Numerical simulation of longitudinal settlement of shield tunnel in the coastal city Shanghai

Until now more than 14 subway lines are in operation and some new lines are being built in the coastal city Shanghai. The longitudinal settlement of shield tunnel has significant effect on the safety of the subway operation. In this paper, the deformation of the shield tunnel and the surrounding soil were analyzed by the establishment of a three-dimensional model. The vertical displacements of four paths (Path 1 is on the ground; Path 2 is at the top of the tunnel; Path 3 is in the middle of the tunnel; Path 4 is at the bottom of the tunnel) are affected by the nature of the soil. The horizontal displacement is smaller than the vertical displacement and horizontal displacement of the clay is larger than that of the sand. The distribution of the pore pressure changes with soil properties around the tunnel. The pore pressure of the sand layer is larger than that of the clay layer at the same depth of underlying soil.     

Examination of loose saturated sands impacted by a heavy tamper

This article examines the densification effects on the loose saturated sands impacted by a heavy steel tamper dropped from a great height (i.e., deep dynamic compaction, DDC). This examination was achieved by carrying out a series of piezocone penetration test (CPTu) soundings before and after the DDC impact. The depths at which densification took place ranged from 6.5 to 9.5 m below the ground surface (BGS) after one pass of DDC, and from 7.5 to 11.0 m BGS after two passes. The propagation of the surface waves generated in DDC disturbed the top 0.3–1.3 m soils. Directly below this disturbed layer, it was the most densified soil layer at the depths of 1.7–4.5 m BGS. The existence of the residual soft peat pockets reduced the densification effects substantially. Both the strength and the stiffness of the loose saturated sands were significantly improved after the DDC treatment. After two passes of impact, the liquefiable soils were densified to the level of unliquefiable along with dramatic reduction in liquefaction probabilities when subjected to earthquake motions.     

14时探空在改进北京地区对流天气潜势预报中的作用

为了探讨增加14时探空对于对流天气短时临近潜势预报的作用。用1995—2005年北京地区22个人工观测站资料统计了夏季常见的对流天气日变化特征。结果表明,41．6％的雷阵雨、61．3％的冰雹以及58．5％的雷暴大风发生在15—-20时之间。利用探空资料计算并对比了出现在2006年7—9月14时探空释放后到20时期问11个雷暴个例的08时和14时BCAPE、DCAPE、CIN等对流参数。结果表明,对于多数个例,在判断对流是否发生时14时探空优于08时。因此,增加14时探空对于提高对流天气有无预报准确率有帮助。     

九江-瑞昌序列震源位置及震源区速度结构的联合反演

采用震源位置和速度结构的联合反演方法确定2005年九江一瑞昌5.7级地震序列的分布和震源区的速度结构.结果显示九江一瑞昌地震序列存在NW330.方向和NE550方向的两组共轭分布,其中NW330.方向的优势分布更为明显;震源深度分布在3～18km的范围.地震主体破裂发生在上地壳-中地壳过渡层的P波速度低速区内,主震发生后余震向东南与西北方向两头扩展,其中往西北方向破裂时可能遇到了障碍体,积累的能量转向西南-北东方向继续破裂,引发了4.8级强余震.     

Carbon Isotope Geochemistry of the Orinoco Basin

Stable carbon isotope ratios have been used to study the sources of particulate organic carbon (POC) and total dissolved inorganic carbon in the Orinoco Basin. The isotopic composition of total dissolved inorganic carbon shows a range of from -8·1 to -23·0 ppt, an indication of dominance of biological processes. The isotopic composition of POC exhibits a range of from -24·1 to -34·6 ppt with little seasonal variation. The isotopic evidence indicates that the POC is predominantly of terrestrial origin rather than a result of in situ planktonic production. The similarity of isotopic composition of POC and coastal sediments suggests that riverine organic detritus has been transported 30-50 km offshore in a direction parallel to the Orinoco river channel.     

