禹城市农村建设用地整理潜力分析

农村居民点的合理规划与布局，农村废弃建设用地的整理，以及农村建设用地的复垦，可相应增加一定数量的城镇建设用地，缓解因工业化发展造成的建设用地高度紧张的现象，同时改善农村面貌，提高人居环境质量。该文结合禹城市农村建设用地现状，对禹城市农村建设用地潜力进行了分析及评价，并提出了促进建设用地置换工作的对策和建议。     

Experimental study of steady seepage in unsaturated loess soil

The complexity of unsaturated soil means that its permeability coefficient and seepage law are important topics in soil mechanics and geotechnical engineering. In this study, a new type of equipment for measuring the seepage of unsaturated soil was used to study the steady seepage of unsaturated loess soil collected from northern Shaanxi province in China. The entire process of the steady seepage of unsaturated soil under different seepage hydraulic gradients was obtained, and the permeability coefficient in the steady seepage state was measured. When the soil water content was low, the soil moisture remained only in small pores or at the junction of soil particles, the effective seepage area of the sample was reduced, and the seepage path was extended. Therefore, the lower the water content, the smaller the permeability coefficient of unsaturated soil and the longer the time required for the seepage to reach a steady state. The matric suction of the unsaturated loess soil was measured under different water contents. With decreasing water content, water remained only in the smaller pores, which provided shrink films with a smaller radius of curvature. This allowed the shrink films to withstand a larger pore air pressure and transmit a smaller pore water pressure, so that the matric suction of the loess soil increased with decreasing soil water content. The Gardner model provided an accurate fit of how the matric suction varied with the volumetric water content of the unsaturated soil. The seepage velocity and seepage hydraulic gradient were correlated well with a linear relationship, indicating that the seepage law of unsaturated loess soil accords with Darcy’s law. The experimental results show that the new unsaturated soil permeameter has good performance and controllability, thereby providing support for studying the steady seepage of unsaturated soil.