沉井预封底水力冲洗下沉工艺在砂质地层中的应用

西气东输二线东段上海支干线途经区域(苏浙沪地区)地质主要为砂质地层,土壤含水率及地下水位较高,为解决顶管隧道沉井涌水涌砂、封底周期长等难题,针对永利河顶管隧道沉井施工现状,采用沉井预封底水力冲洗下沉工艺进行施工.结合工程实例,阐述了地质勘查、工艺制定、设备选择、沉井纠偏、风险预测及防范措施等控制要点.沉井预封底水力冲洗下沉工艺在该工程中的成功应用,有效缩短施工周期约39％,降低施工成本约37.28％,减少了对井外地层的扰动,保证了周围建(构)筑物的安全,降低了公共关系协调难度.     

风罩拉深质量问题及解决方法

介绍一种代替深拉深的变通两体风罩结构,及底部外鼓的解决办法。     

Effects of crop management practices on Echinochloa crus-galli and Chenopodium album seed production in a maize/soyabean rotation

Seed production of residual weed populations needs to be taken into account when estimating the long-term impact of low-input agronomic practices. The objective of this study was to measure the effects and interactions of crop, weed control, tillage practice and nutrient source on the seed production of the dominant residual weed species in a maize/soyabean rotation at two sites: Echinochloa crus-galli (L.) Beauv. on a Sainte-Rosalie clay and Chenopodium album L. on a Duravin clay loam. Seed production per unit area was estimated in each experimental unit. Weed seed production was greater under mechanical weed control compared with chemical weed control. In 1997, E. crus-galli seed production reached over 326 000 seeds m^–2 in mechanical weed control treatments, but averaged less than 500 seeds m^–2 in the chemical weed control treatments. Chenopodium album produced in the range of 766 000 and 73 000 seeds m^–2 in mechanical and chemical weed control treatments respectively. Very few or no weed seeds were produced in soyabean under chemical control. Tillage intensity and nutrient source did not affect seed production of either weed species, with the exception that E. crus-galli produced more seeds in chisel than in mouldboard plough tillage in soyabean. Weed control method had more impact on seed production than tillage intensity and nutrient source in a maize/soyabean rotation.     

《建筑抗震设计规范》中抗震计算方法的归纳

《建筑抗震设计规范》（GB50011-2010）第5.1.2条,明确列出了各类建筑结构的抗震计算方法,归纳有三种方法,即底部剪力法、振型分解反应谱法和时程分析法,本文对此展开分析。     

Ergebnisse zur bodenverlagerung durch bearbeitungserosion in der jungmoränenlandschaft Nordostdeutschlands: Investigations of soil movement by tillage as a type of soil erosion in the young moraine soil landscape of Northeast Germany

Soil translocation by soil tillage can have a considerable importance on arable land. These results were published in the international literature. The aim of the experiments is to quantify the translocation of soil due to tillage with different typical tools. A mouldboard plough and a disc harrow were tested in field experiments on a slope (4° inclination) with sandy soil. The average movement of soil particles of the top soil was determined about the changed tracer concentration. The tracer coloured gravels were most suitable of all tested tracer. The comparison of the tools showed more soil translocation caused by mouldboard plough (145?kg) than by disc harrow (12?kg). The transport was also different: plough 0.50?m and disc harrow 0.11?m average distance.     

云冷杉林风倒区林隙和掘根微立地微气候变化

2013年7月,在小兴安岭凉水国家级自然保护区云冷杉林风倒区1.5 hm2的样地内,选取由掘根倒木形成且包含坑和丘微立地的大、中、小3个代表性林隙。在每个林隙中心安装HOBO自动气象站,测定了7—9月林隙中心以及林隙内丘顶和坑底的总辐射、光合有效辐射(PAR)、空气温度和相对湿度,并在郁闭林分和空旷地设置对照。分析了不同大小林隙之间以及林隙内丘顶和坑底之间小气候在生长季的动态变化及其差异。结果表明:林隙总辐射、PAR以及空气温度依照大林隙、中林隙和小林隙的次序依次降低;同一林隙内,丘顶的总辐射、PAR和空气温度大于坑底,丘顶空气相对湿度小于坑底;月均气温和月均PAR均为7月>8月>9月,绝大多数按照空旷地、大林隙、中林隙、小林隙和郁闭林分的次序递减,仅9月份小林隙的气温大于中林隙。同一林隙的平均气温日较差均为7月>9月>8月,相同微立地(林隙中心、丘顶、坑底)气温日较差均为大林隙>中林隙>小林隙。相同月份丘顶的气温日较差均大于坑底。各林隙空气相对湿度均为8月>9月>7月,并按照空旷地、大林隙、中林隙、小林隙和郁闭林分的次序依次递增。7月份大林隙的总辐射、PAR与8、9月份相比均差异显著。9月不同大小林隙之间的总辐射、PAR差异均不显著。7—9月,大林隙和小林隙中心的空气湿度均差异显著。同一林隙相同月份丘顶和坑底的PAR、空气相对湿度差异均显著,空气温度差异不显著;无论是在林隙内还是林隙内的丘顶和坑底,同一林隙不同月份的温度差异均显著。     

