基于应力传递系数的分析模型优化与土壤压实应力预测
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山西省重点研发计划项目(201703D21102-7)和山西省农业科学院博士基金项目(YBSJJ2015)


Optimization of Analytical Model and Prediction of Soil Compaction Stress Based on Stress Transmission Coefficient
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    摘要:

    针对目前基于有限尺度环刀的土壤应力传递系数(Stress transmission coefficient,STC)取值方法无法满足不同深度土壤条件下集中系数随加载环境变化研究的问题,将土壤剖面分割为有限尺度的土层,基于分析模型推导ΠSTC公式,以多层土壤应力传递系数连乘方式计算田间指定深度土壤应力传递系数。基于传感器技术进行田间原位土壤平板下陷试验,通过控制压板直径和土层厚度实测9种加载状态下土壤的应力传递系数;同时,通过有限尺度(Φ50×50mm环刀)取样于室内,结合土压力传感器进行非扰动土单轴压缩试验,测量各土层(0~50mm、50~100mm、100~150mm、150~200mm)应力传递系数。运用ΠSTC公式计算3种深度(100、150、200mm)土壤的应力传递系数分别为0.30、0.17、0.07,综合实测数据通过双因素方差分析研究应力传递系数随加载环境的变化规律,由此反算不同加载条件的集中系数。结果显示,随着压板尺度的改变,实测与计算所得相同深度土壤的应力传递系数间并无显著差异,表明土壤应力传递系数与压板-土壤接触面当量半径无关,利用ΠSTC公式计算田间土壤应力传递系数方法可行;随土层厚度的增加,应力传递系数显著减小,说明应力传递性能随土层厚度的增加而逐渐减弱;集中系数随压板直径和土层厚度的增加而逐渐减小。利用分析模型较为准确地预测了田间指定加载环境和土壤环境中因连续加载而变化的土壤应力,优化了土壤压实应力传递的研究方法。

    Abstract:

    Predicting soil stress with analytical models requires proper selection of the models’ concentration factor. The parameter is a coupled result from both loading condition and the soil environment. Stress transmission coefficient (denoted as STC) was suggested in other study to investigate the soil state’s effect on the concentration factor. Because the current limitedscale analytical approach of stress transmission coefficient may prevent accurate estimation of soil stress, there was a desperate need to make loading conditions’ impact clear on concentration factor. The function of the concentration factor was transformed and a theory to calculate the soil stress transmission coefficient insitu soil in field, ΠSTC equation, was derived, which complement, associated with the stress transmission coefficient in a limited scale after splitting the soil profile from large. Totally nine loading conditions were tested using insitu soil by controlling three plate diameters and three soil thicknesses, and a modified oedometer testing setup with a soil stress sensor was used to measure stress transmission coefficient of different soil layers (0~50mm, 50~100mm, 100~150mm and 150~200mm) indoor. Stress transmission coefficient for the same depths with field experiment was 0.30, 0.17 and 0.07, and then calculated by ΠSTC equation. Correlation analysis were performed to evaluate both measured and calculated STCs on controlled loading conditions (e.g. equivalent radius of the contact area and soil thickness). Then soil stress was predicted following the concentration factor backcalculated from the acquired STCs. The highly linear correlation between soil stress and applied surface stress indicated a stable STC for a particular soil state in field. In general, a thicker soil layer led to a decreased STC, and there was no significant difference in STCs varied with equivalent radius of the contact area, suggesting that the ΠSTC equation could be used as a specific method to quantify soil stress transmission in field. The backcalculation of concentration factor from measured STCs showed the details of how the concentration factor was affected by the changed loading condition with measured result. A good accuracy of the soil stress prediction based analytical model and ΠSTC equation meant a optimized solution was proposed for soil compacting stress prediction.

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贺亭峰,丁启朔,张伟,姜春霞,刘恩科.基于应力传递系数的分析模型优化与土壤压实应力预测[J].农业机械学报,2020,51(10):292-298. HE Tingfeng, DING Qishuo, ZHANG Wei, JIANG Chunxia, LIU Enke. Optimization of Analytical Model and Prediction of Soil Compaction Stress Based on Stress Transmission Coefficient[J]. Transactions of the Chinese Society for Agricultural Machinery,2020,51(10):292-298.

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  • 收稿日期:2020-05-21
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  • 在线发布日期: 2020-10-10
  • 出版日期: 2020-10-10