Study on the evolution and prediction of stratified burst in hard rocks based on disturbance and interlayer interaction
Aimed at the insufficient research on the stratified blasting in engineering rock mass,and in view of the stratified blasting phenomena in field and in laboratory,the evolution of the stratified blasting in hard rock was analyzed,the evolution model of the stratified blasting was established,the re-lease force of the stratified blasting was defined.Considering the engineering disturbance and inter-strata relationship,and coupled with the evolution of stratified blasting layer before and after tunnel excavation,thereby the prediction models of stratified burst were established under the evolution process,and the necessary and sufficient conditions of stratified blasting were determined.The results in-dicated approximate consistency between the theoretical analysis and the real engineering case,and the proposed prediction model and the preconditions of stratified burst pronounced reasonability and adapta-bility.Take the relationship among unloading-caused tension,engineering disturbance and inter-strata re-lationship into the consideration,then the formula of bursting releasing force during the evolution process of stratified burst was obtained.The first layer of stratified burst could be the key layer of rock burst,controlling of the key layer was vital for the controlling of chain-linked stratified burst,and the strength-ening of key stratum played a key role in controlling the stratified burst.According to the energy evolu-tion,the formula of layers'number at the moment of stratified burst for engineering rock mass was ob-tained.Under the same condition,the tendency of stratified burst in hard rock was higher and more lay-ers could be produced.The critical load,minimum value and critical thickness-to-length ratio were de-fined when the stratified burst occurred in engineering rock mass.With the decrease of the thickness-to-length ratio,the critical stress decreased obviously,and the critical thickness-to-length ratio tended to decrease as the vertical stress decreased.Considering the engineering disturbance and the inter-strata rela-tionship,both of the tendency and the scope of the stratified burst could be higher and wider,which was in line with ac-tual cases.The key layer theory of stratified burst controlling was put forward,the proba-bility of occurrence for stratified burst and burst layers could be lowered by deploying dense-distributed and pre-stressed short bolts,which facilitated the formation of bolted combined beam,thereby new key layer determined by the depth of the bolted zone could be created.
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维普
