倾斜地表下隧道开挖引起的三维地表沉降计算

为研究倾斜地表下隧道开挖引起的地表沉降计算方法,考虑倾斜地表对隧道埋深的影响,建立了倾斜地表下隧道开挖模型和三维情况下单元体开挖计算模型.采用随机介质理论,推导出三维倾斜地表下隧道开挖引起的地表沉降计算公式,并结合工程实例选取监测数据和计算数据对比验证,证明了计算方法的准确性.最后针对地表倾斜角度进行对比分析,表明地表斜面倾角越大,地表不均匀沉降越明显.该倾斜地表沉降计算方法对隧道开挖地表沉降预测有一定的工程价值和指导意义.     

Effect of flexible and rigid roughness elements on aeolian sand transport

In developing countermeasures to reduce the negative effects of strong dust events, the fundamental relationship between surface conditions and sand transport remains problematic. We conducted field observations and wind tunnel experiments to examine the effect on sand transport efficiency of actual frontal area when using flexible roughness elements (artificial grass) and rigid roughness elements (tufts of stiff wire). In the field observations, the sand trap ratio approached a limit as the frontal area of artificial grass, measured as the Actual Frontal Area Index (AFAI), approached 25%, equivalent to a vegetation cover of 20%. The wind tunnel experiments showed that the height of deposited sediment decreased downwind with both roughness elements, due to their reduction of both shear velocity and sand transport rates. The sediment flux decreased as the AFAI increased, and the rigid roughness element trapped more sand particles than the flexible one except at higher wind speeds and lower AFAI values. The sand trapping efficiency was greater for rigid roughness elements than for flexible ones, probably due to their high aerodynamic resistance, and thus wire tufts were more effective for trapping sand than artificial grass at higher AFAI values.     

临策铁路防沙明洞对新月形沙丘沙物质粒度特征的影响分异

本文通过临策铁路防沙明洞影响区内外新月形沙丘各部位粒度特征参数的对比研究,探明了防沙明洞对新月形沙丘粒度特征的影响分异规律。研究表明:(1)防沙明洞改变了影响区内新月形沙丘的自然风场结构,地表沙物质呈现粗粒化、粒径均匀程度提高、粒径分布集中的特点。(2)防沙明洞上风向沙丘各个部位沙物质粗粒化程度均高于下风向沙丘,上风向沙丘迎风坡、下风向沙丘背风坡粒度变化最显著。(3)防沙明洞上风向沙丘运动状态受冬季风控制,风蚀作用强于堆积作用,而下风向沙丘运动状态受夏季风控制,堆积作用强于风蚀作用。     

Influence on new tunnel mechanics behaviorinduced by construction about adjacent spacing

This paper takes Chongqing Two-River Tunnel as the research background, based on the system for structure and surrounding rockmass of the highway tunnel, conducts a three-dimension model test about forked tunnel with different altitude to study new tunnel’s mechanics behavior induced by construction, and uses numerical simulation to analyze model domain. The results show that the displacement on new tunnel’s left hance is larger than the displacement on its right hance. Left hance displacement is larger than hance displacement of the single tunnel, and the right hance displacement is less than hance displacement of the single tunnel. The trend of hance displacement and crown settlement with different adjacent spacing is got. Normalizing hance displacement and crown settlement of model test, the relation between displacement and adjacent spacing is disclosed. The hance displacement and crown settlement gained by numerical simulation is close to the converted result of model test, which indicates that the model test data is consistent with the result of numerical simulation.     

高速气流条件下标准扇形喷头和空气诱导喷头雾化特性

标准扇形喷头与空气诱导喷头均为地面喷雾常用喷头,其在低速条件下的雾化特性已有较多研究,而在高速气流下的雾化特性尚不清楚。为了探究对比2种喷头在高速气流条件下的雾化特性,以及其用作航空喷头的可能性,基于北京农业智能装备技术研究中心自行设计制造的IEA-I型高速风洞,采用马尔文Spraytec喷雾粒度仪对德国Lechler公司生产的LU-120-03标准扇形压力喷头和IDK-120-03空气诱导喷头进行了测试。试验结果表明,两种类型喷头在距离出口0.15 m时,雾滴并未完全雾化。而在距离出口0.35 m时雾滴均已充分雾化。其中LU-120-03扇形压力喷头雾滴体积中径随风速增大从210μm逐渐减小至130μm,在管道压力达0.4 MPa以上时,其雾滴粒径分布跨度随风速增大逐渐从1.3增至1.5。而IDK-120-03空气诱导喷头产生的雾滴粒径相对较大,在风速为120 km/h时,达420~450μm,但其随着风速进一步增加快速减小,在风速达305 km/h时,其产生的雾滴体积中径降低到150μm。试验还发现管道压力变化对LU-120-03扇形压力喷头产生雾滴体积中径影响较大,而对IDK-120-03空气诱导喷头产生的雾滴体积中径影响较小。该研究可为固定翼有人机航空施药方案,如喷头选型、压力选择、作业速度选择等提供试验数据指导。     

