洞庭湖区掺粉煤灰水泥土性能试验研究

Experimental study on performances of fly ash cement soil in Dongting Lake area

采用粉煤灰代替部分水泥作为胶凝材料的水泥土桩法,近年来逐渐在软弱地基的加固处理中得到应用。针对洞庭湖区湖泊相淤泥质软弱地基加固处理问题,结合该区域某分洪闸地基处理工程,在室内开展了不同粉煤灰掺量的水泥土试件的无侧限抗压强度、含水率以及中心部位土样溶液pH值的测定试验,然后探讨建立了不同粉煤灰掺量的水泥土无侧限抗压强度的组合指数式模型。研究结果表明:水泥土试件无侧限抗压强度在60 d龄期前随着粉煤灰掺量的增加而降低,但在90 d龄期时,不同粉煤灰掺量的4组试件强度值较为接近;水泥土试件含水率在28 d龄期之后随着粉煤灰掺量的增加而增加;水泥土试件中心部位土样溶液的pH值始终随着粉煤灰掺量的增加而降低;采用组合指数式强度模型能较好地描述粉煤灰掺量和龄期对水泥土无侧限抗压强度增长规律的影响;通过对不同粉煤灰掺量水泥土桩方案进行比选,建议洞庭湖区水泥土中粉煤灰掺量应在20%左右为宜。

The cement soil pile method using fly ash instead of some cement as a cementitious material has been gradually applied in the reinforcement treatment of weak foundations in recent years.Aiming at solving the problem of soft foundation of the Dongting Lake area,the unconfined compressive strength,water content and pH value of soil samples in the central part of the cement-soil specimens with different fly ash contents were tested indoors,by combining the foundation treatment project of a floodgate in the area.And the combined exponential model of the unconfined compressive strength of cement soil with different fly ash content was established.The results showed that the unconfined compressive strength of cement-soil specimens decreased with the increase of fly ash before 60 day age,but the strength values of four specimens are close at 90 day age.The moisture content of the part increased with the increase of fly ash content after 28 day age.the pH value of the soil sample solution in the central part of the cement soil test specimen always decreased with the increase of fly ash content.The ash content cement soil pile scheme is compared and selected.The combined exponential strength model can better describe the influence of fly ash content and age on the unconfined compressive strength growth law of cement soil.Through the comparison of different cement ash mixed cement soil pile schemes,the amount of fly ash in the cement soil of Dongting Lake area should be about 20%.