This study utilised native denitrifiers of cattle manure to oxidise its organic matter and induce calcium carbonate cementation in a synthetic soft soil. The soft soil is prepared by remoulding a 50% kaolinite + 50% sand mix with ultra-pure water at 21% water content. The prepared specimen is classified as soft soil based on its low unconfined compression strength of 16 kPa. Extraneous calcium nitrate provides nitrate ions (electron acceptors) for the metabolism of denitrifying bacteria and calcium (Ca²⁺) ions for calcium carbonate formation. The facultative anaerobe community peaks and declines between 7 and 14 days. A small addition of magnesium oxide balances the pH reduction caused by acetic acid formation during microbial degradation of cattle manure. Acetic acid serves as a carbon substrate for the metabolic activities of denitrifying bacteria. The CO₂ (gas) released during the metabolic activities of bacteria dissolves in water and forms bicarbonate ions. The anion combines with calcium ions in the alkaline environment to form calcium carbonate cement. In addition, the native extracellular polysaccharide (EPS)-secreting bacteria in cattle manure facilitate EPS bonding of soil aggregates. Soil structure, interfacial frictional resistance mobilised by cattle manure fibres, EPS bonding and calcium carbonate cementation enhance the compression strength of the stabilised specimen by 720%.

中文翻译：

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碳酸盐沉淀和聚合糖的分泌对软土的生物胶结

这项研究利用牛粪的天然反硝化剂来氧化其有机质，并在合成的软土中诱导碳酸钙的胶结作用。通过将50％的高岭石+ 50％的沙子混合物与21％含水量的超纯水重塑来制备软土。所制备的标本因其16 kPa的低无侧限抗压强度而被分类为软土。外部硝酸钙为反硝化细菌和钙（Ca ²⁺）离子形成碳酸钙。兼性厌氧菌群落在7到14天之间达到高峰和下降。少量添加氧化镁可平衡在牛粪微生物降解过程中由乙酸形成引起的pH降低。乙酸充当反硝化细菌代谢活动的碳底物。一氧化碳₂在细菌的代谢活动中释放的（气体）溶解在水中并形成碳酸氢根离子。阴离子在碱性环境中与钙离子结合形成碳酸钙水泥。此外，牛粪中分泌天然细胞外多糖（EPS）的细菌可促进土壤团聚体的EPS结合。土壤结构，牛粪纤维产生的界面摩擦阻力，EPS粘结和碳酸钙胶结使稳定后的试样的抗压强度提高了720％。