Study Of Safty Threshold Of Damage Degree Of Anchorage Tunnel Based On Displacement Rule

Recently, The tunnel-type anchorage was used widely.But unfortunately, the Special study on the PPT which used in the tunnel-type anchorage has not been paid enough attention, and in consequence, valuable experience was deficient when this kind of anchorage was build.In this parper,based on blasting excavation in tunnel-type anchorage of Aizhai suspension bridge, the development low of damage degree and loose circle of surrounding rock under different blasting load is obtained by sonic wave testing method. The corresponding relation between the damage degree of surrounding rock and the Peak Particle Velocity of vibration(PPV) is discussed. Moreover , The threshold which leads to accumulative damage to rock mass is discussed. In view of above-mentioned researches, a reasonable control index of blasting vibration velocity is determined. The result shows that the accumulated vibration effect caused by blasting should be limited. The accumulated vibration damage of surrounding rock is not obvious when the Peak Particle Velocity (PPV) of surrounding rock is below 2cm/s. From the point of view of technology and economy for this project, it is reasonable that the value of PPV is controlled to be 3cm/s-6cm/s.the data which Feedback by Construction Monitoring and Measurement show that, the economic index and the technical index were both given comprehensive consideration, Therefore,the research results there is universal reference significance to the similar projects.In addition, The curveψbetween displacement characteristics and rock damage degree(D) of tunnel-type anchorage are obtained by numerical analysis in a series of finite element models which distinguished by different rock damage degree.The results show that there are two inflection points in curveψwhen D=0.1 and D=0.4,the critical point used to Judges instability for anchorage is D=0.6. The displacements of the surounding rock are mainly with DY and DZ under cable force. Specially, When D=0.2 and D=0.3 the maximum displacements were 1.14mm and 1.17mm respectively,moreover, in condition of D∈[0.2,0.3],the displacements of most region of the model are less than zero. Therefore, The safty threshold of damage degree of tunnel-type anchorage surounding rock(Dcr) Dcr =0.2 can be adopted.Finally, Condition analysis model and contrast model are build which used to evaluate the interplay Degree between anchorage&tunnel. The results show that the interplay degree between anchorage&tunnel Possesses inequality in excavation stage, videlicet,the influence degree of tunnel to anchorage is more significant than the back face.Due to the tunnel,the maximum vertical displacement(DZ) difference of the anchorages under 1P(Design cable force),3P,5P,10P is 0.758mm,0.84mm,0.889mm,1.037mm respectively. Its action effect is lead to the anchorage rotate around the x axis and subsiding, However, x-direction movement and y-direction movement of the anchorage werenot affected.