Tillage effect on C stocks of a clayey Oxisol under a soybean-based crop rotation in the Brazilian Cerrado region

A large area (180 Mha) of central Brazil is occupied by a savanna biome known as the Cerrado. Annual rainfall in this region varies from 1200 to 2000 mm, although there is a long (5 month) dry season with almost no rain. This region is regarded by Brazilians as their agricultural frontier and there is a steady growth in the area dedicated to permanent cropping in the region, which today is estimated to occupy 14 Mha. Owing to the dearth of long-term experiments, the impact of continuous cropping on soil carbon stocks remains unclear. The objective of this study was to evaluate the effects of different tillage systems (zero till (ZT) and conventional tillage (CT)) on the change in soil carbon stocks over a 20-year period of the same crop sequence compared to that under a neighbouring area of native vegetation (NV). Only approximately 10 Mg ha⁻¹ of soil carbon in the 0–100 cm depth interval was lost under continuous ZT. However, under CT systems losses were greater (up to 30 Mg C ha⁻¹) when the mouldboard plough was used and/or tillage was performed twice a year. We did not have access to instrumentation to accurately assess soil charcoal but the C/N data and peroxide and dichromate oxidative techniques suggested that 40% of soil C was in this form. The ¹³C natural abundance of soil profiles indicated that residues of crops (maize) and the spontaneous annual fallow of Brachiaria spp. resulted in integration of significant C₄ residues to a depth of at least 40 cm. It would appear that zero tillage, which is already widely adopted in the Cerrado region of Brazil, will have only a small negative long-term impact on soil C stocks, but ploughing, especially more than once a year, will lead to considerably larger soil C losses.     

变截面钢箱梁曲线形底板单元制造工艺

崇启大桥主桥钢箱粱为二次抛物线变截面高度钢筋梁，其底板单元纵向为曲线形。文章介绍了该曲线形底板单元制作过程中的线形控制技术，经实践证明该方法可靠实用，可为同类型桥梁制造提供参考。     

关于底部大空间结构中墙梁的计算方法初探

作者根据设计经验详细论述了底部大空间结构中的墙梁的具体计算方法和设计原则。对从事该专业的技术人员具有一定的参考价值。     

甘蔗间作花生对不同耕层土壤微生态的影响

甘蔗间作花生是我国华南地区特有的高效种植模式。本文研究了甘蔗/花生间作不同耕层土壤养分、酶、微生物的变化特征及其相关性。结果表明,相比单作而言,0～20 cm间作花生土壤有效氮、有机质、微生物量氮含量、真菌、放线菌数量、蛋白酶活性及间作甘蔗土壤细菌、放线菌、总微生物数量、微生物量氮含量及蛋白酶活性均显著增加;20～40 cm间作甘蔗土壤全磷、全钾、蛋白酶活性及间作花生土壤放线菌、蛋白酶活性显著增加;40~ 60 cm间作花生土壤真菌、蔗糖酶、微生物量碳含量显著增加;相反,间作甘蔗土壤蔗糖酶活性均显著低于单作甘蔗处理;间作土壤有效氮磷钾、有机质含量、脲酶、酸性磷酸酶活性、微生物数量均随着土壤深度的增加而表现出降低的趋势;间作土壤有效养分与脲酶、酸性磷酸酶、微生物量氮及微生物数量呈显著或极显著正相关。表明甘蔗花生间作条件下土壤养分、酶、微生物相互作用,共同维持良好的土壤微生态环境。