| With the development of the economy and the acceleration of the urbanization process,the urban rail transit develops rapidly in China.The number of rail transit operation lines increase.The scale of under-construction and planning lines is expanded.The investment in rail construction continuous increases rapidly.According to the "Guidance on the development of fabricated buildings" carried out by the General Office of the State Council,all regions should vigorously promote the fabricated buildings.Therefore,the development of fabricated subway,both in line with national interests,but also in line with the requirements of urban rail transit development.Jin'anqiao station of Beijing metro line 6 using whole fabricated construction scheme to carry out the construction of subway station main body,on the basis of open-cut.The fabricated construction scheme is adopted on the segment assembly of section tunnel from the starting point to Jin'anqiao Station,on the basis of mining method.Introduce the fabricated construction scheme to the subway construction process,which can not only be adaptable and highly automated,but also can increase the construction speed,ensure the quality of construction,improve the construction site environment,and has a broad vision of application.The waterproofing of underground engineering is related to the normal use of underground engineering functions,the length of the service life and the uneven settlement of the underground engineering and surrounding buildings.The mechanical properties determine the distribution of internal forces of the tunnel section lining under external loads,which is an important factor affecting the safety of the structure.Therefore,to study on the waterproof performances and mechanical properties of fabricated subway construction,to explore the appropriate waterproofing solution,construction control technology,and internal force characteristics,which have an important theoretical and practical significance.The essay relies on the fabricated project of Jin'anqiao Station and the section from the starting point to Jin'anqiao of Beijing Metro Line 6.The theoretical analysis and experimental methods are used comprehensively to study the waterproof performance test of the joints of the subway station wall and the subsurface excavation section segment,and the mechanical properties of the section segment component.Based on the theoretical derivation,the waterproof mechanism of the waterproof material at the joints of the station is studied.The waterproofing materials of the joints are tested,and the program is complied to predict the aging life from the gasket aging test results.The corresponding waterproof test method is designed to choose the waterproofing material of the fabricated subway station.Through the research on the indoor and field waterproof test of the gaskets used on the joints,which provide the basis for the selection of the segment assembly construction parameters.Using theoretical analysis means to study the waterproof mechanism and influencing factors of the gaskets in the segment joints.The influence of apparatus materials on gasket waterproof test is studied.From the point of view of segment joints waterproofing,the control index of the fabricated subway section construction is put forward.Using theoretical analysis method,the factors affecting the internal force of the segment under joint displacement are studied.The specific results of this essay are as follows,The first,study on the gasket waterproof mechanism of the fabricated subway station.According to the waterproof mechanism and construction characteristics of the hydrophilic expansion rubbers used on the joints of the fabricated subway station,the mechanics model of the whole process of the hydrophilic expansion gaskets assembly is established.The calculation formulas of the gaskets' contact stress at different stages of the station assembly are deduced.The influencing factors of waterproof performance of the hydrophilic expansion gaskets are analyzed.In the three stages of hoisting,grouting and using of a fabricated subway station,the waterproof properties of the hydrophilic expansion gaskets have different characteristics at each stage.In the hoisting phase,the gaskets are squeezed to produce a sealing effect.In the grouting phase,the gaskets produce an initial effect of expansion and seal.In the using phase,under the rigid constraint on both sides,the gaskets are re-inflated and the gaskets are self-sealing under the water pressure.The waterproof performance of the gaskets in the joints of the fabricated subway station is affected by the hoisting compression,the hydrophilic volume expansion rate and other factors.Only when the water pressure is greater than the critical water pressure,the gaskets produce a self-sealing effect,which is related to the water pressure,and the Poisson's ratio,the elastic modulus and the volume expansion of the gaskets.The contact stress generated by the hydrophilic expansion gaskets in the hoisting and grouting stage produces the initial water-stopping effect during the using phase.In order to exert the post-expansion effect,the volume expansion of the hydrophilic expansion gasket should be controlled during the grouting stage.The second,the waterproof test of the fabricated subway station.Combined with the engineering application of the fabricated subway station,in order to select the waterproof material for the joints of the station wall,a corresponding waterproof test is designed for four kinds of waterproof materials,20 mm high-strength grouting layer,hydrophilic expansion water-stop glue,hydrophilic expansion rubber gasket and EPDM hydrophilic expansion rubber gasket,which are commonly used in underground engineer,based on the material tests.The test result shows that the waterproof performances of the hydrophilic expansion rubber gasket and EPDM hydrophilic expansion rubber gasket are good,which can be used as the waterproof materials on the fabricated subway station joints.In addition to the preparation of a program that can be used to predict the service life of gaskets in aging test,the waterproof material and the construction control points of the fabricated subway station joints are determined through the waterproof test.The third,study on waterproof mechanism of the gasket used on the fabricated subway subsurface excavation section.By analyzing the stress and deformation mechanism of the gaskets in the joints of the fabricated subway subsurface excavation section segment,the gasket waterproof model of the joints is established.Through the mechanics analysis of the model,the analytical solution of the gasket surface contact pressure under the lateral pressure is derived.According to the constitution of surface contact pressure,the bearing seal resistance and self seal resistance are quantitative studied.It is concluded that the contact area,the elastic modulus,the Poisson's ratio,and the thickness of the gasket itself,and the effective sectional area,the elastic modulus,and the effective tightening length of the bolt and other factors have influences on the waterproof performance of the gaskets used on the segment joints.With the increase of the compression amount of the segment joint,the increase of the equivalent Poisson's ratio of the gaskets,and the self-sealing effect of the gaskets is enhanced.The forth,the waterproof test of the fabricated subway subsurface excavation section.In order to provide assembly parameters to ensure the waterproof of the segment joints in the subsurface excavation section,indoor and outdoor waterproof test of gaskets are carried out respectively.