| In recent years,with the increase of mineral resources exploitation,it is obvious that the mining tendency is gradually extended into depth.The core attention of specialists are attracted by high drivage efficiency in rock roadway with high ground stress environment,fast step in constructing mine production system,safe and high efficiency production.In this paper,theoretical analysis,new geological mechanics model test and ansys/ls-dyna numerical simulation are utilized to explore dynamic response characteristics of rock roadway with two cutting modes of large diameter empty straight hole cut and straight wedge cut with taking into account confining pressure effect in the condition of high ground stress,which provides the reference base for selecting reasonable cutting mode in rock roadway with high ground stress.The main research achievements are as follows:(1)Distribution functions of coupling radial stress and coupling tangential stress are achieved in the combined action of in-situ stress field and explosion stress field with elastic mechanics and rock mass mechanics theories are attained;the characteristics of coupling tangential stress in the different confining pressure levels show that the type is tensional stress in the near area of blast hole in the low confining pressure,and the stress peak is distributed at wall of hole,and the tensional stress area and the peak value are reduced;the coupling tangential stress type is tensional stress or compressive stress in the far area,and the distribution law is unobvious;the coupling radial stress shows compressive stress all the time;the peak value of coupling radial stress in the far area of blast hole is stable,and the coupling radial compressive stress increase along principle stress.(2)The location of empty hole is located at fractured zone of explosion,and the theoretical mode of empty hole is perfected,and the location of coupling tangential tensional peak stress of wall of hole is located at central line between loaded hole and empty hole.The relationship between coupling tangential tensional stress and hole diameter shows positive correlation.To magnify the hole diameter in some degree,which can be able to improve intension degree of adjacent zone at empty hole and to enhance the rock splitting efficiency which is remarkable when space between holes is from 6 to 8 multiple of the radius of loaded hole.Theoretical relationship among coefficient of volumetric expansion of rock medium,diameter of straight hole,diameter of inclined hole and space of holes has been achieved.The theoretical model has been established and reference criterion of groove cavity is attained.(3)Feasibility research on dynamical model test of explosion has been conducted by new experimental system of geo-mechanical model.The strength of loading frame has been checked,and shear stress and deformation of reaction wall has been examined by computator methods in the condition of the worst load combination to testify the ability of anti-deformation.The in-situ stress can be able to simulated veritably.The load can be kept stably by numerical control servo hydraulic system with self-feedback mode.The effective load region and inspection window has been designed reasonably,and the boundary effect has been reduced,and the casting condition of crushed rock has been provided.The feasibility of cut blasting model test in high in-situ stress has been testified.(4)Dimensional analysis method was introduced to dimensionlessly arrange the geometry parameters of the gutterholes,the physical and mechanical parameters of the model materials and the explosives performance parameters.The dimensionless equations were solved using the matrix method,and the similarity criteria applicable to the gutter blasting was obtained.The item provides a certain theoretical basis for the model test design and model material selection.(5)Developed a cement mortar model material suitable for the new geomechanical model experimental system explosion kinetics test,designed orthogonal test,and used the range analysis method and variance analysis method to compare the ratio of sand and cement,the proportion of cement,iron powder and The amount of mixing water is the cut-in point,and the sensitivity and significance of the physical and mechanical characteristics of the similar model material are analyzed.The appropriate matching range of the model material is obtained,and the matching ratio between the explosive and the model material is further determined to determine the matching scheme.(6)The static properties of the model material are characterized by high strength,large elastic modulus,high velocity of longitudinal wave,and match with the high explosive impedance of the explosive;the dynamic response of the model material is good,and the dynamic stress-strain curve can observe the linear elastic phase,bonding Destruction phase,compaction phase,and unloading phase achieved dual goals of static similarity and dynamics.(7)A combined solid model of external force surrounding rock protection layer and gutter area was established,effectively shortening the test period;an improved method for embedding fixed microstrain sensing elements was proposed,and the strain gages were basically coordinated with the deformation of model materials.Objective: Based on the theory of “explosive energy similar to explosives”,the non-coupling charge coefficient was optimized,and the match between explosives and model materials was coordinated,so that the dynamic and static energy distribution ratio of high-explosive black cable gold explosives was more in line with the low detonation force.The interaction between latex explosives and rock mass media satisfies the similar conditions of model test dynamics to the greatest extent.