Vehicle-induced soil compaction occurs when agricultural machinery is working in the fields. The accumulated soil compaction could destroy soil structure and inhibit crop growth. The low degree of visualization of soil compaction has always been an important reason for restricting the development of compaction alleviation technology. Therefore, the main objective of this study was to predict soil compaction based on soil and agricultural implement parameters. The component of soil compaction prediction includes traffic-induced stress transmission evaluation and the quantitative relationship between soil stress and bulk density. The modified FRIDA model was used to elucidate the soil stress propagation, which has been validated by previous studies. The Bailey formula was used to establish the intrinsic relationship between soil stress and bulk density. The soil uniaxial compression test was applied to obtain the parameters of the Bailey formula, and soil samples were prepared with three different levels of water content. After fitting with the Bailey formula, under the condition that the soil moisture contents were 16%, 20%, and 24%, the fitting coefficients of soil bulk density were respectively 0.980, 0.959, and 0.975, which were close to 1. The results indicated that the Bailey formula could be used to calculate soil bulk density based on the stress conditions of the soil. To verify the practicality of the soil compaction prediction model, a field experiment was carried out in Zhuozhou City, Hebei Province, China. The treatment was set for 1, 3, 5, 7, and 9 times compaction with two different loads of compaction equipment. The results showed that the fit coefficient between the predicted and measured values of soil bulk density was greater than 0.641. The slope of the equation was greater than 0.782, proving that the soil bulk density prediction model based on agricultural implements and soil parameters has a good predictive effect on soil bulk density. The soil compaction evaluation model can provide a theoretical basis to further understand the soil compaction mechanism, allowing rational measures of soil compaction alleviation to be made.

To satisfy the design requirements for a hydropneumatic spring damper valve, the inlet–outlet pressure drop (ΔP) and the axial force on the spool (FZ) of a valve were investigated using fluid–solid coupling simulations and multi-objective optimization, along with the effects of the diameters of three internal holes (DA, DB, and DC) in the valve on the ΔP and the FZ. First, a meshed computational fluid dynamics model of a damper valve was established based on its geometric structure. Next, the effects of the flow rate (Q) and the diameter of the damping hole in the internal structure on the ΔP and the FZ of the damper valve were investigated. The results showed that the ΔP and the FZ varied nonlinearly with Q. For a given Q, the ΔP decreased as DA, DB, and DC increased. For a given Q, the FZ was not related to DA and DC, but it decreased as DB increased. Finally, the structure of the damper valve was optimized by defining the ΔP and the FZ as the response variables and DA, DB, and DC as the explanatory variables. The results showed that the best configuration of the hole diameters was DA = 8.8 mm, DB = 5.55 mm, and DC = 6 mm. In this configuration, ΔP = 0.704 MPa and FZ = 110.005 N. The ΔP of the optimized valve was closer to the middle value of the target range than that of the initial valve design. The difference between the simulated and target values of the FZ decreased from 0.28% to 0.0045%, satisfying application requirements.

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