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1.
轮式和履带式车辆行走对农田土壤的压实作用分析 总被引：3，自引：3，他引：0
由履带式行走机构代替轮胎被认为是减缓大型农业车辆对土壤压实的有效手段之一。与轮胎相比,履带具有更大的接地面积,能够有效减小车辆对土壤的平均压力。然而履带与土壤接触面间的应力分布极不均匀,应力主要集中在各承重轮下方,履带减缓土壤压实的能力是目前有待研究的问题。该研究通过在土壤内埋设压力传感器,测试比较了相近载质量的轮胎和履带式车辆作用下,0.15和0.35 m深度土壤内的最大垂直及水平应力,同时研究了车辆行驶速度对土壤内垂直及水平应力大小的影响。基于土壤压实分析模型计算了轮胎和履带压实的0.1~0.7m深度土壤内的最大垂直及水平应力分布。通过对0.15和0.35 m深度的土样进行室内测试,比较了轮胎和履带式车辆压实对土壤透气率、先期固结压力及干容重大小的影响。结果表明,履带相比较于轮胎,能够减小土壤内的垂直及水平应力,但垂直应力的减小量比水平应力大;轮胎对0.15和0.35m深度土壤作用的平均最大垂直应力分别约为履带的2.2及2.0倍,而平均最大水平应力仅分别约为履带的1.2及1.1倍。轮胎作用下的最大垂直及水平应力在表层土壤内明显大于履带,但两者的应力差值随着土壤深度的增加逐渐减小,分别在0.7和0.4 m深度时无明显差别。轮胎和履带压实作用下,0.15和0.35 m深度土壤内的垂直及水平应力均随车辆行驶速度的增加而减小,履带作用下的应力减小速度大于轮胎。履带作用下0.15和0.35 m深度内土壤的透气率均明显小于轮胎,但土壤的先期固结压力及干容重无显著区别。研究结果为可为农业车辆行走机构的选择及使用提供参考。 相似文献
2.
人字形花纹轮胎压实土壤垂直应力分布规律研究 总被引：1，自引：1，他引：0
为了完善人字形花纹轮胎在影响因素下压实土壤形成的垂直应力分布规律,并且明确这些因素对于垂直应力的影响,该文使用应力传感器在自主设计并搭建的单轮土槽试验台架上,进行人字形花纹轮胎压实土壤表层垂直应力分布规律的研究,并利用多元线性回归法建立垂直应力和影响因素之间的预测方程,主要结果:1)当胎压为69kPa时,土壤-轮胎表层垂直应力分布曲线相对平坦并且垂直应力峰值渐渐发生在距离轮胎边缘1/4处,而当胎压为138和207kPa时,垂直应力峰值发生在轮胎中心处;2)载荷对于垂直应力的影响最大,然后依次是胎压、行驶速度、纵向距离和横向距离;3)垂直应力与胎压和行驶速度成线性关系,与载荷、横向距离和纵向距离成抛物线关系;4)轮刺产生的垂直应力是胎面产生的垂直应力的1.2～2.3倍,而且越靠近轮胎宽度方向的边缘,轮刺的影响越大。研究结果能够对拖拉机的通过性分析提供有力的理论分析依据,基于建立的预测方程,在实际应用中通过改变这些影响因素值的大小,减小垂直应力,从而减小土壤压实。该研究可为拖拉机的通过性分析提供理论依据。 相似文献
3.
橡胶履带轮静态接地压力测试与建模 总被引：3，自引：2，他引：1
为快速有效预测橡胶履带轮接地压力,该文针对橡胶履带轮静态接地压力进行了试验研究和数学建模。首先对不同载荷下橡胶履带轮在坚实地面和松软地面的接地压力进行了测试。结果表明:在履带长度方向上,橡胶履带轮接地压力呈多峰值非均匀分布,同时其峰值呈钟罩型分布,且载荷越大,峰值分布越均匀。根据测试结果提出了一种橡胶履带轮静态接地压力分布数学模型,履带长度方向的接地压力采用二次余弦函数表示,履带宽度方向的接地压力采用线性函数表示。相较于其他模型,该模型采用地面硬度参数表征不同的地面条件,避免了进行土壤承压和剪切试验,提高了模型的实用性。最后,基于该模型对橡胶履带轮转向性能进行了仿真计算和试验验证。结果证明:仿真结果与试验数据最大误差约为4.71%,故该模型能够较好地适用于橡胶履带轮的转向性能分析。该文提出的模型可为橡胶履带轮的结构设计和其他性能研究提供参考。 相似文献
4.
