| While encountering the existing pile foundation during shield tunneling,the method of cutting pile directly by the shield is popular to deal with this working condition in recent years.But this technology is not mature at home and abroad,which is easy to cause problems,such as the shield machine being hooped by the reinforcement and the instability of the stratum,causing the high risk of pile cutting.Based on the shield pile cutting project of Shenyang Metro Line 4,the paper introduces abrasive water jet as an auxiliary tool for pile cutting,and makes an in-depth study on the theory and technology of abrasive water jet combined shield tunneling pile foundation.The research results are as follows:(1)The laboratory test of abrasive water jet cutting reinforced concrete was carried out to explore the variation law of reinforced concrete cutting depth under different target distance and transverse velocity.Based on the theory of jet velocity profile and energy conversion,the maximum kinetic energy formula of abrasive water jet is deduced.Based on this formula,the optimal flow ratio of jet is studied,and the theoretical formula of optimal abrasive mass flow is obtained.(2)A numerical model which could simulate the whole process of abrasive water jet cutting reinforcement is established,and the failure mechanism of reinforcement under jet impact is explored.Using sph-fem coupling algorithm,and RHT constitutive model is used to describe the evolution mechanism of concrete damage.The orthogonal simulation test of jet impact on C35 concrete is carried out with three factors: jet velocity,mass flow ratio and jet diameter,and the effects of the three factors on the damage coefficient of concrete are analyzed χ The parameter configuration concept of "high pump pressure,large diameter and multi abrasive" is put forward.(3)A numerical model of tool cutting reinforced concrete was established to explore the mechanical behavior of cutting reinforced concrete with various sizes of tools,and the tool size was optimized.Based on the optimized tool,the finite element model of abrasive water jet combined with tool cutting reinforced concrete is established to study the influence of different jet cutting depth on the force of tool.At the same time,the numerical model of cutting reinforced concrete under circular motion of cutter is established,the stress characteristics of cutter under circular motion are studied.Combining with practical engineering cases,the main causes of cutter cracking in shield pile cutting engineering are analyzed.(4)Carry out the field test of abrasive water jet combined shield pile cutting,prove the feasibility of abrasive water jet combined shield pile cutting,determine the specific construction technology of abrasive water jet combined shield pile cutting,and accumulate valuable experience for abrasive water jet combined shield pile cutting.Figures 123,Tables 23,References 102... |
