Horizontal Bearing Characteristics Of Rock-socketed Piles In Intensively Weathered Rock With Shallow Overburden

In recent years,China has vigorously developed the wind power industry and encouraged the construction of offshore wind power bases.At present,China’s offshore wind power is mainly distributed in the Yangtze River Delta and the Pearl River Delta coastal areas,where the sand cover layer in the Pearl River Delta region,especially in the coastal areas of Fujian Province,is shallow.Rock-socketed pile foundations are often used in the construction of wind farms.At present,there are few studies on the lateral bearing capacity of weathered rock-socketed piles.Therefore,it is necessary to study the influence of different factors on the horizontal load response of rock-socketed piles embedded in weathered rock strata and put forward a reasonable and safe design method for the lateral bearing capacity of rock-socketed piles.This paper first compares and analyzes the current mainstream methods for evaluating the quality of weathered rock,and finds that rock integrity index K_v can objectively and quantitatively evaluate the bearing quality of weathered rock mass.Model wave velocity test and numerical simulation wave velocity test are used to verify the feasibility of rock integrity index K_v to evaluate rock quality.Then,based on the field test data,the applicable scope and limitations of different calculation methods of lateral bearing capacity of rock-socketed piles are analyzed.The results show that the hyperbolic p-y method proposed by Liang is closer to the field test data when the load is large,but due to the lack of considering the influence of weathering on the surrounding rock of the pile,there is a certain gap between the calculated value and the measured value.Based on the formula form of the hyperbolic p-y method,this paper uses 3DEC software to establish a numerical model,evaluates the quality of rock mass with different weathering degrees by rock integrity index K_v,and studies the influence of rock elastic modulus,Poisson’s ratio,pile diameter,weathering degree and other factors on the initial stiffness Ki and lateral ultimate bearing capacity Pu of the two parameters of hyperbolic p-y formula.Finally,the hyperbolic p-y curve method considering multiple factors such as weathering is fitted.The feasibility of the fitting hyperbolic p-y method is verified by the model loading test.The influence of four factors on the lateral bearing capacity of rock-socketed piles is analyzed,including weathering,pile diameter,rock elastic modulus,and main joint surface inclination.The horizontal displacement,bending moment,and the corresponding surrounding rock reaction at different depths of the pile foundation under different working conditions are analyzed and compared with the reaction calculated by the fitting p-y curve method.It is found that the two are close,but due to the limitation of test conditions,the stress concentration between the cylindrical pile foundation and the cube test block is prone to occur,and the test data are less than the theoretical value.Finally,the rationality of the hyperbolic p-y curve fitting method is verified by the design of offshore wind power rock-socketed pile engineering.The p-y curves of the Liang method,m method,and this method at different depths of pile foundation and the horizontal displacement of pile body and the reaction force of surrounding rock under different loads are calculated respectively.The calculation results show that the method is safer and more conservative.