不同施工机械对煤矿区复垦土壤颗粒组成的影响 总被引：3，自引：0，他引：3
以建筑垃圾、粉煤灰、煤矸石作为填充材料,研究自卸汽车和履带式推土机2种不同复垦机械在不同压实次数下,土壤颗粒组成的变化。结果表明:(1)复垦中通过1,3,5,7,9次机械碾压,土壤颗粒中砂粒含量减少,粉粒含量增多,在颗粒组成上有细化现象。(2)自卸汽车复垦,随着压实次数的增加,土壤颗粒均匀指数呈现"W"形变化;履带式推土机压实复垦下,土壤颗粒均匀指数呈现倒"V"形变化。(3)用粉砂质壤土作为覆土复垦时,自卸汽车碾压3次,履带式推土机碾压5次与自然耕地颗粒组成相似度最大,即自卸汽车碾压3次、履带式推土机碾压5次为土地复垦的临界碾压次数。(4)粒径5.86μm是土壤粒径中处于"物理性粘粒"部分含量的最高值。自卸汽车碾压对土壤"物理性粘粒"的影响主要集中在4.83~7.11μm范围内,履带式推土机碾压对土壤"物理性粘粒"的影响主要集中在3.98~8.64μm范围内。 相似文献
5.
机械压实对复垦土壤粒径分布多重分形特征的影响 总被引：6，自引：2，他引：4
在高潜水位矿区复垦施工现场,运用多重分形理论研究不同碾压次数下复垦土壤粒径分布特征,以阐明机械压实对复垦土壤粒径分布非均匀性和异质性的影响。结果表明:机械碾压在46.8%~99.9%程度上解释0~20和20~40 cm土层土壤粒径分布特征的变化,随着碾压次数增加,复垦土壤颗粒呈细粒化趋势,容量维D(0)随之减小,表征粒径分布范围减小;奇异谱对称性Δf随之增加,表征粒径分布不对称性增加;信息维D(1)、信息维/容量维D(1)/D(0)、关联维D(2)和奇异谱谱宽Δα随之波动变化,表征粒径分布集中程度、局部密集程度和均匀性波动变化。研究发现D(1)和D(1)/D(0),D(2)和Δα相关系数分别0.767(P0.01)和-0.488(P0.05),在表征复垦土壤粒径分布集中程度和均匀性上具有相似作用,多重分形参数可多角度描述机械碾压过程中土壤粒径分布的细微差别,其中D(0)、Δα和Δf能够灵敏反映复垦土壤紧实度变化,这为深入研究复垦土壤压实问题提供一种精确分析方法。 相似文献
6.
西瓜的力学特性及其有限元分析 总被引：13，自引：9，他引：4
西瓜的力学特性对减少西瓜贮运损失和设计相关机具等具有重要意义。通过对西瓜进行压缩试验,分析不同加载方式下西瓜的受载特点,获得了西瓜瓜梗垂直和水平受压的弹性模量分别为9.45×105Pa和8.50×105Pa。运用有限元法建立西瓜的压缩力学模型,比较西瓜水平受压的试验值和仿真值,二者最大差异是10%;研究西瓜瓜梗垂直和水平受压的承载特性,验证了仿真数值解的可行性。结果表明:在相同压力作用下,西瓜瓜梗垂直放置时,其受压的应力和应变都小于水平受压的情况。研究结果可为西瓜的贮藏、运输和加工等提供了理论依据。 相似文献
7.
机械压实过程中复垦土壤紧实度影响因素的模拟分析 总被引：13，自引：7，他引：6
机械碾压造成的土壤压实是土地复垦中面临的主要问题之一,影响土壤压实程度的因素很多,除土壤自身的因素以外,还包括压实机械、压实次数以及土层厚度等。该文基于统计学的理论,采用2×5×4的混合试验设计并建立模拟实验区,使用重锤模拟分析了2种压实机械、不同压实次数(1、3、5、7、9次)和不同土层厚度(0~10cm、10~20cm、20~30cm、30~40 cm)上土壤紧实度的变化情况,并在SPSS中进行变量的方差分析和多重比较,试图找到机械压实过程中影响土壤紧实度的因素及其变化水平。结果表明:增加压实机械的承重轮面积能够有效降低对土壤的压实作用;压实机械、土层厚度和压实次数都是影响土壤紧实度的显著性因素且各因素的贡献率(97%)远高于随机误差;自卸汽车在第5次压实之后就已经使上层土壤紧实度达到最大值,而履带式推土机需要压实7次,土地复垦中应尽量选择履带型机械,碾压次数控制在5~7之内;机械压实的过程中,各土层厚度之间土壤紧实度的大小关系并不是一成不变的,中间层次(10~30 cm)的土壤由于同时受到来自上下2个方向的作用力,紧实度相对较高;不同次数的压实对土壤紧实度的影响深度和程度不同,在一定范围内,随着压实次数的增加,单次压实对土壤紧实度的影响逐渐减小。 相似文献
8.