孤立金属尖端的电晕触发阈值

为了得到金属尖端在发生电晕放电时尖端处的电场强度,该文首先采用实验室实验得到不同高度、不同形状、不同材质的金属尖端发生电晕放电时的环境电场阈值;再采用有限元法计算二维泊松方程,得到尖端处电晕触发阈值,由此得出以下结论:环境电场阈值随金属尖端高度的增大基本呈线性减小趋势,随着尖端越来越尖,环境电场阈值呈先减小后增大的变化趋势;高度、形状对金属物尖端处电晕触发阈值无影响,尖端处电晕阈值为定值;给出尖端处电晕触发阈值为158.75 kV·m-1与空间分辨率的拟合公式,可为今后电晕放电数值模拟中判断电晕放电的起始时刻提供参考。     

用超长基线解算分析汶川地震动态形变特征

以远距离的IGS武汉GPS站为参考站,用超长基线双差瞬时精密定位技术,获取汶川Ms8.0地震震时震区连续GPS站1 Hz动态形变序列。同时以较近距离的雅安站为参考站解算动态形变序列,结果显示,两者的形变结果具有很好的一致性。距离断层较近的郫县、成都、绵阳、中江等站形变较大（形变最大的郫县站最大振幅达1.034 m）;位于震中南侧的邛崃、雅安等站形变较小。利用动态时序的地震波到时和震中距离估计地震波地壳平均速度为3.1 km/s。     

Molecular cloning of the heat shock protein 20 gene from Paphia textile and its expression in response to heat shock

P. textile is an important aquaculture species in China and is mainly distributed in Fujian, Guangdong, and Guangxi Provinces. In this study, an HSP20 c DNA designated Pt HSP20 was cloned from P. textile. The full-length c DNA of Pt HSP20 is 1 090 bp long and contains a 5′ untranslated region(UTR) of 93 bp, a 3′ UTR of 475 bp, and an open reading frame(ORF) of 522 bp. The Pt HSP20 c DNA encodes 173 amino acid residues and has a molecular mass of 20.22 k Da and an isoelectric point of 6.2. Its predicted amino acid sequence shows that Pt HSP20 contains a typical α-crystallin domain(residues 77–171) and three polyadenylation signal-sequences at the C-terminus. According to an amino acid sequence alignment, Pt HSP20 shows moderate homology to other mollusk s HSPs. Pt HSP20 m RNA was present in all of the test tissues including the heart, digestive gland, adductor muscle, gonad, gill, and mantle, with the highest concentration found in the gonad. Under the stress of high temperature, the expression of Pt HSP20 m RNA was down-regulated in all of the tissues except the adductor muscle and gonad.     

汶川8.0级地震地表变形局部化样式与建筑物破坏特征关系初步研究

本文以汶川地震地表形变带的实地测量数据为基础,结合沿实测地震地表变形剖面建筑物破坏情况的调查与测量,分析了不同地震地表变形类型及其建筑物破坏特征,定量化地讨论了地表变形梯度与建筑物破坏程度间的关系。提出无论地震地表变形表现为何种类型的断层陡坎,地表破裂、强变形局部化在宽10~30m的地表破裂带内;建筑物受损情况最直接的影响是建筑物所处地点的地表变形梯度,地表变形梯度大于0.1的地段,建筑物均完全被摧毁;地表变形梯度在0.07~0.1间的地段,建筑物遭受严重损坏,产生倾斜及强烈变形等;地表变形梯度在0.03~0.07之间的地段,建筑物可能受到中度损坏,产生倾斜及变形等,具有抗震设防能力的构建筑物一般不会倒塌;地表变形梯度小于0.03的地段具有抗震设防能力的构建筑物一般只会受到轻的损坏或基本完好。     

Effect of loading duration on uncertainty in creep analysis of clay

Some studies suggest that creep parameters should be determined using a greater quantity of creep test data to provide more reliable prediction regarding the deformation of soft soils. This study aims to investigate the effect of loading duration on model updating. One‐dimensional consolidation data of intact Vanttila clay under different loading durations collected from the literature is used for demonstration. The Bayesian probabilistic method is used to identify all unknown parameters based on the consolidation data during the entire consolidation process, and their uncertainty can be quantified through the obtained posterior probability density functions. Additionally, the optimal models are also determined from among 9 model candidates. The analyses indicate that the optimal models can describe the creep behavior of intact soft soils under different loading durations, and the adopted method can evaluate the effect of loading duration on uncertainty in the creep analysis. The uncertainty of a specific model and its model parameters decreases as more creep data are involved in the updating process, and the updated models that use more creep data can better capture the deformation behavior of an intact sample. The proposed method can provide quantified uncertainty in the process of model updating and assist engineers to decide whether the creep test data are sufficient for the creep analysis.