掺粉煤灰和二灰上海软土的力学特性

Mechanical Properties of Shanghai Soft Clay Mixed with Fly⁃ash and Lime Fly⁃ash

粉煤灰和二灰(粉煤灰与石灰的混合料)均为改良软土地基的添加材料。以掺粉煤灰和二灰的上海软土为研究对象,进行次固结试验和直剪试验,研究了掺入率和养护龄期对掺粉煤灰和二灰上海软土的次固结特性和强度特性的影响。次固结试验结果表明,掺粉煤灰和二灰上海软土的次固结系数随着粉煤灰和二灰掺入量的增加而大幅减小,且在相同掺入率条件下,二灰的掺入对其次固结系数影响较大。直剪试验结果表明,粉煤灰和二灰的掺入均能提高上海软土的抗剪强度,与纯上海软土相比,其抗剪强度随着养护龄期的增长而显著增大,最后均会在某一养护龄期趋于稳定。掺粉煤灰的上海软土抗剪强度随粉煤灰掺入率基本成线性增长,最佳养护龄期建议为56 d,二灰的掺入率在10%即可有效提高上海软土的抗剪强度,其最佳养护龄期建议为28 d。上述试验结论可为科学和经济的处理软土地基提供参考。

Fly-ash and lime fly-ash are commonly used for improving soft soil behavior.To investigate the improvement effects of the content and curing time of fly-ash and lime fly-ash on the mechanical be⁃havior of Shanghai soft clay,secondary consolidation tests and direct shear tests were conducted.It was found that the coefficient of secondary consolidation of disturbed soft clay decreases obviously with increasing fly-ash or lime fly-ash content.Under the same condition,the content of lime fly-ash has a greater influence on the secondary consolidation coefficient.The mixture of fly-ash or lime flyash in Shanghai clay can improve the shear strength of the soft clay.With the prolonging of the curing time,the shear strength of the soft clay with different contents of fly-ash or lime fly-ash increases first sharply and then smoothly,and finally it tends to be stable at a certain curing time.The shear strength of Shanghai soft soil mixed with fly ash increases linearly with the content and the best curing age is 56 days.Adding 10%of lime and fly-ash can effectively improve the shear strength,and the best curing age is 28 days.These conclusions can provide a useful reference for soft soil improvement.