| Shield machine has the advantages of high degree of automation,high tunneling speed,and small impact on the surrounding environment.It has become the preferred construction equipment for urban tunnel excavation.However,with the increasing density of urban buildings,tunnel construction faces more complex engineering conditions.When the shield machine encounters the existing underground reinforced concrete obstacles such as pile foundation and diaphragm wall,the traditional mechanical tunneling will cause engineering problems such as steel bar winding cutter head,abnormal damage of cutting tools,and stuck machine,resulting in low safety and slow construction speed.Therefore,the research on shield tunneling through reinforced concrete is of great significance for ensuring the safety of shield tunneling and improving the tunneling efficiency,and has become one of hot topics of construction of shield tunneling method in our country.At present,the ability of shield cutting tool to cut hard structure is limited,and it is difficult to cut the steel bar wrapped in concrete effectively,which is the root cause of many engineering problems.In this paper,the solution of abrasive water jet-tool combined cutting reinforced concrete is proposed.High pressure abrasive water jet cutting metal,rock and other high strength materials with high efficiency and low energy consumption,has been applied in machining,oil mining and other fields,and has great potential for auxiliary shield cutting reinforced concrete.However,at present,the mechanism of shield with abrasive water jet cutting reinforced concrete is not clear,the efficiency law of combined cutting reinforced concrete is not clear,and the method and technology of combined cutting reinforced concrete efficiency is lacking,which restricts the implementation of joint cutting technology.In view of the above problems,laboratory tests,theoretical analysis and numerical simulation are carried out to study the effect and mechanism of shield abrasive water jet-cutter combined cutting reinforced concrete.The law of reinforcing efficiency of combined cutting reinforced concrete is expounded,the mechanism of combined cutting is revealed,and the judgment basis of combined cutting reinforced concrete is put forward.On this basis,the design method of abrasive water jet and tool combined shield cutter head and combined efficient cutting method are established.Finally,the above methods are verified by model test.The main research work and results of this paper are as follows:(1)Research on the effect and mechanism of abrasive water jet cutting reinforced concrete under submerged conditions.The experiment of abrasive water jet cutting steel bar and concrete under shield construction conditions are carried out.The significance ranking of the key parameters of abrasive water jet on the cutting depth of steel bar was expounded,the efficient cutting parameters of abrasive water jet are proposed,and the statistical model of the cutting depth of steel bar is established.Then,the microscopic observation of the fracture morphology of steel bar cutting is carried out and the removal mechanism of deformation wear and shear wear under abrasive impact is revealed.(2)Research on the combined cutting test and efficiency increasing law of reinforced concrete.A combined cutting test device for shield tool is designed and developed,and the test of combined cutting of reinforced concrete with abrasive water jet and cutter is carried out.The law of increasing efficiency of combined cutting reinforced concrete structure is expounded,and the increasing efficiency strategy and efficient parameters of joint cutting are put forward.This provides a basis for the research on the mechanism of the combined cutting of reinforced concrete by abrasive water jet and tool,and also provides a basis for the establishment of the combined efficient cutting method.(3)Research on the mechanism of abrasive water jet-cutter combined cutting reinforced concrete.Firstly,the SPH-FEM coupling method is used to carry out numerical simulation of combined cutting of reinforced concrete by water jet and tool.Then combined with the test results,the failure mode and crack propagation mechanism of the joint cut rebar are found.It is found that the steel bar with jet slits is destroyed by Ⅱ-Ⅲ composite crack propagation mode,which increases the type Ⅲ shear process that tears the steel bar and reduces the cutting load.Finally,the failure criterion of joint cutting of reinforced concrete structure is established.These conclusions provide a theoretical basis for scientific construction of abrasive water jet-tool combined cutting technology.(4)Research on the design and realization of abrasive water jet-cutter combined cutter head.Focusing on the engineering realization of abrasive water jet and mechanical joint cutting,the design method of abrasive water jet and mechanical tool combined cutting cutter head and combined efficient cutting method are put forward.The high pressure water jet and mechanical combined cutting test platform is developed,and the combined driving model test is carried out on this platform,and the effectiveness of the above methods is verified. |
