Research And Application Of Rubber Shotcrete For Roadway Under Complex Environment

With the increasing depth of coal mining,the complex surrounding rock environment has brought severe challenges to the roadway support engineering.Based on the "double carbon" target background and the concept of flexible support,this paper proposes to add industrial waste rubber and fiber into shotcrete.Hybrid-fiber reinforced rubber concrete(HFRRC)with high ductility is developed by orthogonal experiment method.Aiming at the mine service conditions of sulfate corrosion,high ground stress and mining disturbance,the physical and mechanical performance,fatigue performance and creep behavior of shotcrete are studied.Based on Gubei Coal Mine in Huainan and Xinhu coal mine in Huaibei,the engineering application and the analysis of economic and environmental benefits are completed.The main research contents and results are as follows:(1)Based on four factors and three levels orthogonal experiment,rubber particle size,rubber substitution rate,basalt fiber content and polyvinyl alcohol fiber content were selected as the test factors.And the compressive strength,splitting tensile strength,flexural tensile strength,ductility index,pore structure and micro morphology of rubber shotcrete are chosen as evaluation indexes.The influence of various factors on the performance of rubber shotcrete is analyzed.Comprehensively considering various performance indexes,the optimal proportion of shotcrete is obtained as the basis of subsequent experimental research.(2)The sulfate corrosion environment was simulated by two erosion methods:natural soaking and dry-wet cycle.The apparent performance,physical and mechanical performance and the micro-structure of ordinary shotcrete(OC)and hybrid-fiber reinforced rubber concrete(HFRRC)exposed to different erosion ages were tested and analyzed.The results showed that HFRRC has stronger sulfate resistance than OC.When exposed to the same erosion age,the deterioration degree of shotcrete specimens exposed to the dry-wet cycle is higher than that exposed to natural immersion.The deterioration of shotcrete specimens in natural immersion mechanism is dominated by the consumption of sulfate ions on cementitious substances in cement matrix.The deterioration in the dry-wet cycle mechanism includes the combined effect of sulfate crystallization and chemical erosion,which can better reflect the actual environment of the project.(3)Fatigue performance of OC and HFRRC in sulphate environments were studied.The fatigue strength,fatigue deformation and energy evolution characteristics were analyzed by cyclic loading-unloading test.The results show that the fatigue failure stress of shotcrete specimens is always lower than the uniaxial compressive strength exposed to sulfate environment.With the increasing exposure time,the fatigue strength and fatigue coefficient decrease while the fatigue deformation increases.During the same exposure time,fatigue deformation and energy density increase with the increase of loading level,the proportion of dissipative energy shows a trend of first decreasing and then rising,and the sharp increase of dissipative energy indicates the occurrence of fatigue destruction.Compared with ordinary shotcrete,HFRRC has higher fatigue resistance coefficient and slower deterioration rate of fatigue strength with erosion age.It has better integrity under the coupling of sulfate erosion and fatigue loads.(4)The creep behavior of OC and HFRRC exposed to sulfate environment was studied.The evolution of creep deformation,creep rate and long-term strength was analyzed by by multistage creep test.The results show that the creep failure strength of shotcrete under long-term load is lower than that under monotonic load,and the gap increases with the increasing sulfate attack time.Under the same loading stress,the instantaneous strain and creep strain of shotcrete specimens increase with the increasing sulfate attack time,while the creep failure stress and creep duration decrease.The sensitivity of creep parameters to stress increases significantly with the increase of sulfate attack time.At the same erosion time,the instantaneous strain of shotcrete specimen increases approximately linearly with the increase of stress.The creep strain fluctuates at low stress level and increases sharply near the failure stress,showing nonlinear variation characteristics.The ratio of creep strain to total strain(including instantaneous strain and creep strain)decreases first and then increases.The stress at the inflection point can be used to represent the critical stress of creep failure.(5)Based on statistical mechanics,damage mechanics,and rheological mechanics,the shotcrete exposed to sulfate erosion is regarded as the first damage state.The damage factor of sulfate attack effect is defined by relative wave velocity,the fatigue damage constitutive model and creep model of shotcrete considering sulfate attack effect are established.The results show that the proposed model can well describe the fatigue performance and creep behavior of shotcrete exposed to sulfate environment.It can be used to predict the fatigue deformation and creep behavior of shotcrete under sulfate environment.(6)Relying on the Project of Gubei Coal Mine in Huainan and Xinhu Coal Mine in Huaibei,the hybrid fiber reinforced rubber concrete was carried out on site.The results show that the HFRRC has a good role of pressure relief and support.It can effectively uniform the stress distribution of surrounding rock by adjusting the structural,and reduce the stress and deformation of support structure.Compared with the roadway supported by ordinary shotcrete,the surrounding rock pressure of the roadway supported by HFRRC is reduced by about 20%,and the convergence deformation of the roadway is reduced by about 15%.The application of HFRRC plays a positive role in reducing the cracking phenomenon in the shotcrete layer of roadway in high stress area,so as to reduce the rework and maintenance cost in the operation.At the same time,it can realize the recycling of waste belts in mine transportation,which has outstanding economic and environmental benefits.Figure [98] table [26] reference [201]...