Experimental Study On Explosion Stress Field And Damage Mechanism Of Rock Under Confining Pressure

Due to the advantages of simple operation,convenient construction,and fast excavation,the drilling and blasting method is still the main method for excavating underground rock projects.With the increase of excavation depth,the in-situ stress of the deep rock mass increases,and the "pinching" effect on the rock increases,making the blasting more difficult;many studies have shown that the initial static in-situ stress field effect cannot be ignored under high confining pressure,and the rock blasts cracks.The evolutionary law of blasting will also change,and the blasting parameters and technology of engineering blasting construction under high stress sites will also undergo certain changesIn order to study the dynamic fracture mechanism of rock under high geostress environment,the deep mudstone and sandstone are selected as the research objects,and the dynamic mechanical properties,fracture and fracture characteristics and energy dissipation law of mudstone and sandstone are studied by using a 50 mm diameter split Hopkinson test device;according to the similarity criterion,taking the strength similarity as the primary factor,the similar model materials are prepared and the similar material dynamics are carried out The results of dynamic impact mechanical tests under compression,splitting and active confining pressure show that:under the impact load,the mudstone specimen produces circumferential fracture failure and axial splitting tensile failure,and the sandstone specimen produces axial splitting tensile failure and crushing failure;the fragmentation degree of both increases with the increase of impact pressure;the dynamic uniaxial compressive strength presents an exponential with the increase of strain rate The results show that the absorption energy,transmission energy and reflection energy of mudstone increase in the form of linear,logarithmic and quadratic function with the increase of incident energy;the absorption energy can be characterized by unit volume energy consumption density,unit mass energy consumption and specific energy of absorption impedance,all of which increase linearly with the increase of incident energy and quadratic function with strain rate.With the increase of impact pressure,the average strain rate,dynamic strength and peak strain of similar materials increase.The dynamic strength of similar materials increases exponentially with the increase of strain rate,which is consistent with the regularity of the original rock.The dynamic fracturing failure of mudstone similar materials is mainly caused by intermediate cracks,while that of sandstone similar materials is mainly caused by intermediate cracks The dynamic peak strength of mudstone similar material increases with the increase of active confining pressure,and the dynamic strain peak value of sandstone similar material increases nearly twice under active confining pressure.In order to realize the test of explosion stress field under confining pressure and the experimental research of rock damage and failure mechanism,a plane similar explosion test device is developed,which can realize the unequal pressure loading of 200t load in two directions and four sides of plane,and a rock explosion test system combining the ultra dynamic strain test system and high-speed photography system is constructed,and the high-speed photography and ultra dynamic strain mining are realized set system synchronization.According to the theoretical analysis,the attenuation law of the distribution of the explosion stress field,the mechanism of explosion damage and fracture,and the experimental study of the dynamic propagation of the explosion crack under different confining pressures are carried out.The results show that the explosion stress wave of the rock mass decreases exponentially with the increase of the specific distance under the experimental environment of one-way vertical loading,two-way equal pressure loading and two-way unequal pressure loading.With the increase of the load,the absolute value of the radial strain wave attenuation index becomes larger;the absolute value of the circumferential strain wave attenuation index becomes smaller,and the absolute value of the circumferential strain wave attenuation index becomes larger with the increase of the load in the biaxial constant pressure loading test environment.The absolute value of the number decreases with the increase of the confining pressure,especially in the horizontal direction;the radial direction stress decreases with the increase of the loading pressure;the external failure pattern of the similar model of bi-directional equal confining pressure loading gradually changes from an ellipse to a circle,and photoinfor is used to process the high-speed video image,and it can be concluded that with the increase of the action time of the explosion load,the external failure is caused by the explosionThe displacement area becomes larger and larger,and the proportion of blasting fracture area decreases gradually with the increase of bidirectional confining pressure.When the direction of main stress is the same,one-way vertical loading and two-way equal pressure loading,the direction of stress will affect the direction of crack propagation,but the decisive factor of external failure of blasting is the magnitude of main stress.When the loading force is 7MPa,the magnitude of main stress is the same,change the stress.In the direction of force,when the specimen is loaded under one-way(0°),two-way equal pressure(45°)and two-way unequal pressure(30 °,60°),the volume of the blasting failure is approximately equal to about 85ml,and the direction of the crack propagation deviates along the direction of the main stress;in order to reveal the crack tip propagation speed under the confining pressure,based on the crack propagation strain gauge technology,the unidirectional vertical load is acted on.It is found that with the increase of one-way vertical load,the crack propagation direction is better,but the maximum crack propagation speed is restrained,and the crack propagation speed of the middle prefabricated slit specimen tends to 555.6m/s.Figure[128]table[36]reference[125]...