盾构近接立交桥基础安全影响三维数值分析

为了提高盾构近距离穿越立交桥群桩基础施工中的安全性,采用有限元方法建立三维数值模型对盾构穿越群桩基础过程进行动态模拟,分析了群桩基础水平位移的变化规律以及地表受盾构影响的变形规律。结果表明:盾构掘进对桩基础水平位移影响最大,且水平位移增长过程分为盾构到达前、穿越时以及注浆阶段3个阶段,3个阶段水平位移值比例为6∶3∶1;盾构在竖直方向对桩基础水平位移的影响范围为1D（盾构直径）,水平方向为3D;此外,处于盾构左右双线之间的桥梁结构由于受到土层和桩基础沉降的双重影响,会产生较大的位移,实际施工中建议加强该区域桥梁结构的监测。     

动静组合加载作用下块系岩体动力响应分析

深部复杂地质条件下,煤岩破碎更趋呈块系岩体,在动载作用下易于产生超低摩擦效应并失稳诱发煤岩动力灾害。采用FLAC-3D软件模拟块系岩体在垂直冲击载荷和水平静力共同作用下的动力响应,深入分析块系岩体超低摩擦效应发生机理,得到垂直冲击载荷和水平静力共同作用对工作块体位移和应力的影响规律,确定了块系岩体产生残余位移和超低摩擦效应的水平静力特征值条件。研究结果表明:仅垂直冲击载荷作用时,冲击载荷作用强度对残余位移影响并不明显;垂直冲击载荷和水平静力共同作用下,水平静力与残余位移曲线呈半抛物线关系;不同垂直冲击载荷作用下,产生残余位移的突变点不同,且当施加的水平静力处于不同特征值区间时,工作块体运动状态随之不同。     

Large-scale effects on resistivity index of porous media

The estimation of humidity in the unsaturated zone of soils and NAPL saturation in contaminated aquifers may be based on the interpretation of electrical resistivity index logs. In the present work, concepts of the theory of the two-phase flow in pore networks are employed to interpret the form of the equilibrium and dynamic resistivity index curves of large porous samples. A resistivity cell is constructed to measure the capillary and electrical properties of large samples of unconsolidated porous media. The drainage capillary pressure and resistivity index curves of a sand column are measured by using the micropore membrane (porous plate) method, where a 0.5% wt/vol NaCl aqueous solution is displaced by n-dodecane. The dynamic resistivity index curves are measured by using the continuous injection technique for various orientations of the sand column. Based on concepts of the two-phase flow theory, concerning the dominant displacement growth pattern in a pore network and arising from the cooperative effects of capillary, buoyancy, and viscous forces, approximate relationships are developed for the resistivity index and saturation exponent as functions of the water saturation. The saturation exponent decreases as the displacement advances and the fluid distribution across the sand column tends to be homogenized after oil breakthrough. Both the resistivity index and saturation exponent increase as the displacement pattern tends to become compact and stable. In the destabilized flow pattern, as the Bond number decreases, the resistivity index may increase respectably within a narrow range of values of the Bond number. This happens when the thickness of the unstable capillary finger exceeds the lateral dimension of the porous sample and becomes a fractal percolation cluster. The saturation exponent becomes almost constant and independent of water saturation only over the destabilized displacement pattern at high values of the Bond number.     

销接简支钢梁的侧向稳定

销接钢结构广泛应用于结构工程中。销孔间隙会使体系产生初始几何位移 ,并对结构的承载力产生不容忽视的影响。笔者提出折减刚度的概念 ,对销结钢结构体系的稳定承载力进行了一次逼近 ,这提供了一种新方法和新思路。在算例中对六四式铁路军用梁标准三角拼组简支梁考虑初始几何位移对梁的稳定承载力进行了分析 ,给出了该结构考虑稳定时的临界跨度     

Needs assessment of the displaced population following the August 1999 earthquake in Turkey

In August 1999 a major earthquake struck north-western Turkey. An assessment followed to identify the immediate needs of the displaced population. A random cluster sample of displaced families living in temporary shelter outside of organised relief camps was designed. Representatives of 230 households from the four communities worse affected by the earthquake were interviewed. Most families lived in makeshift shelters (84 per cent), used bottled water (91 per cent), obtained food from relief organisations (61 per cent), had access to latrines (90 per cent), had a member on routine medication (53 per cent) and obtained information by word of mouth (81 per cent). Many respondents reported having family members who were over the age of 65 (32 per cent) or under age three (20 per cent), who were pregnant (6 per cent), or who had been ill since the earthquake (64 per cent). The greatest immediate need reported by most families was shelter requirements (37 per cent), followed by food (23 per cent) and hygiene requirements (19 per cent). Ten days after the earthquake, basic environmental health needs of food, shelter and hygiene still predominated in this displaced population. Significant portions may have special needs due to age or illness.     

