微生物分解有机质作用对泥炭土工程性质的影响

Effects of microbial decomposition of organic matter on engineeringproperties of peat soil

微生物分解作用会改变泥炭土有机质含量和组分,影响土的工程性质,为探究这种现象,研发了模型试验装置,利用富集菌液对泥炭土进行了为期90 d的分解,对分解过程中泥炭土的物理力学性质进行分析测试。试验结果表明,(1)90 d内泥炭土有机质含量从67%下降至61.5%,随着分解时长增大,泥炭土颗粒相对密度Gs、饱和重度γsat增大,液限wL有较为明显的下降趋势,塑限wP变化幅度不大;(2)分解后的泥炭土压缩系数a1-2下降,压缩模量Es增大;(3)分解后的泥炭土固结快剪强度普遍有15%~25%的增大,黏聚力ccq从最初的18.3下降为15.6 kPa,内摩擦角φcq从13.9°增大到18.8°;(4)分解时长增大,经过预压重塑泥炭土样的渗透系数有下降趋势。分析表明,泥炭土工程性质的改变不仅和有机质含量下降有关,还可能与组分变化有关。

The microbial decomposition can reduce the organic content of peat soil and change its composition,thus affecting the engineering properties of soil.To explore this phenomenon,a model test device was developed to decompose the peat soil with enriched bacteria solution for 90 days.Then the physical and mechanical properties of the peat soil were analyzed and tested during the decomposition process.The results showed that the organic matter content of peat soil decreased from 67%to 61.5%within 90 days.As the decomposition time increased,the relative density Gs and saturationγsat of peat soil increased,the liquid limit wL decreased significantly,and the plastic limit wP almost maintains constant.The compression coefficient a1-2 of the decomposed peat soil decreased,while the compression modulus Es increased.The fast shear strength of the consolidated peat soil generally increased by 15%-25%after decomposition.The cohesion ccq decreased from the initial 18.3 to 15.6 kPa,while the internal friction angleφcq increased from 13.9ºto 18.8º.The decomposition time increased,and the permeability coefficient of the pre-compressed peat soil sample decreased.The mechanism analysis shows that the change of engineering properties of peat soil is not only related to the decrease of organic matter content,but also related to the change of composition.