紫色土坡地旋耕机耕作侵蚀特征

耕作侵蚀的过程机制和防治技术研究是我国现阶段水土保持科学与技术的重点研究领域,关于小型旋耕机耕作的土壤再分布过程和影响因素研究较少.应用磁性示踪法研究旋耕机等高耕作、向下耕作和向上耕作的土壤再分布模式和强度,查明耕作速度对旋耕机耕作侵蚀的影响.结果表明:不同耕作方向下旋耕机单次耕作过程中均引起土壤同时发生向上坡和向下坡移动,且均导致土壤发生向下坡净位移;不同耕作速度时等高耕作和向上耕作土壤净位移与坡度均呈显著正相关(P＜0.01),而向下耕作二者无显著相关性(P＞0.05);土壤净位移量表现为快挡等高耕作(11.53 kg/m)＞快挡向下耕作(11.40kg/m)＞快挡向上耕作(7.59kg/m)＞慢挡向下耕作(7.33 kg/m)＞慢挡等高耕作(6.87 kg/m)＞慢挡向上耕作(6.29 kg/m);快挡时上下坡交替耕作的耕作侵蚀速率小于等高耕作,但慢挡时二者相当.旋耕机耕作相比传统耕作机具的耕作侵蚀明显下降,其推广应用对于防治紫色土坡地耕作侵蚀和土壤退化有重要作用.     

等高犁耕朝向对紫色土坡面土壤再分布的影响

选择一块坡长15m、坡度14.16%的坡地,采用磁性示踪法分析等高向下犁耕(向下坡方向翻垈)和等高向上犁耕(向上坡方向翻垈)的土壤再分布特征,利用模拟耕作(15次)检验两种等高犁耕的长期作用下对土壤剖面和微地貌演化的影响。结果表明:等高向下犁耕导致土壤发生向下坡移动,土壤位移量为15.62~28.70kg/m,坡度对其影响不显著(p=0.93);等高向上犁耕导致土壤同时发生向下坡和向上坡移动,土壤净位移量为-10.91~8.23kg/m,坡度对其有显著影响(p0.001),土壤净位移方向随着坡度的增大由向上坡转为向下坡,本研究条件下临界坡度为14%;等高向下犁耕15次后坡顶侵蚀深度是原土层深度的132%,耕作后土层深度与耕作深度相当,表明等高向下犁耕加速土壤侵蚀和促进母岩成土的双重作用共同维持着坡顶土层深度的稳定;等高向上犁耕15次后坡顶土层深度增加了12.7%,表明等高向上犁耕具有保护坡顶土层深度的作用。等高向上犁耕是一种防治类似紫色土的薄层土壤耕作侵蚀和土壤退化的有效措施。     

黄土高原丘陵沟壑区坡地耕作方式对土壤侵蚀的影响研究

为研究耕作方式对坡耕地土壤侵蚀的影响,在黄土高原丘陵沟壑区选取典型坡耕地,采用示踪块法,对畜力横向犁耕、人力顺向掏挖、人力逆向锄耕和机械横向犁耕4种主要耕作方式在5°,10°,15°3种坡度条件下进行耕作侵蚀试验。结果表明:不同坡度条件下,耕作方式对土壤颗粒位移的影响较为显著,畜力横向犁耕、人力顺向掏挖和机械横向犁耕随坡度增大,示踪块位移增大;而人力逆向锄耕中,耕作使土块向上坡方向移动,但受重力影响,坡度越大,移动距离越小。同一坡度条件下,耕作模式所产生的水平位移由大到小依次是机械横向犁耕畜力横向犁耕人力顺向掏挖人力逆向锄耕。4种耕作方式中,机械横向犁耕造成土壤颗粒位移和耕作侵蚀量最大,人力逆向锄耕影响最小。为减少耕作侵蚀,针对坡耕地尽可能采用少耕或免耕方式,以减少耕作侵蚀,在不增加劳动强度的情况下,10°以上坡耕地可采用人力逆向锄耕模式耕作。     

