Study Of Cusp Catastrophe Modle And Criterion For The Burst Failure Of Roadway Floor

Roadway floor burst is a common type of coal and rock dynamic disaster,which is a threat to safety production.In this paper,the effects of horizontal stress,physical and mechanical parameters on floor burst failure are analyzed,and the mechanical criterion is obtained.Based on catastrophe theory,the cusp catastrophe model of roadway floor is established,and the catastrophe criterion of roadway floor burst is obtained.Based on the influence of horizontal stress and displacement parameters of roadway floor on the catastrophe state in the model,four dangerous grades of floor burst are divided.By changing the physical and mechanical properties and the way of controlling the stress level in surrounding rock,the technical measures for roadway floor burst control are put forward and applied in engineering practice.The main conclusions are as follows:(1)The influence rule of floor horizontal stress and lithology on roadway floor failure is analyzed.The mechanical mechanism and critical condition of roadway floor failure are obtained.It is concluded that the horizontal stress in the roadway floor is superimposed by the original horizontal stress,the structure horizontal stress and the support stress of the coal body.When the stress of floor exceeds the critical horizontal stress,it will cause the floor failure.(2)The bending structure potential energy of floor rock,which is formed by the cohesion between inner layer and outer layer,is equivalent to the form of sine function.The potential energy catastrophe model of roadway floor burst is established.The evolution rules of the floor burst instability in the catastrophe model are analyzed,and the mechanical model of floor burst is analyzed based on the point mutation theory,finally the necessary and sufficient condition for the floor burst is obtained,(?)Based on the analysis of the main factors affecting the floor burst,the floor burst recognition surface is obtained which is composed of the roadway width a,the elastic modulus E and the horizontal stress ?x of the floor.The failure state of roadway floor can be divided into a stable equilibrium and a catastrophic punching zone.The influence of the three main control factors on the failure state indicates that when the roadway width keeps a,the critical horizontal stress of the roadway burst failure increases with the increasing modulus elasticity E;and when the elastic modulus of roadway keeps E,the critical horizontal stress of the roadway burst failure reduces with the increasing roadway width.(3)Based on the critical condition of roadway floor burst failure,the FLAC3D numerical model is constructed to analyze the interaction relationship between the floor displacement and three parameters,which are the roadway width a,the elastic modulus E and horizontal stress ?X of roadway floor.Under the critical condition of the roadway floor burst failure,the floor displacement shows negative correlation with the floor width and positive correlation with the elastic modulus.(4)Based on the catastrophe criterion of the roadway floor failure and the relationship between the various control parameters,the 3D surface model and recognition criterion of the burst hazard are obtained,which contain the horizontal stress,displacement and elastic modulus of floor.The recognition surface model is divided into four kinds of risk zones to identify the roadway floor hazard,which are non risk,weak risk,medium risk and strong danger,respectively.Using the methods of MS monitoring,CT inversion and drilling monitoring,the stress level of the roadway surrounding rock in the 1307 working face in Guojiahe Coal Mine is measured and analyzed.According to the 3D recognition surface model and the identification criterion of the burst hazard in the roadway floor,the burst hazard in the roadway floor is identified.Based on the main control factor,the method of stress release is carried out and the floor burst risk is reduced effectively.