针对土壤压实度检测的需求,本研究应用CFBLS-100型拉压传感器和基于PCMCIA总线的DAQP-12数据采集卡,在LabVIEW环境下设计了一套土壤压实度现场测试系统。该系统能够实时显示传感器输出电压及所对应的压力变化曲线,并将所采集到的数据存储到计算机中,完成对数据的分析。经标定试验证明:该测试系统所拟合的方程为线性,其相关系数较高,线性度较好,灵敏度较高,系统精度等级小于1级,工作时系统稳定可靠。由室内试验知,在不同水平分层处,土壤压实度与不同模拟压力间均表现出3次多项式的函数关系,显著性较强(α0.05)。且在不同模拟压力下,不同土壤水平分层处的土壤压实度和土壤容重表现出相似的特性,随着模拟压力的增加和土壤分层逐步加深,土壤压实度和土壤容重的增加趋势趋于一致。为研究作物地下组织与土壤之间的根土系统及合理耕层的构建提供理论基础,并为农业机械的研发具有一定的意义。 相似文献
9.
为了改善多桥车辆操纵稳定性和行驶平顺性,通过建立多桥车辆的5+2n自由度动力学模型,设计了主动悬架与多桥转向线性系统二次型最优控制（LQG）综合控制器。通过仿真试验,对比分析了采用与不采用综合控制器2种情况下,多桥车辆不同车速下对阶跃信号的各项性能指标的响应。结果表明：低速情况下,采用综合控制器较不采用控制器的多桥车辆侧偏角峰值减小0.03 rad、横摆角速度峰值减小0.1 rad/s、车身侧倾角峰值减小0.015 rad、俯仰角峰值减小0.015 rad、车身垂直加速度峰值减小0.3 m/s2、轮胎动位移峰值减小0.009 m;高速情况下,以上各性能指标峰值分别减小0.095 rad、0.4 rad/s、0.075 rad、0.09 rad、2.1 m/s2、0.018 m。多桥车辆采用综合控制器相对于不采用控制器时的操纵稳定性和行驶平顺性都有显著改善。 相似文献
10.
以食盐溶液为雾化介质,对静电雾化中不同径向位置处的滴径分布及局部流量进行了试验测试。结果表明：雾化轴线处的平均滴径最大,沿径向方向的增大,平均滴径逐渐减小。在滴径分布特征上,轴线处和雾化边缘处的滴径分布呈现单峰分布特征,尺寸分布较窄,而在轴线至雾化边缘的中间区域滴径分布呈现双峰分布规律,尺寸分布较宽;雾化中心处的局部流量最大,沿径向位置的增大,局部流量逐渐减小。当总流量增大时,各径向位置处的局部流量均有所增大,但径向位置较小区域的局部流量增大幅度较大,而径向位置较大区域的局部流量增幅很小;当总流量不变而电压增大时,径向位置较大区域的局部流量增大,而径向位置较小区域的局部流量减小。 相似文献
11.
The use of heavy machinery is increasing in agriculture, which induces increased risks of subsoil compaction. Hence, there is a need for technical solutions that reduce the compaction risk at high total machine loads. Three field experiments were performed in order to study the effects of dual wheels, tandem wheels and tyre inflation pressure on stress propagation in soil. Vertical soil stress was measured at three different depths by installing probes into the soil horizontally from a dug pit. In one experiment, also the stress distribution below the tyre was measured. Beneath the dual wheels, vertical stresses at 0.15 and 0.3 m depth were lower between the two wheels than under the centre of each wheel, despite the gap between the wheels being small (0.1 m). At 0.5 m depth, vertical stress beneath the wheels was the same as between the two wheels. The stress interaction from the two wheels was weak, even in the subsoil. Accordingly, measured stresses at 0.3, 0.5 and 0.7 m depth were highest under the centre of each axle centre line of tandem wheels, and much lower between the axles. For a wheel load of 86 kN, tyre inflation pressure significantly affected stress at 0.3 m depth, but not at greater depths. Stress directly below the tyre, measured at 0.1 m depth, was unevenly distributed, both in driving direction and perpendicular to driving direction, and maximum stress was considerably higher than tyre inflation pressure. Calculations of vertical stress based on Boussinesq's equation for elastic materials agreed well with measurements. A parabolic or linear contact stress distribution (stress declines from the centre to the edge of the contact area) was a better approximation of the contact stress than a uniform stress distribution. The results demonstrate that stress in the soil at different depths is a function of the stress on the surface and the contact area, which in turn are functions of wheel load, wheel arrangement, tyre inflation pressure, contact stress distribution and soil conditions. Soil stress and soil compaction are a function of neither axle load nor total vehicle load. This is of great importance for practical purposes. Reducing wheel load, e.g. by using dual or tandem wheels, also allows tyre inflation pressure to be reduced. This reduces the risk of subsoil compaction. 相似文献
12.
