Study On Optimization Of Blasting Parameters Of Special Shaped Hole On Highway Slope

Our country is in the stage of rapid development of infrastructure construction,and the transportation industry is developing vigorously.There are many rock slopes on the highway.The demand of rock slope excavation engineering is very large every year.In the process of highway slope excavation,blasting is the most frequently used and the most effective rock breaking means.Traditional blasting technology can obtain regular excavation profile by optimizing blasting parameters,but how to accurately control the surrounding formation,reduce the vibration,flying rock and dust disasters caused by blasting,reduce the damage of blasting to rock mass and protect the stability of slope has always been the focus of many blasting experts and field engineers.In order to improve the blasting efficiency,directional fracture controlled blasting technology has a long-term development,but there is a lack of relevant research on special-shaped hole blasting.The special-shaped hole blasting is an evolution of directional fracture controlled blasting of slotted hole.There is obvious stress concentration at the end of semicircle notch of special-shaped hole blasting,which can make the rock fracture along the semicircle notch direction of special-shaped hole with good directivity,The blasting vibration is very small,so it can be used in highway slope excavation blasting engineering to reduce blasting vibration,flying rock and dust disasters and avoid disaster accidents.Therefore,it has significant theoretical and practical significance to optimize the blasting parameters of highway slope special-shaped blasthole.The contents and main achievements of this paper include the following aspects(1)According to several existing basic blasting theories,based on the mechanism of rock blasting and ordinary round hole smooth blasting,the blasting mechanism of irregular hole is analyzed.Special shaped hole blasting is developed on the basis of smooth blasting.It is an evolution of slotted hole blasting in directional fracture controlled blasting.Its directional effect is obvious.It can change the stress around the hole and produce stress concentration.According to the theoretical formula,the radius of crack area of special-shaped hole blasting is 1.52 m,which is about twice of that of circular hole blasting(0.78m).(2)Through the comparative analysis of single irregular hole and single round hole blasting,the numerical simulation of blasting mechanism of single irregular hole is carried out,and the stress distribution and vibration propagation law around the blasting are obtained.The results show that the stress concentration appears at the semicircle groove end of the special-shaped hole,which proves that the direction of the semicircle groove end of the special-shaped hole is the first place where the crack occurs;At the same time,the peak value of compressive stress of special-shaped hole blasting is smaller than that of round hole blasting,the energy required for crack initiation and expansion is smaller than that of ordinary round hole blasting,and the vibration of special-shaped hole blasting is much smaller than that of round hole blasting,which is conducive to reducing blasting vibration and flying rock hazards;The radius of the crack zone is 0.80 M for the round hole blasting and 1.59 M for the special-shaped hole blasting.The numerical results are close to the theoretical results.The radius of the crack zone for the single special-shaped hole blasting is about twice that of the single round hole blasting;The error of the radius of the fracture zone is about 2.5% for the single round hole blasting,and about 4.6% for the single special-shaped hole blasting.Therefore,the rationality of the theoretical analysis of the special-shaped hole blasting mechanism is verified in the numerical solution.(3)The numerical simulation of blasting mechanism and parameter optimization of multiple irregular holes is carried out by using the comparative analysis of double irregular holes and double circular holes,and the numerical calculation model of four irregular holes with different hole spacing parameters of 60 cm,70cm,90 cm and 120 cm respectively,The results show that the blasting with double irregular holes is better than that with double circular holes,the stress wave propagates preferentially along the cutting direction of the semicircle auxiliary hole,and the horizontal vibration acceleration at the cutting end of the semicircle is the main factor causing the damage.The application of irregular hole in smooth blasting of highway slope is better than round hole blasting under the same conditions,which provides a theoretical basis for the application of directional fracture control blasting of irregular hole in Highway Slope Blasting.The results show that the directional fracture effect is the best and the blasting effect is the best when the hole diameter is 42 mm,the explosive diameter is 42mm(coupling charge),the minimum resistance line is 60 cm and the distance between holes is 90 cm,It provides a theoretical basis for the optimization of blasting parameters of special-shaped blasthole on highway slope.