通能岩土工程有限公司 桩基低应变动测报告
reflector, the
Theoretical curves shown in Figure 2. In the case of better conditions, the pile can be significantly
The end of the reflected wave (Figure 3), the curve is the sensor by the high damping rubber cement bonded, forced vibration rod in a pile on the site measured. At this point, we can use velocity c, and the reflection time t pile length the relationship between L (ie L = ct?2) to estimate the pile length or velocity. and then according to the relationship between velocity and concrete strength to assess the strength of concrete pile [4].
Figure 2 a complete theory of wave curves of pile
Figure 3, the measured waveform curve intact pile 2.2 expanding pile wave curve
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通能岩土工程有限公司 桩基低应变动测报告
Expanding in the pile at a Q 1 = Q
2, c1 = c2, A 1
estimate the position of expanding L ', that is L' = ct'? 2. For the actual pile, due to the expanding influence of reflected wave at the pile end of reflection is often not obvious (Figure 5).
Figure 4 Theory expanding pile wave curve
Figure 5 post expanded diameter curves measured waveform
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通能岩土工程有限公司 桩基低应变动测报告
2.3 necking wave curve of pile Necking in the pile at a Q 1 = Q
2, c1 = c2, A 1> A 2, so the reflection coefficient R <0, so the reduced diameter at the incident and reflected waves in phase (Figure 6). The same basis of the average longitudinal wave speed c and reflected wave travel time difference t ', can estimate the location of necking L', that is L '= ct'? 2. the actual measured waveform curve pile shown in Figure 7.
Figure 6 necking theory of wave curves of pile
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通能岩土工程有限公司 桩基低应变动测报告
e
Figure 7 necking measured waveform curve e pile 2.4 breaking wave curve of pile
In the pile breaks in, the reflection coefficient R = 1, that total reflection occurs in the pile breaks in, then can often see multiple reflected waves, reflection pile Signal is difficult to see. Figure 8 shows the site of a pile, the pile 2. 7 m at fault, can be seen in Figure 8 multiple reflections.
2.5 Segregation, poorly cemented pile wave curve Segregation and poorly cemented in the pile at a Q 1 = Q
2, c1 = c2, A 1 = A 2, the reflection coefficient R> 0, so the reflected wave and incident wave theory should be the same
Phase, but because of velocity changes, make changes in the frequency of waves, the high frequency components decay rapidly, making the waveform becomes flat (Fig. 9).
As is caused by segregation or poorly cemented, they have the situation with the construction and geological reports and other auxiliary data to be distinguished.
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通能岩土工程有限公司 桩基低应变动测报告
Figure 8 Fracture pile curve measured waveform
Figure 9, the measured waveform curve segregation pile
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