Research On Fuzzy Random Reliability Of Outer Freezing Shaft Lining Structure In Deep Alluvium

With the shallow coal resources nearly exhausted in our country since 1998, the depth of coal exploitation becomes increasing. Accordingly, more and more deep freezing vertical shafts through 450m deep alluvium have been built in the central and eastern regions of China. However, safety accidents of outer freezing shaft lining have occurred frequently in the process of construction and operation, so the reliability problem has become one of the hot issues in the domestic domain of mine construction. Compared with shallow vertical shaft, the hydrological formation and geological environment of deep freezing shaft is more complex, thus making the mechanical properties of permafrost, temperature and thickness of freezing wall, freezing pressure and ultimate bearing capacity obviously uncertain. Hence, regarding deep alluvium and freezing shaft as fuzzy random force field, the paper combines the methods of the theoretical analysis, laboratory test, numerical simulation and field measurement to have the further research on reliability of outer freezing shaft lining structure in deep alluvium. It has important theoretical significance and application value to improve the scientificity of the shaft design and ensure the construction safety.The uniaxial compressive strength and creep test have been conducted on the artificial frozen clay, which leads to the effect laws of temperature and stress level for frozen clay creep. Based on this, the traditional ant colony algorithm has been optimized into fuzzy ant colony algorithm according to optimal-solution pheromone of fuzzy coefficient, hoping to increase search efficiency and avoid local optimum. It is used in random inversion for the creep compliance of the common model, then the dual factors objective function for comprehensive selection is built by taking precision and complexity into consideration, after that, the optimized model is obtained under three different stresses with appropriate fuzzy weight calculation method.According to the field monitoring results in Huainan and Huaibei mining area, the freezing pressure distribution in deep alluvium was regarded as the uneven fuzzy random force field. Therefore variation coefficient is introduced to characterize the uneven features. For both considerations of fuzzy random theory and monitoring data, fuzzy random formulas of vertical shaft freezing pressure have been obtained in clay layer and calcareous clay layer, and verified by an engineering example.On account of test results of ultimate bearing capacity of reinforced concrete shaft lining model in deep alluvium, four evaluation factors are defined as concrete compressive strength, thickness to diameter ratio, reinforcement ratio and ultimate bearing capacity. Consequently, shaft lining structures of high strength reinforced concrete are fuzzy comprehensive evaluated by the improved grey relation analysis. Based on the sample data set of shaft lining structure parameters of high strength reinforced concrete in Huainan and Huaibei mining area, the uncertainty distribution of structural materials, geometric parameters and calculation model are analyzed to get the corresponding fuzzy random distributive rules. Using triangular membership function in fuzzy sets formation, ultimate bearing capacity fuzzy random model of high strength reinforced concrete shaft lining has been set up, and proved more real and effective.Combining fuzzy random analysis of shaft freezing pressure and shaft ultimate bearing capacity, the fuzzy random limit state equation is obtained for outer shaft lining structure of high strength reinforced concrete in deep alluvium. Application of the improved center point method deduces the analytical solution for the fuzzy random reliability of outer shaft lining structure, and puts forward the fuzzy random reliability sensitivity range model of each variable. Engineering example shows that the fuzzy random reliability with characterization of interval value is more reasonable than conventional reliability method of fixed value manifestation.Constitutive relation and failure criterion of reinforced concrete material are blurred to get the fuzzy random failure function of shaft lining structure. According to the input and output fuzzy random variables, fuzzy random finite element analysis model of reinforced concrete outer shaft lining structure is established. Finally PDS system in ANSYS is used to numerically calculate the outer shaft lining structure reliability of actual engineering condition, which leads to fuzzy random finite element reliability in 95% confidence level. It turned out that the interval value of reliability is close to fuzzy random analytical value. Fuzzy random sensitivity analysis manifests that the main influencing factors to outer shaft lining structure reliability are in accordance with the order of shaft freezing pressure, concrete compressive strength and thickness to diameter ratio.