Model Test Research On The Distribution Law Of Water Pressure Upon Lining And The Stress Characteristics Of Lining Structure In Subject To Subsea Tunnel

With the development of the social economy, our country will have to construct several subsea tunnels in the next several years. It is ineviTab.meeting many problems while people construct tunnels under the sea with the constant high hydraulic pressure. The high valuable problems are the setting of waterproof and drainage system, the value of the water pressure acting on the lining structure, the characteristics of the lining structure in coupled field with the interaction of water load and soil load. Considering the first subsea tunnel by drilling and blasting method in China mainland——subsea tunnel on Xiamen Xiang'an as the engineering background, using model test for the major research method, combined with other methods, such as the theoretical calculations, the numerical simulation analysis and so on, this thesis has made research on the distribution law of water pressure upon lining and outer surface of grouted ring, and the stress characteristics of lining structure in stress filed, seepage filed and coupled filed. Major research results are as follows:(1)Based on the study of the similar theory and the principles of model test, the similar criteria in stress filed, seepage filed and coupled filed, the theory analysis formula of the water pressure at outer surface of grouted ring and lining back in case of highway tunnel waterproof and drainage style are deduced. The relationship between the water pressure on lining back and the permeability coefficient of the surrounding rock, the permeability coefficient and the thickness of the grouted ring, the controlled drainage volume are analyzed in practical engineering.(2)Using the model test system researched by Tunnel &Underground Engineering Test Research Center, and the Fiber Bragg Grating Strain-testing System, as the tunnel project S5d in the strong decomposed bag F4 for the prototype, the distribution law of the water pressure at the outer surface of the grouted ring and the lining back in the process of the entire plugging, limited drainage and increasing the water load are researched. The law of water pressure reduction by grouted ring is attained. The model test in stress filed, seepage filed and coupled filed are carried out.(3)Using the concept of water pressure action coefficient, the distribution and change law of the water pressure at the outer surface of the grouted ring and the lining back were vividly illustrated. The distribution of the water pressure at the outer surface of the grouted ring approximates a circle. The distribution of the water pressure at the lining back approximates a calabash. The setting of ring blind pipe is advantageous to the structure.(4)By the precise date collected by the FBG, the deformation characteristics and the stress change law of the lining structure in stress filed, seepage filed and coupled field are attained. The runnel structure is the most disadvantageous in the coupled field, next is in the seepage field, and finally is in the stress field. The most unfavorable part of the tunnel structure is the inner surface of the invert, next is outer surface of the arch foot, and finally is in the inner surface of the vault crown. For design the tunnel structure, the water load is the main load.(5)The stress of the tunnel structure is in proportion to the groundwater static water head approximately. In the process of the limited drainage, with the increasing of the displacement, water pressure action coefficient decreases, the safety coefficient of the tunnel lining structure increases, the stress of the lining structure decreases. The groundwater seepage flow changes the structure of the soil, so the seepage body force and the seepage pressure act on the lining structure, the stress increment of the tunnel structure is produced. So for acting on the lining structure, the influence of the coupled field is more than the superposition influence of the stress field and the seepage field.(6)Combined with similar theory and the characteristics of the model test, the similar criteria of returning to engineering prototype, the formula of the stress and the internal force of the lining structure are deduced. Finally the safety factor of the lining structure in the stress field, the seepage field and the coupled field are attained.