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

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.