| With the development of deep geotechnical engineering and underground space construction,the traditional drilling and blasting method which can achieve high-efficiency rock fragmentation is facing new challenges.The problems of poor safety,low mechanization and serious dust pollution are becoming more and more prominent.Therefore,a new method of rock breaking is needed to improve these problems.Based on the principle of blasting rock breaking,the study of rock breaking by mechanical shock and high pressure foam fracturing is carried out.Based on the theory of linear elastic fracture,the stress field and displacement field near the end of the rock compression crack are analyzed by using the rock material model.Based on this,the stress distribution of surrounding rock with various drilling arrangement types is analyzed and studied.According to pore pressure and effective stress analysis,the process of rock stress and deformation is controlled.According to the principle of high pressure foam fracturing,the impact characteristics of rock and the failure process of rock under blast load are analyzed.In view of the contents of the research,we built mechanical shock drilling and confining pressure loading test rig,high pressure foam mixer and generating system,and high pressure foam rock breaking and rock breaking system test platform.According to the rock similarity criterion,the rock samples were prepared and tested for the mechanical properties of rock.The uniaxial compressive strength,uniaxial tensile strength,elastic modulus,Poisson ratio,displacement load relationship and stress-strain relationship curve were obtained.Based on the impact drilling and confining pressure loading test-bed,the experimental study on the influence of mechanical impact drilling on the stress-strain variation of rock surface is carried out.According to the test data,the stress and strain are positively correlated.Through the comparative analysis and Experimental Research on the impact drilling and different drilling conditions,it is concluded that the impact drilling can increase the rock surface stress,and the mechanical impact process has little effect on the change of rock surface stress.On this basis,the influence of different drilling depth and confining pressure on rock surface stress and strain is studied.The results show that the stress and strain of rock surface increase with the increase of drilling depth;The stress and strain increase with the increase of confining pressure.The experimental study shows that the empty hole can increase the stress value of surrounding rock.Through the experimental study of different empty hole distance and number,it is found that the effect is not obvious when the empty hole distance is about 5 times the diameter of the empty hole;The stress of surrounding rock increases with the increase of the number of voids.Based on the mechanism of high pressure foam breaking and rock breaking,the images of high-pressure foam fracturing and rock breaking test and the real-time pressure signal curve of foam chamber are compared and analyzed.The results show that the fracture performance of rock can be improved to some extent by comparing and analyzing the effect of rock fracture under the condition of whether there is any hole.The influence of different void distance and different number of empty holes on the performance of high pressure foam fracturing is studied.It is found that with the increase of the distance between the holes,the average radius of rock fracture increases gradually and the volume of rock fracture increases gradually.The space-time hole with the distance of 150-200 mm is in the broken area.With the increase of the number of holes,the average radius and volume of fracture increase.When the number of holes is 3,the change rate of fracture volume is the largest.In the actual construction process,the rock crushing performance can be improved by increasing the number of holes properly.The paper has 64 figures,10 tables,and 95 references. |
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