黄土发育表土结皮过程和微结构分析的试验研究

Experimental Study of Surface Crusts Process and Microfabric Analysis on Loess Soil

对采自晋西离石的马兰黄土进行了模拟降雨试验，研究表土微结构与表土结皮发育过程的关系．模拟降雨强度为１．２ｍｍ／ｍｉｎ，降雨历时为１～３０ｍｉｎ．通过对表土微结构的变化观测可以清楚看到，在３０ｍｉｎ降雨过程中经历了两次表土结皮的形成过程．初始形成的表土结皮是很不稳定的，在表土结皮的初期发育阶段较容易被破坏．在稍后阶段形成的表土结皮会更加稳定．观测到的表土微结构变化过程揭示出它们是呈周期性变化：团聚体被破坏、土壤颗粒发生垂直和水平位移、表土结皮层和淋溶层的孔隙和结构不断形成和破坏、表土结皮的形成破坏、表土变得比较密实．土壤抗剪强度可以用标准锥体贯入仪来测定，由土壤含水量和土壤抗剪强度关系得到的表土结皮强度指标与观测到的表土微结构变化密切相关．

Disturbed Malan Loess soil samples from Lishi, Shanxi Province, were testedin the laboratory to investigate changes in micro fabric which were related to soilsurface development. They were subjected to simulated rainfall at an intensity of1. 2mm/min and for duration ranging from 1 to 30 minultes. It can be inferredfrom the observed microfabric rearrangements that two complete cycles of crustformation and possible three levels of stable crusts have developed during the 30minutes simulated rainstorm. The initial crusts were not very stable and were disrupted during the early stage of crust development. Crusts that were formed in thelater stages appear to be more stable. The observed processes of microfabric rearrangement. some of which may be cyclic, include breakdown of aggregates, vertical and lateral translocation of particles, formation and destruction of vesicles, textural modification in a crust layer, complete seal off, and surface compacting. Soilstrength was determined by using a standard falLcone penetrometer. A cruststrength index derived from soil moisture and soil strength relations was found tobe consistent with the observed fabric changes.