Stability of pile foundations base on warming effects on the permafrost under earthquake motions

The Qinghai–Tibet Railway (QTR) is approximately 1142 km long, of which 275 km are underlain in warm permafrost regions (mean annual round temperatures range from 0 °С to 1.5 °С), where the stability of the embankment would be greatly affected by minor temperature variations. Furthermore, since the Qinghai–Tibet Plateau (QTP) is in an active seismic zone, special attention needs to be paid to the relationship between earthquakes and soil temperature. Using a refrigeration system, a series of shaking table tests for the 1/100 scaled model of the pile foundation in the Qingshui-river Bridge along the Qinghai–Tibet Railroad were conducted for soil temperatures of below 0 °С around the pile. The results indicated that the seismic mechanical properties are extremely sensitive to soil temperature. The change of temperature around the pile foundation during the earthquake motions was monitored, and the warming effects on the permafrost were assessed. In addition, the seismic stability coupled with the effect of soil temperature of the pile foundation in the Qingshui-river Bridge was evaluated.     

Amphibious Territories

Since 2005, when Hurricane Katrina wreaked havoc on the Gulf Coast and New Orleans, our polarised perception of land and water has been irrevocably shifted by the failure of static levee flood-control systems. Ila Berman explains how a more fluid geographical approach to land and water, which places an emphasis on continuous mutable ecologies, is key to a more sustainable future. She describes four experimental projects that are ground-breaking in their treatment of the relationship between the aquatic and terra firma. Copyright © 2010 John Wiley & Sons, Ltd.     

Microstructure and mechanical properties of 7A09 aluminium alloy after isothermal compression and solution treatment

In this paper, the effect of processing parameters on the microstructure was investigated during the isothermal compression of 7A09 aluminium alloy. The optimal deformation parameters for the hot compression of 7A09 aluminium alloy were determined to be 733 K and a strain rate of 0.01 s⁻¹. The effect of solution temperature and solution time on the microstructure and mechanical properties of 7A09 aluminium alloy after isothermal compression was also investigated. A low deformation temperature was beneficial for preventing the grain coarsening, while a high deformation temperature contributed to the dissolution of the second phase particles and the occurrence of static recrystallisation during the solution treatment process. The second phase particles were more dissolved in the Al matrix as the solution time increased. The optimal solution treatment of 7A09 aluminium alloy was 723 K for 55 min, followed by rapid quenching in water and an ageing treatment at 413 K for 16 h. The tensile yield strength, ultimate strength, and elongation of 7A09 aluminium alloy after the optimal solution treatment were 580 MPa, 630 MPa, and 11.5%, respectively.     

Change in the hydromechanical characteristics of embankment material due to compaction state conditions

In recent years, earthquakes and heavy rains have frequently caused soil embankments to collapse. In order to prevent the collapse of embankments, it is well known that sufficient compaction and drainage control are necessary. Although numerous research findings have described compacted soils, compaction management has been essentially based on simple parameters such as dry density, degree of saturation or air content. It is important for the construction of a stiff embankment that the effect of compaction condition on the mechanical properties and inherent anisotropy of compacted soil should be recognized in detail. In the present study, the relationships between the compaction condition and the mechanical properties obtained from laboratory tests using saturated specimens are presented. Specifically, undrained monotonic and cyclic shear strength, shear modulus, and permeability are reported. The arrangements of soil particles were also observed with a microscope. From the observation of fabric characteristics of soil particles, an inherent anisotropy of compacted soil is discussed. Furthermore, a conceptualization of the relationship between the fabric of soil particles and the mechanical characteristics for each compaction condition is suggested.     

Characterization of potassium glycinate for carbon dioxide absorption purposes

Aqueous solutions of potassium glycinate were characterized for carbon dioxide absorption purposes. Density and viscosity of these solutions, with concentrations ranging from 0.1 to 3 M, were determined at temperatures from 293 to 313 K. Diffusivity of CO₂ in solution was estimated applying the modified Stokes-Einstein relation. Solubilities of N₂O at the same temperatures and concentrations were measured and the ion specific parameter based on Schumpe's model was determined for the glycinate anion; the solubilities of CO₂ in these solutions were then computed.The reaction kinetics of CO₂ in the aqueous solution of potassium glycinate was determined at 293, 298 and 303 K using a stirred cell reactor. The results were interpreted using the DeCoursey equation for the calculation of the enhancement factor. The rate of absorption as a function of the temperature and solution concentration for the conditions studied was found to be given by the following expression:

     

09MnNiD钢马氏体大压下量温轧及低温退火后的组织与力学性能

利用Gleeble-3500热模拟试验机测定了不同温度下试验钢温变形的流变应力,对淬火09MnNiD钢板条马氏体组织进行了多道次压下量大于70％的温轧及低温退火试验。用透射电镜（TEM）观察分析了经过不同温变形以及不同温度退火后的微观组织,利用TEM暗场弦线法和X射线衍射谢乐法测定并计算了晶粒尺寸,在热模拟试验机上对退火样品进行拉伸试验。结果表明,温轧后在300～600℃进行退火可获得细小的纳米晶粒和超细晶粒钢板;拉伸试验表明,温轧钢板在〈450％下退火后的抗拉强度变化不大,当退火温度在550％及以上时抗拉强度显著下降。     

黑曲霉TNA-09中α-葡萄糖苷酶基因敲除的研究

以柠檬酸生产菌黑曲霉TNA—09为原始菌株,通过农杆菌介导的方法,将其α-葡萄糖苷酶基因敲除,得到基因敲除菌株TGA101。对原始菌株黑曲霉TNA-09和基因敲除菌TGA101 α-葡萄糖苷酶活力测定,结果相对于TNA—09菌株,TGA101菌株α-葡萄糖苷酶活力下降61．15％。在柠檬酸发酵试验中表现出相对于黑曲霉TNA-09,TGA101菌株发酵液中异麦芽糖含量降低84．67％,柠檬酸提高2．34％,糖酸转化率提高2．34％。     

7A09C T73铝合金挤压型材热处理工艺研究

航空航天器对7A09C T73铝合金挤压型材提出了十分苛刻的质量要求。为了获得符合技术条件要求的综合性能，本文较系统地讨论了热处理工艺，特别是双级时效工艺对7A09C T73型材组织性能的影响，初步确定了热处理工艺与组织、性能之间的关系，并在此基础上拟订了较合理的热处理工艺：淬火温度465～470℃，保温时间（盐浴）0．9～1．0min／mm（厚度）；I级时效制度110℃／6h；II级时效制度175℃／8h。该热处理工艺虽然使抗拉强度损失了15％左右，但可提高型材的塑性、断裂韧性、疲劳强度等，特别是可明显改善抗拉应力腐蚀性能，全面提高材料的综合性能。