Study On Blasting Damage Scale By Uncoupling Charge In Typical Strata In Chongqing

With the development of China’s economy,the construction of the infrastructure is advancing rapidly,the application of engineering blasting is more and more extensive.Blasting technology speeds up the progress of the construction in the project,but it also affects the surrounding environment.Blasting is a complex process,explosives produce high temperature,high pressure and high energy,they all act on the rock.The physical and mechanical properties and structural characteristics of rock mass are complex and changeable,which leads to the difficulty in determining the effect of blasting.In engineering,excavation and protection of the surrounding rock is often contradictory.On the one hand,the request of explosive in accordance with section design of the rock blasting down,but this is bound on the remain rock caused damage and destruction;on the other hand,it needs to protect remaining rock,prevent the deterioration of performance,prevent the formation of carrying capacity.Therefore,it is needed to control the blasting damage range of surrounding rock in blasting engineering.By means of damage range and damage variable,the damage scope of the surrounding rock can be directly seen,which in turn can be optimized by the optimization of blasting parameters.In this paper,based on the Chongqing rail transit circle line Yulu station project,several methods such as numerical simulation,theoretical derivation,field testing are used to study the uncoupling charge blasting damage range.Firstly,some parameters are corrected based on the radius estimation of the existing blasting fracture zone.Considering the effect of explosion gas on the crack propagation,the formula is remodified.Secondly,the software LS-DYNA was used to calculate the uncoupling charging laws under different diameter,different charging density and different media.Finally,in combination with the measured blasting vibration data of Chongqing rail transit circle line Yulu station project,PPV method is used to estimate the range of damage,and compare with the damage range calculated by LS-DYNA software.Though the study of this paper,several conclusions are drawn as follow:(1) Based on existing radius formula,the initial pore wall pressure,the radius of the blasting hole and the shock wave attenuation is stress wave are modified.The formula is modified again by considering the effect of explosion gas on the crack propagation.Compared with the original formula,the new formula is more in linewith the engineering practice,which can be used to estimate the range of blasting damage.(2) The blasting damage range is different under different blasting hole diameter,the smaller the hole diameter,the larger the damage range.Line density and the blasting damage range is roughly linear relationship,slope is 0.26.The linear charge density is small,the blasting damage range is also small.The blasting damage in the water medium is larger than that of the air,and the difference of the wall pressure of the two holes is 18%.(3) Compared with the calculation results of the new formulas and numerical simulation,the results show that the revised computational formula than numerical calculation result is relatively large.When the uncoupling coefficient is 1,the error of the result is the biggest,about 30%,error in other conditions is no more than 15%.(4) When smooth blasting,damage range of holes is increaseing with the increase of time,the range of the two holes is not damaged gradually reduced.Borehole pressure is less than the compressive strength of rock,and larger than the tensile strength of rock,it cracks in tensile force.The tensile stress in the center of the hole is larger than the tensile strength of the rock,and the crack in the middle of the hole is formed.In the calculation of PPV method,the damage range of21.76cm~33.77 cm without considering the effect of group holes.The damage range of numerical simulation is about 20.0cm~30.0cm,and the results between the two methods are in good agreement.