B. D. SOANE 《European Journal of Soil Science》1973,24(3):311-323
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. 相似文献
13.
《Soil & Tillage Research》2004,75(1):37-52
Precompression stress has been proposed as a criterion for subsoil compression sensitivity in regulations, limiting mechanical loads by vehicles, trafficking on agricultural and forest soils. In this study we investigated the applicability of this criterion to the field situation in the case of tracked heavy construction machinery. ‘Wet’ and ‘dry’ test plots at three different test sites (soil types: Eutric Cambisol and Haplic Luvisol under crop rotation and Dystric Cambisol under forest) along an overland gas pipeline construction site were experimentally trafficked with heavy tracked machines used for the construction work. The comparison of samples taken from beneath the tracks with samples taken from non-trafficked areas beside the tracks showed that no significant increase in precompression stress occurred in the subsoil. Comparing calculated mean and peak vertical stresses with precompression stress in the subsoil, only little compaction effects could have been expected. Precompression stress was determined by the Casagrande procedure from confined uniaxial compression tests carried out in the laboratory on undisturbed samples at −6 kPa initial soil water potential. Dye tracer experiments showed little differences between flow pattern of trafficked and non-trafficked subsoils, in agreement with the results of the precompression stress, bulk density and macroporosity measurements. The results indicate that Casagrande precompression stress may be a suitable criterion to define the maximum allowable peak stresses in the contact area of a rigid track in order to protect agricultural and forest subsoils against compaction. 相似文献
14.
四橡胶履带轮式车辆转向力学性能分析与试验 总被引：5，自引：4，他引：1
橡胶履带轮是一种能够与轮胎整体快速互换,降低接地比压、提升越野机动能力的特殊行走装置。该文以某型四橡胶履带轮式车辆转向系统为研究对象,首先通过建立断开式转向梯形机构数学模型,得到内轮、外轮转角与油缸位移关系,以及转角特性曲线;通过转向油压测试,得到两轮和四轮转向时转向油缸输出最大转向驱动力及其随左前轮转向角变化曲线。然后对履带轮在混凝土地面上转向受力分析,建立最大平均转向阻力矩数学模型,得到单轮最大平均转向阻力矩。最后提出了基于转向杆件应力应变测试分析转向阻力矩的方法,得到履带轮在混凝土地面2轮和4轮原地转向时转向阻力矩随转角变化的规律,对比分析最大总转向驱动力矩与总转向阻力矩,验证了数学模型和该分析方法的正确性。该文的研究也可对四履带轮式车辆转向系统的结构参数设计和履带轮的接地尺寸、接地比压、轮系布置研究提供参考。 相似文献
15.
Measurement, interpretation and modelling of soil compaction 总被引：1，自引：0，他引：1
D.L.O. Smith 《Soil Use and Management》1987,3(3):87-93
Abstract. The analysis of some experimental field results is used to illustrate the problem of measuring and evaluating compaction treatment effects below wheel ruts of different depths. A solution to the problem is described which traces vertical soil movement to allow comparisons between treatments to be made using soil elements which derive from the same depth in the undisturbed profile, irrespective of their depths in the compacted profile.
A soil compaction model, which predicts the changes in dry bulk density resulting from the passage of wheels, is briefly described. Examples are given of its use in comparing the compaction caused by various types and arrangements of wheels and in assessing the contribution made by a particular input variable. 相似文献
A soil compaction model, which predicts the changes in dry bulk density resulting from the passage of wheels, is briefly described. Examples are given of its use in comparing the compaction caused by various types and arrangements of wheels and in assessing the contribution made by a particular input variable. 相似文献
16.
