Fractured Rock Mass Strain Softening Damage Constitutive Model And Application In The Soft And Broken Roadway

As the continuous in-depth development of coal mining, the ground stress decreases, engineering and geological environment has become extremely complex and worse, the joints and cracks begin to develop gradually, rock mass deformation modulus and various mechanical parameters decrease, strain-softening phenomenon of rock mass is increasingly obvious, the roadway surrounding rock becomes soft and broken, the roadway is extremely difficult to support. To effectively maintain the stability of soft and broken roadway surrounding rock, it is necessary to do further study of the failure mechanism of soft and broken surrounding rock, the research results can provide reasonable suggestions for supporting.In order to study engineering and geological characteristics of the soft and broken roadway surrounding rock, this paper starts with the cracks. According to the field observation of joints and cracks, the observation data is processed by statistical mathematics methods to determine cracks permeability tensors. Because of the existence of cracks in surrounding rock of roadway, crack rock mass is viewed as the continuum of damage, the expansion of cracks cause damage evolution. Consideration of post-peak strength softening, the huge amount of cracks growth, according to damage mechanics and fracture mechanics, crack rock mass initial damage and damage evolution constitutive equation is obtained. Based on FLAC3D, in VC++development environment, fractured rock mass strain softening damage constitutive model is developed. Respectively by using the strain softening model and custom constitutive model for numerical simulation of a numerical example, surrounding rock deformation, plastic zone distribution and safety coefficient of the two models were analyzed, to validate the rationality of the model. The impact of crack length and crack angle on the stability of surrounding rocks was researched by means of numerical simulation, the results show that, the plastic zone and displacement increase first and decrease afterwards with the increase of crack angle, there is a most disadvantage angle, under this angle, the surrounding rocks is the most dangerous. Along with the increase of crack length, the deformation and plastic zone of roadway surrounding rock is increased obviously.Taking a practical engineering as an example, the custom constitutive model is applied to the stability analysis of-590alleys under the working face. By computer simulation, we analysis and study the law of surrounding rock stress, displacement and plastic zone distribution characteristics, the study indicates that combined support scheme of anchor cable spray and cable with grouting can effectively control the deformation and failure of roadway.The research results of theoretical analysis and numerical simulation are applied to soft and broken surrounding rock and field observations indicate that the good effect of supporting. The simulate result is roughly consistent with Observation of the deformation. The custom constitutive model can provide reasonable guidance for engineering practice.