Study On Cumulative Damage And Drainage Reinforcement Technology Of Dry-wet Freeze-thaw Blasting In Seepage Soft Rock Slope

Under the long-term repeated action of seepage and blasting vibration,the soft rock slope of large open-pit mine is prone to shallow landslide.Although the disaster-causing ability of shallow landslide is weak,it will affect the safety production management because of its scattered location and undetectable omen.In order to reduce the damage of seepage and blasting disturbance to shallow soft rock slope and improve the stability of seepage soft rock slope in open-pit mine,the damage mechanism and prevention and control methods of soft rock slope under dry-wet cycle,freeze-thaw cycle and blasting vibration were studied.The research results have important theoretical and practical significance for improving the stability of the seepage soft rock slope,and can be extended to guide the seepage soft rock slope treatment of similar mines.In this thesis,theoretical analysis,laboratory test,field test,numerical simulation and engineering verification were combined to study the damage of soft rock slope caused by dry-wet cycle,freeze-thaw alternation and blasting vibration.The damage law of soft rock under dry-wet and freeze-thaw conditions of seepage was obtained,and the damage characteristics of seepage soft rock after blasting vibration were studied.Finally,the inclined drainage technology was proposed.The main research results are as follows :(1)In order to study the nonlinear creep damage problem of water-permeable soft rock,based on the classical Burgers model,the nonlinear viscoplastic mechanical element is introduced to establish the dry-wet cycle creep damage mechanical model of water-permeable soft rock.The nonlinear mechanical damage characteristics of water seepage soft rock under dry-wet cycle are studied,and the influence of dry-wet cycle time on creep damage of soft rock is revealed.The research shows that the soft rock has obvious creep damage under the dry-wet cycle.With the extension of the action time,the creep amount shows the characteristics of rapid growth in the early stage and slow progress in the later stage.In addition,through the indoor disintegration test of dry-wet cycle,it is found that the disintegration rate of soft rock increases with the increase of the number of dry-wet cycles,and has the damage law of rapid disintegration in the early stage and slow disintegration in the later stage.In addition,the study also shows that there is a positive correlation between the disintegration rate and the block volume of the test sample.Finally,through the analysis of the deformation time history curve of the field slope in the rainy season,under the action of dry-wet cycle after rain,the surface displacement of the seepage soft rock slope has the characteristics of violent fluctuation in the early stage and gentle fluctuation in the later stage,but the shallow deformation of the seepage soft rock slope has the characteristics of cumulative increase.(2)In order to study the damage problem of seepage soft rock at low temperature,a mechanical model of freeze-thaw alternating creep damage of seepage soft rock at low temperature is established by introducing a temperature-controlled nonlinear viscoplastic mechanical element.The mechanical damage characteristics of seepage soft rock under the coupling action of dry-wet and freeze-thaw were studied,and the creep damage law of seepage soft rock in winter was obtained.The research shows that although the creep damage caused by freeze-thaw alternation to soft rock is similar to the damage law of dry-wet cycle,the creep damage under freeze-thaw alternation damage is more intense.Through the indoor disintegration test of freeze-thaw alternation,it is obtained that the disintegration rate of soft rock caused by freeze-thaw alternation is 9 times more serious than dry-wet cycle under the same number of cycles,and the stable inflection point of disintegration rate of freeze-thaw alternation is earlier than that of dry-wet cycle for 4-5 cycles.In addition,through the study of the surface displacement data of the water seepage soft rock slope during the freezing and thawing period,it is obtained that the deformation of the water seepage soft rock slope lags behind the freezing and thawing time,and the shallow fracture layer of the water seepage soft rock will form an inert protective layer,which will slow down the freezing and thawing damage and deformation response of the rock mass surface.(3)In order to study the damage problem of water-permeable soft rock under blasting vibration,based on the creep damage mechanics model of dry-wet cycle and freeze-thaw alternation,the periodic function of blasting vibration load is introduced,and the damage mechanics model of water-permeable soft rock under blasting vibration load is established.The damage law of water-permeable soft rock under periodic load stress is studied.The research shows that the blasting vibration load will aggravate the damage of dry-wet cycle and freeze-thaw cycle to the rock mass.Under the sine wave periodic load of blasting vibration,the seepage soft rock is subjected to strong periodic cyclic load in milliseconds.At this time,the damage of seepage soft rock has been developed from creep damage to fatigue damage.(4)Through the analysis of the cumulative damage theory of micro-crack propagation of rock under blasting vibration,the theory of water seepage channel and the influence of water on the loss of blasting energy propagation path,the damage law of soft rock under the coupling of dry-wet cycle and blasting vibration and freeze-thaw alternation and blasting vibration is obtained.The study shows that blasting causes crack expansion in soft rock.On the one hand,the expansion of cracks weakens the strength of rock,on the other hand,it provides space for the migration and storage of water seepage.In addition,when there is water or ice in the rock mass,the loss of blasting vibration energy in its propagation path will be reduced,and the rock fragmentation ability of blasting will be enhanced.Therefore,under the coupling effect of seepage and blasting vibration,the damage of soft rock will be aggravated.(5)The seepage water source of the soft rock slope in the open-pit mine in the arid area first enters the slope rock mass through the underground seepage channel,and then seeps out of the slope surface through the cracks of the shallow rock mass of the seepage soft rock slope which is coupled and cumulatively damaged.In the case of sufficient water storage in the back rock mass,the seepage volume of the seepage soft rock slope is determined by the degree of coupling damage it bears.Through the calculation of the coupling damage range of the shallow rock mass of the seepage soft rock slope,the perforation parameters and the hole arrangement of the inclined drainage can be obtained.By using the inclined drainage technology,it can effectively reduce the water content in the shallow range of the seepage soft rock slope,reduce the cumulative coupling damage of the seepage soft rock under dry and wet,freeze-thaw and blasting,enhance the strength of the seepage soft rock mass,and improve the stability of the seepage soft rock slope.