锥盘式颗粒肥撒施机构抛撒性能分析与试验

为了提高颗粒肥撒施的均匀性和一致性,该文设计了一种锥盘式撒肥机构,通过对锥盘式撒肥机构工作性能的分析,建立了肥料颗粒的受力方程。通过撒肥试验,研究喂入区大小、甩盘转速、甩肥高度对撒肥区域内肥料分布规律的影响。试验结果表明：喂入区大小对肥料颗粒的横向幅宽分布影响较大,对纵向分布影响较小,施肥作业中合理的喂入角为75°;随着甩盘转速的增加,有效施肥区域的横向幅宽和纵向距离均逐渐增大,而且施肥的均匀性和一致性也不断提高,合理转速为600 r/min;施肥高度对施肥幅宽分布和一致性没有显著影响。研究结果可为颗粒肥撒施机的设计提供参考。     

不同通风方式下猪舍病毒颗粒分布的数值研究

为了研究不同通风方式对猪舍内病毒颗粒分布的影响,本文利用离散轨道模型模拟病毒颗粒的轨迹,并与模拟气流运动的标准k-ε湍流模型相耦合的方法,对猪舍的横向、纵向2种通风方式的气流运动以及病毒颗质量粒浓度分布与排除进行数值研究。结果表明,在相同的送风量、压力条件和颗粒特性下,横向通风案例方案对比纵向通风有更好的控制病毒颗粒扩散的能力,然而纵向通风方式有更好的排污效率,能够使更多的颗粒逃逸、颗粒悬浮更少,但有更多颗粒沉积,会引起二次污染。2种方式在不同的角度有各自的优点,从防止病毒扩散,控制病毒的交叉感染角度来讲,横向通风方式能够对病毒颗粒有很好的控制作用,形成更均匀的气流,而纵向通风方式会使病毒颗粒在舍内进行大范围的扩散,容易产生交叉感染,因此横向通风方式更有优越性。     

黄土高原藓结皮覆盖土壤的穿透阻力特征及其影响因素

生物结皮的发育显著地影响并改变了表层土壤的理化性状,从而影响土壤穿透阻力。为探明生物结皮层对土壤穿透阻力的影响,针对黄土高原风沙土和黄绵土两种典型土壤,利用高精度土壤贯入仪测定并比较了不同含水量下藓结皮土壤和无结皮土壤的穿透阻力差异,定量分析了藓结皮层对土壤穿透阻力的影响及其与土壤性质(含水量、容重和有机质含量以及颗粒组成)的关系。结果表明:风沙土和黄绵土藓结皮层最大穿透阻力的变化范围为0.38~3.74 MPa和0.43~8.01 MPa,分别为同等深度下无结皮土壤的2.14~9.45倍(P=0.001)和1.38~6.27倍(P=0.051)。藓结皮对风沙土穿透阻力的影响深度为表层2~12 mm(P=0.028),而对黄绵土的影响深度为3~24 mm(随含水量变异较大)。同时,与无结皮土壤的穿透阻力随深度增加而线性增加的趋势不同,藓结皮土壤的穿透阻力随深度增加在结皮层呈先增后减的趋势,在结皮下层呈线性增加的趋势。此外,藓结皮土壤的横向穿透阻力和纵向穿透阻力差异显著(P≤0.03),但在无结皮土壤上差异不显著(P≥0.052)。藓结皮土壤的穿透阻力与含水量呈显著的幂函数关系(P<0.001),与容重、有机质含量以及砂粒含量呈线性关系,这些因素均为藓结皮改变表层土壤穿透阻力的重要途径。     

冻土冲击贯入力学特性分析

利用自动式冲击贯入仪在实验室和野外对冻土进行了一系列的冲击贯入试验,进而分析了冲击贯入冻土过程机理。应用动态球腔扩张理论,建立了冲击贯入方程、冲击次数表达式和贯入阻力与贯入深度的关系。     