航空植保作业用喷头在风洞和飞行条件下的雾滴粒径分布

为了获得GP-81A系列航空喷头的雾滴粒径分布情况,该文针对GP-81A系列航空喷头进行了风洞条件和飞行条件下的雾滴粒径及分布测试,通过高速风洞测试系统模拟飞行时产生的高速气流开展了气流大小对雾滴粒径及分布的影响研究;基于农用航空常用的Y5B飞机开展了不同型号喷嘴航空喷雾时的雾滴粒径及分布研究;同时,比较了相近喷雾压力条件下,相同喷嘴在风洞条件和飞行条件下的雾滴粒径及分布差距。试验结果表明,风洞条件测试时,当风速小于33.8 m/s时,雾滴粒径随气流的增加而增大;而当风速大于33.8 m/s时,雾滴粒径随气流的增加而减小,足够大的气流可以使雾滴进一步雾化。当气流在33.8 m/s时,7#喷嘴雾滴粒径最大,为491.1μm;当气流在84.87 m/s时,2#喷嘴雾滴粒径最小,为202.1μm。该系列喷头的6种不同喷孔的喷头的雾滴粒径均大于150μm,说明该喷头航空喷雾时的飘移损失较小。在喷雾压力基本相同的条件下,风洞条件下的雾滴粒径测试结果略高于飞行试验结果,主要原因是距离喷头出口的测试位置不同。风洞条件和飞行条件下的雾滴谱相对宽度S值均较小,表明雾滴分布较均匀,而飞行条件下的雾滴分布更均匀些。该研究为进一步优化航空喷头的作业参数,开展减少雾滴飘移研究提供参考。     

番茄品种春季大棚栽培评价

针对当地大棚番茄主栽品种单一而生产和消费多元化需求的问题,从国内外引进百利、格雷、雪莉、曼西娜、美杰罗2号、抗线晶美、东粉3号、粉宝等番茄新品种,以强选4号为对照,在杨凌示范区种植,从农艺性状和经济性状方面综合评价,筛选适宜春季塑料大棚栽培品种。结果表明,与对照品种相比,供试品种均植株高大;晚疫病发病较普遍,灰霉病以抗线晶美、曼西娜和格雷较普遍或严重;美杰罗2号、东粉3号、抗线晶美和雪莉的早期产量与对照无显著性差异,百利和东粉3号总产量较高,美杰罗2号、粉宝、格雷、雪莉和抗线晶美的总产量与对照无显著性差异。综合商品性和营养品质较好的品种有美杰罗2号、东粉3号、抗线晶美、粉宝、百利、曼西娜和雪莉。试验认为,美杰罗2号、东粉3号、粉宝和抗线晶美可作为粉红果品种在杨凌地区大棚栽培中示范,并优先选用美杰罗2号和东粉3号;百利作为中型红果品种可以示范种植;曼西娜作为小型红果串收番茄可以示范种植。     

作物残茬覆盖农田地表风沙流分布规律

利用移动式风蚀风洞对秋翻地和作物残茬覆盖农田进行原位测试,探讨作物残茬覆盖农田地表风沙流的分布规律.结果表明:作物残茬覆盖农田地表的单位面积输沙量随风速与距地表高度的增加而明显增大,残茬盖度越大,输沙量越小;风沙流的活动主要集中在直立残茬高度范围内,在距地表300mm高度内的输沙量占输沙总量的86％以上;在高风速下65％以上盖度的残茬覆盖农田,具有更佳的风沙流截留效果.     

Effects of Runner Tip Size and Plugging Date on Fall Flowering in Short-Day Strawberry (Fragaria × ananassa Duch.) Cultivars

Abstract

Producing strawberry transplants from runner tips that were plugged ～1 month earlier (early July) than the standard time (early August) promoted fall flowering in some short-day strawberry cultivars. In 2002,100% of ‘Chandler’ transplants produced in early July flowered in the fall, but none of the August-plugged ‘Chandler’ transplants flowered in the fall. In 2003, 73% of ‘Chandler’ transplants produced in mid-July from average-size runner tips and less than half of transplants from small-size runner tips flowered in the fall. Again, August-plugged plants did not flower in the fall. Flowering was absent in ‘Northeaster’ plants. Under protected cultivation, July-plugged ‘Sweet Charlie’ plants bloomed earlier and produced more fruit in November and December than those plugged in August. This study showed that fall flowering in ‘Chandler’ and ‘Sweet Charlie’ strawberry is possible if the transplants are prepared by plugging runner tips in early July. This novel technique for propagating strawberry transplants for annual plasticulture combined with production under high tunnels creates an opportunity for strawberry production in early winter and again in the spring (double cropping) in the mid-Atlantic coast region.