Horizontal Bearing Characteristics Of Single Pile Based On Three-dimensional Soil Spatial Variability

Horizontally loaded piles are common in engineering,such as piles in offshore wind power and port projects.The deterministic analysis method is used in current pile foundation design,and the unified safety factor is used to guarantee the reliability of foundation.The foundation soil is a product of nature and has natural spatial variability.Therefore,it is necessary to take the soil as a random field and consider the influence of the spatial variability of the soil on the pile foundation.In this paper,the undrained strength of the soil is used as a random variable,and a three-dimensional model is established for the offshore wind turbine single-pile foundation.The stochastic finite element method(RFEM)is used to study the influence of the spatial variability of soil properties on the horizontally loaded pile.The main work and results are as follows:(1)To solve the problem that the random field units generated by the three-dimensional random field spectral representation method is a regular cuboid of the same size,and its data cannot be directly imported into irregular hexahedral finite element units of different sizes,an effective coordinate space conversion method is proposed.The coordinate space conversion method realizes the corresponding process from regular random field elements to irregular finite element elements.(2)Considering the undrained strength of the soil as a random variable and recommending different correlation distance,a three-dimensional simulation analysis of a single pile foundation under horizontal load was carried out.The results show that the mean of the horizontal bearing capacity of a single pile considering the spatial variability of the soil is less than the deterministic analysis result.The correlation distance of the random field has no significant effect on the average bearing capacity,while the standard deviation of the bearing capacity and the coefficient of variation increase with the increase of the relative distance.In addition,the horizontal bearing capacity of a single pile considering the spatial variability of the soil conforms to a lognormal distribution.(3)A three-dimensional simulation of a horizontally loaded pile under non-stationary random field was carried out,and a comparative analysis was carried out with the result of stationary random field.The results show that with the increase of the non-stationary coefficient of the soil random field,the horizontal bearing capacity of a single pile gradually increases,and the coefficient of variation gradually decreases.Compared with the horizontal bearing capacity of a single pile in stationary random field,the mean of horizontal bearing capacity of a single pile in a non-stationary random field is larger,and the coefficient of variation is smaller.(4)A two-dimensional simulation of a single pile foundation under horizontal load was carried out,and a comparative analysis was carried out with the three-dimensional random simulation results.The results show that the horizontal bearing capacity of a single pile under a two-dimensional random field is consistent with the results calculated under a threedimensional random field.The mean value is not affected by the correlation distance,and increases with the increase of the non-stationary coefficient.The coefficient of variation increases with the increase of the correlation distance,and decreases with the increase of the non-stationary coefficient.However,the normalized mean value of the single pile bearing capacity simulated by the three-dimensional random field is larger than the two-dimensional simulation results,and the coefficient of variation is smaller than the two-dimensional calculation results.The changes in the correlation distance and non-stationary coefficient have a greater impact on the horizontal bearing capacity of the two-dimensional single pile.