Under the working condition of mud cake, the continuous action between the shield cutter head and the soil on the excavation surface can generate high temperature in the process of shield tunneling and excavation, which changes the characteristic of the adhesion between the soil and the cutter head to intensify the phenomenon of making a mud cake on cutter, finally leading to a vicious circle. To study the effect of temperature on the characteristics of the adhesion of the soil on the surface of the structure, the soil adhesive situation and adhesion force at different interface temperatures were tested through a self-made experiment device. According to the result, it was indicated that the moisture content has a significant effect on the adhesion force of the soil, and the adhesion force firstly increased and then decreased with the increased of the moisture content and reached the maximum value near the plastic limit moisture content. The adhesion force changes very gently when the interface temperature is low. When the temperature reached 50°C, the adhesion force continues to increase as the interface temperature continuously increases except for the soils with high moisture content; moreover, the interface temperature has a great influence on the content of soil adhered on the structure surface. As for the soil with moderate moisture content ( ω = 21.21 ~ 31 %), this content of the adhered soil increased exponentially with the increase of interface temperature; this content firstly decreased and then increased when the moisture content was high. When the soil was dry, there was almost no adhered soil on the surface and the interface temperature had no effect on the adhesive situation. By comparing and analyzing the adhesion state of the soil on the surface of the structure, the influence of temperature on the adhesion characteristics is mainly reflected on the variation of the soil moisture content within the influence range of the interface, the variation of the energy required for the destruction of the adhesion interface, and the change of the location of the weakest antistripping plane induced by both before. This research can better understand the law of formation and development of mud cakes and provided a new idea of solving the problem of mud cakes on the cutter head.
A new type of composite lining structure consisting of segments, steel pipes, and concrete lining can be adopted in the water conveyance tunnel to bear large internal water pressure. However, there is still no effective analysis model and calculation method for the parameter influence effect of this new composite lining. In this paper, the load structure method and the elasticity theory are adopted, the stress analysis model and theoretical calculation method of a new type of composite lining of water conveyance tunnel are given, and the influence law of lining structure parameters is studied. Each part of the shield assembled lining is regarded as a stressed spring, and a formula for calculating the equivalent elastic modulus of the overall structure at the joint of the lining under partial tension and partial compression is given. The stress and deformation of each layer of lining are deduced based on the theory of thick-walled cylinders. According to the actual project, the rationality of the calculation method is verified by comparing the results of finite element analysis, and the influence of the thickness of intermediate concrete lining and inner lining parameters on the distribution of force transmission among lining layers is further analyzed. The results show that the radial displacement and circumferential stress of each layer of lining structure decrease with increasing the thickness of the concrete lining. The larger the elastic modulus of the inner lining material is, the smaller the radial displacement of each lining structure will be, but the circumferential stress of the inner lining will increase. In addition, when the thickness of the steel pipe lining is reduced or the internal water pressure is increased, the circumferential stress and radial displacement generated by the inner lining will increase. This analysis model and method considering the deformation coordination relationship solves the problem of setting the parameters of the lining structure and has obvious advantages in the calculation of the stress and deformation of the new composite lining water conveyance tunnel structure, which can provide a theoretical basis for related engineering design.
Shield double-layer lining structure is used to bear large internal water pressure in water conveyance tunnel engineering, but the mechanism of joint stress of structure and force transmission between linings is still unclear. In this paper, a stress calculation model of the double-layer lining structure of shield water conveyance tunnel considering the influence of transition layer between the inner lining and the outer lining is presented. By analyzing the inner lining and outer lining separately, the calculation formulas of radial displacement and circumferential stress are obtained. Then, according to the deformation coordination condition, the relationship between the inner and outer lining radial displacements is established. Thus, the magnitude of the unknown interaction force among the structures is calculated. Finally, through the stress analysis of the lining structure, the axial force, shear force, and bending moment acted on the structure are obtained. By comparing finite element calculation results with analytical calculation results, the rationality of analytical solutions is verified. Based on the proposed analytical method, the influence of inner lining thickness and material parameters of transition layer on the internal force and deformation of lining structure is analyzed. The results show that with the increase of the thickness of the inner lining, the axial force and bending moment increase, while the internal pressure shared by the outer lining decreases. The larger the elastic modulus of the transition material, the smaller the difference between the internal force and deformation of the inner and outer linings.
The internal water pressure condition influences the internal force of the circular hydraulic tunnel lining. However, calculating the lining’s internal force of this type of tunnel still lacks practical theory. Based on the modified routine method and the theory of structural mechanics, the internal stress model of the tunnel section is established in this paper. The general calculation formula of lining internal force is deduced by considering arbitrary water level height and different water conveyance pressures. The formula is used to calculate the internal force of the lining under the action of internal water pressure and the influence laws of water level height and water conveyance pressure are explored, respectively. In addition, case analysis was carried out for several typical projects. The results show that the maximum internal force of the lining increases with the increase of water pressure and inner radius and the maximum internal force is in a fixed special position when the water is conveyed under pressure. When the water is conveyed without pressure, the internal force of the lining will increase with the increased water level. However, the maximum bending moment and axial force will reduce at the special water level. This calculation theory considering different working conditions of internal water pressure solves the calculation problem of the internal force of a circular hydraulic tunnel. It improves the design theory of tunnel structure and provides a theoretical basis for this type of tunnel’s structural design and safe operation.
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