(8)The morphological characteristics of the cavity after explosion in different confining pressure loading schemes were analyzed.Combined with the analysis of fragmentation sieve and fractal dimension calculation results,the effect of confining pressure effect on the effect of cavity blasting cavity formation was summarized.The results showed that: when the maximum horizontal principal stress direction In parallel with the direction of rock driving,the confining pressure effect helps to break the rock into a cavity.The fragmentation rate is relatively low,and the distribution of blockiness is uniform.When perpendicular to the direction of rock driving,the rock fragmentation is blocked and the effect of rock fragmentation is not Significantly,the high fragmentation rate and uneven distribution of block size;in the same confining pressure environment,the mass ratio of the wedge-retaining composite rock cuttings is smaller than that of large-diameter holes,and the size of the straight rock is larger Block-rate confining pressure has a relatively high degree of sensitivity and a wide range of changes.(9)The radial and tangential hyperdynamic strain signals of the surrounding rock medium were collected by pre-embedding strained bricks in the near and far areas around the trough.The confining pressure effect characteristics of the surrounding rock strain dynamic evolution around the trough were obtained.The performance was as follows: The radial compressive strain peaks and the tangential tensile strain peaks are approximately equal in the zone.Far away from the trench,the radial compressive strain peaks and the tangential tensile strain peaks differ greatly in the direction of the maximum principal stress,the signal attenuation is slower,and the explosion stress is Bora.The effect of rock extension and compression phase rock breaking is strong,and the macroscopic appearance is that explosion crack propagation direction is approximately consistent with the direction of maximum principal stress.(10)The damage degree of surrounding rock around the cavity after blasting was detected and analyzed by the ultrasonic flat test method.The damage evolution law of surrounding rock in the near and far area of the cavity environment under different confining pressure loading environment was obtained.The performance was as follows: The dual effects of explosive dynamic load and confining pressure constrained the impact of explosive dynamic load on the dominant role,and the restraint effect of confining pressure was not significant.In the far area of the gutter,the confining pressure constrained function dominated,which hindered the internal damage degree of the medium.(11)The box-counting dimension is used to characterize the damage evolution law of confining pressure effect in rock mass media.Quantitative information such as the expansion profile of the cavity,the distribution and development path of blasting cracks,and the development degree of micro-fissures are quantified in different regions and directions to explore different loading schemes.The morphological characteristics of the cavity after explosion and the attenuation characteristics of the cavity volume increasing with the depth of the tunneling show that: in the near region of the trench,the damage degree of the surrounding rock is high,and the regional or directional distribution characteristics are not significant;The macroscopic crack propagation is more restrained by confining pressure constraints,the distribution area of the fracture area is reduced,and the directional characteristic is that the crack propagation path is deflected to the direction of the maximum principal stress.The area near the maximum principal stress direction has a larger box-counting dimension and a higher degree of damage;On the different levels of the driving direction,the damage area at the empty surface is the largest,and the depth of the media on the boring depth gradually decreases.The damage value decreases most significantly under the hydrostatic pressure condition.When the direction of the maximum principal stress coincides with the driving direction,the damage value slowly decreases.(12)Numerical simulation research methods were used to analyze the dynamic response characteristics of the effective stress of the two guttering methods,and the evolution of the effective stress distribution around the surrounding rock was investigated.The results showed that under the confining pressure environment,the peak stress of the surrounding rock around the trough was better.Small,the propagation velocity of explosive stress wave changes significantly;the difference of the effective stress peaks of the two kinds of guttering methods is relatively low,and there is a difference in the effective stress after the peak: the effective curve of effective stress after a straight gutter is oscillatingly damped;composite gutter holes At the bottom,an effective stress concentration zone is formed,and the stress level is higher in the later peak,contributing to the crushing of the rock mass and the formation of cracks in the surrounding rock. |
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