循环荷载下柔性桩复合地基永久沉降影响因素的试验研究

Experimental study on influence factors for permanent settlement of composite ground with flexible piles under cyclic loadings

通过室内循环荷载作用下水泥土桩复合地基的模型试验,考虑复合地基的垫层、加固区及下卧层的相互作用,研究复合地基加固区内桩的水泥掺入比、置换率以及下卧层土体性质对复合地基永久沉降的影响,试验结果表明:在满足地基承载力的前提下,当循环应力比相同且较小时,增大桩的水泥掺入比对于减小复合地基的永久沉降效果并不明显;随着置换率的不断增加,在相同的循环应力比情况下复合地基产生的永久沉降不断减小;不同土质下卧层对其永久沉降影响显著,下卧层土质较好的产生的永久沉降值较小。得出结论:对复合地基永久沉降影响最大的是下卧层土体的性质,其次是置换率的影响,而水泥掺入比的影响较小,因此,在实际工程中,当软土层不是很厚时,最好加固整个土层。

Large-scale model tests on composite ground with cement-soil piles under cyclic loadings are performed.Considering the interaction of cushion,reinforced area and substratum,the effects of cement mixing ratio,replacement ratio and properties of substratum on the permanent settlement of composite ground are studied.The results of model tests show that when the bearing capacity is satisfied and the cyclic stress ratio is equal,the increase of the cement mixing ratio has relatively small effect on the decrease of the permanent settlement.The permanent settlement of composite ground will decrease with the increase of the replacement ratio.The properties of the substratum have remarkable effect on the permanent settlement.The permanent settlement will decrease when the properties of the substratum are better.The conclusion is drawn that the greatest effect on the permanent settlement is the properties of the substratum,the second one is the replacement ratio,and the cement mixing ratio has relatively smallest effect on the settlement.Therefore,when the soft layer is thinner,the whole soft layer should be strengthened.