4.1 Research object
Based on the model described in Chapter 2, we then study the dynamic response of the lining when the distance between the tunnel faces of the preceding and following tunnels is 0m, 10m, 20m, 30m, and 40m, including the vibration speed of the lining and the lining Displacement caused by the tunnel.
4.2 Speed influence research
After the blasting load is generated, the maximum speed of the lining at different times. First study the impact of the blasting of the back hole (right hole) on the blasting of this hole and adjacent tunnels.
Table 2 Effect of the blasting of the trailing hole (right hole) on the speed of the preceding hole (left hole)
time(s)
|
The speed of the advance hole at different locations (cm/s)
|
0m
|
10m
|
20m
|
30m
|
40m
|
0.018
|
1.25
|
2.35
|
1.86
|
2.74
|
1.64
|
0.022
|
2.02
|
3.16
|
2.72
|
3.57
|
3.67
|
0.028
|
2.78
|
2.67
|
2.98
|
2.55
|
2.99
|
0.035
|
4.97
|
5.29
|
5.48
|
5.70
|
5.71
|
0.043
|
3.42
|
3.85
|
4.30
|
4.45
|
4.69
|
0.053
|
3.50
|
3.65
|
4.23
|
4.53
|
5.61
|
0.063
|
2.21
|
2.42
|
2.57
|
3.03
|
3.19
|
0.073
|
1.52
|
2.44
|
2.64
|
2.84
|
3.25
|
0.083
|
3.51
|
3.66
|
3.95
|
4.16
|
4.29
|
0.093
|
2.13
|
2.52
|
2.78
|
2.44
|
2.90
|
0.103
|
2.03
|
2.48
|
2.82
|
2.33
|
2.76
|
0.113
|
1.37
|
1.42
|
1.55
|
2.01
|
2.11
|
0.123
|
1.20
|
1.27
|
1.43
|
1.33
|
1.80
|
0.133
|
1.20
|
1.39
|
1.43
|
1.53
|
1.61
|
0.143
|
0.96
|
0.98
|
0.97
|
0.98
|
1.23
|
Table 3 Effect of blasting on the speed of the hole in the back hole (right hole)
time(s)
|
0.0028
|
0.0056
|
0.0071
|
0.0089
|
0.012
|
0.0176
|
0.022
|
0.276
|
0.345
|
speed
(cm/s)
|
1.406
|
8.079
|
14.30
|
17.22
|
17.40
|
11.43
|
15.72
|
7.137
|
4.553
|
time(s)
|
0.531
|
0.731
|
0.831
|
0.931
|
0.531
|
0.631
|
0.731
|
0.831
|
0.931
|
speed
(cm/s)
|
6.112
|
2.884
|
2.504
|
2.195
|
2.802
|
3.160
|
2.443
|
1.390
|
1.810
|
From the above data, it can be seen that the impact of blasting on the cave is much higher than that of adjacent caves. The vibration velocity at multiple points in time has been greater than 10cm/s, which is higher than the specified critical velocity, and the cloud diagram shows that after the blasting load was applied, The maximum velocity of this hole is always near the blasting position, which conforms to the objective law of the maximum vibration dynamic response near the blasting position. In view of this, the study of the vibration velocity in this paper mainly focuses on the influence of blasting on adjacent tunnels.
It can be seen from the velocity curve that after the blasting load is applied, the velocity curve first rose in a wave form, the tunnels with different tunnel face spacings all reach the peak velocity at 0.0345s, and then continue to gradually decrease in the form of waves. After 0.0831s, the speed change range of different tunnel face spacings gradually tends to be the same. The peak speed tends to increase with the increase of the distance between the tunnel faces. When the distance between the tunnel faces is 40, the peak speed is the largest, which is 5.709cm/s. When the distance between the tunnel faces is 0, the peak speed is the smallest. The value is 4.973cm/s, which is less than the critical speed, indicating a safe state.
