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Based on the perspective of flight technology and flight safety, the unsaturated clayey foundation soil of a high plateau airport in the mountainous area of southwest China is taken as the research object, and the calculation method of the composite modulus of CFG pile composite foundation with the soil between the piles as the unsaturated soil is established according to the relevant characteristics of unsaturated soil, and the calculation method of the composite foundation's settlement is carried out on the basis of this method. At the same time, Plaxis finite element analysis software is used to model the actual project and numerically analyze the settlement characteristics of the composite foundation. Finally, the calculation results of the two methods are compared and studied with the actual settlement monitoring values on site. The study shows that: 1) the theoretical analysis method is able to consider the effects of pile length, pile modulus, and matrix suction in unsaturated soil of rigid piles on the composite modulus, which is more in line with the reality than the conventional composite modulus method that does not consider the unsaturated nature of the soil between the piles; 2) the resultant values computed by the theoretical and numerical analysis methods recommended in this paper are both smaller than those measured at the site but the difference is within the range of 10%, so that in the actual plateau of the High Plains airports can choose the two analysis methods recommended in this paper to conduct related research. [ABSTRACT FROM AUTHOR]

Soil properties are crucial in forest ecological management and rare vegetation protection. In this study, Fanjing Mountain, a typical subtropical forest, was used to investigate and analyze the differences in soil properties and climate change characteristics of Fanjing Mountain in 1982 and 2014. Then redundancy analysis was used to analyze the influence of climate factors on soil properties. The results showed that: 1) Compared to 1982, the soil properties of Fanjian Mountain changed significantly in 2014. The soil texture evolved from a silty loam in 1982 to a silty clay loam in 2014. There was a significant increase in soil clay particles. In addition, the soil showed acidification, weakened cation exchange capacity, and relatively stable soil total nitrogen but significant loss of soil organic matter and total phosphorus nutrients. 2) In the past 32 years, the environmental climate of Fanjing Mountain has shown the characteristics of increasing annual average temperature and annual rainfall, frequent extreme temperature, widening the annual temperature range and decreasing annual relative humidity. 3) Soil type and maximum annual temperature have a highly significant effect on the evolution of soil properties, while annual rainfall and slope orientation significantly affect the evolution. Conclusion: The evolution of soil properties in subtropical forests is dominated by their type differences and climate warming. [ABSTRACT FROM AUTHOR]

Jatropha cake is a residue rich in nutrients that when used as organic fertilizer can contribute to plant development and soil properties improvement. Thus, this study aimed to evaluate Jatropha cake, digested and non-digested, on common bean plant (IPR-Colibri) growth and in soil properties. A greenhouse experiment was carried out in a sand-clay-loam soil to assess the effect of Jatropha cake (non-digested and digested) on soil Ca2+, Mg2+, Al3+, pH, organic carbon and clay dispersion in water and on plant leaf area, height, stem diameter, number of nodules, dry mass of root and shoot and, phosphorus (P) uptake in the shoot. The amount of Jatropha cake applied was calculated based on the equivalent to P content (50, 100, 200 and 300 kg P ha-1). It included two treatments: control and mineral fertilization. The Jatropha non-digested cake in doses of 200 and 300 kg P ha-1 inhibited seedling emergence, while a dose of 50 kg P ha-1 had positive influence on the development of the plants and in the P uptake in the shoot. There were water-dispersed clay values reduction and an increase in organic carbon with applications of Jatropha non-digested cake into the soil. [ABSTRACT FROM AUTHOR]

In temperate climate zones, fast-growing willow species harvested in short harvest rotations of 3 to 10 years are an interesting source of biomass for energy or industrial purposes. The aim of this study was to determine morphological traits and biomass yields of three willow cultivars and three clones cultivated on three different types of marginal soils at two densities. Willow was grown in the Eko-Salix system, with no ploughing, with limited fertilization and cultivation measures, harvested in a 7-year rotation. The experiment showed that willow can be produced in the Eko-Salix system in extensive cultivation; however, the yield was strongly differentiated by the marginal soils and by the cultivars and clones under study and ranged from 4.4 to 17.8 Mg ha-1 year-1 DM. The mean yield from all the sites for all the cultivars and clones as well as planting densities in the experiment was 8.0 Mg ha-1 year-1 DM. The biomass yield obtained on peat-muck soil and humic alluvial soil was similar and significantly higher than on very heavy clay soil. The Ekotur cultivar gave plants with better morphological traits and the significantly highest mean yield (12.9 Mg ha-1 year-1 DM). [ABSTRACT FROM AUTHOR]

This paper deals with the prediction of free heave in expansive soils from central Poland. Thirty-nine soil samples differing in plasticity were selected for a comparative analysis. The soil types examined – Neogene clays, alluvial soils, and glacial tills – differ in CLOD index (Cw) values, which range from 0.027 to 0.019, with values for undisturbed samples being higher than those for the remoulded ones. The variability of the Cw index correlates best with the sand-to-clay ratio. Studies of soils contaminated with diesel oil (ON) have revealed that the Cw index decreases with growing ON content. Calculations of the potential heave, assuming a 1% moisture change for a 1 m thick soil layer, show the heave to be 18 to 12 mm and 15 to 11 mm for Neogene clays and glacial tills, respectively, depending on the in situ void ratio. Petroleum contamination significantly reduces the potential heave of the soil. The present analysis clearly suggests that glacial tills are more susceptible to oil-derived contamination than Neogene clays. [ABSTRACT FROM AUTHOR]