| Composite foundation with artificial hard shell layer has been applied in engineering.Since the artificial hard shell layer has a certain strength and stiffness,when it is used as a load transfer platform,the interaction and coordination deformation mode between the embankment fill,pile and foundation soil is bound to be different from the traditional reinforced cushion composed of granular material and multi-layer reinforcement.If we still refer to the previous pile-borne embankment construction design,it is inconsistent with the reality and needs to be improved.Therefore,it is of great engineering significance to study the bearing capacity of composite foundation with artificial hard shell layer and the load transfer behavior of composite foundation with artificial hard shell layer under embankment load,which can provide a basis for engineering practice.Supported by National Natural Science Foundation: “Experimental and theoretical study on dynamic bearing characteristics of in-situ solidified hard shell layer composite Foundation for road engineering”.Firstly,the load plate experiments of single pile,soil between piles,single pile composite foundation and multi-pile composite foundation under different artificial hard shell layer thickness and different pile spacing are carried out through laboratory model experiments,and the effects of different artificial hard shell layers and different pile spacing on the bearing performance of composite foundation with artificial hard shell layer are analyzed.Secondly,based on the results of the load plate model experiment,the laboratory model experiment is conducted to explore the load transfer law of the composite foundation with artificial hard shell layer under embankment filling.Finally,based on load plate experiment and embankment filling model experiment,the behavior of artificial hard shell layer under load is analyzed,and the calculation method of settlement and pile-soil stress ratio of artificial hard shell layer composite foundation is explored.The results show that:1.With the increase of the thickness of the hard shell layer,the maximum bearing capacity of the foundation is greatly improved,and the increase of the thickness of the hard shell layer thickness or the spacing of the pile can lead to a significant increase in the resistance of the pile,and the maximum value of the lateral friction resistance is at the bottom of the pile.In the project,the ratio of the thickness of the artificial hard shell layer thickness and the spacing of the pile is arranged as 1.4～ 1.8.the performance of the composite foundation of the artificial hard shell layer and the economy of the construction can be given.The pile-soil stress is compared to the design calculation parameter,which should be taken up to 34～38 is appropriate.2.The artificial hard shell layer can play a role in the initial loading stage,transferring the upper load to the pile end quickly,and the load transfer ability is excellent.Compared with reinforced cushion,artificial hard shell layer as a load transfer platform can further reduce the differential settlement between pile and soil.Compared with reinforced cushion composite foundation,artificial hard shell layer composite foundation has a higher pile-soil stress ratio of about 30 in the later filling stability.After adding reinforced cushion to hard shell layer,the pile-soil stress ratio can be further increased.After stabilizing,it can increase to about 45.72.With the increase of the load of the upper embankment,the position of the neutral surface of the composite foundation of the three structural forms gradually moves down.3.Considering the characteristics of the artificial hard shell layer and the impact shear model,the calculation method of settlement and pile-soil stress ratio derived from "equal settling surface" theory is more closed to the measured value compared with the composite modulus method.This calculation method can be used as an accurate prediction method for settlement and pile-soil stress comparison in practical engineering.As the calculation method in this paper considers that the pile is driven on the good bearing layer and the settlement of the pile is ignored,it is impossible to predict the settlement and pile-soil stress ratio under the condition that the pile is driven into the bearing layer with large displacement and the underlying lying layer with large compressibility in the engineering.Therefore,there are certain limitations in the calculation. |
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