Study On Stability Decay Mechanism And Engineering Treatment Of Coal Gangue Embankment In Subsidence Area

This paper mainly focuses on the urgent technical problems of the railway special line and highway embankment in the coal-mining subsidence area of Huainan Mining Group.Using a combination of laboratory tests,inversion calculations,theoretical analysis,and numerical simulations,the stability evolution law of coal gangue embankment under complicated engineering conditions and key techniques for embankment reinforcement and treatment are studied.Based on the decay characteristics of physico-mechanical parameters of coal gangue under natural factors,the evolution law of embankment stability under the influence of natural factors,foundation with soft soil layer and mining influence is developed,the reasonable forms of section and the reinforcing method for coal gangue embankment under different mining and sinking conditions are proposed.The key technical methods for reinforcing the coal gangue embankment have very important engineering significance for ensuring the safety and stability of coal gangue embankment.The main research results and conclusions are as follows:(1)Based on the results of on-site screening test of coal gangue embankment with different weathering time,the indoor static triaxial test was carried out,and the decay law of mechanical parameters of coal gangue experienced different weathering and saturated water time was obtained.Long-term water immersion parameters of coal gangue were calculated through actual engineering inversion calculation.The results show that with the increase of weathering time,the cohesive force of coal gangue filler increases gradually,whereas,the internal friction angle decreases gradually.As the saturation time increases,the cohesive force decreases sharply,and the internal friction angle fluctuates between 30°to 32°.After long-term immersion in water,the cohesive force of the coal gangue filler decays to zero,and the internal friction angle decays to 27°.(2)In order to guarantee the stability of coal gangue embankment in subsidence area,the research on the stability evolution law of coal gangue embankment in subsidence area under complicated engineering conditions(different weathering time,different soaked time and combined with weathering and saturation,foundation with soft soil layer,mining influence)has been conducted.The results show that coal gangue embankment has the highest safety factor and the best stability after construction.With the increasing of weathering time,the weathering decay of coal gangue filler and the influence of rainfall immersion,the stability of embankment gradually decreases.The stability of coal gangue embankment with larger height and steep slope greatly reduces.The coal gangue embankment with larger height and steep slope has small safety factor and poor stability,and there are safety hazards.The physico-mechanical parameters of the coal gangue embankment is reduced during the rainy season,the stability of the coal gangue embankment cannot meet the minimum safety factor of 1.3 required by the railway subgrade specification.It is necessary to strengthen the railway embankment in the subsidence area.(3)Numerical simulations on the stability evolution law of coal gangue embankment in subsidence area under complex engineering conditions(high embankment,high water level,foundation with soft soil layer,unstable filler,overweight traffic load,and impacted by mining)were studied.The results show that when the highway embankment is 9m in high,the slope is 1:1.5 or 1:1.75,the safety factor meets the requirements of the minimum of 1.2 for normal working conditions in the design code of highway subgrade and 1.15 for the minimum safety factor of abnormal working conditions.When the railway embankment with the height less than 5m,the coal gangue decay has little impact on the railway embankment safety.With the increase of the height of the mining subsidence embankment and the decay of coal gangue,the stability of the embankment gradually decreases.When the embankment is 10 m in high,in the weathering and rainfall condition,the safety factor of foundation with soft soil layer and affected by mining is less than the minimum safety factor of 1.3 for the railway embankment,and the targeted reinforcement measures are needed.(4)Based on the theoretical analysis and numerical simulation results of the stability evolution of coal gangue embankment,combined with the application of the maintenance and reinforcement project of the soft soil foundation of the special railway line in the central area and northern area of the Zhangji Mine,the rational section form and the key reinforcing methods for the coal gangue embankment under different mining conditions and foundation conditions are proposed.The safety and stability of the coal gangue embankment was ensured.According to the stability calculation,the width of the back berm of the railway special line in North Zhangji Mine is 10?16m.The coal gangue embankment in the central area of Zhangji Mine,which is located in the high-fill and high-water subsidence area affected by mining,the soft soil foundation reinforcement method for the slipable ultra-wide back berm was innovatively proposed.The ultra-wide width is 15 m.The paper has 190 figures,107 tables,and 169 references.