Theory Analysis Of Composite Slope Deformation And Instability Mechanism And Key Factors Optimization

This thesis conducts a research on the Formation and deformation mechanism of Composite slope in surface mining.The deformation of the slope is dominated by the vertical action of the rock mass self-weight and the effect of surcharge due to the dump load.The work acknowledges that the ground stress and displacement induce by loading and excavation during the process of Surface mining are critical for safety and the production of the mineral resource.According to the dynamic development characteristics of a composite slope,the slope structure remains in a dynamic state and with continuous advancement in mining depth and increase in dumping height results in a dynamic slope condition that is critical to the safe operation of a surface mines.Hence on the basis of the engineering process of excavation and surcharge,the calculation formula of composite slope computational angle,the calculation formula of stresses due to dump progressive loading,and the computational equation for the depth of the zone of active wedge beneath the dump which relates the stresses due to the dump loading to the surface area of a composite slope is deduced.From the composite slope computational criteria it is seen that there exist a functional relationship between the various geometrical parameters of a composite slope to the composite slope overall angle as that the depth of active wedge Z reduces along the slip reference plane as the dump is moved away from the edge of the slope.The work further establishes the relationship between the loading conditions and the geometrical parameters of a surface mines slope on the induced stress field and factor of safety of a composite slope by means of analytical and numerical simulations.The results from numerical simulation shows that the increase in slope height and angle results in an increase in stress within the geo-stress field of a composite slope and the settlement induced by the dump loading is larger beneath the dump and decreases away from the point of application.This highlights the sensitivity in simulating the effect of the waste dump at different position when computing slope stability analysis which is often ignored in all 2-dimensional limit equilibrium analysis when the dump does not load the sliding surface.The thesis also establishes the influence rule of the key geometrical parameters of a composite slope on the factor of safety.The result illustrates that these parameters are key factors influencing the stability of composite slope and their interaction and coupling effect can either improve the factor of safety or greatly decreases it.It is seen that an inverse selection between the slope height and slope angle presents a higher factor of safety than when both parameters are high.When the slope angle and excavation depth are couple with a loading such as that of a waste dump,the factor of safety further reduces but a suitable dumping position can prove vital to enhancing stability.The primary cause of this phenomenon is such that the stresses induced by the waste dump decreases as the dump is moved away from the crest of the slope and the stress induced within the zone of active wedge beneath the dump reduces on the reference slip plane.Furthermore,the result shows that the improvement in the factor of safety as the dump is move away from the critical sliding surface is defined by the area of a parallelogram whose base is equivalent to the distance move and its height and angle is determined by the waste dump.Hence,from the result,the position of the waste dump in the formation of a composite slope plays a key role in enhancing stability.The stress,which derives from repeated excavation and dumping on weak layers,brings about unbalanced stress unloading within a weak layer and promotes the development of deformation on weak layers.Thus,according to the weak layer mechanical model and strength parameters,the effect of the weak layer angle and thickness on soft rock slope is determined,and by means of numerical simulations,the influence rule of the weak layer on the development of soft rock slope is reveal.The result shows that the weak layer angle and thickness are key factors with adverse effects on the stability of composite slope.On the basis of the weak layer influence rule,a comprehensive analysis of the dumping conditions at Shengli surface coal mines was conducted and on the basis of numerical simulations,the factor of safety for different dumping position along with the most critical dumping distance of d(28)300m is obtained.The research provides a guiding role in understanding the influence of the key geometrical parameters of a composite slope on the factor of safety and the induced stress field during the development of a surface mines.Finally,a well design composite slope plays a critical role affecting the total cost of a surface mining operation.