Study On The Mechanical Properties And Design Theory Of The Functionally Graded Shaft Lining

There is gold in the deep earth and energy in the deep sea,and marching to the deep part of the earth is a strategic scientific and technological problem that we must solve.With the gradual depletion of shallow mineral resources,resource development continues to move deeper into the earth,and mineral extraction is developing in the direction of deepening and massification.The depth of mining is increasing,and the thickness of shaft wall required for the traditional form of shaft wall support in kilometer-deep mines is too large,and the bearing capacity of the outer shaft wall cannot be fully utilized.This paper proposes a multi-layered functional graded lining(N-FGL)structure,applying the idea of functional gradient material to the design of deep buried thick-walled concrete cylinders,by changing the radial concrete material of the well wall,so that the radial concrete modulus of the well wall changes in a gradient,thus changing the internal stress distribution of the well wall,reducing the stress concentration on the inner side of the well wall,realizing the radial structure of the "Flexible Let Pressure ",improve the bearing capacity of the well wall structure,give full play to the performance of the outer concrete material,and make the well wall structure reach the optimal design.This paper takes multi-layered functional graded lining as the research object,through theoretical analysis,numerical calculation and numerical simulation,combined with indoor specimen test and physical model test,the mechanical properties of FGL,the method of model test,functional gradient concrete materials are studied,and the design theory of N-FGL is proposed and the corresponding structural design software package is developed independently.The main work and research results of this thesis are as follows.(1)Based on the elastic mechanics and concrete multi-axis damage criterion,the mechanical properties of functional gradient vertical well walls were theoretically analyzed and numerically calculated using MATLAB,and the influence laws of structural parameters and gradient distribution functions of FGL on the mechanical properties were obtained.The results show that the main factors affecting the ultimate bearing capacity of the structure are the concrete compressive strength,the thickness-to-diameter ratio,the Poisson's ratio,the number of layers,and the change in elastic modulus;the main factors affecting the maximum circumferential strain at the inner edge of the well wall during damage are the elastic modulus,the concrete compressive strength,the thickness-to-diameter ratio,the Poisson's ratio,the number of layers,and the change in elastic modulus.The main factors affecting the maximum circumferential strain of the wall are the modulus of elasticity,compressive strength of concrete,thickness-to-diameter ratio,Poisson's ratio,number of layers and the change in modulus of elasticity.The tangential stress at the inner edge of the well wall decreases with the increase of the thickness-to-diameter ratio,number of layers and the variation constant of the elastic modulus;the circumferential strain at the inner edge of the well wall decreases with the increase of the thickness-to-diameter ratio,elastic modulus and Poisson's ratio;the circumferential strain at the inner edge of the well wall increases with the increase of the number of layers and the variation constant of the elastic modulus;the ultimate bearing capacity of the well wall increases with the increase of the thickness-to-diameter ratio,compressive strength,Poisson's ratio,number of layers and the variation constant of the elastic modulus.The maximum tangential strain increases with the increase of elastic modulus,compressive strength,Poisson's ratio,number of delaminations,variation constant of elastic modulus and thickness-to-diameter ratio.Unlike the damage pattern of homogeneous well walls,the occurrence of damage in FGL depends on the occurrence of damage at the inner edge of each layer of the lining.Changing the modulus of elasticity can effectively reduce the stress concentration in the inner side of the well wall and improve the bearing capacity of the wall.Under the typical function,the order of significance of the influence of each factor on the ultimate bearing capacity of FGL from primary to secondary is concrete compressive strength,thickness to diameter ratio,modulus of elasticity,and number of FGL stratification;under the general function,the order of significance of the influence of each factor on the ultimate bearing capacity of the FGL from primary to secondary is well wall thickness to diameter ratio,number of FGL stratification,concrete compressive strength,modulus of elasticity change constant,and the outermost elastic modulus of the lining.(2)ABAQUS was used to numerically simulate the real physical model test environment.The axisymmetric structure with 1/12 model was efficient and the results were more accurate,and the influence law of four test factors on the test results of the well wall model was analyzed.The results show that the axial pressure loading method has almost no effect on the calculation results of ultimate bearing capacity of the well wall,and has a slight effect on the radial displacement and circumferential strain when the well wall is damaged;the axial pressure has no significant effect on the radial stress distribution and circumferential stress distribution in the middle section of the well wall;the test bench has the same range of influence on the end of the well wall structure under different axial pressures;the increase of axial pressure will increase the bearing capacity of the well wall structure,and the corresponding radial displacement and circumferential strain when it is damaged.The radial displacement and circumferential strain on the inner side of the well wall increase accordingly;the well wall is first damaged at both ends of the well wall under the action of axial pressure,and as the axial pressure continues to increase,the damage occurs in the middle of the outer side of the well wall,and then begins to expand to the inner part of the well wall;the range of influence of the test bench on the end of the well wall structure is approximately the same under different friction coefficients;the height-to-diameter ratio of the well wall has a great influence on the test results,and the larger the height-to-diameter ratio,the greater the influence of the end effect on the well wall structure.The larger the ratio,the smaller the effect of the end effect,generally take the wall height to diameter ratio greater than 1.5 can better meet the test requirements.(3)Through the indoor concrete mechanical properties test,the functional gradient concrete formulation test was carried out,and the influence law of fiber type,fiber admixture and sand rate on the mechanical properties of concrete was obtained,and the functional gradient concrete material formulation was initially explored.The results show that the degree of influence of three factors on the cubic strength,prismatic strength and elastic modulus of fiber concrete are all ranked as sand rate>fiber admixture>fiber type;the optimal combination of three factors for cubic strength and prismatic compressive strength is: basalt fiber,fiber admixture of 0.3%,sand rate of 35%;the optimal combination of three factors for elastic modulus is:polypropylene fiber,fiber admixture of 0.3%,sand rate of 35%;the optimal combination of three factors for elastic modulus is: polypropylene fiber,fiber admixture of 0.3%,sand rate of 35%.With the increase of fiber admixture,the strength and modulus of elasticity of fiber concrete are increasing and then decreasing,and with the increase of sand rate,the strength and modulus of elasticity of fiber concrete are decreasing and then increasing;the compressive strength and modulus of elasticity of fiber concrete are not in a single linear relationship,and the fiber concrete with the same compressive strength and different modulus of elasticity can be obtained by changing the fiber admixture and sand rate;the admixture of Steel fibers can effectively improve the strength of concrete,the increase in elastic modulus is not obvious after the amount of more than 1%.(4)Through the similar modelling design,physical model test was carried out,and the FGL fabrication technology was proposed,the FGL force deformation law was obtained,and it was found that the physical model test results were less different from the theoretical results.Based on the theoretical research results,the structural design method of FGL was established,and the functional graded lining design software was developed using MATLAB App Designer to provide technical support for the design and promotion of functional graded lining.This paper is an advanced exploration of the functional gradient shaft wall structure,and the research results are of great significance for the implementation of the national strategy of "marching deeper into the earth" and the construction of future super-kilometer deep mines.The thesis has 106 figures,43 tables,and 140 references.