| More and more attention has been paid to the tunnel anchorage in the construction of highway suspension bridge,anchor tunnel use the interact of surrounding rock mass to the anchor body to balance tension,because of its own variable cross-section,small clearance and other engineering characteristics,the integrity and stability of the surrounding rock of the anchor tunnel are higher.Blasting is the main method of tunnel excavation,it is of great significance to study the effect of blasting excavation to anchor anchorage tunnel stability.This article combine with Yakang highway large daduhe suspension Ya'an shore anchorage tunnel project,using vibration velocity field monitoring and numerical simulation analyze the stability of surrounding rock,sum up the conclusions with practical significance,guide the construction of similar tunnel,contents and achievements of this article are as follows:According to the engineering characteristics of anchorage tunnel,based on site monitoring data of excavation blasting,analyze the peak value of vibration velocity,vibration frequency and damping rate,use deformation verify the stability of surrounding rock.According to the analysis results,the maximum vibration velocity of the first blasting face is caused by the hole blasting;In order to ensure the independence of millisecond blasting,the delay time of each section should be greater than maximum vibration duration;The peak value of vibration velocity takes the face as the center and then increases with the distance,the rear vibration velocity attenuation rate is greater than the front,the attenuation law of vibration velocity does not satisfy the Sa Rodolfo J Ki formula;Crown settlement of the first hole is 11.5mm,maximum settlement rate is 1.5mm/d,crown settlement of the rear hole is 8mm,maximum settlement rate is 2mm/d,meet safety requirements,the stability of surrounding rock is pretty good.The ANSYS/LS-DYNA is used to establish the numerical model,the critical value of the peak velocity of rock damage is 30cm/s,calculate the damage range of rock in the surrounding hole blasting.From the calculation results can be seen,With the increase of the distance between the particle and the hole wall,the peak value of the particle velocity decreases rapidly,when the distance is more than 20cm,the attenuation amplitude decreases obviously.The particle velocity peak at 30cm is 33cm/s,the particle velocity peak at 35 cm is 28cm/s,it can be inferred that the damage range is about 33cm.In order to analyze the influence of various factors on the stability of tunnel surrounding rock,in this paper,the software is used to discuss buried depth,net spacing,tunnel section size,longitudinal spacing and other conditions by controling variable method.The following conclusions are obtained:When the tunnel is shallow,with the increase of the depth,the vibration velocity of the first arch will decrease,when the depth increases to 20m,the vibration velocity is no longer changed;The greater the distance,the smaller the vibration speed;The dimension of the section has no influence on the vibration velocity of the first side of the arch;The variation of longitudinal distance has no obvious effect on the peak value of the detonation velocity of the first hole,the affected area of the front surrounding rock is less than 15m,the affected area of the rear surrounding rock is less than 7m.Finally,the influence of the longitudinal spacing on the settlement of the vault is analyzed,come to conclusion:The first three steps have the greatest influence on the settlement of the tunnel vault,the smaller the distance,the greater the settlement,it also accounts for the greater share of the total settlement;the influence of tunnel construction on the settlement of surrounding rock dome is about 12m,in order to ensure the safety of the project,the longitudinal spacing of this project is 15m. |
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