Experimental Research and Numerical Simulation on Grouting Quality of Shield Tunnel Based on Impact Echo Method

Table 2

Acoustic parameters of SG samples.

Group	Segment wave velocity (); (m/s)	Segment acoustic impedance (); (kg/m^2s)	Grouting wave velocity (); (m/s)	Grouting acoustic impedance (); (kg/m^2s)	Reflectance ()
SG-A	4390	10.98 × 10^6	1354	2.08 × 10^6
SG-B	4390	10.98 × 10^6	2081	3.98 × 10^6
SG-C	4390	10.98 × 10^6	2643	5.22 × 10^6