Improving engineering properties of peaty soil by biogeotechnology
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摘要: 提出利用微生物技术制备原生菌高浓度菌液,用来加快土中有机质分解速率,实现在较短时间内显著降低有机质含量、改善土的工程性质的目的。为验证其可行性,从昆明市2个场地采取了泥炭土样,研发了2套模型装置,分别模拟厌氧、好氧环境下泥炭土有机质分解过程,并测试分析了分解后泥炭土的烧失量、界限含水率及一维固结蠕变特性。试验结果表明：厌氧环境下,菌液浸泡的泥炭土生物气产量比纯水浸泡的有大幅度提高,其产气动力学特征符合修正Gompertz模型。好氧环境下,分解30 d左右时,2个场地泥炭土烧失量分别减少了10.3%和15.6%,减少量比厌氧环境下的大。界限含水率试验表明,泥炭土液限随微生物分解反应时间的增长有所降低,而塑限变化幅度不大。一维固结蠕变试验表明,有机质分解后的泥炭土次固结系数下降,分解时间越长,次固结系数下降越显著。对新技术的特点进行了分析,并对其理论及应用研究进行了展望；该技术有望发展为一项生态友好型的泥炭土地基新型处理方法,改良泥炭土有望成为微生物岩土技术一个潜在应用领域。Abstract: It is suggested that the microbial enrichment technology should be used to increase the number and activity of primary bacteria in peaty soil so as to accelerate the degradation rate of organic matters in soil and achieve the purpose of significantly reducing the content of organic matters and improving the engineering properties of soil in a short time. In order to verify its feasibility, peaty soil samples are taken from two sites in Kunming City, and two sets of model devices are developed to simulate the degradation process of organic matters of peaty soil under anaerobic and aerobic environments, respectively. The combustion loss, limit moisture content and one-dimensional consolidation deformation characteristics of peaty soil after being decomposed are tested. The results show that under the anaerobic environment, the biogas yield of peaty soil soaked in the enriched bacteria solution is significantly higher than that of pure water immersion, and its gas production kinetic characteristics are in line with the modified Gompertz model. Under the aerobic environment, when the microbial degradation lasts for about 30 days, the burning loss of peaty soil in the two sites decreases by 10.28% and 15.58%, respectively, which is larger than that under the anaerobic environment. The experimental results show that the liquid limit of peaty soil degraded by microorganism decreases with the increase of the reaction time, and the plastic limit does not change much. The one-dimensional consolidation tests show that the secondary consolidation coefficient of peat soil after degration of organic matters decreases, and the longer the degration time, the more significant the reduction of the secondary consolidation coefficient. The characteristics of the new technology are analyzed, and its theory and application are prospected. This technique is expected to be an ecological friendly new treatment method for peat soil foundation, and improving peat soil foundation is expected to have a potential application field of biogeotechnology.
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Keywords:
- biogeotechnology /
- peaty soil /
- organic matter degradation /
- biogas /
- ignition loss
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致谢: 本文的试验方案设计得到了南京水利科学研究院谈叶飞博士的指导；文中微生物提取及培养等工作主要在江苏省疾病预防控制中心病原微生物研究所完成；还有部分工作是在昆明理工大学食品安全技术研究所程桂广博士、生命科学与技术学院陈伟博士的帮助下完成的,在此一并感谢！
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图 5 厌氧环境有机质分解模拟装置图（左）及生物气收集试管实物（右）
Figure 5. Schematic diagram of model devices for anaerobic environment organic matter degradation (left) and glass tube for biological gas collection (right)
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图 6 好氧环境有机质分解模拟装置图（左）及实物（右）
Figure 6. Schematic diagram of model devices for organic matter degradation in aerobic environment (left) and real object (right)
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图 7 累积生物气体积与反应时间的关系
Figure 7. Relationship between volume of accumulated biogas and reaction time
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图 9 界限含水率与反应时间的关系
Figure 9. Relationship between limit water content and reaction time
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图 10 界限含水率与有机质含量的关系
Figure 10. Relationship between limit water content and organic matter content
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图 11 e-lgt曲线与分解时长的关系
Figure 11. Relationship between time of degration and the e-lgt curve
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图 12 次固结系数与分解时间的关系
Figure 12. Relationship between secondary consolidation coefficient and reaction time of degration
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图 13 微生物技术改良泥炭土地基施工技术设计
Figure 13. Design of construction technology of improving peaty soil ground by biogeotechnology
表 1 试样的物理性质指标
Table 1 Physical parameters of peaty soil samples
取样点 取样深度/m 颜色 含水率w/% 孔隙比e0 重度γ/(kN·m-3) 塑限wp/% 液限wl/% 烧失量wi/% 残余纤维量wf/% pH值 场地一 8.0~8.5 黑色 215.3 4.6 11.9 125.2 189.3 48.1 <1.0 6.5 场地二 1.2~1.8 灰褐 416.1 6.6 10.3 — — 69.3 15.2 6.3 
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表 2 泥炭土中原生细菌数量
Table 2 Number of aboriginal bacteria in peaty soil
土样场地 培养基类型 稀释倍数 平板菌落数/个 土中细菌数量/(CFU·g-1) 场地一 葡萄糖肉汤 100 99 1.23×105 LB肉汤 100 91 1.13×105 场地二 葡萄糖肉汤 100 87 1.08×105 LB肉汤 100 102 1.26×105
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表 3 配制菌液的浓度
Table 3 Concentration of bacterium solution after cultured
土样 场地 OD600吸光度值 菌液浓度/(cells·mL-1) A B C 均值 场地一 0.360 0.340 0.319 0.338 1.96×107 场地二 0.833 0.664 0.735 0.744 5.74×107
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表 4 泥炭土分解产气的修正Gompertz模型拟合参数
Table 4 Parameters fitted by modified Gompertz model for peaty soil degradation
土样场地 修正Gompertz模型参数 P0/mL Rmax/(mL·d-1) λ/d R2 场地一 53.2 9.2 11.4 0.98 场地二 82.8 1.3 0.7 0.92
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表 5 纯水及废液中的溶氧量及pH值
Table 5 Dissolved oxygen contents and pH values in pure water and waste solution
反应时间t/d 试验组 溶氧量/(mg·L-1) pH值 7 纯水-1 5.26 7.00 废液-1 2.93 5.98 废液-2 3.80 5.85 废液-3 3.24 5.72 废液-4 3.91 5.82 14 纯水-2 5.22 7.00 废液-5 4.40 5.68 废液-6 4.02 5.67 废液-7 3.91 5.69 废液-8 4.21 5.76 21 纯水-3 4.10 6.68 废液-9 3.81 5.67 废液-10 3.92 5.78 废液-11 3.87 5.46 30 纯水-4 4.16 7.73 废液-12 4.60 5.70 — — — — — —
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