机械压实过程中复垦土壤紧实度影响因素的模拟分析

Simulation analysis on influencing factors of reclamation soil compaction in mechanical compaction process

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。

Soil compaction resulted from mechanical rolling is one of the major problems in land reclamation. There are a lot of factors that influence soil compaction apart from soil properties, and also mechanical pressure, soil layer, and times of compaction etc. Based on the statistical theory, this article focused on a 2×5×4 mixed experimental design and established a simulation experimental area that employed a heavy punch to simulate the two compact machineries for respectively once, three times, five times, seven times, and nine times. Each fall depth for every compact punch on the soil would be measured. Afterwards, the soil compaction gauge was used to measure the soil compaction changes in different layers. At last, variance analysis in SPSS was conducted and a comparison of random pairs, with the intention of finding influential factors of soil density in the mechanical compaction process and the varied range and preconditions of each factor. The results derived were as follows：（1） A size increase of the compact machinery roller wheels can effectively reduce mechanical compaction on the soil. Since the ground contact area was relatively small when the wheel dumper ran, soil compaction was increasingly seriously affected in the land reclamation process. In the process of machinery compaction, soil fall depth reflects the soil compaction degree, to some extent, and can serve common farmland cultivation as one of the indicators for a preliminary judgment on soil compaction. （2） Compact machinery, soil layer, and times of compaction are all notable factors influencing soil compaction, all of whose contribution rate is highly above random error. The interactive effect, especially between the compact machinery and times of compaction, had a remarkable and profound effect on soil compaction. （3） Different compact machineries of varied weights and ground contact areas would lead to different compaction effects. The dump truck crushed down into 30cm on the upper layer and realized the maximum compaction after five times of compaction, while the crawler dozer needed seven times for the same outcome. （4） In the process of machinery compaction, the soil compaction in different layers did not remain the same. When the soil was less compacted, the upper layer would experience a skyrocketing soil compaction, and the compaction degree declines in a deeper layer. When times of compaction are increased, the soil compaction difference between each layer narrows. The mid-layer （〉20-30cm） features a comparatively high compaction under upward and downward stress. （5） The times of machinery compaction had a remarkable effect on soil compaction. Five times of dump truck compaction and seven times of crawler dozer compaction generally achieve the same compaction degree in comparative soil. In addition, the physical property of soil was severely destroyed, which resulted in soil clay or hardening. Therefore, the type of construction machinery and times of compaction must be controlled in land reclamation. （6） Different compaction times had different depth influences and degrees on soil compaction. Initial compaction is most obvious on soil compaction. Single compaction effect on soil compaction will be gradually reduced when the times of compaction are increased in a certain range. A continuous increase of compaction times enforces lower layer compaction though, yet crawls slowly upward. Repeated single compaction of small pressure on soil indeed cannot be ignored. （7） Models were establish built on correlations between soil compaction and press, times of compaction, and soil layer to judge rough soil compaction under different conditions. In addition, improvement measures for land reclamation are defined as the next research focus.