高密实度模拟月壤力学特性试验研究

为保证月面采样任务顺利实施,该文以钻取采样的JLU5系列模拟月壤(JLU5-1、JLU5-2和JLU5-3,探月工程内场试验采用)为对象,利用振实装置进行高密实度模拟月壤整备,开展不同密实度条件下(相对密度为0.85、0.9、0.95和0.99)模拟月壤剪切和贯入特性力学试验,分析了相对密度对剪切强度、内聚力、内摩擦角、圆锥指数和圆锥指数梯度的影响规律。试验结果表明,剪切强度和内聚力随相对密度增加总体呈现增加规律,平均变化率分别为11.1%和35.8%;3种模拟月壤内摩擦角随相对密度增加无明显变化趋势,范围为53.3o～67.7o;圆锥指数和圆锥指数梯度随相对密度增加而增加,且圆锥指数和圆锥指数梯度平均变化率较剪切强度和内聚力的大;相同试验条件下,颗粒较细的JLU5-3型模拟月壤较JLU5-1和JLU5-2具有更大的剪切强度、内聚力和圆锥指数,JLU5-2内摩擦角总体上较JLU5-1和JLU5-3的小。利用EDEM软件建立贯入特性试验数值模型,仿真结果表明:不同模拟月壤圆锥指数仿真值总体小于实际试验值,且随相对密度变化规律一致,建立了仿真与试验值线性关系。研究结果可为采样任务顺利实施、钻取机构优化设计、采样触月部件与月壤相互作用力学模型建立提供参考。     

颗粒尺寸对螺旋加料机定量加料性能的影响

为提高螺旋加料机定量加料性能,开展颗粒尺寸对加料量稳定性和准确性的影响研究。以粒径3~5 mm的球形谷物颗粒单圈加料约40 g螺旋加料机为研究对象,基于软球模型,通过对螺旋加料过程颗粒物料力链及颗粒群运动分析,建立具有分料装置的螺旋加料机离散元仿真模型;应用PFC3D(particle flow code in 3dimensions)软件对粒径3、4及5 mm颗粒物料进行螺旋加料过程仿真分析,并以粒径3、4及5mm的球形散珠为试验对象,进行颗粒运动和定量加料试验。综合分析得到:随着球形颗粒粒径的逐步减小,最大接触力逐渐减小,力链分布愈均匀浓密,颗粒间运动的一致性得到提高,物料混合运动趋势逐步减弱,定量加料的稳定性和准确性逐步提高。粒径3 mm球形散珠螺旋加料转动60°,平均加料量为6.477 g,加料量标准差为0.537,加料量最大相对误差为±0.153%。     

基于工控机的汽车主锥预紧力测量机控制系统设计

该文分析了汽车主锥中圆锥滚子轴承的预紧力与轴向位移、压紧轴承的锁紧螺母拧紧力矩之间的关系,以及轴向位移量与启动摩擦力矩之间的内在联系,并研制出具有锁紧螺母预紧力矩和轴承启动摩擦力矩自动测量功能的主锥自动装配设备的控制系统。该系统以工控机为控制核心,以Visual C++作为软件开发工具,使系统既具有较高的稳定性及灵活性,又有直观、友好用户界面。控制系统对锁紧螺母拧紧力矩和轴承摩擦力矩采用闭环控制的实时测量,可精确控制轴承的预紧力,提高主锥总成的装配质量和生产效率。     

Changes in penetration resistance of Ultisols from southern China as affected by shearing

Shear stresses and soil properties modified due to stress play an important role during formation of seals in a series of rainfall events and during tillage. The objectives of the study were to evaluate the effects of the penetrometer geometry on the penetration resistance as affected by shearing under different initial soil conditions and to use the information on soil strength to elucidate shearing process. Nine homogenous air-dried soils (<2 mm) were sprayed and stored so as to obtain equilibrium soil water contents. The moist soils were sheared by horizontal displacement of layers of soil particles/aggregates in between hands in one direction. The soil cores were prepared with comparable bulk density before the measurement of maximum penetration resistance (P_max) with a small flat tip and a cone tip penetrometers. At a wide range from 0.05 to 6.2 MPa, P_max was linearly correlated between the small flat tip and the cone tip penetrometers. The conversion ratio was higher under the saturation condition irrespective of the shearing effect. The penetrometer with the small flat tip was more sensitive for the weak soils. Shearing generally increased P_max in most cases, but it decreased P_max for some sandy soils under both saturated and unsaturated conditions and for a clayey soil under the saturated condition. The soil consisting of swelling clay exerted a decrease in P_max. Rearrangement and/or sliding of particles/aggregates and increase in soil suction during shearing were attributed to the increase in P_max. Increase in porosity due to the aggregation during shearing was ascribed to the decrease in P_max. In addition, it was shown that agricultural cultivation resulted in a reduction in soil strength.     