Coping strategies developed as a result of social structure and conflict: Kosovo in the 1990s

The end of 1989 brought with it political and economic decisions which resulted in Kosovo being stripped of its autonomy and the Albanian population being expelled from their jobs. These facts combined with ethnic tensions created a decade of conflict and oppression affecting hundreds of thousands of innocent civilians. Thousands of Kosovars moved overseas to seek work to support families at home, altering the way of life of the population of Kosovo irredeemably. The loss of income had serious repercussions on food security throughout the 1990s; possibilities of purchasing food were diminished, control on goods in 1998 reduced availability of foodstuffs, conflict affected accessibility to markets and shops and consequently food intake and nutritional status was compromised. The most vulnerable were those who had no family members overseas. Mass displacement of population due to ethnic cleansing during the war of spring 1999, further jeopardised food security status. Destruction at this time rendered large parts of Kosovo useless and resulted in a shift in the determinant of vulnerability in the post-war period: destruction of houses, land, livestock and agricultural products as well as loss of family members, became a far more pertinent indicator of food insecurity. The strong and clear links between conflict, socio-economic issues and food security are highlighted and discussed in this paper.     

反应位移法在盾构隧道横断面抗震设计中的应用

介绍了反应位移法的基本原理,以及该方法在盾构隧道抗震设计时计算及分析隧道横断面上产生地震时的断面内力的方法,并结合武汉长江隧道工程实例,阐述了该方法的具体计算过程,为盾构隧道抗震设计提供了经验。     

某基坑土钉支护结构阴角和阳角效应分析

土钉支护结构中,基坑的阴角和阳角部位空间效应较明显,存在明显的三维效应。一般分析往往对基坑进行简化,将基坑中剖面的分析结果应用于基坑角部部位,结果与实际情况存在差异。通过基坑监测和三维有限元分析,证实了土钉支护结构角部部位具有明显的空间效应,基坑阴角处较阳角处具有较高的安全性。     

排水刚性桩处置可液化倾斜场地的振动台试验研究∗

排水刚性桩将竖向排水体和刚性桩相结合,是一种有效的地基抗液化处理措施。但目前对排水刚性桩在可液化倾斜场地中抗液化侧向变形的性能研究还比较缺乏,制约了其推广与应用。通过振动台试验,开展了可液化倾斜场地中排水刚性桩和普通刚性桩的对比研究,从土体内部动孔压响应、液化土体的流动性质、桩顶水平位移等角度研究了排水刚性桩对可液化倾斜场地的处理效果,并考虑了群桩布置形式的影响。结果表明,排水刚性桩是一种有效的加固可液化倾斜场地的处理措施,可以较好的限制液化土体侧向变形;相同群桩布置形式下,排水刚性桩限制土体流动变形效果优于普通刚性桩,且这种限制效果在坡顶位置更为明显;对于普通刚性桩,群桩梅花形布置形式相对于正方形布置形式能更好的阻止液化土体的流动变形,而对于排水刚性桩,群桩布置形式影响较小。     

尾矿库在线监测系统中位移数据分析方法探讨

尾矿库的安全稳定在矿山安全生产和环境保护中具有十分重要的意义,国家已明确要求三等及三等以上尾矿库应安装在线监测系统。本文在总结我国尾矿库在线监测系统结构和建设情况基础上,分析了当前已建成系统中坝面位移或坝内位移处理方法的现状和存在的不足,并提出科学合理地分析位移数据是关系到尾矿库在线监测系统有效性和适用性的关键技术之一。在总结归纳尾矿库安全领域坝体变形和稳定安全评价方法的基础上,提出了尾矿库在线监测系统中坝面位移和坝内位移定量分析处理的新思路,指出尾矿坝变形过程的数值仿真是校核在线监测系统所得位移数据,进而有效地分析和预测尾矿坝变形趋势的重要手段之一。