Study On Mechanical Properties Of Composite Lining Of Agricultural Diversion Tunnel With Sprayed Waterproofing Membranes

Agricultural water diversion and irrigation projects have greatly improved the uneven spatial and temporal distribution of water resources in China and the limitation of insufficient water resources on agricultural development.During the"13th Five-Year Plan"period,China has built a large number of water conservancy projects to continuously improve the agricultural water supply and water-saving capacity,strengthen the system of China’s backbone water conservancy facilities,and consolidate the agricultural foundation.In the future,the country will continue to accelerate the construction of water-saving water conservancy projects.In the agricultural water conservancy project,the agricultural diversion tunnel plays an important role in the optimal allocation of water resources,but the seepage and water leakage of the diversion tunnel is a difficult problem that has long troubled the engineering field.At present,the traditional waterproofing type of diversion tunnel has many disadvantages.With the application of spray film waterproofing technology,the development of compound lining structure of agricultural diversion tunnel is also a great innovation.Nowadays,although spray film waterproof technology has been successfully applied in some underground structure projects,the role of composite structure has not been fully considered in the design,mainly because the research on mechanical properties,design principles and numerical simulation methods of composite lining structure is not in-depth enough.This article relying on Jiangxi province in northern new pumped-storage power station,the in-situ survey,theoretical analysis,numerical simulation,the method of combining the spray membranes are reviewed in this paper waterproof technology application in underground engineering,explores the spray membrane water diversion tunnel of numerical analysis method,studies the agricultural water diversion tunnel composite lining structure stress deformation characteristics and optimization of structural design,the main research contents and results were as follows:（1）According to the structural design code of agricultural diversion tunnel and related theories of material mechanics,the waterproof membrane can avoid cavity,fall off,puncture,bad lap and squeeze the damage of damage in the process of construction,determine the composite lining structure stress distribution at cross section of law,the traditional water diversion tunnel of composite lining structure similar to composite beam stress,spray membrane water diversion tunnel due to the waterproof membrane has double-sided adhesive composite lining is similar to the finite element stress,and stress distribution characteristics of different structure between the layers by waterproof membrane interface characteristics and complex degree of size effect is obvious.（2）Based on finite difference software FLAC^3D discontinuity analysis theory,the introduction of FLAC^3D built-in contact elements of headrace tunnel composite lining structure,to simulate the layer between the waterproof layer and the waterproof layer can simulate reliable in structure of interlayer compressive stress,shear stress and shear stress,and can reflect the early,the waterproof layer and of the interaction between the second lining,prove that combined lining contact elements to simulate the discontinuous deformation is effective and feasible structure layers and the spray for membrane water diversion tunnel composite lining structure mechanical properties research provides a new way of thinking.（3）The FLAC^3D is adopted to establish the water diversion tunnel simulation model based on the engineering practice,reflects the waterproof membrane in the numerical simulation in a composite lining structure can pass the compressive and tensile stress and shear stress,the double layer produced by bonding shear capacity to a certain extent between early constraints and the relative sliding of second lining,make greater coordination between the different structural layer the stress and deformation,thus improve the bearing capacity of composite lining structure;Moreover,the composite lining structure of the sprayed film waterproof diversion tunnel can bear greater load on surrounding rock and release more stress on surrounding rock,which can better reduce the displacement and deformation of surrounding rock and improve the stability of surrounding rock.（4）According to the research of diversion tunnels under 18 different working conditions,the application range of water-jet film and waterproof diversion tunnels has been expanded to a certain extent.The results show that the reasonable reduction of composite lining thickness has no obvious effect on the deformation of surrounding rock,and has no effect on the safety of composite lining structure.Therefore,in the design of composite lining structure of spray film waterproof diversion tunnel,it is necessary to consider appropriately reducing the thickness of composite lining according to the engineering conditions to optimize the structure design,which can not only reduce the amount of tunnel excavation,but also save building materials,so as to greatly save the cost of excavation and support of diversion tunnel and improve economic benefits.