The Study On The Moisture Content Of Fine-Silty Sand Affecting The Pulling Failure Behavior Of The Extended-Pile

The concrete plates-expanded pile is consist of single or multiple the bearing plates and more cross section pile.It is the interaction between the bearing plate and the soil on the bearing plate that make the bearing capacity of the concrete plates-expanded pile have greatly improved compared with the traditional equal cross section pile.In addition,the concrete plates-expanded pile has some other advantages,for example,the concrete plates-expanded pile has reduced the displacement of foundation,widely used,saves costing and so on.In order to used widely,it is necessary to further study the new type of pile.In the paper,the stress state of the concrete plates-expanded pile is studied when the concrete plates-expanded pile is set in the fine-silty sand.First,the ultimate bearing capacity of single pile and failure state of the soil around the pile are studied by test study on small model and half section pile with different moisture content of soil,studies have shown that there is separation between the bearing plate and the soil under the bearing plate when the model at the early stage of the load,in addition,there is horizontal crack at the end of the bearing plate and the soil on the bearing plate is gradually pressed densely.As the load increased gradually,the edge of pressed soil on the bearing plate appears sliding failure,and it is recycling within a certain range on the bearing plate,as a result,the arc-shaped sliding line is formed and the soil on the bearing retainer is sliding,the diagonal crack gradually is appeared at the 45° on the both side of the pile,the model is damaged completely when the sand within the diagonal crack range appears punching failure.According to the test result,the bearing capacity of the concrete plates-expanded pile when the moisture of fine-silty sand below 15% is higher than the moisture of fine-silty sand above 15%.Secondly,according to the moisture and shear strength parameters of thefine-silty sand that was used in the test,analysis models are built by ANSYS software,the results such as the load displacement,stress and strain of the concrete plates-expanded pile are analyzed.Studies have shown that the uplift bearing capacity of the concrete plates-expanded pile is decreased obviously and the vertical displacement is lager when the moisture of fine-silty sand above 15%,it is lower cohesive force that makes the bearing capacity of the concrete plates-expanded pile is lower when the moisture of fine-silty sand is higher.Thirdly,it is find that the test results is roughly matched with finite element simulation results in the range of allowable error by the comparison between test models and finite element models,and through discussing the calculation mode of the sliding failure and the punching failure,the calculation formula of ultimate bearing capacity is provided whether the surface of bearing retainer is restraint or not,and it is corrected when the surface of bearing retainer is not restrained.In the paper,the uplift bearing capacity of the concrete plates-expanded pile and the failure state of the soil around the pile are studied when the moisture of fine-silty sand is different.To a certain extent,the theoretical basis of the concrete plates-expanded pile has been perfected.