206 Ground improvement by deep vibratory methods
In a first step (Table 6.3), the PPV values can be predicted for the average
(50%) and the worst case (2.25%) using the appropriate vibrator energy E
and distance r. With the resultant ground PPV G,res the PPA G,res follow using
Equation 6.2. In a second step, the propagation of the vibrations within
the building need to be estimated. Neglecting unlikely resonance effect,
the maximum vertical PPV for floor slabs can be roughly estimated by
applying a transfer coefficient TC of 2 to the vertical foundation PPV. The
horizontal PPV at the top floor level can be assumed equal to the horizontal PPV at foundation level. The third step compares PPVs so established
with design values from relevant regulation, such as given in Tables 6.1
and 6.2. Whenever worst case values are below design values, no building
damage is likely to occur. However, if predicted values, particularly the
average values, exceed the design values, caution is necessary. Direct vibration measurements should be carried out, which could necessitate increasing the distance from the closest vibro probe, or alternatively usage of a less
Table 6.3 Risk assessment method for potential building damages due to vibratory
deep compaction
Step
Description/equation
1
Prediction of foundation and ground vibration intensities:
Foundation, horizontal:
For P = 50%: PPV F, h = 10.3(E 1/2 )/r
For P = 2.25%: PPV F, h = 23.1(E 1/2 )/r
Foundation, vertical:
For P = 50%: PPV F, z = 7.3(E 1/2 )/r
For P = 2.25%: PPV F, z = 17.0(E 1/2 )/r
Foundation, resultant:
PPV
PPV
PPV
F, res
F , z
2
F, h
2
1/2
=
+
(
)
2
Ground, resultant:
For P = 50%: PPV G, res = 37.2(E 1/2 )/r
For P = 2.25%: PPV G, res = 95.2(E 1/2 )/r
PPA G, res = 2πf PPV G, res
2
Transfer coefficient TC = PPV/PPV F :
For horizontal vibrations of walls and floors:
TC h = 1.0
For vertical vibrations of floors and slabs, if no resonance is to be expected:
TC z = 2
PPV h = TC h PPV F, h
PPV z = TC z PPV F, z
3
Comparison with design values/assessment:
PPV F, res ≤ DPPV F, res for P = 2.25% and P = 50%
PPV h ≤ DPPV h for P = 2.25% and P = 50%
PPV z ≤ DPPV z for P = 2.25% and P = 50%
PPA G, res ≤ DPPA G, res for P = 2.25% and P = 50%
Source: Achmus, M. et al., Building vibrations due to deep vibro processes, in 7th Conference on
Ground Improvement Techniques, Seoul, South Korea, 2010.
In a first step (Table 6.3), the PPV values can be predicted for the average
(50%) and the worst case (2.25%) using the appropriate vibrator energy E
and distance r. With the resultant ground PPV G,res the PPA G,res follow using
Equation 6.2. In a second step, the propagation of the vibrations within
the building need to be estimated. Neglecting unlikely resonance effect,
the maximum vertical PPV for floor slabs can be roughly estimated by
applying a transfer coefficient TC of 2 to the vertical foundation PPV. The
horizontal PPV at the top floor level can be assumed equal to the horizontal PPV at foundation level. The third step compares PPVs so established
with design values from relevant regulation, such as given in Tables 6.1
and 6.2. Whenever worst case values are below design values, no building
damage is likely to occur. However, if predicted values, particularly the
average values, exceed the design values, caution is necessary. Direct vibration measurements should be carried out, which could necessitate increasing the distance from the closest vibro probe, or alternatively usage of a less
Table 6.3 Risk assessment method for potential building damages due to vibratory
deep compaction
Step
Description/equation
1
Prediction of foundation and ground vibration intensities:
Foundation, horizontal:
For P = 50%: PPV F, h = 10.3(E 1/2 )/r
For P = 2.25%: PPV F, h = 23.1(E 1/2 )/r
Foundation, vertical:
For P = 50%: PPV F, z = 7.3(E 1/2 )/r
For P = 2.25%: PPV F, z = 17.0(E 1/2 )/r
Foundation, resultant:
PPV
PPV
PPV
F, res
F , z
2
F, h
2
1/2
=
+
(
)
2
Ground, resultant:
For P = 50%: PPV G, res = 37.2(E 1/2 )/r
For P = 2.25%: PPV G, res = 95.2(E 1/2 )/r
PPA G, res = 2πf PPV G, res
2
Transfer coefficient TC = PPV/PPV F :
For horizontal vibrations of walls and floors:
TC h = 1.0
For vertical vibrations of floors and slabs, if no resonance is to be expected:
TC z = 2
PPV h = TC h PPV F, h
PPV z = TC z PPV F, z
3
Comparison with design values/assessment:
PPV F, res ≤ DPPV F, res for P = 2.25% and P = 50%
PPV h ≤ DPPV h for P = 2.25% and P = 50%
PPV z ≤ DPPV z for P = 2.25% and P = 50%
PPA G, res ≤ DPPA G, res for P = 2.25% and P = 50%
Source: Achmus, M. et al., Building vibrations due to deep vibro processes, in 7th Conference on
Ground Improvement Techniques, Seoul, South Korea, 2010.