| Frame wharf structure has been widely used in inland river port construction due to its advantages in design,construction and operation.Although frame structure form is similar to the traditional high-pile wharf,the interaction mechanism between pile foundation and bank slope still needs to be further studied due to the complex problems in working environment,such as steep slope,large variation of reservoir water level and heaping load in land area.In order to explore stress characteristics of wharf frames pile foundation,this paper carry out field research and review relevant research progress at home and abroad firstly,a model test system for interaction between structure and foundation is developed according to stress condition of wharf frames pile foundation in sandstone-mudstone filled location,a large-scale physical test model is designed to test the stress characteristics of wharf frames pile foundation.Combining the model test and finite element numerical simulation,this paper analyzes the stress characteristics and influencing factors of frame wharf pile foundation under the condition of heaping load and reservoir water level variation,a method for calculating the stress characteristics of wharf frames pile foundation is presented.The main work and innovative achievements of this paper are as follows:(1)A large-scale physical test model for the stress characteristics of wharf frames pile foundation is designed,a model test system for interaction between structure and foundation is developed.An experimental model is simplified according to the typical deep-filled frame wharf and bank slope,a model test system for interaction between structure and foundation is developed to solve the problem of interaction between structure and foundation under the complex conditions,such as dry and wet circulation,groundwater interaction.The system has the advantages of applying seepage water pressure,and varying loads at different positions in both vertical and horizontal directions,it can be used in many geotechnical engineering tests,such as bearing capacity of soil foundation,vertical bearing capacity of single or multiple piles,horizontal bearing capacity of single or multiple piles,soil stress of retaining wall,soil slope failure,horizontal bearing capacity,soil seepage deformation.(2)The stress characteristics of frame wharf pile foundation are obtained through the simulation test under heaping load in land area.The initial horizontal lateral soil stress is close to static soil pressure behind the pile,and active soil pressure in front of the pile,earth pressure cell has a high reliability.The horizontal lateral stress before and after pile,the horizontal soil pressure acting on the pile,the bending moment and axial force of the pile increase with the increase of heaping load.The closer to the pile load field,the greater the horizontal soil pressure action and stress,the maximum horizontal soil pressure occurs at 1/2 to 2/3 of the overburden thickness,the maximum bending moment occurs at 2/3 of the pile length from the transverse connecting beam to the bedrock.Simply considering horizontal soil stress effect but ignoring side friction resistance and vertical soil pressure of the deformed pile will cause large bending moment at the bottom of the pile foundation,result in high cost and waste.(3)The stress characteristics of frame wharf pile foundation are investigated through the simulation test under variation of reservoir level.The distribution of horizontal stress before and after the pile is mainly triangular tensile stress.The horizontal soil pressure acting on the pile foundation is distributed as a parabolic,and the maximum value occurs at 1/2 to 2/3 of the overburden thickness.The bending moment of pile foundation is distributed as an "S" shape between transverse connecting beam and the bedrock,bending moment which influenced by variation of reservoir level can be ignored due to the weak influence.The axial resultant force is distributed as a triangle and its influence cannot be ignored.The change about soil stress and pile internal force caused by water level decline is reduce,it’s only half vaule which caused by water level rise,the main reason is that water in bank soil have not enough time to seep out in water level decline,and it’s parameters softened.(4)The finite element numerical simulation is carried out and the influence of different pile spacing and row spacing on the stress characteristics of frame wharf pile foundation is explored.Numerical simulation results show a slightly smaller value and similar distribution compared with the physical model tests due to the influence of parameter values,such as horizontal soil stress before and after pile,horizontal stress soil between the supports,axial resultant force,shear force and bending moment of pile foundation.Sand-mudstone particle mixture shear strength was weakened after 20 cycles of saturation and drying,it is safe to simulate with weakened parameters.It will has great influence on the pile force distribution by change pile spacing but not shelf spacing.The pile internal force will increase with the increase of frame spacing due to soil arching effect,but the influence is weakened when shelf spacing is greater than 8 times pile diameter because the soil arching effect will disappears.(5)Based on soil pressure theory of retaining structure,a load calculation method for frame wharf pile foundation under heaping load is proposed.The frame wharf pile foundation in sandstone-mudstone filled location has small deformations when subjecte to soil earth pressure,beceuse it’s a statically indeterminate structure.Model test and numerical simulation show that the pile foundation which has maximum stress and internal force is closest to the land area.According to this characteristic,the influence of deformation of frame wharf pile foundation is ignored,and a limit equilibrium equation is established based on soil pressure theory to calculate horizontal and vertical soil pressure on pile foundation.According to the law of theoretical analysis and experiment,the distribution calculation is carried out,and the reliability of the calculation method is verified by comparing the calculated value with the experimental value. |
