Research On Pile Driving Analysis System Based On Improved Pile-soil Dynamic Response Model

As offshore wind power continues to grow,the installation of large-diameter single-pile foundations for wind turbines remains at a high level.For large diameter single pile foundations,factors such as pile cost,safety during pile construction,and successful implementation of construction that affect construction costs are all critical factors to consider before pile driving.To address the engineering considerations mentioned above,pile drivability analysis can be conducted prior to pile driving by simulating the pile driving behavior.This involves using numerical simulation methods to predict the difficulty of pile driving at the pile driving point under different input energies,analyzing and determining the hammer energy input that can ensure construction safety while completing the pile driving faster,and using it to guide the on-site pile driving.Among the existing commercial pile driving software,the GRLWEAP software can perform the above-mentioned drivability analysis.The software simulates the pilesoil response process based on the SMITH model and conducts finite element analysis to simulate the driving process.With the development of research on pile-soil dynamic response models,it can be considered that there is a large room for improvement in the behavior of analyzing pile-soil response using the SMITH model in the software,and users cannot adjust the built-in model of the software when using it.Based on the above problems,the research goal of this paper is to construct a pile driving analysis system that can achieve drivability analysis,and consider achieving the modifiability of the pile-soil dynamic response model from the construction of the system.Secondly,an improved pile-soil dynamic response model is proposed,and an improved system is constructed based on this model for further research.To achieve the above key issues and research objectives,this paper conducts relevant research using theoretical analysis,unit testing,numerical simulation,and onsite comparison.The specific research content and innovation points are summarized as follows:1、This introduces the relevant information about the commercial pile driving software GRLWEAP.Subsequently,a linear pile-soil model and a numerical pile hammer model were constructed using MATLAB.The beam element was used to build the main structure of the pile body in COMSOL,and finite element analysis was conducted based on the COMSOL with MATLAB framework.A pile driving analysis system based on the linear pile-soil response model was developed,which can simulate the response of pile displacement and stress under the action of hammering.The technical route and input information of the system were introduced,and the specific process of piliability analysis was given based on the output relationship between the penetration degree and depth.The differences and similarities between GRLWEAP software and this system in terms of pile-soil and pile hammer model details were compared and analyzed.Then,the differences in penetration calculation between the pile driving analysis system and the GRLWEAP software were compared,and the system reliability verification analysis was carried out based on this,which analyzed the error sources between the software and the system.Finally,the actual pile driving records from the site were compared with the simulated calculation results of the pile driving analysis system,and the limitations of the linear system were analyzed.2、Based on the t-z,Q-z spring + related damping model,new dynamic response models for pile sides and pile bottoms are proposed,and linear pile-soil response models are modified in areas such as "soil nonlinearity","hysteresis damping","radiation damping",and "viscous damping".This model can be constructed based on a large number of existing t-z,Q-z spring models,and the effectiveness of the improved system can be further improved by improving the above spring models.Furthermore,in order to improve the t-z spring model for pile lateral dynamic response model,based on the existing relevant t-z spring model research,a new t-z spring model suitable for pile driving analysis in sand was explored and proposed.This model comprehensively considers various aspects such as soil nonlinearity,full process analysis of loadingunloading-reloading,the impact of cumulative displacement on cyclic weakening,and the contribution of plastic displacement to weakening.Similarly,based on the existing one-way loading Q-z spring model,a Q-z spring model suitable for full process pile driving analysis mode was proposed.The above pile-soil response models were constructed sequentially using MATLAB and applied to the analysis system.Based on the improved system,simulation calculations were conducted for the field pile driving case in Chapter 2,and a comparative analysis was carried out between the calculated results of the improved and linear systems and the recorded field data.3、This paper introduces the on-site conditions of the Jiangsu waters,clarifies the existence of a large amount of silt in the soil layer,and conducts large displacement silt-steel interface ring shear tests based on this,exploring the factors and characteristics that affect the friction angle of the silt-steel interface.It reveals the influence of pile driving behavior on the interface friction angle and provides the basis and suggestions for determining the interface friction angle when conducting systematic analysis.In addition,for the pile driving locations on site,an inversion analysis of the ultimate soil resistance on the pile side is carried out,and the recommended correction parameters for the ultimate soil resistance on the pile side at the above-mentioned locations are given.Furthermore,the modified coefficient is used to correct the ultimate soil resistance on the pile side,and then the improved system is used to simulate the pile driving process at the on-site locations.The improved pile-soil response model and the reliability of the improved system are verified.Sensitivity analysis of key parameters in the system is conducted,and guidance suggestions are made for pile design from the perspective of construction cost.