Tunnel engineering is a concealed works, which is often affected by various harmful geological structures. If the harmful geological structures cannot be predicted or forecast before or during tunnel construction, the engineering progress may be affected, and a disastrous catastrophe may occur.

TSP is the abbreviation of Tunnel Seismic Prediction, which is a multi-wave and multi-component high resolution seismic reflection detection technology. In this technology, seismic waves (elastic waves) are generated by a series of regularly arranged artificial micro seismic sources and form a seismic source section. Seismic waves travel in the rock as spherical waves, and some of the seismic waves are reflected when they encounter different impedance interfaces (such as fracture zones, faults or weak interlayers).  The reflected wave signals will be received and recorded by two highly sensitive three-component seismic sensors (geophones) placed on the left and right walls of the tunnel. The propagation speed, delay time, waveform, amplitude and direction of these reflected waves are closely related to the properties and distribution of the corresponding harmful geological structures. By processing the data with software, the distribution of wave field of P wave and S wave can be obtained. Finally, the reflection in-phase axis intersecting the tunnel axis in front of the tunnel surface and the results of geological interpretation are displayed.  According to the corresponding density, the physical and mechanical parameters of the rock in the forecast area can be calculated, and then the integrity of the surrounding rock in this area can be analyzed.

The Principle of TSP Forecast Diagram

Recently, the TSP method was used to implement the advanced forecast of a tunnel by SmartSolo IAU-19 intelligent acquisition unit connected with 60Hz three-component geophone. The purpose is to detect the harmful geological structure in front of the tunnel surface and further investigate the engineering geological and hydrogeological conditions in front of the tunnel excavation working face. As a result, it reduces the construction risk and guide the smooth construction of the project.

Data Process and Analyse:

Result of TSP Depth Migration：

ZK0+513 Tunnel Surface TSP Depth Migration Image

Reflection Interface Extraction:

ZK0+513 Tunnel Surface TSP p-wave reflection interface

The processing results of the detection data are matching the actual tunnel operating. SmartSolo IAU-19 intelligent unit successfully assisted the engineers to carry out the tunnel advance forecast.