锥-板环形水槽的研制及其在颗粒起动试验中的应用

在颗粒起动观测试验中,传统长直型水槽及环形水槽试验无法观测流体长期作用下的颗粒运动,依据锥-板转子流变仪原理,设计了一种锥-板环形水槽装置;采用无量纲拖曳力作为起动时的流体力学指标,结合CCD(电荷耦合组件,charge coupled device)成像技术及PIV(粒子图像测速,particle image velocimetry)技术,运用该装置对层流时无黏性均匀颗粒在流体长期作用下的运动形态及起动规律进行了观测,观测发现流体长期作用下颗粒的起动为连续的起动过程,存在2个不同的临界状态,分别为初始临界状态和饱和临界状态,初始临界状态下的起动拖曳力和经典Shields曲线的取值基本一致,饱和临界状态下的起动拖曳力明显高于Shields曲线的取值,表明锥-板环形水槽是一种合理有效的颗粒起动观测装置,特别适用于流体长期作用下的颗粒起动规律研究。     

涌泉根灌湿润体特征值变化规律研究

在米脂山地微灌枣树示范基地进行原状土涌泉根灌人渗试验,研究了不同流量、不同灌水历时条件下涌泉根灌湿润体特征值的变化规律.结果表明:湿润体的水平扩散半径、向上人渗距离、向下人渗深度随流量的增大而增大,且均与入渗时间有显著的幂函数关系;在相同流量情况下,向上人渗最快.水平扩散次之,向下人渗最慢;湿润体体积受灌水量和流量的影响;在不同流量条件下,湿润体体积与灌水量间,湿润体水平扩散半径、垂直扩散距离与灌水量间均存在极显著的幂函数关系;针对五年生枣树根系分布特征,确定了枣树适宜灌水时间和灌水量.     

Pipeline right‐of‐way construction activities impact on deep soil compaction

A 762‐mm‐diameter pipe 1,886 km long was installed to transfer crude oil in the USA from North Dakota to Illinois. To investigate the impact of construction and restoration practices on long‐term soil productivity and crop yield, vertical soil stresses induced by a Caterpillar (CAT) pipe liner PL 87 (475 kN vehicle load) and semi‐trailer truck (8.9 kN axle load) were studied in a farm field. Soil properties (bulk density and cone penetration resistance) were measured on field zones within the right‐of‐way (ROW) classified according to construction machine trafficking and subsoil tillage (300‐mm‐depth tillage and 450‐mm‐depth tillage in two repeated passes) treatments. At 200 mm depth from the subsoiled surface, the magnitude of peak vertical soil stress from trafficking by the semi‐truck trailer and CAT pipe liner PL 87 was 133 kPa. The peak vertical soil stress at 400 mm soil depth appeared to be influenced by vehicle weight, where the Caterpillar pipe liner PL 87 created soil compaction a magnitude of 1.5 greater than from the semi‐trailer truck. Results from the soil bulk density and soil cone penetration resistance measurements also showed the ROW zones had significantly higher soil compaction than adjacent unaffected corn planted fields. Tillage to 450 mm depth alleviated the deep soil compaction better than the 300‐mm‐depth tillage as measured by soil cone penetration resistance within the ROW zones and the unaffected zone. These results could be incorporated into agricultural mitigation plans in ROW construction utilities to minimize soil and crop damage.     

