剂,以CT细观机理观测为研究手段,开展了不同初始含水率条件下粗颗粒填料的一系列冻融循环试验,探究了温度场和冻深变化、水分迁移图像、补水量变化、最终含水率分布及CT值变化规律等。试验结果表明,冻深基本随冻融循环的次数增加不断加深,初始含水率越大,不同冻融循环作用下冻深的变化越稳定。外界补水量和液态水迁移高度与初始含水率呈负相关。CT扫描结果分析表明,经历多次冻融循环后,试样中的水分迁移导致土体孔隙结构及颗粒构造发生变化,试样的密度普遍增加,孔隙率以减小为主,进而导致土体发生相应变形。     

实时相关跟踪图像处理系统

文章介绍了怀柔太阳观测基地最近完成的一套实时高分辨太阳磁场观测系统。系统采用局部相关跟踪算法来提高磁场观测数据的空间分辨率，同时对相关跟踪算法的实现程序进行了优化以满足常规太阳磁场观测的要求。通过对试观测和常规观测数据的分析，我们发现：1）该系统能够大大提高单色像、磁场数据的对比度和空间分辨率；2）对相关跟踪算法的优化大大提高了系统的时间分辨率，系统可以投入常规观测使用。     

Analysis of small-scale heterogeneity in clastic rocks by using computerized X-ray tomography (CT)

The aim of this study is to recognize the basic clastic rock types on the basis of Hounsfield Units (HUs) by using statistical methods (hypothesis tests, distribution fitting, and confidence intervals). How does this recognition depend on depositional history of samples tested? Does the numerical pattern of HUs obtained from small-scale analyzing of some particular sedimentary structures coincide to the textural expectations of those sedimentary structures? Are the HU values provided by the CT measurements capable of evidencing micro-cycles belonging to a particular depositional history?For testing the numerical recognition, we analyze macroscopically homogeneous argillaceous marl, siltstone and fine sandstone samples with similar depositional background, age, and degree of diagenesis. The preliminary research shows that the Hounsfield Units can identify different sedimentary rocks considerably well. There are significant differences among the confidence intervals belonging to the different rock types. However, there also have been some slight overlaps among them.For analyzing the effects of the depositional processes in case of a particular rock type, samples from channel sandstone, distributary mouth-bar, massive (structureless) sandstone from a delta-fed turbidity fan, and channel sandstone with traction carpet origin from a delta-fed turbidity fan (all coming from Pannonian basin filling series) are used. The results prove again the significant differences in the terms of both confidence intervals and distribution-types; however, some overlapping also occurs.     

The use of X-ray tomography in the study of water repellents and consolidants

To reduce the weathering rate of natural building stones, a wide variety of water repellents and consolidants are commercially available. Although a lot of research is performed on these products, it remains difficult to determine which product is appropriate to use for a certain type of building stone. Each type of building stone has its own petrographic characteristics (mineralogy, texture, …), leading to typical physical and technical properties which influence its rate of decay. The localisation of the products inside a stone type is not only depending on the properties of the products themselves, but also linked to the texture and structure of the stone. The impregnation depth of the products strongly influences their efficiency and is therefore a key issue in the determination if a product is functional for a certain type of stone. X-ray micro-CT has recently been introduced as a non-destructive material evaluation technique for engineering and geology purposes. The fact that micro-CT can provide information about the internal structure and properties of natural building stones, is a major advantage in the study of their conservation. Firmly linked with more classical research techniques, this non-destructive technique offers an extra dimension to the cultural heritage research.In this paper, non-destructive X-ray computed micro-tomography (micro-CT) turns out to be a powerful tool as it can visualise the presence of water repellents and consolidants inside the stone and can help to detect the influence that these treatments exert on porosity and pore-size distribution. For the visualization of the product its atomic number and density and the amount of product inside the natural building stone is crucial. Besides the contrast in attenuation, the resolution of the micro-CT also needs to be taken into account to obtain a good contrast between stone and product. By doping with 3-bromopropyltrimethoxysilane, more contrast occurs between the stone material and the conservation product. When the amount of product inside the samples is very low and the product is homogeneously spread inside the sample, the doped product is difficult to distinguish from the stone material due to the resolution of the micro-CT. When the amount of doped product inside the stone material reaches a certain threshold value, the dope will appear in the 2D cross-sections derived from micro-CT, creating a good visualization of the products inside the stone samples.     

不同充填介质下的溶洞跨孔电阻率CT探查数值模拟

城市地铁修建过程中常常会遇到溶洞等不良地质条件,为更加准确探查地下溶洞的位置和大小,采用有限元法和最小二乘法正反演数值模拟手段,利用孔距、电极距和与钻孔距离三个变量构建了地下溶洞的地电模型,分析并总结了跨孔电阻率CT法对充气、充水和部分充水溶洞的电阻率响应特征及规律。结果表明:部分充水溶洞的水、气分界面明显,低阻区域和高阻区域与溶洞充水、充气部分位置大小一致,且随着溶洞充水量的增加,溶洞低电阻率响应增强,其异常范围向溶洞顶部扩大;跨孔电阻率CT法能够有效识别溶洞充填性状。      

缝洞型碳酸盐岩气藏多类型储集层孔隙结构特征及储渗能力——以四川盆地高石梯-磨溪地区灯四段为例

为全面表征缝洞型碳酸盐岩气藏多类型储集层的孔隙结构特征及储渗能力,借助多种测试技术对四川盆地高石梯-磨溪地区灯四段储集层样品进行分析与研究。首先利用铸体薄片和扫描电镜技术定性刻画了储集层的岩性、物性、储集空间和喉道特征,然后根据高压压汞得到的毛管压力曲线对储集层进行分类,最后基于多尺度CT扫描定量表征了3类样品的二维、三维孔隙结构特征。结果表明：研究区储集空间既有受组构控制的粒间溶孔、粒内溶孔和晶间溶孔等,又有不受组构控制的溶洞、溶缝和构造缝;喉道以缩颈、片状和管束状为主;根据毛管压力曲线特征,储集层可划分为缝洞型、孔洞型和孔隙型;缝洞型大孔隙与溶洞发育,分布均匀且连通性好,喉道粗大且数量较多,微裂缝与溶洞串接呈串珠状分布,沟通了孤立的储集空间,具有最好的储渗能力;孔洞型多尺度孔隙与溶洞发育,储集能力强,喉道粗大但数量较少,连通性较差,各储集空间无法有效沟通,渗流能力受限;孔隙型细小孔隙发育且分布不均,大部分区域被岩石骨架占据,喉道数量少且连通性极差,储渗能力弱。     

螺旋CT原理,扫描参数和图像重建

螺旋ＣＴ最显著的特征是Ｘ线球管围绕病人旋转时,扫描床上病人连续通过机架,由于滑环技术的发明螺旋ＣＴ于１９８９年投入临床应用,它被广泛接受并成功地应用于人体各个部位的检查。由于产生容积数据,螺旋ＣＴ产生较少的呼吸遣漏扫描且可行允许重建,提高了Ｚ轴的分辨率。     

CT诊断胸部平片隐匿部位肿瘤的检出价值

本文对２２７例胸部肿瘤中的３４例Ｘ线不易发现的肿瘤进行了Ｘ线与ＣＴ诊断的对照分析,此组病例共占胸部肿瘤的１４．９％,胸部隐匿部位的肿瘤在传统Ｘ光正位胸片上受组织重叠的影响是不易看到的,容易漏诊,须通过ＣＴ扫描检查方可观察到,ＣＴ扫描是诊断胸部隐匿部位肿瘤的最好,最有效的检查方法之一。