Research On The Mechanical Behavior Of Opening Model With Typical Cross-section Under Biaxial Servo Loading

As an important part of hydraulic engineering construction,the stability of surrounding rock of cavern is paid more and more attention.To explore different opening shape cavern excavation at various stages in the process of the surrounding rock stress problems,analysis of opening shape on the influence of surrounding rockmass mechanics characteristics,the similar material model by biaxial compression loading method to explore the different cross section shape of surrounding rockmass in the whole stressstrain curves under different confining pressure loading mechanics characteristic in the process of change,by adopting the technology of digital image,the record and the evolution process of the full strain analysis model,and through the numerical simulation of the follow-up,the influence of the opening shape on the mechanical behavior of surrounding rock model was further explored.The conclusions are as follows:(1)By preparing cement mortar and combining with 3D printing technology,four kinds of cave models were made: circle,straight wall arch,horseshoe and rectangle;The peak compressive strength of all kinds of cavity models decreased with the increase of the size of the cavity.When the orifice size was small,the model was prone to crack initiation at the boundary,and when the orifice size was large,the crack initiation location was generally at the orifice,and the number of secondary cracks was significantly reduced.(2)As the confining pressure increases,the failure modes of the medium-size and large-size cavern models will be affected from the tensile strain to the composite failure of tension and shear.In contrast,the effect of confining pressure on the small-size cavern model is not obvious.(3)According to the field strain evolution nephogram analysis,it can be found that the strain concentration area of the circular opening will shift up and down laterally with the increase of confining pressure.The strain value of the floor of the opening is higher,and the strain value increases with the increase of confining pressure.The horseshoe opening is prone to form a high strain concentration area at the boundary of both sides and the upper and lower sides,and its range expands with the increase of confining pressure.The rectangle opening is easy to form a strain concentration area at the top and bottom of the opening,which increases with the increase of confining pressure.(4)On both sides of the opening strain increase with the increase of confining pressure,the displacement value increases with the increase of confining pressure,when the confining pressure is small,the shape of the straight wall arch,horseshoe,rectangle side up and down in the city caused by elastic loading tension crack,but plastic stage is restrained,the hole on the surface of the free particles constantly inward movement,cause the hole shrinkage deformation,opening shrinkage deformation and damage increase with confining pressure increasing.(5)The evolution law of cracks and acoustic emission events in the model was analyzed based on statistical method.In the plastic stage,the number of cracks and acoustic emission events and the degree of change with confining pressure are greater than that in the elastic stage,according to the model in the elastic stage and plastic stage variation law of thought,the influence of confining pressure on the cavity model damage rankings for circular > straight wall arch>rectangle > horseshoe.