Study On Deformation And Stability Of Soil-rock Composite Ground Of Wind Turbine Foundation

The construction of wind turbine foundation in mountainous areas usually faces the problem of uneven soil-rock composite ground,especially in karst mountainous areas where the relationship between soil and rock is more complicated.However,there is no systematic and comprehensive quantitative calculation and evaluation method in the Code of the industry for the soil-rock composite ground.Based on a wind power project in a karst mountainous area,a 3D geological model of soil-rock composite ground and a 3D finite element calculation model of soil-rock composite ground-wind turbine foundation were established according to the geotechnical investigation data.Theoretical calculation and numerical simulation with ABAQUS were used to analyze the ground deformation,the ratio of the foundation disengagement and ground-foundation stability of the soil-rock composite ground and the ground after replacement treatment under the circular spread foundation of the representative wind turbine site.The theoretical calculation results and the numerical simulation results are basically consistent.The research results show that the ratio of the foundation disengagement and the anti-sliding stability coefficient of the foundation along the soil-rock contact surface under the two load conditions does not meet the requirements of the Code;and the indexes of the soil-rock composite foundation after simultaneous replacement in both vertical and horizontal directions inside and outside the range of the foundation pit meet the Code’s requirements.The main research conclusions are as follows:(1)When calculating the average additional stress coefficient of the ground soil,the triangular additional stress distribution load on the non-complete circle area of the circular spread foundation of the wind turbine can be approximately equivalent to the triangular distribution load on the rectangular area with the relevant parameters;(2)When calculating the settlement deformation of the soil-rock composite ground should consider the deformation increase coefficient of the rigid underlying layer to the overlying soil layer;(3)The calculation direction of the most unfavorable profile of the soil-rock combination foundation should be the perpendicular direction of the soil-rock boundary,the direction of the maximum settlement deformation of the soil-rock composite ground is similar to the perpendicular direction of the soil-rock boundary,rather than the direction where the thickness of the soil in the composite ground is the largest,and the change of the load direction has little effect on the direction of the maximum settlement deformation;(4)The disengagement area of the foundation on the soil-rock composite ground is similar to the distribution area of the rock in the soil-rock composite ground;(5)The simultaneous vertical and horizontal replacement treatment inside and outside the foundation pit can effectively reduce the basement detachment area and enhance the anti-sliding stability of the foundation along the soil-rock interface.