针对当前中国自走式蓝莓采收机作业通过性差等问题,建立轮壤接触力学模型,分析车轮驱动力矩、负载、沉陷量及挂钩牵引力等力学行为,得到车轮通过性影响因素为土壤属性、车轮结构参数和行走速度。采用离散元法建立蓝莓采收机轮壤接触模型,以车轮结构参数(宽度195、205、215 mm,直径615、627、639 mm)、行走速度0~11 km/h为试验因素,车轮结构参数或行走速度增加时,车轮阻力矩和土壤波动速度随之增加。依据车轮阻力矩设计行走驱动系统,采用闭式静液压四轮行走驱动系统,通过工况适应性仿真验证各车轮输出特性一致,稳定行走;系统可以克服车轮沉陷,平稳越障。通过样机田间试验得到行走驱动系统满足行驶速度范围0~11 km/h要求,运行平稳;车轮沉陷越障时无非目的性转向偏移,越障时间为3.3 s,与仿真结果一致;行走驱动系统与采收系统匹配性良好,采收效率为7.01 kg/min,果树采净率为92%,果树损伤率为11.5%。研究表明建立的轮壤接触模型可靠,行走驱动系统作业通过性效果好,可为蓝莓采收机研发提供参考。 相似文献
17.
A simplified soil mechanical model was constructed to predict compaction beneath agricultural wheels when running on soils of certain characteristics. Soil strength functions were developed from in situ measurements of field soils and some laboratory measurements. Soil strain was measured by surface sinkage and changes of dry bulk density by gamma-ray transmission methods. Soil stresses were measured by deformable spherical transducers and compared to predicted stresses using equations developed by Söhne. A method of analysis was devised to identify a form of the virgin compression line from field data. Changes of the slope and intercept of this line were monitored over a range of moisture contents for two soils and used in the prediction model. The prediction model was tested against compaction measured during independent experiments at different sites. Good prediction was found for soils of initial dry bulk density greater than 1.1 g cm?3 and cone resistance greater than 500 kPa, using a 30°, 12.9mm diameter cone. On looser and weaker soils the predicted compaction was often less than measured values. Using the model for simulation of compaction beneath a range of wheels revealed that contact pressure alone can be a misleading guide to compaction. Increases of bulk density below 10cm are considerably influenced by wheel load. The most effective way of reducing compaction requires the use of both a minimum load and a maximum contact area. 相似文献
18.
Field traffic may reduce the amount of air-filled pores and cavities in the soil thus affecting a large range of physical soil properties and processes, such as infiltration, soil water flow and water retention. Furthermore, soil compaction may increase the mechanical strength of the soil and thereby impede root growth.
The objective of this research was to test the hypotheses that: (1) the degree of soil displacement during field traffic depends largely on the soil water content, and (2) the depth to which the soil is displaced during field traffic can be predicted on the basis of the soil precompression stress and calculated soil stresses. In 1999, field measurements were carried out on a Swedish swelling/shrinking clay loam of stresses and vertical soil displacement during traffic with wheel loads of 2, 3, 5 and 7 Mg at soil water contents of between 11 and 35% (w/w). This was combined with determinations of soil precompression stress at the time of the traffic and predictions of the soil compaction with the soil compaction model SOCOMO. Vertical soil displacement increased with increased axle load. In May, the soil precompression stress was approximately 100 kPa at 0.3, 0.5 and 0.7 m depth. In August and September, the soil precompression stress at 0.3, 0.5 and 0.7 m depth was 550–1245 kPa. However, when traffic with a wheel load of 7 Mg was applied, the soil displacements at 0.5 m depth were several times larger in August and September than in May, and even more at 0.7 m depth. An implication of the results is that the precompression stress does not always provide a good indication of the risk for subsoil compaction. A practical consequence is that subsoil compaction in some soils may occur even when the soil is very dry. The SOCOMO model predicted the soil displacement relatively well when the soil precompression stress was low. However, for all other wheeling treatments, the model failed to predict that any soil compaction would occur, even at high axle loads.
The measured soil stresses were generally higher than the stresses calculated with the SOCOMO model. Neither the application of a parabolic surface load distribution nor an increased concentration factor could account for this difference. This was probably because the stress distribution in a very dry and strongly structured soil is different from the stress distribution in more homogeneous soils. 相似文献
19.
Abstract In this paper we describe the susceptibility of Swedish subsoils to compaction and discuss strategies for prevention of traffic-induced subsoil compaction against the background of experiences from wheeling experiments conducted in Sweden during recent years. The susceptibility of Swedish subsoils to compaction must be considered high because subsoils are often wet during field operations and machinery with high wheel loads is used. The risk of subsoil compaction could be reduced by technical solutions, such as the use of dual and tandem wheels instead of single wheels, low tyre inflation pressure or tracks. However, each of these solutions has its limitations. Results from several wheeling experiments on different soils indicate that residual deformations occur even when the applied stress is lower than the precompression stress. Hence, soil compaction could not be avoided completely by limiting the applied stress to the precompression stress. 相似文献