Evolution Law Of Life-Cycle Bearing Capacity Of Pile Foundation Of Inland Port

With the large number of inland river ports and docks in the upper reaches of the Yangtze River completed and put into operation,the inland river shipping capacity has been rapidly improved.How to ensure the safety and stability of the port terminals and normal operation has become the key to the smooth flow of inland river shipping.Under the periodic water level change of the inland wharf pile foundation,the strength of the rock and soil body around the pile weakens to affect the bearing capacity of the pile foundation.At the same time,under CO₂ corrosion,the carbonization of the pile foundation concrete will cause corrosion of the steel bar and will also reduce the bearing capacity.This paper aims at the safety and durability of port pier foundations in the upper reaches of the Yangtze River under the effects of periodic water level changes and CO₂ erosion,relying on the transportation technology project of the Sichuan Provincial Department of Communications"Inland River Port Wharf Foundation Life Cycle Performance Evolution and Safety Control",Through laboratory tests,theoretical derivation and other methods,the evolution law of the full life cycle bearing performance of pile foundation in inland service environment is discussed.The specific research contents and conclusions are as follows:（1）Research on the weakening model of pile foundation bearing capacity under the action of periodic water saturation and dredge.By analyzing the measured data of the properties of a large number of saturated water-drainage rock and soil,the strength weakening law of sandstone,mudstone and soil in the saline zone under periodic saturated water-drainage is clarified:As the dryness increases,the cohesion of the soil and the strength of the sand and mudstone show a logarithmic decay trend,and the internal friction angle of the soil shows a linear decay law.The deterioration rate of the compressive strength of sand and mudstone decreases with the increase of the initial compressive strength,but its total deterioration degree increases with the increase of the initial compressive strength.Based on the existing test data,a normalized model for the weakening of the mechanical properties of the rock and soil mass under periodic flooding-sparseness is established.On this basis,a weakening model of the full life-cycle bearing capacity of the pile foundation of the inland wharf under the vertical load is established.（2）Experimental study on carbonation of pile foundation concrete in inland river service environment.A concrete carbonization test chamber was used to carry out accelerated carbonation tests of concrete in general atmospheric environment and alternating dry and wet environments to clarify the concrete carbonation law in different environments.The test results show that the carbonization rate of concrete in the general atmospheric environment is higher than that in the alternating dry and wet environment;the compressive strength of the concrete in the general atmospheric environment is increasing,and the compressive strength of the concrete in the alternating dry and wet environment is decreasing and then increasing.（3）Research on the prediction model of the concrete carbonation depth of the pier foundation in the inland service environment.Based on the concrete carbonation test simulating inland service environment,the variation of carbonation depth and compressive strength of concrete specimens in the general atmospheric environment and alternating dry and wet environments was revealed.On this basis,the depth analysis of the carbonation depth and compressive strength of concrete specimens under different environmental conditions was carried out,and it was proposed to use the dry and wet alternating environmental impact coefficient to quantitatively evaluate the effect of dry and wet alternating on the carbonation depth of concrete,combined with the existing carbonization The model established the prediction model of the carbonation depth of the wharf concrete material and the compressive strength prediction model during the design period of the inland service environment.（4）Research on the evolution law of the bearing life performance of the pile foundation of the inland river wharf.Based on the prediction model of concrete carbonation depth and compressive strength,combined with the steel bar corrosion model,a stochastic simulation method for the evolution process of the pile foundation horizontal bearing capacity caused by concrete carbonization and steel bar corrosion during the design period of the inland water service environment was established.The probability distribution of the horizontal flexural bearing capacity of the pile foundation at different times during the reference period is obtained.Through regression analysis,the probability statistical parameters of pile foundation flexural bearing capacity under different service time are fitted.On this basis,a time-varying probabilistic model of the full life-cycle horizontal flexural bearing capacity of the pier pile foundation in the inland river service environment is established to evaluate the evolution process of the flexural bearing capacity of the inland river pier pile foundation with time under horizontal load.