Rheological Properties And Sliding Mechanism Of Weak Interlayer In High Slope Under The Influence Of Rainfall And Blasting

With the implementation of China’s"western development"strategy,infrastructure construction has become the basis of long-term national economic development,in which limestone mineral resources are an important source of building materials for China’s infrastructure construction.Permian limestone strata are widely distributed in Southwest China,but there are multilayer gently inclined weak interlayers in this stratum.Under the influence of rainfall and blasting vibration,the rheological effect of weak interlayer is significantly enhanced,and the slope is prone to slide along the gently-inclined weak interlayer.It is very important to research on the special rheological properties and sliding mechanism of weak interlayer.This paper relies on the key project of the National Natural Science Foundation of China(Yunnan joint fund)"Research on the disaster mechanism and control theory of high mine slope containing gently-inclined weak interlayers in Yunnan region"(U1802243).Taking the high slope of Jinding limestone mine as the research object,by means of field monitoring,indoor rheological mechanics test,numerical simulation and theoretical analysis,the rheological characteristics and sliding mechanism of weak interlayer under rainfall and blasting were revealed,and the slope parameters were optimized.The specific research results are as follows:(1)The nonlinear damage evolution law of weak interlayer under the influence of rainfall and blasting were revealed.The wet and dry cycles of rainfall and blasting vibration have a significant deterioration and damage effect on the rheological properties of weak interlayer.With the increase of wet and dry cycles of rainfall and blasting vibration times,the shear strain of weak interlayer increases continuously,the fluctuation of rheological rate intensifies continuously,the long-term strength decreases gradually,and the rheological aging characteristics increase significantly.The Weak interlayer expands and softens after rainfall,and argillaceous cemented filling dissolves,and the dehydration shrinkage changes the arrangement of mineral particles and reduces the cementation degree.The blasting vibration destroys the cemented filling between the mineral particles in the weak interlayer,and the mineral particles are sheared and cut off.The combined action of rainfall and blasting forms a damage circulation system in the weak interlayer,which accelerates the damage deterioration of the weak interlayer.(2)The transition method of rock and rock mass parameters based on improved Hoek-Brown strength criterion was proposed.The cumulative damage rate of rainfall and blasting was introduced as the disturbance parameter D,and the GSI_m quantitative value table based on the integrity coefficient k _V,rock mass structure grade SR,rock mass structural surface grade SCR and structural condition factor J_C was established.The improved Hoek Brown strength criterion was obtained,and a new transition method of rock and rock mass mechanical parameters considering rainfall and blasting damage was constructed.(3)The DMANA constitutive model of weak interlayer considering the influence of rainfall and blasting was established.Based on the unified rheological mechanical model,the rheological model of weak interlayer was identified.The MANA constitutive model describing the whole rheological process of weak interlayer was established by introducing fractional order Abel element.The DMANA constitutive model was established by introducing rainfall and blasting vibration damage into MANA constitutive model.The finite difference form of DMANA constitutive model was deduced,and the secondary development of DMANA constitutive model was realized.Finally,the reliability of the constitutive model was verified.(4)The rheological sliding mechanism of mine high slope under the action of rainfall and blasting vibration was revealed.Under the combined influence of rainfall and blasting vibration,a damage circulation system is formed in the rock mass(inside the weak interlayer)of the slope with gently-inclined weak interlayer.The micro cracks produced by blasting vibration provide a channel for rainwater infiltration.The softening of the weak interlayer caused by the wet-dry cycle of rainfall makes the blasting vibration more prone to damage.The two factors are superimposed,and the damage of the weak interlayer is aggravated.In addition,the limestone load on the weak interlayer is squeezed,and the plastic breakthrough area is finally formed,which causes landslide disasters.(5)A slope parameter optimization method based on rheological sliding mechanism was proposed.The long-term rheological stability coefficient was defined,and the design safety coefficient suitable for mine slope was determined based on the principles of mine production safety and avoiding resource waste.The distance between the weak interlayer and the slope toe(final slope angle)has a great influence on the long-term stability of high slope with gently-inclined weak interlayer.Considering the slope stability and increasing the stripping ratio as much as possible,the final slope angle after optimization was determined to be 38.5°.According to the engineering geological information revealed in the actual mining,the slope parameters can be optimized and analyzed by using the slope parameter optimization method,forming a dynamic optimization analysis chain of"real-time update of mining scheme+real-time optimization calculation+real-time monitoring on-site".