After the blasting load of the trailing tunnel is applied, the maximum velocity cloud diagram of the advance tunnel lining is shown in Fig. 7 under the conditions of different distances between the tunnel faces.
It can be seen from Fig. 7 that the position at the time of maximum speed appears in the arch waist part of the tunnel on the explosion-incoming side, and this part needs to be reinforced during the construction process.
It can be seen from the velocity graph that when the blasting load is applied to the advance hole, the peak velocity of the lining of the advance hole (left hole) gradually decreases with the increase of the distance between the tunnel faces, with the increase of the distance between the tunnel faces, the speed change amplitude gradually Decrease, and finally tend to be the same, as the distance between the tunnel faces increases, the time when the blasting affects the back hole (left hole) gradually lags: when the lining speed first appears 1.5cm/s, the time for the tunnel face is 0m is about 0.0175s, the time for the tunnel face is 10m is about 0.022s, the time for the tunnel face is 20m is 0.0276s, the time for the tunnel face is 30m is 0.0345s, and the time for the tunnel face is 40m is 0.0431s.
After the blasting load of the advance hole is applied, the maximum speed cloud diagram of the back hole lining under different distances between tunnel faces conditions is as follows:
It can be seen from the cloud diagram that the maximum velocity effect of the blasting of the leading hole (right hole) on the trailing hole (left hole) is mainly concentrated on the lining near the tunnel face, and this part needs to be reinforced during the construction process.
4.3 Research on the influence of displacement
We have studied the displacements in the three directions of X (radial), Y (circular), and Z (axial) and found that the displacement in the Z direction has a similar change trend with the combined displacement. The displacement trend in the X and Y directions is quite different from the combined displacement trend, and the change in the whole process is very small, so here we study the displacement part of the lining, we only study the displacement U3 in the Z direction.
The following is the displacement U3 of the tunnel lining in the Z direction.
The influence of the blasting of the trailing hole on the Z-direction displacement of the leading hole: As can be seen from the curve in the figure, in the whole process, under different working conditions, the displacement of the lining Z-direction shows a similar trend over time in the case of. Taking the peak time 0.0431s as the demarcation point, the maximum displacement in the first half is increased at a larger rate, and after reaching the peak, the second half is decreased again at a smaller rate. After 0.0732s, the displacement change gradually stabilized. During the blasting process, the maximum displacement showed a trend of gradually decreasing with the increase of the distance between the tunnel faces. Among them, when the distance between the tunnel faces was 0, the maximum displacement was 0.441mm, and when the distance between the tunnel faces was 40, the maximum displacement was 0.361mm. But overall, the scope of change is relatively small.
The cloud diagram of the maximum displacement of the lining of the advance tunnel under different distances between the tunnel faces after the blasting load is applied is as follows:
It can be seen from the above cloud diagram that the maximum displacement effect of the blasting of the trailing hole (left hole) on the leading hole (right hole) appears on the front hole’s front blast side arch waist, and with the change of the distance between the tunnel faces, this location has always been near the same location as the rear tunnel. During the construction process, this location should be reinforced.
It can be seen from the curve in the figure that as the distance between the tunnel faces increases, the maximum displacement of the tunnel lining gradually decreases, and the time for the maximum displacement gradually goes back, and as the distance between the tunnel faces increases, before reaching the peak of displacement, the rate of change of the ascending section gradually decreases, and after reaching the peak, the rate of change of the descending section is closer. When the distance between the tunnel faces is different and the displacement is about 0.09s, the changes begin to tend to be the same.
After the blasting load of the advance tunnel is applied, the maximum displacement cloud diagram of the back tunnel lining is as follows:
From this series of cloud diagrams, it can be seen that the largest displacement impact of the front hole (right hole) blasting on the back hole (left hole) is concentrated in the vicinity of the tunnel face of the back hole, including the arch and vault on the side of the explosion. During the construction process, this part should be reinforced.