壤中滴灌条件下植被混凝土水分运移规律

以复合人造土壤为研究对象,研究滴头流量、坡度因子对植被混凝土水分运移过程的影响效应,揭示壤中滴灌条件下植被混凝土湿润锋运移动态变化及含水率时空分布特征,探讨植被混凝土与天然土壤在水分运移方面的异同,为高陡边坡生态恢复下壤中滴灌系统的灌溉布局与灌溉制度提供理论参考。结果表明:滴头流量、坡度对垂直向上方向的水分运移影响最大,对水平方向的影响较小。灌水前期,土壤基质吸力的影响远大于重力,水分在垂直方向上的运移距离与水平方向相近;灌水中期,垂直向上与水平方向的渗透速率随坡度增大而变缓;灌水后期,垂直向下的渗透速率逐渐趋于由重力为主要诱使因素的稳定速率;相同灌水量下,流量越小,湿润锋运移距离越远;水分再分布时段,受重力梯度和基质势的综合影响,垂直向下的运移距离最远,水平方向次之,垂直向上最近;含水率等值线呈椭圆形分布,且垂直向下的含水率均大于垂直向上和水平方向的含水率。采用幂函数与二次函数均可拟合植被混凝土湿润锋运移距离与入渗时间的关系,其中幂函数拟合程度更佳(R²>0.95),但R²略小于一般天然土壤,拟合结果扩大了土壤水动力学理论在复合土壤的适用范围。     

Anisotropy of penetration resistance in four soil profiles in Chile

Penetrometer resistance was measured horizontally and vertically down to a depth of 150 cm with individual penetrations of no more than 12 cm in four soils in pastures and arable land near Valdivia, Chile, cleared from natural forest approximately 40 years ago. Maximum vertical resistance was found near the soil surface and attributed to recent soil development. Downward the values decreased sharply at first and then became constant or increased slightly. Relations of horizontal to vertical resistance increased generally downward in the profiles and was greatest in the plough-sole area of the profile in arable land.     

TECHNIQUES FOR MEASURING CHANGES IN THE PACKING STATE AND CONE RESISTANCE OF SOIL AFTER THE PASSAGE OF WHEELS AND TRACKS

Methods are described for measuring the changes in the horizontal and vertical distribution of packing state and cone resistance following the passage of wheels and tracks over prepared beds of soil. A gamma-ray transmission system was employed with automatically controlled scanning in a 2 × 2 cm grid in soil sections of 1.08 m length by 0.3 m depth, using a scintillator/photomultiplier detector assembly with stabilized pulse-height analysis and magnetic tape recording. Changes in cone resistance were measured in a 2 cm (vertical) by JO cm (horizontal) grid in a section 1.4 m length by 0.5 m depth using an electrically driven penetrometer with load and displacement simultaneously recorded on an XY plotter and magnetic tape. Results were analysed and displayed graphically by computer with packing state expressed by a number of optional properties (dry bulk density, total porosity, air-filled porosity, void ratio, or specific volume). Pronounced differences in packing state and soil strength were observed as a result of the passage of a two-wheel-drive tractor, with and without cage wheels, and a crawler tractor. Adding a cage wheel decreased slightly the compaction below the rubber tyre, but formed a partially compacted zone below the cage wheel. Increases of dry bulk density and soil strength were recorded below the crawler track but the values for these properties did not reach the maximum values found below the rubber tyre.     

沙地刚性轮构型仿生设计及牵引性能数值分析

为了提高车轮牵引性能,改善车辆在松散沙土介质环境的通过能力,该文以善于沙地奔跑的鸵鸟足部关键部位—足趾甲为仿生原型,通过仿生优化轮刺结构,设计出具有高牵引性能的仿生轮刺式沙地刚性轮,并以一种模拟月壤作为试验松散沙土介质材料,采用离散元软件PFC2D?的内置语言FISH和相关命令,建立了适用于非规则结构刚性轮的轮壤相互作用动态模拟系统,并获得试验验证。通过仿生轮刺式刚性轮与模拟月壤相互作用离散元模拟,并与矩形轮刺式刚性轮模拟结果对照,从轮下模拟月壤颗粒细观运动、接触力场、速度场以及车轮挂钩牵引力角度,验证了仿生轮刺式刚性轮具有优越的牵引性能,在车轮滑转率50%的稳定运行状态下,仿生轮刺式刚性轮的牵引性能可提高5.2%左右。该研究为提高刚性轮在松散沙土介质环境中的牵引性能提供了全新设计和研究手段。     

