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PDF(8399 KB)
PDF(8399 KB)
高延性固化粉土的力学特性及微观结构
Mechanical Properties and Microstructure of High Ductility Solidified Silt
[Objectives] The silt foundations of Qiantang River seawalls exhibit weak impermeability and are prone to water erosion and loss. During periods of strong tidal bores and floods, soil flowing and piping are likely to occur, leading to seawall defects and seepage deformation or cavities in the seawall foundation. To address these issues, solidification and improvement measures are necessary. [Methods] This paper focuses on the different improvement properties of curing agents and employs a controlled-variable method to conduct silt solidification ratio experiments. The improvement of solidified silt were analyzed through unconfined compressive strength tests and permeability tests. XRD was employed for changes in mineral composition and chemical products before and after silt solidification, and SEM tests were conducted to observe the microstructural changes caused by the addition of chemical reagents. ImageJ software with machine learning capabilities was utilized to process SEM images to quantify the correlation between mechanical properties and microstructural characteristics. [Results] The optimal solidifying agent composition consisted of 4% cement, 1% fly ash, 1% lignin, 1% HV, and 1% CMC. This formulation resulted in a 28-fold increase in failure strain and a lower permeability coefficient than that of the original silt. In a permeable environment, the permeability coefficient of the solidified silt gradually decreased over time until it stabilized. SEM revealed hydrated calcium silicate (C-S-H) and ettringite (AFt) from cement hydration in the solidified silt, as well as glassy silica-alumina in a spherical fly ash morphology filling the pores. Quantitative analysis using Image J software indicated that the C4H1-solidified silt exhibited the greatest increase in failure strain and porosity, achieving the best ductility effect. Curve-fitting uncover that the correlation between pore count and strength in the modified solidified silt was not significant, while failure strain showed a positive correlation with porosity. [Conclusion] By transcending the limitations of traditional research, which often focuses on a single property (strength or impermeability), this study achieves synergistic improvement of both high ductility and impermeability, providing a more comprehensive solution for engineering applications. Additionally, the use of ImageJ software for quantitative analysis of pore structure has revealed a positive correlation between porosity and failure strain, offering a microscopic explanation for macroscopic properties.
高延性固化粉土 / 微观结构 / 破坏应变 / 强度 / 渗透性
high ductility solidified silt / microstructure / failure strain / strength / permeability
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水泥土已经广泛应用于公路、建筑、水利等领域,本文针对内蒙古河套地区粉质粘土,着重探讨水泥掺量、养护龄期、及掺加粉煤灰、石灰对水泥土抗渗性的影响,并通过电镜试验,分析水泥土及复合水泥土微观结构的变化.结果表明水泥掺量越大、龄期越长,水泥土抗渗性能越好,其微观原因是水泥土孔隙随着龄期的增长,数量减少,尺寸减小.单掺粉煤灰对水泥土抗渗性能影响较小,但是加入石灰就可以激发粉煤灰的火山灰作用,生成不溶于水的水化硅酸钙.本文针对河套地区粉质粘土得到抗渗性能良好的配比:水∶水泥∶粉煤灰∶石灰∶粉质粘土=1.45∶1.00∶0.15∶0.0375∶7.3625.这种配比相对粉煤灰水泥土提高抗渗性能50％以上.
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水泥土已经广泛应用于公路、建筑、水利等领域,本文针对内蒙古河套地区粉质粘土,着重探讨水泥掺量、养护龄期、及掺加粉煤灰、石灰对水泥土抗渗性的影响,并通过电镜试验,分析水泥土及复合水泥土微观结构的变化.结果表明水泥掺量越大、龄期越长,水泥土抗渗性能越好,其微观原因是水泥土孔隙随着龄期的增长,数量减少,尺寸减小.单掺粉煤灰对水泥土抗渗性能影响较小,但是加入石灰就可以激发粉煤灰的火山灰作用,生成不溶于水的水化硅酸钙.本文针对河套地区粉质粘土得到抗渗性能良好的配比:水∶水泥∶粉煤灰∶石灰∶粉质粘土=1.45∶1.00∶0.15∶0.0375∶7.3625.这种配比相对粉煤灰水泥土提高抗渗性能50％以上.
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To investigate the feasibility of the silt subgrade solidified by lignin-based industrial by-product, a series of laboratory tests including unconfined compression strength test, water resistance test, and wetting-drying test were conducted to analyze the effect of the additive content and the curing period on mechanical properties and durability of lignin treated silt. The improvement of lignin was also compared with the lime. Based on the results of microscopic analysis, the stabilization mechanism of lignin solidified silt was explained. Moreover, the field test of subgrade silt solidified by lignin was carried out, whilst the road performance tests including California bearing capacity ratio (CBR) test, rebound deflection value test, dynamic cone penetrometer (DCP) test and evaluation of environmental impact of solidified silt were conducted. The results show that lignin can effectively improve the compression strength and durability of silt. The optimum percentage of lignin of the silt is 12%. The specimen treated with 12% lignin after 28 days of curing has a water resistance coefficient of 0.52. And after suffering 4 times wetting-drying cycle, the mass loss rate of sample is less than 20%. The durability of lignin treated silt is much better than that of lime treated silt. Hydrolysis, protonation, and electrostatic reaction between lignin and silt take place, and a more stable and compact soil structure is formed after the treatment. The road performance indicators of 12% lignin solidified silt after 15 days of curing are better than those of 8% lime treated silt, and the rebound deflection value is not more than 1mm. The penetration resistance with the variation of the curing period and depth can be employed to reflect the strength characteristics of treated silt subgrade. In addition, the environmental quality of the silt subgrade solidified by lignin meets the requirements of the secondary quality standard. The feasibility and environmental friendliness of the technology of silt subgrade solidified by lignin based industrial by-product is well verified.
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