(1)The result of the indoor waterproof test shows that the EPDM gasket is suitable for the fabricated metro section,and the assembly force of the assembly machine shall not be less than 17.3 kN/m.Combined with the result of the section field waterproof test,in order to make the EPDM gasket to achieve the waterproof requirements,it is necessary to apply a certain preload torque value to each bolt,which should be calculated by the equivalent axial force produced by the test torque value 312 N·m.(2)In the assembly process of the section segments,from the waterproof point of view,the segment joints construction control should follow the principle that the opening amount as dominant and dislocation amount as assistance.Not only do well with the orientation control and attitude adjustment,but also to take measures to reduce the differential settlement of the tunnel.(3)In the indoor waterproof test,the water pressure breakthrough position of the rectangular gasket is common near the flat joint.In the production of the gaskets,the joints should be made of the rubber with a reasonable elastic modulus.In the processing of the gaskets,the control of the joints' frame process should be strengthened.(4)In the field waterproof test,the position of the water pressure can break through the joint waterproof is the contact surface of the gaskets and the segment grooves,under the maximum dislocation amount.The fifth,study on the impact mechanism of the apparatus material on the waterproof test of the gaskets used on the segment joints.The research results of indoor waterproof test and field waterproof test are different,and in the metro shield tunnel gasket waterproofing test,steel apparatus is conventionally used instead of concrete apparatus to carry out the gasket water resistance test.Aimed at above questions,the influence of the apparatus material on the gasket waterproof test is studied.By theoretical analyzing the restrained state of the gasket in the segment joint,the elastic mechanical theory is used to establish the mechanical model of the gasket in a restrained state,and the surface compressive stress of the gasket is deduced.The influences of the apparatus performance on the gasket waterproof are analyzed.The waterproof test is designed to get the gasket corresponding data of the opening amount,water resistance and vertical pressure.The test shows that under the same vertical stress,the gasket water resistance value in the steel apparatus is higher than that in the concrete apparatus.The program complied can be used to analyze the impact of the steel apparatus and the concrete apparatus on the waterproof performance of the gasket.We can get the following conclusion.The lateral deformation and the restraint stiffness have an effect on the contact pressure of the gasket,which in turn affects its waterproof performance.When the opening amount is constant,the water pressure of the gasket in the steel apparatus is higher than that in the concrete apparatus,and the concrete apparatus should be used to carry out the water resistance test of the gasket.Test data should be applied through the transformation method,when using the steel apparatus instead of the concrete to carry out the water resistance test.The test data of the assembly force and water resistance of the gasket in the two apparatuses both fit well with the power function,inverted power function,exponential function and inverted index function.Therefore,the above four functions can be used to predict the assembly force and water resistance of the gasket.The sixth,study on the segment assembly control technology of the fabricated subway subsurface excavation section.By analyzing the assembling error of the fabricated subway subsurface excavation section segment,the segment angle model is established,the opening amount and the dislocation amount at the center of the segment gasket are derived theoretically.The opening amount of the gasket is positively correlated to the opening amount on the inside of the joint,the distance from the gasket to the inside of the segment,and the maximum height difference between the inner surface of the adjacent segments.The opening amount of the gasket is negatively correlated with the segment width and the dislocation amount of the adjacent segments.And the influence of the corner on the dislocation amount of the joint gasket of the adjacent segments is negligible.According to the research results of the waterproof test and the segment geometrical parameters of the fabricated subway subsurface excavation section,the maximum height difference between the inner surface of the adjacent segments and the control value of the curvature radius of the tunnel longitudinal bending are obtained.The factors affecting the maximum height difference between the inner surface of the adjacent segments are further studied.The seventh,study on the mechanical properties of the segment component of the fabricated subway subsurface excavation section.According to the mechanical characteristics of the segment used on the fabricated subway subsurface excavation section,the mechanical model of the circular arch segment component under the constraint of elastic support is established.The superposition principle is used to study the mechanical properties of the segment component under the joints displacement.Through compiling the program,the distribution of the internal forces of the segment component is obtained,and the internal force of the segment component under the joints rotation and dislocation is analyzed.We can get that the displacements of the segment joint causes internal force unloading at the joint,resulting in the internal force redistribution of the whole segment component.The variation of the internal force of the segment is related to flexural rigidity of the joints,the radius of the segment component,semi-arc central angle,the flexural rigidity of the section and other factors. |
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