| With the rapid development of national infrastructure construction,the scale of tunnel construction continues to expand.During tunnel construction,when the tunnel passes through the section of soft surrounding rock,it is easy to cause engineering problems such as overdeformation,cracking and even collapse.Therefore,it is necessary to study the mechanical characteristics of the tunnel.Based on the study and summary of the stress characteristics and deformation mechanism of soft surrounding rock,this paper,taking the railway tunnel as the engineering background,USES the laboratory test method,numerical simulation and field monitoring test to reveal the physical characteristics of soft surrounding rock,and analyzes the stress characteristics and the stability of soft surrounding rock tunnel rich in water.The main research contents include:(1)Combined with the general situation of Zijing tunnel project,the physical and mechanical properties of soft surrounding rock of Zijing railway tunnel are tested,and the indexes of weight,water content and strength of rock samples are obtained.The average weight of soft rock sample is about 22.83 kn / m3,and the water content W is 14.01% ? 18.87%,which is in a high water bearing state.When the loading rate of uniaxial compression test is 0.05mm/min,the peak deformation is 0.483 mm and the peak strength is 14.242 MPa;the cohesion value of rock samples is determined to be C = 3.8 MPa and the internal friction angle is ? = 41.3 ° in the triaxial compression test.(2)Based on the characteristics of stress analysis and the deformation mechanics mechanism of the surrounding rock of the tunnel,based on the combined arch theory,the bolt-Shotcrete supporting parameters of the tunnel structure were analyzed and calculated,and the secondary lining design and propulsion support design were carried out.(3)The finite element software MIDAS/GTS was used to establish the numerical calculation model of the soft surrounding rock of The Zijin Railway tunnel,and the deformation regularity and distribution of the vertical displacement and horizontal displacement of the surrounding rock along with the tunneling step,as well as the mechanical characteristics and distribution of the stress of the surrounding rock and the shotcrete bolt along with the tunneling step during the construction process were analyzed.(4)The field test and analysis are carried out on the surrounding rock stress,vault settlement,clearance horizontal convergence deformation,steel frame stress and secondary lining concrete stress of Zijing tunnel.The monitoring results show that the vault settlement variable is 4.5 mm,the horizontal convergence deformation is 0.33 mm,and the vault settlement is far greater than the horizontal convergence.The maximum pressure of measuring point 1 is 600 k Pa.The maximum pressure at the right arch waist reaches 350 k Pa,and the maximum pressure at the arch foot of the right inverted arch reaches 300 k Pa.After a period of time,the change of each measuring point tends to be gentle.(5)The fuzzy comprehensive evaluation method is applied to evaluate the surrounding rock grade of Zijing tunnel.The hierarchical analysis method is used to analyze and adjust the index of each factor,determine the classification standard of each factor index,establish its corresponding membership function,and determine the corresponding fuzzy weight according to its different influence on the surrounding rock grade of the tunnel,and finally establish the fuzzy comprehensive evaluation model of tunnel surrounding rock classification,and carry out the safety evaluation of surrounding rock stability of Zijing tunnel.This paper consists of 67 figures,32 tables and 79 references... |
PDF Full Text Request