竖管地表滴灌下风沙土稳定入渗率与湿润体估算模型

为了量化解决竖管地表滴灌过程中滴头流量与竖管结构参数(竖管直径和竖管埋深)、土壤湿润体与植物根系的匹配问题,该研究通过12组竖管内积水(2 cm水头)入渗试验(9组率定,3组验证),测定不同竖管直径(8.8、10.6、12.6、14.2 cm)和竖管埋深(15、20、25 cm)条件下风沙土累积入渗量变化过程,并采用Philip入渗模型拟合。结果表明:竖管直径一定时,稳渗率随埋深的增大而减小,竖管埋深一定时,稳渗率随管径的增大而增大,稳渗率与竖管直径和竖管埋深之间符合幂函数关系(决定系数R20.99),幂函数指数分别为2.01和-0.64。利用所建稳定入渗率估算式确定与竖管结构参数相匹配的滴头流量(保证竖管内无积水),设计9组竖管地表滴灌室内试验(7组率定,2组验证),观测不同滴头流量(0.9、1.2、1.5 L/h)、竖管直径(10.6、12.6、14.2 cm)和竖管埋深(15、20、25 cm)条件下风沙土湿润锋运移过程,并进行幂函数拟合,发现滴头流量对垂直向下湿润锋运移距离显著,滴头流量越大,垂直向下湿润锋运移距离越大,而水平方向和垂直向上湿润锋运移距离差异较小;在3个方向上湿润锋运移距离均随竖管直径的增大而减少;随竖管埋深增加,垂直向上和垂直向下湿润锋运移距离均有所减小,但水平方向湿润锋运移距离变化很小。确定了灌溉水到达竖管底孔所需时间计算式,在此基础上,构建了包括滴头流量、竖管直径、竖管埋深和灌水时间在内的竖管地表滴灌湿润体预测模型,验证所建模型的可靠性,平均绝对误差和均方根误差平均值分别为0.74和0.92 cm,纳什效率系数均大于0.91,说明预测效果良好。该研究所建稳定入渗率和湿润体预测模型对于竖管地表滴灌优化设计具有重要意义。     

Effects of freeze–thaw cycles and the soil water content on carbon and nitrogen changes in different soil types of Heilongjiang Province,China

To reveal the influence of freeze–thaw cycles (FTCs) on soil carbon and nitrogen changes, six typical soils in Northeast China were selected as the research objects to conduct a FTC simulation test in an artificial climate chamber. Three soil volumetric water contents (10%, 20%, 30%) and eight FTCs (0, 2, 4, 6, 8, 10, 15, 20) were set. The results showed that the soil organic carbon (SOC) and microbial biomass carbon (MBC) contents of different soil types under the FTCs initially exhibited a downward and then an upward trend, while the dissolved organic carbon (DOC) content exhibited an upward and then a downward trend. Otherwise, the fourth and sixth FTCs were the key points of change. The SOC, MBC and DOC contents in paddy fields were higher than those in dry fields, showing upward and then downward trends spatially from northeast to southwest. The SOC and MBC contents in each soil type were the highest at the 20% water content, and the DOC content gradually increased with increasing water content. The ammonium nitrogen (NH₄⁺-N) content in different soil types at different water contents under the FTCs showed an upward trend first, then a downward trend and finally an upward trend. The NH₄⁺-N content in paddy fields was higher than that in dry fields. The nitrate nitrogen (NO₃^‒-N) content showed a downward trend first, then an upward trend and finally a downward trend. The NO₃^‒-N content in dry fields was higher than that in paddy fields. The NH₄⁺-N contents in the three soil types on the Sanjiang Plain were significantly higher than those on the Songnen Plain. The NH₄⁺-N and NO₃^‒-N contents showed upward trends with increasing water content, but the differences were not significant. The results have implications for the study of different types of soils and provide references for research on the mechanism of soil carbon and nitrogen transformation in typical farming areas in Northeast China.